stencel

explanation blue bibcodes open ADS page with paths to full text

Author name code: stencel
ADS astronomy entries on 2022-09-14
author:"Stencel, Robert E."

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Title: Spectropolarimetry of the disk of epsilon Aurigae during the
2010 total eclipse
Authors: Melnick, D.; Stencel, R. E.
2020AAS...23614301M Altcode:
We used spectro-polarimetry to pursue a detailed exploration of
structure in HD 31964, the ɛ Aurigae system. As a single-line
spectroscopic binary, it consists of a variable F-type supergiant star
that is eclipsed by an accretion disk surrounding an unseen companion
(probably a B-type star). A total eclipse occurs every 27 years and
lasts for almost 2 years. We re-examined 50+ epochs of high dispersion
optical spectro-polarimetric data from the ESPaDOnS instrument at the
Canada-France-Hawaii Telescope, obtained before,during and after the
most recent eclipse (2009-2011). Software was developed to optimize
signal to noise, and to find the phase-dependent appearance of linear
and circular polarization in spectral lines. Using a multi-point box
kernel and requiring at least 6σ confidence above the coefficient of
variation, we found the linear and circular polarization signal in
these spectra. We present here spectral lines the wavelength region
461 to 468 nm as representative of intermediate strength lines in
the spectra, and find a preponderance of circular polarization signal
during early (2009) and late eclipse phases (2011), and a preponderance
of the linear polarization signal during mid-eclipse (2010). Finally,
we are grateful to the estate of William Herschel Womble for support
of astronomy and astrophysics at the University of Denver.

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Title: Setting the Stage for the Planet Formation Imager
Authors: Monnier, John; Aarnio, Alicia; Absil, Olivier; Alonso-Herrero,
Almudena; Anugu, Narsireddy; Baines, Ellyn; Bayo, Amelia; Berger,
Jean-Philippe; Danchi, William; Elias, Nicholas; Gai, Mario; Gandhi,
Poshak; Gardner, Tyler; Gies, Douglas; Gonzalez, Jean-François;
Haniff, Chris; Hoenig, Sebastian; Ireland, Michael; Isella, Andrea;
Kane, Stephen; Kirchschlager, Florian; Kishimoto, Makoto; Klarmann,
Lucia; Kluska, Jacques; Kraus, Stefan; Labadie, Lucas; Le Bouquin,
Jean-Baptiste; Leisawitz, David; Linz, Hendrik; Mennesson, Bertrand;
Morlok, Andreas; Norris, Ryan; Pope, Benjamin; Quiroga-Nuñez, Luis
Henry; Rau, Gioia; Regaly, Zsolt; Reynolds, Mark; Riva, Alberto;
Roettenbacher, Rachael; Schaefer, Gail; Setterholm, Benjamin; Smith,
Michael; Stencel, Robert; ten Brummelaar, Theo; Tristram, Konrad R. W.;
van Belle, Gerard; Vasisht, Gautam; Weigelt, Gerd; Wittkowski, Markus
2019BAAS...51g.133M Altcode: 2019astro2020U.133M
The Planet Formation Imager (PFI) is a next-generation infrared
interferometer designed to image the active phases of planet formation
and to take planetary “snapshots” of young systems. We outline
a technology plan to make PFI a reality, identifying a potential
breakthrough opportunity for making inexpensive large telescopes
available.

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Title: Polarization Observations and Models Constrain the Properties
of the Bow Shock around HD 230561
Authors: Lin, Austin A.; Shrestha, Manisha; Wolfe, Tristan M.; Hoffman,
Jennifer L.; Stencel, Robert E.
2019RNAAS...3..121L Altcode: 2019RNAAS...3h.121L
No abstract at ADS

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Title: Binary and Multiple Star Systems at High Angular Resolution
Authors: Schaefer, Gail; Duchene, Gaspard; Farrington, Christopher D.;
Gardner, Tyler; Gies, Douglas R.; Kraus, Adam; Monnier, John D.; Prato,
Lisa; Ridgway, Stephen; Roettenbacher, Rachael; Stencel, Robert E.;
ten Brummelaar, Theo; van Belle, Gerard
2019BAAS...51c.483S Altcode: 2019astro2020T.483S
Binary and multiple star systems provide laboratories for measuring
stellar masses and studying star formation, stellar evolution, and
dynamical evolution over time. This paper outlines several areas in
the context of binary stars that can be advanced over the next decade.

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Title: Structure in the disc of epsilon Aurigae - analysis of ARCES
and TripleSpec spectra from the 2010 eclipse
Authors: Gibson, Justus L.; Stencel, Robert E.; Ketzeback, William;
Barentine, John; Coughlin, Jeffrey; Leadbeater, Robin; Saurage,
Gabrelle
2018MNRAS.479.2161G Altcode: 2018MNRAS.tmp.1511G; 2016arXiv161205287G
Worldwide interest in the recent eclipse of epsilon Aurigae resulted in
the generation of several extensive data sets, including high-resolution
spectroscopic data sets. This lead to the discovery, among other things,
of the existence of a mass transfer stream, seen notably during third
contact. We explored spectroscopic facets of the mass transfer stream
during third contact, using high-resolution spectra obtained with
the ARCES and TripleSpec instruments at Apache Point Observatory. One
hundred and sixteen epochs of data were obtained between 2009 and 2012,
and equivalent widths and line velocities of high- and low-eccentricity
accretion disc lines were measured. These data sets also enabled
greater detail to be measured of the mid-eclipse enhancement of the He
I 10 830 Å line, and the discovery of the P Cygni shape of the Pa β
line at the third contact. We found evidence of higher speed material,
associated with the mass transfer stream, persisting between third and
fourth eclipse contacts. We visualized the disc and stream interaction
using SHAPE software, and used CLOUDY software to estimate that the
source of the enhanced He I 10 830 Å absorption arises from a region
with nH = 1011 cm-3 and temperature
of 20 000K, consistent with a mid-B-type central star. Van Rensbergen
binary star evolutionary models are somewhat consistent with the current
binary parameters for their case of a 9 plus 8 solar mass initial
binary, evolving into a 2.3 and 14.11 solar mass end product after
35 Myr. With these results, it is possible to make predictions which
suggest that continued monitoring prior to the next eclipse (2036) will
help resolve standing questions about the mass and age of this binary.

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Title: The first polarimeter in astronomy to use a stress-engineered
optic (SEO)
Authors: Wolfe, Tristan M.; Stencel, Robert E.; Ariyawansa, Ashan;
Brown, Thomas G.
2018SPIE10706E..3BW Altcode:
We present a new single-shot, full-Stokes optical astro-polarimeter
design using stress-engineered optics (SEOs). The SEO is a cylindrical
glass window under static stress by radially-inward forces in three
symmetrically-space regions, producing spatially-varying birefringence
throughout (Spilman and Brown, Applied Optics IP, 46, 2007), and
can be produced by using o-the-shelf supplies and some machining. By
collimating light collected by a telescope through the SEO and then
focusing it onto a detector, the system's point spread function (PSF)
acquires a shape uniquely dependent on the full polarization vector
of the input light (Beckley and Brown, Proc. SPIE, 757011, 2010). By
measuring the imaged PSFs, the full-Stokes polarization states of all
point sources (stars) in the field can ideally be determined from a
single exposure and without division of amplitude techniques. Prior
to our instrument, these techniques and technology had not yet been
applied to astronomy. Aside from filter wheels and focusing elements,
our instrument contains no moving parts. The instrument will operate
by first taking a set of calibration exposures of 100% polarized
light using swap-in polarizers in one of its filter wheels. Once the
calibration images are taken, the polarizers are removed form the
light path, and the science target (star) is imaged. Using techniques
described in this paper, the calibration images allow one to determine
the unknown polarization of the science target. This process is repeated
in multiple photometric bands at visible wavelengths for color-dependent
studies. The successful application of this polarimeter technology
in astronomy would mark a step forward for increasing polarimetry
efficiency (no temporal modulation required) and simplicity of
instrumentation (no spatial modulation required). Contained in this
paper are the on-sky commissioning results of our polarimeter on an 0:2m
(8in) telescope at the University of Denver, and an in-depth look at the
effect of Earth's atmospheric turbulence on the polarization-dependent
PSF detection. We have also begun testing the instrument's capabilities
in measuring both linear and circular interstellar polarization,
and a look at the variability of historic polarized and unpolarized
"standard" stars. Better understanding of the interstellar component
of the polarization of stars and the nature of calibration stars are
required for all future polarimetric measurements. The authors are
grateful to the estate of William Herschel Womble for the support of
astronomy at the University of Denver.

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Title: Structure in the Disk of epsilon Aurigae -- Analysis of ARCES
and TripleSpec data from the 2010 eclipse
Authors: Gibson, Justus; Stencel, Robert E.; ARCES Team; Ketzeback, W.;
Barentine, J.; Bradley, A.; Coughlin, J.; Dembicky, J.; Hawley, S.;
Huehnerhoff, J.; Leadbeater, R.; McMillan, R.; Saurage, G.; Schmidt,
S.; Ule, N.; Wallerstein, G.; York, D.
2018AAS...23231501G Altcode:
Worldwide interest in the recent eclipse of epsilon Aurigae resulted
in the generation of several extensive data sets, including high
resolution spectroscopic monitoring. This lead to the discovery, among
other things, of the existence of a mass transfer stream, seen notably
during third contact. We explored spectroscopic facets of the mass
transfer stream during third contact, using high resolution spectra
obtained with the ARCES and TripleSpec instruments at Apache Point
Observatory. One hundred and sixteen epochs of data were obtained
between 2009 and 2012, and equivalent widths and line velocities
measured for high versus low eccentricity accretion disk lines. These
datasets also enable greater detail to be measured of the mid-eclipse
enhancement of the He I 10830A line, and the discovery of the P Cygni
shape of the Pa-beta line at third contact. We found evidence of higher
speed material, associated with the mass transfer stream, persisting
between third and fourth eclipse contacts. We visualized the disk and
stream interaction using SHAPE software, and used CLOUDY software
to estimate that the source of the enhanced He I 10830A absorption
arises from a region with log nH = 11 cm-3 and temperature
of 20,000 K, consistent with a mid-B type central star. We thank the
following for their contributions to this paper: William Ketzeback,
John Barentine, Jeffrey Coughlin, Robin Leadbeater, Gabrelle Saurage,
and others. This paper has been submitted to Monthly Notices.

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Title: Astronomy In Denver: Polarization of Stellar Wind Bow Shocks
Authors: Lin, Austin A.; Shrestha, Manisha; Wolfe, Tristan; Stencel,
Robert E.; Hoffman, Jennifer L.
2018AAS...23211705L Altcode:
When a star with stellar wind moves through the interstellar medium
(ISM) at a relative supersonic velocity, an arch like structure known
as a stellar wind bow shock is formed. Studying the characteristics of
these structures can further our understanding of evolved stellar winds
and the composition of the ISM. Observations of these structures have
been performed for some time, but the recent discovery of many bow shock
structures have opened more ways to study them. These stellar wind bow
shocks display aspherical shapes, which cause light scattering through
the dense shock material to become polarized. We selected a target
star for observation using a catalog compiled from previous studies and
observed it in polarized light with the University of Denver’s DUSTPol
instrument. Our group has also simulated the polarization of stellar
wind bow shocks using a Monte Carlo radiative transfer code. We present
the data from our observations and compare them with the simulations. We
also discuss the contribution of interstellar polarization to the data.

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Title: MESA models for the evolutionary status of the epsilon Aurigae
disk-eclipsed binary system
Authors: Stencel, Robert E.; Gibson, Justus
2018AAS...23231502S Altcode:
The brightest member of the class of disk-eclipsed binary stars is
the Algol-like long-period binary, epsilon Aurigae (HD 31964, F0Iap +
disk, http://adsabs.harvard.edu/abs/2016SPIE.9907E..17S ). Using MESA
(Modules for Experiments in Stellar Astrophysics, version 9575), we
have made an evaluation of its evolutionary state. We sought to satisfy
several observational constraints, including: (1) requiring evolutionary
tracks to pass close to the current temperature and luminosity of the
primary star; (2) obtaining a period near the observed value of 27.1
years; (3) matching a mass function of 3.0; (4) concurrent Roche lobe
overflow and mass transfer; (5) an isotopic ratio 12C /
13C = 5 and, (6) matching the interferometrically determined
angular diameter. A MESA model starting with binary masses of 9.85 +
4.5 solar masses, with a 100 day initial period, produces a 1.2 +
10.6 solar masses result having a 547 day period, plus a single
digit 12C / 13C ratio. These values were
reached near an age of 20 Myr, when the donor star comes close to
the observed luminosity and temperature for epsilon Aurigae A, as a
post-RGB/pre-AGB star. Contemporaneously, the accretor then appears as
an upper main sequence, early B-type star. This benchmark model can
provide a basis for further exploration of this interacting binary,
and other long period binary stars. This report has been submitted to
MNRAS, along with a parallel investigation of mass transfer stream
and disk sub-structure. The authors are grateful to the estate of
William Herschel Womble for the support of astronomy at the University
of Denver.

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Title: Astronomy in Denver: Centenary of the 1918 total solar eclipse
across Denver
Authors: Stencel, Robert E.
2018AAS...23211701S Altcode:
Totality during the 2017 August 21 solar eclipse (Saros 145) traveled
along a path across the United States similar to that which occurred
for the eclipse on 1918 June 8 (Saros 126), but with
a less west-northerly track. This placed Denver and its then new
Chamberlin Observatory in the path of totality. Denver University
astronomy Professor Herbert Howe offered use of the Chamberlin
Observatory 20-inch f/15 refractor, with its Clark doublet lens and
Saegmueller mounting, in service of eclipse-related research. In
preparation for the eclipse, Professor Howe and assistants had spent
the last three months of 1917, refurbishing mechanical aspects of
the telescope. Edwin Frost, then Director of Yerkes Observatory
expressed interest and made a reconnaissance visit to the area in
September 1917, reporting results in the Feb. 1918 issue of Popular
Astronomy ( http://adsabs.harvard.edu/abs/1918PA.....26R.103F ). Frank
Schlesinger, then director of Allegheny Observatory, asked if he might
attach a special camera for star photography to the telescope at the
eclipse, to test displacement of stars, in order to test a prediction
of relativity theory. Among the additional visiting astronomical
luminaries present on that June day in 1918 were Annie J. Cannon
(Harvard), John Duncan (Wellesley), Herbert R. Morgan (U.S. Naval
Observatory) and Robert Trumpler (Berkeley). To learn the results
of all this eclipse preparedness, you will need to attend my talk in
order to get “the rest of the story” or visit our twitter feed at:
https://twitter.com/Chamberlin_Obs .

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Title: Astronomy in Denver: Probing Interstellar Circular Polarization
with Polvis, a Full Stokes Single Shot Polarimeter
Authors: Wolfe, Tristan; Stencel, Robert E.
2018AAS...23212602W Altcode:
Measurements of optical circular polarization (Stokes V) introduced by
dust grains in the ISM are important for two main reasons. First of
all, the polarization itself contains information about the metallic
versus dielectric composition of the dust grains themselves (H. C. van
de Hulst 1957, textbook). Additionally, circular polarization can help
constrain the interstellar component of the polarization of any source
that may have intrinsic polarization, which needs to be calibrated
for astrophysical study. Though interstellar circular polarization
has been observed (P. G. Martin 1972, MNRAS 159), most broadband
measurements of ISM polarization include linear polarization only
(Stokes Q and U), due to the relatively low circular polarization
signal and the added instrumentation complexity of including
V-measurement capability. Prior circular polarization measurements
have also received very little follow-up in the past several decades,
even as polarimeters have become more accurate due to advances in
technology. The University of Denver is pursuing these studies with
POLVIS, a prototype polarimeter that utilizes a stress-engineered optic
("SEO", A. K. Spilman and T. G. Brown 2007, Applied Optics IP 46)
to produce polarization-dependent PSFs (A. M. Beckley and T. G. Brown
2010, Proc SPIE 7570). These PSFs are analyzed to provide simultaneous
Stokes I, Q, U, and V measurements, in a single beam and single image,
along the line-of-sight to point source-like objects. Polvis is the
first polarimeter to apply these optics and measurement techniques
for astronomical observations. We present the first results of this
instrument in B, V, and R wavebands, providing a fresh look at full
Stokes interstellar polarization. Importantly, this set of efforts
will constrain the ISM contribution to the polarization with respect
to intrinsic stellar components. The authors are grateful to the
estate of William Herschel Womble for the support of astronomy at
the University of Denver, and for funding provided by the Mt. Cuba
Astronomical Foundation.

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Title: MESA models of the evolutionary state of the interacting
binary epsilon Aurigae
Authors: Gibson, Justus L.; Stencel, Robert E.
2018MNRAS.476.5026G Altcode: 2018MNRAS.tmp..618G; 2018arXiv180306392G
Using MESA code (Modules for Experiments in Stellar Astrophysics,
version 9575), an evaluation was made of the evolutionary state
of the epsilon Aurigae binary system (HD 31964, F0Iap + disc). We
sought to satisfy several observational constraints: (1) requiring
evolutionary tracks to pass close to the current temperature and
luminosity of the primary star; (2) obtaining a period near the
observed value of 27.1 years; (3) matching a mass function of
3.0; (4) concurrent Roche lobe overflow and mass transfer; (5) an
isotopic ratio 12C/13C = 5 and, (6) matching the
interferometrically determined angular diameter. A MESA model starting
with binary masses of 9.85 + 4.5 M⊙, with a 100 d initial
period, produces a 1.2 + 10.6 M⊙ result having a 547 d
period, and a single digit 12C/13C ratio. These
values were reached near an age of 20 Myr, when the donor star comes
close to the observed luminosity and temperature for epsilon Aurigae
A, as a post-RGB/pre-AGB star. Contemporaneously, the accretor then
appears as an upper main-sequence, early B-type star. This benchmark
model can provide a basis for further exploration of this interacting
binary, and other long-period binary stars.

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Title: Epsilon Aurigae's dark side: A thermal phase curve
investigation of the near-eclipse phases
Authors: Pearson, Richard L.; Stencel, Robert E.; Howell, Steve B.;
Hoard, D. W.; Kim, Daryl L.; Russell, Ray W.; Sitko, Michael L.
2017AAS...23020104P Altcode:
The epsilon Aurigae disk-eclipsing binary system moves through a
primary eclipse that lasts just over two years and occurs every
27.1-years. It comprises of a warm F0Ia-star (around 7750 K) and an
opaque, circumstellar disk hiding an internal B-star (with a temperature
greater than 15,000 K). We present new infrared observations from
Spitzer's Infrared Array Camera (IRAC, at 3.6 and 4.5 microns) and The
Aerospace Corporation’s Broadband Array Spectrograph System (BASS,
a 116-element prism system spectrograph spanning 3 - 14 microns) in
order to extract the thermal signature of the disk. Previous findings
indicate a variable temperature of the disk, depending on its location
within the system’s orbit: a 550 +\- 50 K temperature was identified
during eclipse phases, while a 1150 +\- 50 K temperature was found near
secondary—or anti-eclipse—phases by Hoard et al. (2010) and Hoard
et al. (2012). We use the latest observations in combination with
previously published IRAC and BASS data to compile a more complete
thermal phase curve (TPC) of the disk across nearly one-third of the
system’s orbit. The TPC indicates heating and cooling effects of
the disk, pointing to specific ranges of material properties and disk
structure. The observations, process, results, and implications will
be presented.

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Title: Developing a Single-shot Polarimeter for Astronomy with
Stessed-engineered Optics
Authors: Wolfe, Tristan; Stencel, Robert E.
2017AAS...22915518W Altcode:
True single-shot polarimetry can be accomplished by utilizing a
stress-engineered optic, with birefringence that varies spatially
along its cross-section (Ramkhalawon et al. 2012). As light passes
through such an optic, it will acquire a PSF that is unique to its
polarization, providing the ability to measure all four Stokes
parameters in a single image. This technique has not yet been
adapted to astronomy. Our effort to do so faces several challenges,
including the measurability of these PSFs for low polarizations, and
through atmospheric turbulence. Current research demonstrates that
low polarizations can remain measurable with the correct selection
of stressed-optic and CCD parameters. Additionally, if signal is
adequate (10^7 photons), then we demonstrate that turbulence does not
negatively impact measurability. These results are leading toward the
University of Denver's development of the first polarimeter to utilize
these techniques in astronomy. This instrument will have intended
applications of studying exoplanets and contributing to polarimetry
surveys. The authors are grateful to the estate of William Herschel
Womble for the support of astronomy at the University of Denver.

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Title: Re-development of the Mount Evans Womble Observatory
Authors: Stencel, Robert E.
2017AAS...22915501S Altcode:
Mount Evans in the Colorado Front Range hosts one of the highest
altitude observatories in the USA, at an elevation of 14,148 ft
(4,312 m). The observatory is operated under a Forest Service use
permit, recently renewed for another 30 years. At times, observing
conditions (seeing, water vapor column, etc.) can be as good as
anywhere. The existing twin 0.72 m f/21 R-C telescopes are solar
powered and internet connected. However, jet stream winds in 2012
destroyed the 15 year old, 22.5 ft diameter Ash dome. The replacement,
custom dome design/install was rushed, and suffers from a number of
flaws. Given that, plus the aging telescope and operating system, we
are planning, and seeking partners and investor funds, to re-develop
the facility. Facets of this may include replacing the twin apertures
with a single full-aperture telescope for remote operations and sky
monitoring, replacing the flawed dome with an innovative dome design,
renewable power upgrades, and outreach programs for the many thousands
of mountain visitors seasonally. As elsewhere, we are grappling with
increases in atmospheric water vapor and out-of-control regional light
pollution growth, but believe that the site continues to hold great
potential. Interested parties are invited to contact the first author
for further information. Website: http://www.du.edu/~rstencel/MtEvans .

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Title: Interferometric studies of disk-eclipsed binary star systems
Authors: Stencel, Robert E.
2016SPIE.9907E..17S Altcode:
As sky surveys continue to document an increasing number of transient
celestial phenomena, an intriguing subset of objects are emerging
that show variations in brightness, interpreted as the transit
of a circumstellar disk in front of a companion star in a binary
system. The brightest member of this class is the F0 supergiant star
plus disk binary, epsilon Aurigae, along with more than a dozen new
candidates sharing similarities. Better-known cases include EE Cep,
BM Ori and KH15D. Characteristics of all of these are discussed in
terms of their suitability for interferometric study. Next generation
interferometric imaging offers the potential to detect disk structures
that are driven by dynamical forces, chemical transitions and thermal
gradients. These include observable effects of tidal spiral density
waves, dust and planetessimal formation/evolution in disks, and orbital
phase-dependent heating of the disk by the external companion star.

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Title: Commissioning Results of a New Polarimeter: Denver University
Small Telescope Polarimeter (DUSTPol)
Authors: Wolfe, T. M.; Stencel, R.; Cole, G.
2015IAUS..305..200W Altcode:
DUSTPol is a dual-beam polarimeter that operates in optical wavelengths,
and was built to promote the study of linear polarimetry with smaller
telescopes. DUSTPol's performance has demonstrated low instrumental
polarization at 0.05 ± 0.02%. This poster presents commissioning
results as well as early science observations, and describes software
used for data reduction. Recent polarimetric results of RS CVn systems
and Wolf-Rayet stars, discussed herein, indicate shape and interaction
parameters. By promoting the development of similar polarimeters at
other institutions, DUSTPol will serve to establish new collaborative
surveys of cool active stars, as well as systems showing evidence of
containing complex stellar environments.

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Title: Probing disk inhomogeneities using spectropolarimetry in the
extreme binary epsilon Aurigae
Authors: Geise, Kathleen; Stencel, Robert
2015IAUS..305..293G Altcode:
The ɛ Aurigae system is a single-line spectroscopic binary system
that consists of a variable F0 supergiant star and an occulting
disk surrounding an unseen object, probably a B star. The eclipse
occurs every 27 years and lasts for almost 2 years. Spectral features
attributed to the disk exhibit line shifts due to the rotation of the
disk that are easily observed in spectra. We obtained 50+ epochs of high
dispersion optical spectropolarimetric data from the ESPaDOnS instrument
at the Canada-France-Hawaii Telescope before, during, and after the
most recent eclipse (2009-2011). We found numerous 3-sigma (or greater)
linear polarization features in the spectra and associated these with
atomic absorption features also present in the spectra. We observed
dramatic changes to polarization and position angles with time during
eclipse, particularly around 3rd contact. The increased
polarization could be due to a localized increased number of scatterers.

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Title: Interferometry of ɛ Aurigae: Characterization of the
Asymmetric Eclipsing Disk
Authors: Kloppenborg, B. K.; Stencel, R. E.; Monnier, J. D.; Schaefer,
G. H.; Baron, F.; Tycner, C.; Zavala, R. T.; Hutter, D.; Zhao, M.; Che,
X.; ten Brummelaar, T. A.; Farrington, C. D.; Parks, R.; McAlister,
H. A.; Sturmann, J.; Sturmann, L.; Sallave-Goldfinger, P. J.; Turner,
N.; Pedretti, E.; Thureau, N.
2015ApJS..220...14K Altcode: 2015arXiv150801909K
We report on a total of 106 nights of optical interferometric
observations of the ɛ Aurigae system taken during the last 14
years by four beam combiners at three different interferometric
facilities. This long sequence of data provides an ideal assessment of
the system prior to, during, and after the recent 2009-2011 eclipse. We
have reconstructed model-independent images from the 10 in-eclipse
epochs which show that a disk-like object is indeed responsible for
the eclipse. Using new three-dimensional, time-dependent modeling
software, we derive the properties of the F-star (diameter, limb
darkening), determine previously unknown orbital elements (Ω, i),
and access the global structures of the optically thick portion of
the eclipsing disk using both geometric models and approximations of
astrophysically relevant density distributions. These models may be
useful in future hydrodynamical modeling of the system. Finally, we
address several outstanding research questions including mid-eclipse
brightening, possible shrinking of the F-type primary, and any warps
or sub-features within the disk.

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Title: Transient Carbon Monoxide (Co) Absorption and Persistent
Brackett Alpha (Brα) Emission in the Spectrum of ɛ Aurigae
Authors: Stencel, R. E.; Blatherwick, R. D.; Geballe, T. R.
2015AJ....149..109S Altcode:
We obtained high-resolution infrared spectroscopy of the long period
binary, ɛ Aurigae, in the vicinity of the near-infrared overtone
band of CO, at four epochs during 2011-2012. These observations
span the period from late phase of the recent eclipse, to after the
eclipse. Lines of both 12CO and 13CO were
observed, confirming the report from the 1983 eclipse that these
features were present during the second half of the eclipse. The bands
were absent post-eclipse, consistent with their formation only in the
several AU diameter disk that has been shown to cause the eclipse. We
fitted the eclipse spectra with CO column densities 8 × 1019
cm-2 at 1275 K when nearer to mid-eclipse, and 1.5 ×
1020 cm-2 at 1050 K during third contact. We also
found that 12C/13C = 5 ± 1 in the disk. Assuming
that mass transfer from the primary star formed the disk, this implies
a helium core burning evolutionary state for the primary star. We
also obtained a high-resolution post-eclipse spectrum of the 4.05 μm
Brackett α emission line. The small radial velocity difference of the
emission, relative to a nearby photospheric line of primary star origin,
indicates that the emission may arise from nearer the system center
of mass, such as a recombination region larger than the immediate
vicinity of the unseen companion star surrounded by the disk. The
combination of CO and Brα lines provides important diagnostics for
resolving ongoing questions about the evolutionary state of this system.

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Title: Spitzer observations of epsilon Aurigae's disk temperature
Authors: Pearson, Richard L.; Stencel, Robert E.; Hoard, Donald W.;
Howell, Steve B.
2015AAS...22534903P Altcode:
We present observations from Spitzer's two IRAC bands at 3.5 μm and
4.5 μm spanning six years (2009-2014), almost 1/4 of this eclipsing
binary's orbit. We remove the contribution of the optically bright,
primary F0Ia star from the observations in order to analyze the
epoch-to-epoch changes of the opaque disk enshrouding the hidden
secondary. Previous work suggested the existence of a two-temperature
disk: a cooler side at 550 ± 50 K (as observed near eclipse)
and a hotter side at 1150 ± 50 K (as observed near the secondary
eclipse). The continual monitoring of this unresolved system in
the infrared from mid-eclipse to the present demonstrates physical
properties of the dusty disk, i.e. thermal inertia effects. How the
disk temperature changes adds constraints to the system, particularly
the structure and composition of the disk. Monte Carlo radiative
transfer codes investigate the parameter space and the impact of the
IRAC observations---see Pearson and Stencel, 1 Nov 2014 ApJ.

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Title: &amp;epsilon; Aurigae: A Two Century Long Dilemma Persists
Authors: Stencel, Robert E.
2015ASSL..408..107S Altcode:
The bright star ɛ Aurigae, an eclipsing binary with the longest known
orbital period and eclipse, has been slow to reveal it secrets. The
most recent eclipse, 2009-2011, was monitored with an array of new
and old astronomical techniques, leading to new evidence concerning
the nature of the eclipsing body and its contents. While this has led
to new insights about the state of the F superigant star and to more
clues about the evolutionary state of the system and components,
a high-mass versus low-mass model dilemma persists. This chapter
examines some of the recent developments and attempts to place the
system among the pantheon of binary types. It also offers suggestions
for observational tests prior to the next eclipse in 2037.

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Title: Constraints from Asymmetric Heating: Investigating the Epsilon
Aurigae Disk
Authors: Pearson, Richard L., III; Stencel, Robert E.
2015ApJ...798...11P Altcode:
Epsilon Aurigae is a long-period eclipsing binary that likely contains
an F0Ia star and a circumstellar disk enshrouding a hidden companion,
assumed to be a main-sequence B star. High uncertainty in its parallax
has kept the evolutionary status of the system in question and,
hence, the true nature of each component. This unknown, as well as
the absence of solid state spectral features in the infrared, requires
an investigation of a wide parameter space by means of both analytic
and Monte Carlo radiative transfer (MCRT) methods. The first MCRT
models of epsilon Aurigae that include all three system components
are presented here. We seek additional system parameter constraints
by melding analytic approximations with MCRT outputs (e.g., dust
temperatures) on a first-order level. The MCRT models investigate
the effects of various parameters on the disk-edge temperatures;
these include two distances, three particle size distributions,
three compositions, and two disk masses, resulting in 36 independent
models. Specifically, the MCRT temperatures permit analytic calculations
of effective heating and cooling curves along the disk edge. These
are used to calculate representative observed fluxes and corresponding
temperatures. This novel application of thermal properties provides the
basis for utilization of other binary systems containing disks. We find
degeneracies in the model fits for the various parameter sets. However,
the results show a preference for a carbon disk with particle size
distributions &gt;=10 μm. Additionally, a linear correlation between
the MCRT noon and basal temperatures serves as a tool for effectively
eliminating portions of the parameter space.

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Title: A Look Inside the Disk in the ɛ Aurigae Binary System
Authors: Stencel, R. E.
2014ASPC..487..383S Altcode:
Interferometric imaging, combined with spectroscopy, is providing a
powerful way to unlock the long-kept secrets of the engimatic eclipsing
system, ɛ Aurigae, that has puzzled astronomers for many decades. A
sequence of H-band MIRC images obtained at the CHARA Array during
the 2010 eclipse, is augmented with spectra obtained by a worldwide
network of observers participating in the eclipse campaign. The
MIRC images confirm the hypothesized dark disk, revealing it to
have dimensions of ∼8 AU long by ∼0.7 AU thick, that occults the
southern hemisphere of the 135R⊙ F-star primary; however,
these dimensions are dependent on the assumed distance, which still
is not settled. Spectra reveal a wealth of changes caused by facets of
the disk that can be associated with substructure, including possible
rings, a central ionized region, and evidence for accretion onto a hot
embedded object. Results reported here are due to the help of numerous
observers to whom I am indebted, and support for this effort that was
derived in part from a bequest of William Herschel Womble in support
of astronomy at the University of Denver, from NSF grant 1016678,
and from JPL RSA 1414715 to the University of Denver.

---------------------------------------------------------
Title: Resolving The Future Of Astronomy With Long-Baseline
Interferometry
Authors: Creech-Eakman, M. J.; Guzik, J. A.; Stencel, R. E.
2014ASPC..487.....C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Constraining Disk Characteristics Using Broadband and
Spectropolarimetric Observations of the Eclipsing Binary System
epsilon Aurigae
Authors: Geise, K.; Stencel, R.
2013AGUFM.P43B2012G Altcode:
Epsilon Aurigae is a single-lined spectroscopic binary system that
consists of a variable F0 supergiant star and an occulting disk,
providing special knowledge of geometry, surrounding an unseen object,
probably a B star. The eclipse occurs once every 27 years and lasts
for almost 2 years. We tested the large grain (&gt;100 microns)
hypothesis by looking for polarization sign changes at angles less than
15 degrees, an important geometric constraint for the system, comparing
polarization angles derived from Mie scattering theory to published
broadband polarimetric data over two eclipse cycles. We determined
that particles larger than the Rayleigh scattering regime were the
greatest contributors to broadband polarization from dust grains in
the disk. We also evaluated spectropolarimetric data obtained from
the Canada-France-Hawaii telescope (CFHT) ESPaDOnS instrument to probe
both the primary star and the occulting disk before, during and after
the most recent eclipse (2009-2011). We determined that spectral linear
polarization features largely arose from Fe I and singly ionized species
such as Ti II, Fe II and Cr II in all observed epochs. Persistent
anisotropies in the F star photosphere contributed to polarization
features in spectral lines in out-of-eclipse epochs. Position angles
associated with these polarization features clustered around low angles
(circa 0°×20°). Additional polarization position angles near 60°
became prevalent by mid-eclipse from scattering by gas species present
in the disk.

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Title: As the Disk Turns... Monitoring the Azimuthal Thermal Gradient
of the Irradiated Dust Disk in Epsilon Aurigae
Authors: Hoard, Donald; Howell, Steve; Stencel, Robert
2013sptz.prop10008H Altcode:
Epsilon Aurigae is the eclipsing binary star with the longest known
orbital period, showing a single long (~2 yr) eclipse every 27.1
yr. For the last ~200 years, the nature of the eclipsing object defied
explanation. We recently showed that epsilon Aur most likely consists
of a high luminosity F0 post-AGB star, and a B5 V star surrounded by a
solar system size (~8 AU diameter) disk of dusty material. We propose
to continue our IRAC monitoring of epsilon Aur, to characterize the
disk's azimuthal thermal variation as its irradiated, warm (1150 K)
portion increasingly comes into view. We request 0.2 hr to obtain 2
IRAC observations. If Cycle 10 is extended through Jan 2015, we request
another 6 visits (0.6 hr) in Dec 2014, coinciding with the predicted
start of coherent pulsations of the F star, which occur every ~3000
days. The most recent eclipse was in Aug 2009-Jul 2011; we are now
in the post-eclipse phase, when the heated side of the disk begins
rotating into view. During the majority of our past IRAC observations
(starting a few months prior to the eclipse ingress), only the cool
(550 K) side of the disk was visible. In 2014-2015, as we move toward
quadrature, the effect of heating due to the F star will increase
the IRAC ch1/ch2 flux ratio. The eclipse of epsilon Aur is a rare
event and a unique astrophysical opportunity, since backlighting of
the disk by the luminous eclipsed star reveals details that cannot
be detected in similar disks around single stars. This is one of the
very few astrophysical disks where azimuthal thermal gradients can be
mapped and interpreted. Observations of the warm side of the disk are
crucial to test and constrain new models of disk structure. As part
of our overall monitoring campaign with Spitzer, Hubble, Herschel,
and numerous ground-based facilities, the proposed observations will
make an important contribution to the understanding of binary stars,
including mass transfer and evolution, along with new insights into
astrophysical disks and post-AGB star evolution.

---------------------------------------------------------
Title: Three-dimensional Models of the Epsilon Aurigae Disk System
Authors: Pearson, Richard L.; Stencel, R. E.
2013giec.conf20103P Altcode:
The evolutionary state of the long-term binary star system, epsilon
Aurigae, remains in question. Three-dimensional (3D), radiative
transfer modeling with the HYPERION code (Robitaille 2011) enables
inspection of the azimuthal temperature gradient found on the disk
enveloping the secondary star (about 1150 K on the primary-facing side,
i.e. ”noon"; about 550 K on the ”midnight" side). This modeling
method requires specifications of the system's parameters, some of
which are the following: binary separation, stellar masses, disk
radius, disk composition, dust density, and dust size distribution. A
systematic parameter selection provides constraints on both the
disk material and binary separation, which directly corresponds
to distance determination and evolutionary status. The importance
of this work involves the inclusion of the F0 primary star in a 3D
modeling environment. Preliminary results are presented. The authors
are grateful to the estate of William Herschel Womble for support of
astronomy at the University of Denver.

---------------------------------------------------------
Title: Spectrally-Polarized Features in Epsilon Aurigae In and Out
of Eclipse
Authors: Geise, Kathleen M.; Stencel, R. E.
2013giec.conf20201G Altcode:
The epsilon Aurigae system is a single-lined spectroscopic binary
system that consists of a variable F0 supergiant star and an occulting
disk surrounding an unseen object, probably a B star. The eclipse
occurs once every 27 years and lasts for almost 2 years. We used
spectropolarimetric techniques to probe both the primary star and
the occulting disk before, during and after the most recent eclipse
in order to better understand the origin and evolution of the disk in
the system. We obtained 50+ epochs of high dispersion optical spectra
from the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii
Telescope (CFHT) during 2006-2013. These spectra included eclipse
and out-of-eclipse observations rich with polarization features
attributable to both the F0 star and the disk. We identified
4-sigma (or greater) linear polarization features in the spectra
and matched them against absorption features also present in the
spectra. Out-of-eclipse spectra revealed variable linear polarization
features largely arising from Fe I and singly ionized species such as Ti
II, Fe II, Sc II and others. Polarization features from these species
demonstrated a preferred equatorial orientation. Hydrogen absorption
features exhibited position angles that varied with orbital phase. Our
CFHT observations revealed that polarization increased dramatically
during eclipse. The increase in polarization across many species was
consistent with spectral line behavior and may help constrain the
density and temperature distribution of material in the outer layer
of the disk. Out-of-eclipse linear polarization features attributed to
the F star suggest that persistent anisotropies exist in mid- to upper
layers of the stellar atmosphere, are consistent across those layers,
and have a specific geometry in the stellar frame. Position angles
calculated from eclipse spectra suggest that scattering processes
likely arise from both the upper and lower outer layers of the disk,
as well as leading and trailing edges of the disk and trailing material
in the system. Position angles associated with hydrogen absorption
polarization suggests that hydrogen absorption features likely consist
of both stellar and extra-stellar components.

---------------------------------------------------------
Title: Merging Recent and Historic Spectra of ɛ Aurigae: Properties
of the System’s Components, and Discovery of a Mass Transfer Stream
Authors: Griffin, R. Elizabeth; Stencel, Robert E.
2013PASP..125..775G Altcode:
This study of new CCD spectra of ɛ Aur recorded in the blue and
near-UV during the 2010 eclipse has been reinforced and extended by
the inclusion of some 130 digitized historic spectra from Mount Wilson
(dating back to the 1930s) and from the DAO (dating from 1971). The
precise repetition of disk-related spectral-line changes during three
successive eclipses indicates that the structure of the disk does not
alter appreciably on a time-scale of a least a century. We deduce
that the disk has an extensive but optically thin outer layer, and
a flat structure that is tilted near to edge-on. We discover that it
is receiving from the supergiant a very confined stream of material
that is enriched in rare-earth elements. The stream has an approach
velocity very similar to the projected rotational velocity of the
F star; it has an extremely small velocity dispersion, and is only
visible between specific egress phases. We surmise that the F star is a
horizontal-branch star though its own photosphere appears, on average,
to have a solar composition. We also uncover variable broad emission
in the system and find a possible correlation with the F-star’s
Cepheid-like ∼67-day pulsations that cause its photometric variations.

---------------------------------------------------------
Title: Selected results from the epsilon Aurigae eclipse campaign,
and what lies ahead
Authors: Stencel, Robert E.
2013giec.conf20101S Altcode:
The torrent of data generated during the 2009-2011 eclipse of the
enigmatic binary, epsilon Aurigae, has provided abundant opportunity
to test and refine the many ideas associated with this system. The
UBVRIJH photometric light curves established times of ingress and
egress, and also revealed that the differential color of the disk
varied, relative to pre- or post- mid-eclipse phase. Inter-eclipse
monitoring indicated secular variations suggestive of a rapidly evolving
F supergiant star. Interferometric imaging decisively identified the
eclipse-causing agent to be an opaque disk (CHARA+MIRC). Spectroscopy
has shown that a hot source occupies the center of this disk (He I
10830A, Far-UV excess), that the disk exhibits substructure (K I 7699A)
and may have an extended atmosphere (CHARA+VEGA), and that the disk
is isotopically-enhanced in 13C (GNIRS) and in rare-earth elements
during a third contact "still-stand" in the light curve, suggestive of
a mass transfer stream. Polarimetry and spectro-polarimetry provided
additional constraints on the F star atmospheric variation and the
nature of the dust scattering in the disk. Numerical models of the disk
are exploring its relationship to the wider class of transitional and
debris-type disks, and how differential heating of the dust may reveal
properties not otherwise detected spectroscopically. As the system
moves to quadrature in coming years, continued observing opportunities
will continue to exist. I am grateful for support from the estate of
William Herschel Womble for astronomy at the University of Denver,
which has made possible two decades of research on this star that
otherwise has revealed its secrets only very slowly.

---------------------------------------------------------
Title: Results of the Recent \varepsilon Aurigae Eclipse Campaign
Authors: Stencel, R. E.
2013CEAB...37...85S Altcode: 2013arXiv1303.7128S
Results of the 2010 eclipse campaign are described, and preliminary
interpretations proposed. These include photometric, interferometric,
spectroscopic, astrometric and polarimetric observational results. Next
steps, along with continued monitoring, include simulations and other
future work. Numerous acknowledgements are appropriate for the many
participants in making this international effort a success.

---------------------------------------------------------
Title: Revealing the Hot Side of Epsilon Aurigae
Authors: Hoard, Donald; Stencel, Robert; Howell, Steve
2012sptz.prop90097H Altcode:
We request a small investment of 24 minutes of Spitzer time, to obtain
four IRAC observations of epsilon Aurigae. A naked eye object located
near Capella, epsilon Aurigae is the eclipsing binary star with the
longest known orbital period, showing a single long duration (~2 yr)
eclipse every 27.1 yr. For much of the last 200 years, the nature of
the eclipsing object defied explanation. We recently demonstrated that
epsilon Aurigae consists of a high luminosity F0 post-AGB star in orbit
with a B5 V star surrounded by a solar system sized (~8 AU diameter)
disk of cool, dust-dominated material. The eclipse of epsilon Aurigae
is a rare event; moreover, it is a unique astrophysical opportunity,
since the backlighting of the disk by the high luminosity eclipsed
star reveals details that cannot be detected in similar dusty disks
around single stars. The current eclipse started in August 2009 and
ended in July 2011; we are now in the post-eclipse phase, when the
irradiation-heated side of the disk will begin rotating into view. The
goals for these observations include: (1) extend our ongoing IRAC
monitoring campaign covering the current eclipse to post-eclipse
visits; (2) provide a consistent, well-calibrated space-based set
of IR photometry for comparison with ongoing ground-based work; and
(3) use the composite results to constrain the thermal profile of the
disk. A key expectation of these particular observations is to reveal
the irradiation-heated portion of the disk, which will be visible on its
trailing side following eclipse. Observations of this side of the disk
will be crucial to test and constrain new models of disk structure. As
part of our overall monitoring campaign with Spitzer, Hubble, Herschel,
and numerous ground-based facilities, these proposed observations will
make an important contribution to the understanding of stellar evolution
in binary stars, including mass transfer and evolution studies, along
with new insights into astrophysical disks and post-AGB star evolution.

---------------------------------------------------------
Title: Eclipse Spectropolarimetry of the ɛ Aurigae System
Authors: Geise, K.; Stencel, R. E.; Manset, N.; Harrington, D.;
Kuhn, J.
2012JAVSO..40..767G Altcode:
The recent eclipse of the enigmatic binary star system, epsilon Aurigae,
offered a special opportunity to explore the role of spectropolarimetry
in discovery of unknown facets of the objects involved. Here we present
spectropolarimetric results for H-alpha, H-beta, Ca I (422.6 nm),
and K I (769.9 nm) based on more than 50 epochs of high dispersion
spectra obtained with the ESPaDOnS instrument at CFHT during 2006-2012.

---------------------------------------------------------
Title: An Analysis of the Long-term Photometric Behavior of epsilon
Aurigae
Authors: Kloppenborg, B. K.; Hopkins, J. L.; Stencel, R. E.
2012JAVSO..40..647K Altcode: 2013arXiv1303.6871K
The lure of a 50% reduction in light has brought a multitude of
observers and researchers to epsilon Aur every twenty-seven years,
but few have paid attention to the system outside of eclipse. As early
as the late 1800s, it was clear that the system undergoes some form
of quasi-periodic variation outside of totality, but few considered
this effect in their research until the mid-1950s. In this work we
focus exclusively on the out-of-eclipse (OOE) variations seen in this
system. We have digitized twenty-seven sources of historic photometry
from eighty-one different observers. Two of these sources provide
twenty-seven years of inter-eclipse UBV photometry which we have
analyzed using modern period finding techniques. We have discovered
the F-star variations are multi-periodic with at least two periods that
evolve in time at DP ≈ -1.5 day/year. These periods are detected when
they manifest as near-sinusoidal variations at 3,200-day intervals. We
discuss our work in an evolutionary context by comparing the behavior
found in epsilon Aur with bona-fide supergiant and post-AGB stars of
similar spectral type. Based upon our qualitative comparison, we find
the photometric behavior of the F-star in the epsilon Aur system is more
indicative of supergiant behavior. Therefore the star is more likely
to be a "traditional supergiant" than a post-AGB object. We encourage
continued photometric monitoring of this system to test our predictions.

---------------------------------------------------------
Title: Modeling the Disk in the Îµ Aurigae System: a Brief Review
With Proposed Numerical Solutions
Authors: Pearson, R. L.; Stencel, R. E.
2012JAVSO..40..802P Altcode:
Parameters associated with the opaque disk in epsilon Aurigae are
explored in the context of circumstellar and proto-planetary disk
theory. The observed blackbody temperatures of the disk, at 550
and 1150 K, are primarily discussed. Brief reviews of previous work
are included that describe and attempt to explain this temperature
gradient. Heating from only the central B star provides a basal
temperature of about 250 K. An accretion rate (from the disk to the
B star) of 10^-7 M⊙/yr also provides a similar basal temperature;
a rate of 1.5 x 10^-5 M⊙/yr produces temperatures greater than 3000
K in the disk plane. To include the F star contribution, Monte Carlo
radiative transfer tools can be used to examine numerous separation
distances between the two stellar components, with the goal of matching
the observed and modeled temperatures. An estimation of the distance to
e Aurigae can then be extracted. The proposed method is described here.

---------------------------------------------------------
Title: A high angular and spectral resolution view into the hidden
companion of ɛ Aurigae
Authors: Mourard, D.; Harmanec, P.; Stencel, R.; Bério, Ph.; Chesneau,
O.; Clausse, J. M.; Ligi, R.; Nardetto, N.; Perraut, K.; Stee, Ph.;
Tallon-Bosc, I.; McAlister, H.; ten Brummelaar, T.; Ridgway, S.;
Sturmann, J.; Sturmann, L.; Turner, N.; Farrington, C.; Goldfinger,
P. J.
2012A&A...544A..91M Altcode:
The enigmatic binary, ɛ Aur, is yielding its parameters as a result
of new methods applied to the recent eclipse, including optical
spectro-interferometry with the VEGA beam combiner at the CHARA
Array. VEGA/CHARA visibility measurements from 2009 to 2011 indicate the
formation of emission wings of Hα in an expanding zone almost twice
the photospheric size of the F star, namely, in a stellar wind. These
may be caused by shocks in the atmosphere from large scale convective or
multi-periodic pulsation modes emerging from the star. During the total
eclipse phase in 2010, when the disk was in the line of sight, we saw
broadening of the Hα absorption and a less steep drop of the visibility
curve, consistent with the addition of neutral hydrogen in the line of
sight but extended above and below the plane of the interferometrically
imaged disk itself. This provides a unique constraint on the scale
height of the gaseous component of the disk material, and, based on
some additional assumptions, points to a mass of the central object
being 2.4 to 5.5 M⊙ for a distance of 650 pc or 3.8 to
9.1 M⊙ for a distance of 1050 pc. These results can
be tested during coming observing seasons as the star moves from
eclipse phase toward quadrature. Based on observations with the
VEGA/CHARA spectrointerferometer.Appendix A is available in electronic
form at <A href="http://www.aanda.org">http://www.aanda.org</A>FITS
files of the calibrated visibilities are only available at the CDS
via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/544/A91">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/544/A91</A>

---------------------------------------------------------
Title: VizieR Online Data Catalog: {epsilon} Aur visibility
measurements (Mourard+, 2012)
Authors: Mourard, D.; Harmanec, P.; Stencel, R.; Berio, P.; Chesneau,
O.; Clausse, J. M.; Ligi, R.; Nardetto, N.; Perraut, K.; Stee, P.;
Tallon-Bosc, I.; McAlister, H.; Ten Brummelaar, T.; Ridgway, S.;
Sturmann, J.; Sturmann, L.; Turner, N.; Farrington, C.; Goldfinger,
P. J.
2012yCat..35440091M Altcode: 2012yCat..35449091M
VEGA/CHARA interferometric observations in differential mode are
provided in the attached files, according to the OIFITS format. (2 data files).

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Title: High Cadence Measurement of Neutral Sodium and Potassium
Absorption During the 2009-2011 Eclipse of epsilon Aurigae
Authors: Leadbeater, R.; Buil, C.; Garrel, T.; Gorodenski, S. A.;
Hansen, T.; Schanne, L.; Stencel, R. E.; Stober, B.
2012JAVSO..40..729L Altcode: 2012arXiv1206.6754L
The results of a spectroscopic survey of epsilon Aurigae during eclipse
using a network of small telescopes are presented. The spectra have
a resolution of 0.35 to 0.65Å and cover the period 2008 to 2012
with a typical interval of four days during eclipse. This paper
specifically covers variations in the KI 7699Å, Na D, and Mg II
4481Å lines. Absorption started increasing in the KI 7699Å line
three months before the eclipse began in optical photometry and had not
returned to pre-eclipse levels by the end of the survey in March 2012,
seven months after the broadband brightness had returned to normal
outside eclipse levels. The contribution of the eclipsing object to
the KI 7699Å line has been isolated and shows the excess absorption
increasing and decreasing in a series of steps during eclipse ingress
and egress. This is interpreted as an indication of structure within
the eclipsing object. The F star is totally obscured by the eclipsing
object at the Na D wavelength during eclipse. The radial velocity of
the F star and the mean and maximum radial velocity of the eclipsing
material in front of the F star at any given time have been isolated
and tracked throughout the eclipse. The quasi-periodic variations seen
in the F star radial velocity (RV) outside eclipse continued during
the eclipse. It is hoped that these results can be used to constrain
proposed models of the system and its components.

---------------------------------------------------------
Title: Lessons Learned During the Recent ɛ Aurigae Eclipse Observing
Campaign
Authors: Stencel, R. E.
2012JAVSO..40..239S Altcode:
(Abstract only) The eighteen-month-long eclipse of the third-magnitude
star, epsilon Aurigae, is forecast to end during May 2011,
based on six eclipse events, in 2010, 1982, 1955, 1930, 1902,
and 1874. In partnership with AAVSO, Hopkins Phoenix Observatory,
and others, we have organized observing campaigns during the past
several years in order to maximize data acquired during this rare
event and to promote reporting and analysis of observations of all
kinds. Hundreds of registered participants have signed up for alert
notices and newsletters, and many dozens of observers have contributed
photometry, spectra, and ideas to the ongoing effort - see websites:
www.CitizenSky.org and www.hposoft.com/Campaign09.html. In this
presentation, I will provide an update on the participation leading to
extensive photometric results. Similarly, bright star spectroscopy has
greatly benefited from small telescope plus spectrometer capabilities,
now widely available, that complement traditional but less-frequent
large telescope high dispersion work. Polarimetry provided key insights
during the last eclipse, and we promoted the need for new data using
this method. Finally, interferometry has come of age since the last
eclipse, leading to the direct detection of the transiting dark
disk causing the eclipse. Along with these traditional measurements,
I will outline campaign-related efforts to promote Citizen Science
opportunities among the public. Support for these efforts derives in
part from AAVSO/NSF-Informal Science Education, NSF AAG grant 10-16678,
and a bequest to the University of Denver Astronomy Program by alumnus
William Herschel Womble, for which I am grateful.

---------------------------------------------------------
Title: epsilon Aurigae - an Overview of the 2009-2011 Eclipse
Campaign Results
Authors: Stencel, R. E.
2012JAVSO..40..618S Altcode:
Evidence is provided from the array of observations amassed during the
2009-2011 eclipse, that defines the enigmatic binary epsilon Aurigae
as comprised of an unstable F0-1 Iab star in orbit around a comparable
mass upper main sequence star (or stars) enshrouded in a disk resulting
from F star mass loss. In this picture, the F star may be undergoing
rapid evolutionary changes, and the recent 67-day primary quasi-period
may make it suitable for asteroseismic studies. The hidden star(s)
may have gained mass from the F star, and the disk itself provides
opportunities for study of accretion, dust evolution, and dynamics.

---------------------------------------------------------
Title: Collaborative Research Efforts for Citizen Scientists
Authors: Kloppenborg, B. K.; Price, A.; Turner, R.; Henden, A. A.;
Stencel, R. E.
2012JAVSO..40..426K Altcode:
(Abstract only) The AAVSO's Citizen Sky project encourages participants
not just to collect and categorize data, but to critically analyze and
publish research findings. Our participants form teams of different
yet complementary skills that work together towards a common goal. Each
team has a leader and a professional astronomer assigned to act as an
advisor. In this work we explore the formation of teams, by what means
they find research topics, and how they manage their collaborations. We
acknowledge support from the NSF Informal Science Education Division
under grant DRL-0840188 to the AAVSO and the University of Denver.

---------------------------------------------------------
Title: The Invisible Monster Has Two Faces: Observations of epsilon
Aurigae with the Herschel Space Observatory
Authors: Hoard, D. W.; Ladjal, D.; Stencel, R. E.; Howell, S. B.
2012ApJ...748L..28H Altcode: 2012arXiv1202.6643H
We present Herschel Space Observatory photometric observations of
the unique, long-period eclipsing binary star epsilon Aurigae. Its
extended spectral energy distribution is consistent with our previously
published cool (550 K) dust disk model. We also present an archival
infrared spectral energy distribution of the side of the disk facing
the bright F-type star in the binary, which is consistent with a warmer
(1150 K) disk model. The lack of strong molecular emission features
in the Herschel bands suggests that the disk has a low gas-to-dust
ratio. The spectral energy distribution and Herschel images imply
that the 250 GHz radio detection reported by Altenhoff et al. is
likely contaminated by infrared-bright, extended background emission
associated with a nearby nebular region and should be considered an
upper limit to the true flux density of epsilon Aur.

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Title: UV-Blue (CCD) and Historic (Photographic) Spectra of epsilon
Aurigae - Summary
Authors: Griffin, R. E.; Stencel, R. E.
2012JAVSO..40..714G Altcode: 2012JAVSO.tmpE..02G
While there are numerous "new spectroscopic studies" of epsilon Aurigae
reported in this special edition of JAAVSO, the one summarized here
is believed to be unique on two counts: it concentrates on the blue
and near-UV spectral regions, and it incorporates historical spectra
from the previous eclipses of 1983 and 1956. The more data that can
be collated, across all wavelength and time base-lines, the more
conclusive the final model of this baffling object is likely to be. A
more lengthy paper that includes illustrations of the spectra is being
prepared for publication elsewhere. This short contribution summarizes
the effort that has so far gone into data acquisition and preparation,
and the principal results that are now emerging.

---------------------------------------------------------
Title: An End in Sight
Authors: Stencel, Robert
2012S&T...123c..18S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Infrared Studies of Epsilon Aurigae in Eclipse
Authors: Stencel, Robert E.; Kloppenborg, Brian K.; Wall, Randall E.,
Jr.; Hopkins, Jeffrey L.; Howell, Steve B.; Hoard, D. W.; Rayner,
John; Bus, Schelte; Tokunaga, Alan; Sitko, Michael L.; Bradford,
Suellen; Russell, Ray W.; Lynch, David K.; Hammel, Heidi; Whitney,
Barbara; Orton, Glenn; Yanamandra-Fisher, Padma; Hora, Joseph L.;
Hinz, Philip; Hoffmann, William; Skemer, Andrew
2011AJ....142..174S Altcode:
We report here on a series of medium resolution spectro-photometric
observations of the enigmatic long period eclipsing binary epsilon
Aurigae, during its eclipse interval of 2009-2011, using near-infrared
spectra obtained with SpeX on the Infrared Telescope Facility (IRTF),
mid-infrared spectra obtained with BASS on AOES and IRTF, MIRSI on
IRTF, and MIRAC4 on the MMT, along with mid-infrared photometry using
MIRSI on IRTF and MIRAC4 on the MMT, plus 1995-2000 timeframe published
photometry and data obtained with Denver's TNTCAM2 at WIRO. The goals
of these observations included: (1) comparing eclipse depths with prior
eclipse data, (2) confirming the re-appearance of CO absorption bands
at and after mid-eclipse, associated with sublimation in the disk, (3)
seeking evidence for any mid-infrared solid state spectral features
from particles in the disk, and (4) providing evidence that the
externally irradiated disk has azimuthal temperature differences. IR
eclipse depths appear similar to those observed during the most
recent (1983) eclipse, although evidence for post-mid-eclipse disk
temperature increase is present, due to F star heated portions of the
disk coming into view. Molecular CO absorption returned 57 days after
nominal mid-eclipse, but was not detected at mid-eclipse plus 34 days,
narrowing the association with differentially heated sub-regions in
the disk. Transient He I 10830A absorption was detected at mid-eclipse,
persisting for at least 90 days thereafter, providing a diagnostic for
the hot central region. The lack of solid-state features in Spitzer
Infrared Spectrograph, BASS, and MIRAC spectra to date suggests the
dominance of large particles (micron-sized) in the disk. Based on
these observations, mid-infrared studies out of eclipse can directly
monitor and map the disk thermal changes, and better constrain disk
opacity and thermal conductivity.

---------------------------------------------------------
Title: Spectral and photometric analysis of the eclipsing binary ɛ
Aurigae prior to and during the 2009-2011 eclipse
Authors: Chadima, P.; Harmanec, P.; Bennett, P. D.; Kloppenborg, B.;
Stencel, R.; Yang, S.; Božić, H.; Šlechta, M.; Kotková, L.; Wolf,
M.; Škoda, P.; Votruba, V.; Hopkins, J. L.; Buil, C.; Sudar, D.
2011A&A...530A.146C Altcode: 2011arXiv1105.0107C
A series of 353 red electronic spectra (from three observatories,
mostly from 6300 to 6700 )A obtained between 1994 and 2010, and of
171 UBV photometric observations (from two observatories) of the
2010 eclipse, were analyzed in an effort to better understand ɛ
Aur, the well-known, but still enigmatic eclipsing binary with the
longest known orbital period (~27 yrs). The main results follow. (1)
We attempted to recover a spectrum of the companion by disentangling
the observed spectra of the ɛ Aur binary failed, but we were able to
disentangle the spectrum of telluric lines and obtain a mean spectrum
of the F-type primary star. The latter was then compared to a grid of
synthetic spectra for a number of plausible values of Teff
and log g, but a reasonably good match was not found. However, we
conclude that the observed spectrum is that of a low gravity star. (2)
We examined changes in the complex Hα line profiles over the past 16
years, with particular emphasis on the 2009-2011 eclipse period, by
subtracting a mean out-of-eclipse Hα profile (appropriately shifted
in radial velocity) from the observed spectra. We find that the
dark disk around the unseen companion has an extended "atmosphere"
that manifests itself via blueshifted and redshifted Hα "shell"
absorptions seen projected against the F star. Significantly, the
Hα shell line first appeared three years before first contact
of the optical eclipse when the system was not far past maximum
separation. (3) Analyses of radial velocities and central intensities of
several strong, unblended spectral lines, as well as UBV photometry,
demonstrated that these observables showed apparent multiperiodic
variability during eclipse. The dominant period of 66.21d was common
to all the observables, but with different phase shifts between these
variables. This result strongly supports our earlier suggestion that the
photometric variability seen during eclipse is intrinsic to the F star,
and therefore, the idea of a central brightening due to a hole in the
disk should be abandoned. Although variability on similar timescales
is also seen in the spectrum and in photometry out of eclipse, we were
unable to find a coherent periodicity in these data. Nevertheless,
theseresults appear to rule out regular stellar pulsations as the cause
of this variability. Based on spectra obtained at the Dominion
Astrophysical Observatory, Ondřejov Observatory and Castanet-Tolosan
Observatory and on UBV photometry gathered at the Hvar Observatory and
Hopkins Phoenix Observatory.Tables 1 and 2 are only available at the
CDS via anonymous ftp to cdarc.u-strasbg.fr (130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/530/A146">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/530/A146</A>

---------------------------------------------------------
Title: Discovery Of Strong Helium 10830A Absorption In The Mid-eclipse
Disk Of Epsilon Aurigae
Authors: Stencel, Robert E.; Kloppenborg, B.; Sitko, M.; Rayner, J.;
Tokunaga, A.
2011AAS...21822504S Altcode: 2011BAAS..43G22504S
During the 2010 eclipse of the enigmatic binary, epsilon Aurigae (F0p
+ B5?), we obtained a series of near-infrared spectra with the SpeX
instrument at NASA's IRTF, primarily to detect the re-appearance of
CO (2-0) at 2.29 microns after nominal mid-eclipse, 2010 August 4 (JD
2,455,400). To our surprise, the well-known He I 10830A line appeared
in absorption, in the spectrum closest to mid-eclipse (Aug.24, RJD
55433), persisting in spectra Sep.27 (55467), Oct.24 and 29 (55494,
55499). The line weakened by Nov.12 (55513), and was gone Dec.7 (55537)
and 2011 Jan.7 (55569). The extra absorption, up to 6A equivalent width,
appeared atop a weaker, persistent 1A equivalent width feature. With
Van de Kamp's distance (580 pc) and orbital velocities during eclipse
phase, the duration of the extra absorption implies a region 1.0
+/- 0.2 AU in radial extent, in the middle of the eclipse-causing
dark disk with its 3.8 +/- 0.2 AU radius. He I 10830 arises from a
metastable triplet from a lower level at 19.82 volts, representing
plasma in excess of 25,000K. If the disk-center star were B5V type
and experiencing a modest amount of accretion, it would create a 1
AU Stromgren He+ sphere. This assumes a mean gas density of 10^{10}
cm^{-3}, which is the lower limit to the column density established
by non-detection of soft Xrays. This heated region could represent the
presence of an upper main sequence object and accretion onto the hidden
star inside the disk, in analogy to Be stars, symbiotics, zeta Aurs
and YSOs. This work was supported in part by the bequest of William
Herschel Womble in support of astronomy at the University of Denver,
by NSF grant 1016678 and JPL RSA 1414715 to the University of Denver,
and by NASA ADP grant NNX09AC73G to the University of Cincinnati.

---------------------------------------------------------
Title: Polarimetry of Epsilon Aurigae from Mid Eclipse to Third
Contact
Authors: Cole, Gary M.; Stencel, Robert E.
2011SASS...30..103C Altcode:
In a previous paper, the author discussed the construction of an
automated dual beam imaging polarimeter and of observations made in the
November 2009 to February 2010 period. Here, we discuss observations and
instrumental improvements that span the period from late August 2010
through third and into fourth contacts in Spring 2011. Approximately
930 linear polarization measurements of the target star in BVR bands
were obtained during 99 nights of observation. Additional measurements
were made of both known polarization standards and zero polarization
stars to verify instrument calibration. The polarization of Epsilon
Aurigae was observed to vary by nearly 0.4% peak to valley during
this period. These variations occurred in several major cycles of
varying duration. Measurement error is estimated to be on the order
of +/-0.05%. The observed variations resemble excess polarization
seen during the 1984 eclipse egress, but may show some differences
in detail. During this project, a new optical rotator was developed
in conjunction with Optec, Inc., and used for the last two months of
observations. This project was initiated at the suggestion of Dr. Robert
Stencel at the May 2009 SAS meeting to extend measurements done during
the 1984 eclipse by Dr. Jack Kemp and followed up by his student,
Dr. Gary Henson thereafter.

---------------------------------------------------------
Title: Collaborative Research Efforts For Citizen Scientists
Authors: Kloppenborg, Brian K.; Price, A.; Turner, R.; Henden, A.;
Stencel, R.
2011AAS...21812612K Altcode: 2011BAAS..43G12612K
The AAVSO's Citizen Sky project encourages participants not just to
collect and categorize data, but instead to critically analyze and
publish research findings. Our participants form teams of different,
yet complementary skills that work together towards a common goal. Each
team has a leader and a professional astronomer assigned to act as an
advisor. In this work we explore the formation of teams, by what means
they find research topics, and how they manage their collaborations. We acknowledge support from the NSF Informal Science Education
Division under grant DRL-0840188, to the AAVSO and the University
of Denver.

---------------------------------------------------------
Title: Accretion in the Disk of epsilon Aurigae: Results of Monte
Carlo Radiative Transfer Modelling
Authors: Pequette, Naomi; Stencel, R.; Whitney, B.
2011AAS...21822505P Altcode: 2011BAAS..43G22505P
Epsilon Aurigae is a mysterious eclipsing binary system that has been
observed for more than 175 years. Current theory remains undecided
whether the system is made up of a massive F-supergiant star and an
equally massive, but hidden, companion, or a post-AGB F-star and a
binary companion made up of a B5V which is surrounded by a transitional
or debris disk. We used a Monte Carlo Radiative Transfer Model (MCRTM,
written by Barbra Whitney of the Space Sciences Institute) to model
the B-star and surrounding disk. By using this model, our goal was
to reproduce the observed Spectral Energy Distribution (SED, Hoard,
Howell and Stencel, HHS, 2010) of the B-star and disk components
of the epsilon Aurigae System. Our initial parameters utilized the
results of HHS. The initial run of MCRTM did not result in matching
the observed SED. Subsequently, we explored previously unknown disk
parameters, most importantly disk mass and accretion rate. We found
that to reproduce the observed 10:1 ratio of IR to Far-UV flux,
we must have a non-zero rate of accretion occuring in the disk. To
avoid depleting the disk too quickly, our simulations find that a more
massive disk becomes too opaque due to increased scattering and does
not reproduce the observed SED. Thus, we propose the extra mass might
be in the form of planetesimals. The high accretion rate also implies
dust mass replinishment, possibly due to a high rate of collisional
interaction among planetesimals embedded in the disk. This work was
supported in part by the bequest of William Herschel Womble in support
of astronomy at the University of Denver, by NSF grant 1016678 and
JPL RSA 1414715 to the University of Denver.

---------------------------------------------------------
Title: Towards A Full Orbital Solution For Epsilon Aurigae
Authors: Kloppenborg, Brian K.; Hemenway, P.; Jensen, E.; Osborn,
W.; Stencel, R.
2011AAS...21823005K Altcode: 2011BAAS..43G23005K
Epsilon Aurigae is an eclipsing binary with a 27-year period that
has baffled investigators for almost two centuries. The data from
present and prior eclipses have strengthened our understanding of
the system, but a comprehensive understanding of it's evolutionary
state has remained illusive. There are presently two competing views:
(1)the F-star primary is a supergiant of 15 Mo with a companion that is
equally massive, yet obviously much smaller, that has yet to evolve off
the MS or (2)the F-star is a post-AGB object of 4 Mo with a MS companion
of 6-7 Mo that is enshrouded in an accretion disk of debris from the
F-star. Deciding between the two models depends on having an
accurate distance to the system. Published parallaxes all agree within
their formal uncertainties, but have error bars larger than the nominal
value. We have found that all astrometric results either neglected
orbital motion or relied on orbital elements that are not congruent
with spectroscopy (Stefanik et al. 2010) and with the recent in-eclipse
interferometric observations (Kloppenborg et al. 2010). For example,
all astrometric orbital solutions (van de Kamp 1978, Strand 1959,
Heintz and Cantor 1994) assumed an eccentricity that does not agree
with present value, e = 0.22-0.26 (Stefanik et al. 2010, Chadima et
al. 2010), rather than solving for it. Likewise the HIPPARCOS parallax
used Heintz's orbit that we argue is incorrect. We are deriving new
orbital solutions for both components in the system. The solution for
the F-star will use radial velocity and astrometric observations. The
solution for the eclipsing object comes from the relative motion of the
components implied by interferometric imaging. The University of
Denver participants are grateful for support under NSF grant 10-16678
and the bequest of William Hershel Womble in support of astronomy at
the University of Denver.

---------------------------------------------------------
Title: Epsilon Aurigae at the End of Eclipse
Authors: Hoard, Donald; Stencel, R.; Howell, S.
2011sptz.prop80017H Altcode:
We request a small investment of 24 minutes of Spitzer time, to obtain
four IRAC observations of epsilon Aurigae. A naked eye object located
near Capella, epsilon Aurigae is the eclipsing binary star with the
longest known orbital period, showing a single long duration (~2 yr)
eclipse every 27.1 yr. For much of the last 150 years, the nature of
the eclipsing object defied explanation. We recently demonstrated that
epsilon Aurigae consists of a high luminosity F0 post-AGB star in orbit
with a B5 V star surrounded by a solar system sized (~8 AU diameter)
disk of cool, dust-dominated material. The eclipse of epsilon Aurigae
is a rare event; moreover, it is a unique astrophysical opportunity,
since the backlighting of the disk by the high luminosity eclipsed
star reveals details that cannot be detected in similar dusty disks
around single stars. The current eclipse started in August 2009 and
is expected to reach its photometric conclusion in May 2011 (with the
spectroscopic conclusion as late as December 2011). The goals for
these observations include: (1) extend our ongoing IRAC monitoring
campaign covering the current eclipse to late-phase and post-eclipse
visits; (2) provide a consistent, well-calibrated space-based set
of IR photometry for comparison with ongoing ground-based work; and
(3) use the composite results to constrain the thermal profile of the
disk. A key expectation of these particular observations is to reveal
the irradiation-heated portion of the disk, which will be visible on its
trailing side following eclipse. Observations of this side of the disk
will be crucial to test and constrain new models of disk structure. As
part of our overall monitoring campaign with Spitzer, Hubble, Herschel,
and numerous ground-based facilities, these proposed observations will
make an important contribution to the understanding of stellar evolution
in binary stars, including mass transfer and evolution studies, along
with new insights into astrophysical disks and post-AGB star evolution.

---------------------------------------------------------
Title: Lessons Learned During the Recent Epsilon Aurigae Eclipse
Observing Campaign
Authors: Stencel, Robert E.
2011AAS...21810305S Altcode: 2011BAAS..43G10305S
The 18 month long eclipse of the 3rd magnitude star, epsilon Aurigae, is
forecast to end during May 2011, based on six eclipse events, in 2010,
1982, 1955, 1930, 1902 and 1874. In partnership with AAVSO, Hopkins
Phoenix Observatory and others, we have organized observing campaigns
during the past several years in order to maximize data acquired during
this rare event and to promote reporting and analysis of observations of
all kinds. Hundreds of registered participants have signed up for alert
notices and newsletters, and many dozens of observers have contributed
photometry, spectra and ideas to the ongoing effort - see websites:
www.CitizenSky.org and www.hposoft.com/Campaign09.html . In this
presentation, I will provide an update on the participation leading to
extensive photometric results. Similarly, bright star spectroscopy has
greatly benefited from small telescope plus spectrometer capabilities,
now widely available, that complement traditional but less-frequent
large telescope high dispersion work. Polarimetry provided key insights
during the last eclipse, and we promoted the need for new data using
this method. Finally, interferometry has come of age since the last
eclipse, leading to the direct detection of the transiting dark
disk causing the eclipse. Along with these traditional measurements,
I will outline campaign-related efforts to promote Citizen Science
opportunities among the public. Support for these efforts derives in
part from AAVSO/NSF-Informal Science Education, NSF AAG grant 10-16678
and a bequest to the University of Denver Astronomy Program by alumnus
William Herschel Womble, for which I am grateful.

---------------------------------------------------------
Title: VizieR Online Data Catalog: Spectral and UBV analysis of
{epsilon} Aur (Chadima+ 2011)
Authors: Chadima, P.; Harmanec, P.; Bennett, P. D.; Kloppenborg, B.;
Stencel, R.; Yang, S.; Bozic, H.; Slechta, M.; Kotkova, L.; Wolf,
M.; Skoda, P.; Votruba, V.; Hopkins, J. L.; Buil, C.; Sudar, D.
2011yCat..35300146C Altcode: 2011yCat..35309146C
The file table1a.dat contains measurements of a central intensity (CI),
an equivalent width (EW) and a radial velocity (RV) of various lines
(H-alpha, Si6347, Si6371, Fe6417 and Fe6433) made on spectra secured
at the Ondrejov Observatory (OND). The file table1b.dat contains the
same measurements but for spectra secured at the Dominion Astronomical
Observatory (DAO) and the file table1c.dat for spectra secured at the
Castanet-Tolosan Observatory (CTO). For CTO spectra, the H-alpha line
was not measured. Note that the H-alpha line during an eclipse has
two absorption cores and both were measured. But a word of caution is
needed here - these measurements are done on original spectra, not
on spectra after the correction presented in Sect. 4 of the related
paper. The radial velocity of the Halpha emission was measured
by matching V and R peak maxima of a normal and an inversed line
profile. Note that table1a.dat tabel1b.dat and table1c.dat contain
"blanks" for measurements which were not done. Its was due to a
high asymetry of a particular line or its high degree of blending
with strong teluric lines (or disappearing of an Halpha peak) which
disables a reasonable measurement of given line characteristics. The
file table2b.dat contains U,B,V photometry of eps Aur secured at the
Hvar Observatory. The file table2a.dat contains U,B,V photometry of HR
1644 (a check star for eps Aur photometry presented in table2a.dat)
secured at the Hvar Observatory. Entire information about all data
sets can be found in the related paper in Sect. 2. (5 data files).

---------------------------------------------------------
Title: Infrared Studies of Epsilon Aurigae in Eclipse 2010
Authors: Stencel, Robert E.; Kloppenborg, B.; Wall, R.; Howell, S.;
Hoard, D.; Rayner, J.; Bus, S.; Tokunaga, A.; Sitko, M.; Russell,
R.; Lynch, D.; Brafford, S.; Hammel, H.; Whitney, B.; Orton, G.;
Yanamandra-Fisher, P.; Hora, J.; Hoffman, W.; Skemer, A.
2011AAS...21725709S Altcode: 2011BAAS...4325709S
We report a series of observations of the enigmatic long period
eclipsing binary epsilon Aurigae during its eclipse interval 2009-2011,
using near-infrared spectra &amp; photometry obtained with SpeX/IRTF,
Spitzer/IRAC, mid-infrared data with BASS on IRTF &amp; AEOS, MIRSI
on IRTF and MIRAC4 on MMT, along with MIRSI on IRTF and MIRAC4 on MMT
&amp; Denver's TNTCAM2 at WIRO, and an Optec SSP-4 J&amp;H photometer at
Mt.Evans Observatory. The objective of these observations include: (1)
confirm the appearance of CO absorption bands at and after mid-eclipse,
due to the dark disk, and (2) seek evidence for any mid-infrared
solid state spectral features from particles in the disk, seen during
different portions of total eclipse. The results to date show that the
infrared eclipse is less deep than the optical one, and the implied
disk temperature has begun to increase from 550K toward 1100K as
eclipse progresses past midpoint and heated portions of the disk come
into view. Material properties of the disk are consistent with large
particles. This work was supported in part by the bequest of William
Herschel Womble in support of astronomy at the University of Denver,
by NSF grant 1016678 and JPL RSA 1414715 to the University of Denver,
by NASA ADP grant NNX09AC73G to the University of Cincinnati, by The
Aerospace Corporation's Independent Research and Development Program.

---------------------------------------------------------
Title: Ring-like Structures Around Epsilon Aurigae Companion
Authors: Seebode, Sally; Howell, S. B.; Drumheller, D.; Stanford,
D.; Hoard, D. W.; Stencel, R. E.
2011AAS...21725708S Altcode: 2011BAAS...4325708S
Epsilon Aurigae, a 27.1 year eclipsing binary, consists of a post-AGB
F giant and a main sequence B star. The B star is surrounded by a
large dust disk. Our team obtained and analyzed over 60 red(5800 -
6600A) and blue (3800 - 4600A) spectra using the College of San Mateo
(CSM) Meade 8” telescope, with SBIG SGS spectrograph, and the Kitt
Peak National Observatory Coude feed spectrograph. Measurements of the
equivalent widths of a number of elements indicate density variations in
the dust disk surrounding the companion B star of epsilon Aurigae. This
disk substructure is similar to that suggested by Leadbeater and
Stencel (2010, http://arxiv.org/abs/1003.3617v2) and agrees with the
theoretical rings proposed by S. Ferluga (1990, A&amp;A, 238,270)
based on observations of the 1982 eclipse. Our data was collected and
analyzed from February 2009 (pre-eclipse) through April 2010. We are
continuing to obtain spectroscopic observations through eclipse and
egress in order to provide further data and evidence for the possible
ring structure in the dusty disk. This study is part of the NASA/IPAC
Teacher Archive Research Project (NITARP).

---------------------------------------------------------
Title: Interferometric Images Of The Transiting Disk In The Epsilon
Aurigae System
Authors: Kloppenborg, Brian K.; Stencel, R.; Monnier, J. D.; Schaefer,
G.; Zhao, M.; Baron, F.; McAlister, H.; ten Brummelaar, T.; Che, X.;
Farrington, C.; Pedretti, E.; Sallave-Goldfinger, P.; Sturmann, J.;
Sturmann, L.; Thureau, N.; Turner, N.; Carroll, S.
2011AAS...21725703K Altcode: 2011BAAS...4325703K
We have been using the CHARA Array with the MIRC beam combiner to obtain
the first-ever interferometric observations of the enigmatic binary,
epsilon Aurigae. The first two in-eclipse images, obtained in 2009,
prove that the eclipsing body is a thin, opaque disk of material akin
to transitional or debris disks. From these data we have derived a mass
ratio that shows the F-type star is 3.6 ± 0.7 M⊙, making it the less
massive component in the system and thus not a high-mass supergiant as
was classically believed. Four additional observations were scheduled in
2010. In this work we present reconstructed images from all epochs using
two new image reconstruction algorithms, SQUEEZE and GPAIR. We discuss
the progress towards our goals: to determine the evolutionary status
of the components in the binary; and define the composition, density,
and temperature structure of the disk. The CHARA Array, operated
by Georgia State University, was built with funding provided by the
National Science Foundation, Georgia State University, the W. M. Keck
Foundation, and the David and Lucile Packard Foundation. This research
is supported by the National Science Foundation as well as by funding
from the office of the Dean of the College of Arts and Science at
Georgia State University. MIRC was supported by the National Science
Foundation. The University of Denver participants are grateful for
support under NSF grant 10-16678 and the bequest of William Hershel
Womble in support of astronomy at the University of Denver.

---------------------------------------------------------
Title: Development of DSLR Photometry as an Example of a Citizen
Sky Team
Authors: Kloppenborg, Brian K.; Stencel, R. E.; Price, A.; Turner,
R.; Henden, A.
2011AAS...21715812K Altcode: 2011BAAS...4315812K
One of the primary goals of the Citizen Sky project is to foster
the development of Teams of every-day people with an interest in
astronomy. These groups are composed of people with different, yet
complementary skill sets who work together towards a common goal. Each
team has a team leader and a professional astronomer assigned to act as
an advisor. Here we highlight the work of one particular team who has
produced documentation and software to teach first-time observers how
to use consumer-grade digital cameras to produce accurate photometric
magnitudes. We present a short history, the completed products, and
lessons learned from this team. We acknowledge support from the
NSF Informal Science Education Division, to the AAVSO and the University
of Denver.

---------------------------------------------------------
Title: Analysis of Epsilon Aurigae light curve from the Solar Mass
Ejection Imager
Authors: Clover, John; Jackson, B. V.; Buffington, A.; Hick, P. P.;
Kloppenborg, B.; Stencel, R.
2011AAS...21725702C Altcode: 2011BAAS...4325702C
The Solar Mass Ejection Imager (SMEI) was launched aboard the Coriolis
spacecraft in 2003. It is equipped with 3 CCD cameras to measure the
brightness of Thomson-scattered electrons in the heliosphere. Each
CCD images a strip of the sky that is 3°x60°. The three cameras are
mounted on the satellite with their fields of view aligned end-to-end
so that SMEI sweeps nearly the entire sky each 102 minute orbit. SMEI
has now accumulated stellar time series for about 5700 bright stars,
including epsilon Aurigae, for each orbit where data is available. SMEI
data provide nearly year-round coverage of epsilon Aurigae. The baffled
SMEI optics provide more accurate photometric data than ground-based
observations, particularly at mid-eclipse when epsilon Aurigae is close
to the Sun. We present an analysis of the brightness variations of
the epsilon Aurigae system, before and during the eclipse. The
University of Denver participants are grateful for support under
NSFgrant 10-16678 and the bequest of William Hershel Womble in support
of astronomy at the University of Denver.

---------------------------------------------------------
Title: Spectroscopic Wonders During The 2010 Eclipse Of Epsilon
Aurigae
Authors: Leadbeater, Robin; Buil, C.; Garrell, T.; Gorodenski, S.;
Hopkins, J.; Mauclaire, B.; Ribeiro, J.; Schanne, L.; Thizy, O.;
Stencel, R.
2011AAS...21725704L Altcode: 2011BAAS...4325704L
Remarkable spectroscopic coverage is reported of the 2009-2011 eclipse
of the enigmatic binary, epsilon Aurigae. Due to the availability of
new spectrographs and digital detectors, unprecedented monitoring by a
network of observers using small telescopes has revealed a number of
details and surprises that must be taken into account in any updated
model for the over-luminous F star and the dark disk companion,
recently detected interferometrically. Over 400 spectra were obtained
during 2007 to 2010 (pre eclipse to post mid eclipse). They include
R 12000 echelle spectra giving broad coverage from 4300-7000A and
detailed spectra at R 17000-25000 covering the Sodium D, Hydrogen
alpha and Potassium 7699A line regions. Evidence of the eclipsing body
was first seen in the 7699A line profile 83 days before photometric
first contact. During ingress, the strength of this line increased in
a stepwise fashion suggesting structure in the disc. During the first
half of totality, the line strength trend deviated from that seen during
the last eclipse. Radial velocity measurements of the 7699A line during
ingress are consistent with the disc material orbiting a central object
of 5.3 solar masses. Changes in the Hydrogen alpha line profile during
totality reveal the presence of a foreground emission source centered
at the systemic radial velocity. A small transient emission line has
been seen at 6604A on two occasions during the eclipse. This work was
supported in part by the bequest of William Herschel Womble in support
of astronomy at the University of Denver, and by NSF grant 1016678 to
the University of Denver. We are grateful for the assistance of the
epsilon Aurigae spectral monitoring team at Apache Point Observatory
(W. Ketzeback, J.Barentine, et al.) and all observers participating
in the international eclipse monitoring campaign.

---------------------------------------------------------
Title: Campaign Photometry During The 2010 Eclipse Of Epsilon Aurigae
Authors: Hopkins, Jeff; Stencel, R. E.
2011AAS...21725701H Altcode: 2011BAAS...4325701H
Epsilon Aurigae is a long period (27.1 years) eclipsing binary star
system with an eclipse that lasts nearly 2 years, but with severe
ambiguities about component masses and shape. The current eclipse began
on schedule in August of 2009. During the previous, 1982-1984 eclipse,
an International Campaign was formed to coordinate a detailed study of
the system. While that Campaign was deemed successful, the evolutionary
status of the star system remained unclear. Epsilon Aurigae has
been observed nearly continuously since the 1982 eclipse. The current
Campaign was officially started in 2006. In addition to a Yahoo forum we
have a dedicated web site and more than 18 online newsletters reporting
photometry, spectroscopy, interferometry and polarimetry data. High
quality UBVRIJH band photometric data since before the start of the
current eclipse has been submitted. We explore the color differences
among the light curves in terms of eclipse phases and archival data. At
least one new model of the star system has been proposed since the
current Campaign began: a low mass but very high luminosity F star
plus a B star surrounded by a debris disk. The current eclipse and in
particular the interferometry and spectroscopic data have caused new
thoughts on defining eclipsing variable star contact points and phases
of an eclipse. Second contact may not be the same point as start of
totality and third contact may not be the same point as the start of
egress and end of totality. In addition, the much awaited mid-eclipse
brightening may or may not have appeared. This paper identifies the
current Campaign contributors and the photometric data. This work was
supported in part by the bequest of William Herschel Womble in support
of astronomy at the University of Denver, by NSF grant 1016678 to the
University of Denver.

---------------------------------------------------------
Title: Citizen Sky, An Update on the AAVSO's New Citizen Science
Project
Authors: Turner, Rebecca; Price, A.; Henden, A.; Stencel, R.;
Kloppenborg, B.
2011AAS...21715811T Altcode: 2011BAAS...4315811T
Citizen Sky is a multi-year, NSF-funded, citizen science project
focusing on the bright variable star, epsilon Aurigae. Citizen
Sky goes beyond simple observing to include a major data analysis
component. The goal is to introduce the participant to the full
scientific process from background research to paper writing for a
peer-reviewed journal. The first year of the project, 2009-10, was
dedicated to developing project infrastructure, educating participants
about epsilon Aurigae, and training these participants to observe the
star and report their data. Looking forward, years two and three of
the project will focus on assembling teams of participants to work
on their own analysis and research. Results will be published in a
special issue of the peer-reviewed Journal of the AAVSO. This project
has been made possible by the National Science Foundation.

---------------------------------------------------------
Title: Interferometric Imaging of Epsilon Aurigae
Authors: Stencel, Robert E.
2011AAS...21722405S Altcode: 2011BAAS...4322405S
One of the remarkable advances since the 1983 eclipse of epsilon
Aurigae is the maturation of interferometric imaging. I will report
on a series of images obtained at the CHARA aary at Mt. Wilson since
2008 that show the encroachment of the dark disk, substructure in the
disk and recent post-mid-eclipse phenomena.

---------------------------------------------------------
Title: Hubble Space Telescope Ultraviolet Observations of Epsilon
Aurigae
Authors: Howell, Steve B.; Stencel, R. E.; Hoard, D. W.
2011AAS...21725707H Altcode: 2011BAAS...4325707H
We present the initial observations from our multi-epoch COS
program, with three planned observations of Epsilon Aurigae. The
first observation was obtained on 2010 Sept 1st, shortly after
mid-eclipse. The remaining two are scheduled for mid-December 2010,
during totality, and during egress in mid-April 2011. Epsilon Aurigae
is a complex binary system consisting of a post-AGB F giant orbited
by a B star encircled by a large dust cloud. The B star dominates
the spectral energy distribution only in the far-UV portion of the
spectrum. We use our 900-2050A COS results to 1) model the B star
yielding its Teff and log g, 2) search for warm circumbinary material,
and 3) confirm the nature of the B star as input to our recent work
providing the most detailed SED model yet developed for Epsilon Aurigae
(http://adsabs.harvard.edu/abs/2010ApJ...714..549H).

---------------------------------------------------------
Title: XMM-Newton Observations of the Enigmatic Long Period Eclipsing
Binary Epsilon Aurigæ: Constraining the Physical Models
Authors: Wolk, Scott J.; Pillitteri, Ignazio; Guinan, Edward;
Stencel, Robert
2010AJ....140..595W Altcode:
We report on an XMM-Newton observation of the unusual, long period
(F0 supergiant + cool disk companion) eclipsing binary star epsilon
Aurigæ observed in X-rays prior to the onset of the 2009-2011
eclipse phase. While it appears certain that a disk-like body is
obscuring the star, it remains unclear what kind of object is at the
center of the disk. The XMM-Newton observation had a duration of ~25
ks. The X-ray image does not show a source at the optical position
of the star. We have determined a limiting X-ray flux of about 2.5
× 10-15 erg cm-2 s-1. This flux
is equivalent to a luminosity of about log LX ~ 29.3-29.7
erg s-1 for an unabsorbed source at the assumed distance,
estimated to be between 650 and 1300 pc. The direct emission from an
otherwise unobscured primary is excluded at a level above LX
~ 4 × 1029 erg s-1. We explore the physical
constraints that these limits put on the primary and several proposed
models for the system secondary. For a black hole, we find that the
direct absorption required by the disk is approximately N H
&gt;= 1025 cm-2. While not unreasonable for
a protoplanetary disk, the lack of secondary X-rays makes this
model unlikely. For high-mass models, in which the disk harbors
pre-main-sequence stars, we find a minimum disk absorption of N
H &gt;= 1023 cm-2. Since this is
not unlikely for a protoplanetary disk, this is not a significant
constraint. For low-mass models, in which the disk harbors older stars,
the known line-of-sight absorption is nearly enough to account for
the non-detection. The data do not discriminate between these models.

---------------------------------------------------------
Title: Taming the Invisible Monster: Infrared Monitoring of Epsilon
Aurigae During Eclipse
Authors: Stencel, Robert; Hoard, Donald; Hoard, Donald W.; Howell,
Steve
2010sptz.prop70006S Altcode:
We propose to continue a sequence of warm IRAC photometric measurements
of the unusual binary star, Epsilon Aurigae, during the rest of its
ongoing total eclipse throughout Cycle 7, in order to better constrain
the degree of heating of the now interferometrically-imaged disk. As
heated portions of the disk rotate into view, IRAC channels one and
two provide a sensitive diagnostic of the infrared excess, which is
expected to change as our view of the 550 K cold side of the disk is
replaced by the portion heated to &gt;1,000 K by the nearby F0 star,
now rotating into view.

---------------------------------------------------------
Title: The interface between the stellar wind and interstellar medium
around R Cassiopeiae revealed by far-infrared imaging
Authors: Ueta, T.; Stencel, R. E.; Yamamura, I.; Geise, K. M.; Karska,
A.; Izumiura, H.; Nakada, Y.; Matsuura, M.; Ita, Y.; Tanabé, T.;
Fukushi, H.; Matsunaga, N.; Mito, H.; Speck, A. K.
2010A&A...514A..16U Altcode: 2009arXiv0911.4918U
 Aims: The circumstellar dust shells of intermediate initial-mass
(~1 to 8 M⊙) evolved stars are generated by copious mass
loss during the asymptotic giant branch phase. The density structure of
their circumstellar shell is the direct evidence of mass loss processes,
from which we can investigate the nature of mass loss. Methods:
We used the AKARI infrared astronomy satellite and the Spitzer space
telescope to obtain the surface brightness maps of an evolved star
R Cas at far-infrared wavelengths, since the temperature of dust
decreases as the distance from the star increases and one needs to
probe dust at lower temperatures, i.e., at longer wavelengths. The
observed shell structure and the star's known proper motion suggest
that the structure represents the interface regions between the dusty
wind and the interstellar medium. The deconvolved structures are fitted
with the analytic bow shock structure to determine the inclination
angle of the bow shock cone. Results: Our data show that
(1) the bow shock cone of 1 - 5 × 10-5 M⊙
dust mass is inclined at 68° with respect to the plane of the sky;
and (2) the dust temperature in the bow shock cone is raised to more
than 20 K by collisional shock interaction in addition to the ambient
interstellar radiation field. By comparison between the apex vector of
the bow shock and space motion vector of the star we infer that there
is a flow of interstellar medium local to R Cas whose flow velocity
is at least 55.6 km s-1, consistent with an environment
conducive to dust heating by shock interactions. Based in part
on observations with AKARI, a JAXA project with the participation of
ESA, and with the Spitzer Space Telescope, which is operated by the
Jet Propulsion Laboratory, California Institute of Technology under
a contract with NASA.

---------------------------------------------------------
Title: Taming the Invisible Monster: System Parameter Constraints
for epsilon Aurigae from the Far-ultraviolet to the Mid-infrared
Authors: Hoard, D. W.; Howell, S. B.; Stencel, R. E.
2010ApJ...714..549H Altcode: 2010arXiv1003.3694H
We have assembled new Spitzer Space Telescope IRAC observations
of the mysterious binary star epsilon Aurigae, along with archival
far-ultraviolet to mid-infrared data, to form an unprecedented spectral
energy distribution (SED) spanning 3 orders of magnitude in wavelength
from 0.1 μm to 100 μm. The observed SED can be reproduced using a
three-component model consisting of a 2.2+0.9 -0.8
M sun F-type post-asymptotic giant branch star, and a 5.9 ±
0.8 M sun B5±1 type main-sequence star that is surrounded
by a geometrically thick, but partially transparent, disk of gas and
dust. At the nominal HIPPARCOS parallax distance of 625 pc, the model
normalization yields a radius of 135 ± 5 R sun for the
F star, consistent with published interferometric observations. The
dusty disk is constrained to be viewed at an inclination of i &gt;~
87°, and has an effective temperature of 550 ± 50 K with an outer
radius of 3.8 AU and a thickness of 0.95 AU. The dust content of the
disk must be largely confined to grains larger than ~10 μm in order
to produce the observed gray optical-infrared eclipses and the lack
of broad dust emission features in the archival Spitzer mid-infrared
spectra. The total mass of the disk, even considering a potential
gaseous contribution in addition to the dust that produces the observed
infrared excess, is Lt1 M sun. We discuss evolutionary
scenarios for this system that could lead to the current status of the
stellar components and suggest possibilities for its future evolution,
as well as potential observational tests of our model.

---------------------------------------------------------
Title: Infrared images of the transiting disk in the ɛ Aurigae system
Authors: Kloppenborg, Brian; Stencel, Robert; Monnier, John D.;
Schaefer, Gail; Zhao, Ming; Baron, Fabien; McAlister, Hal; ten
Brummelaar, Theo; Che, Xiao; Farrington, Chris; Pedretti, Ettore;
Sallave-Goldfinger, P. J.; Sturmann, Judit; Sturmann, Laszlo; Thureau,
Nathalie; Turner, Nils; Carroll, Sean M.
2010Natur.464..870K Altcode: 2010arXiv1004.2464K
Epsilon Aurigae (ɛ Aur) is a visually bright, eclipsing binary star
system with a period of 27.1years. The cause of each 18-month-long
eclipse has been a subject of controversy for nearly 190years
because the companion has hitherto been undetectable. The orbital
elements imply that the opaque object has roughly the same mass as
the visible component, which for much of the last century was thought
to be an F-type supergiant star with a mass of ~15Msolar
(Msolar, mass of the Sun). The high mass-to-luminosity ratio
of the hidden object was originally explained by supposing it to be a
hyperextended infrared star or, later, a black hole with an accretion
disk, although the preferred interpretation was as a disk of opaque
material at a temperature of ~500K, tilted to the line of sight and
with a central opening. Recent work implies that the system consists
of a low-mass (2.2Msolar-3.3Msolar) visible
F-type star, with a disk at 550K that enshrouds a single B5V-type
star. Here we report interferometric images that show the eclipsing
body moving in front of the F star. The body is an opaque disk and
appears tilted as predicted. Adopting a mass of 5.9Msolar
for the B star, we derive a mass of ~(3.6+/-0.7)Msolar for
the F star. The disk mass is dynamically negligible; we estimate it
to contain ~0.07M⊕ (M⊕, mass of the Earth)
if it consists purely of dust.

---------------------------------------------------------
Title: Structure in the disc of epsilon Aurigae: Spectroscopic
observations of neutral Potassium during eclipse ingress
Authors: Leadbeater, Robin; Stencel, Robert
2010arXiv1003.3617L Altcode: 2010arXiv1003.3617S
Variations in the equivalent width of the neutral potassium line at
7699A are reported, during ingress and into totality of the current
eclipse of the enigmatic eclipsing binary epsilon Aurigae. The increase
and plateaus of line strength are correlated with new system parameters
and interferometric imaging constraints, plus ancillary data being
reported contemporaneously. Together, these data reveal structural
details of the transiting disc, never before measured. Measured ring and
gap placements do not immediately fit any proposed model using simple
tidal estimation. However, we predict egress times of interest and urge
continued monitoring of this star during the balance of its eclipse, and
encourage theoretical treatment of the disc substructure to be pursued.

---------------------------------------------------------
Title: IRAC warm observations of epsilon Aurigae, first half of
eclipse
Authors: Stencel, Robert; Hoard, Donald; Howell, Steve
2010sptz.prop..543S Altcode:
Epsilon Aurigae is one of the most unusual and famous eclipsing
binary stars in all of astronomy, the subject of studies since 1824,
and long defying explanation. We are requesting less than one total
hour of Spitzer IRAC time to obtain a pair of IRAC channels 1 &amp;
2 observations, during the 2010 April window, of the enigmatic
binary, epsilon Aurigae, now in totality for the first time in 27
years. The goal of these observations includes the following: (a)
having demonstrated during spring 2009 that IRAC could safely and
accurately measure this bright star using a special method invented for
the purpose, (b) we expect to derive precise photometric flux and color
information about the relative contribution of the 550K disk and the
7500K F star to the light at these IRAC channels during a very unique
orbital phase.

---------------------------------------------------------
Title: Diverse Team Working on Epsilon Aurigae Enigma
Authors: Seebode, Sally; Stanford, D.; Drumheller, D.; Howell, S.;
Hoard, D.; Stencel, R.
2010AAS...21541937S Altcode: 2010BAAS...42..282S
After 175 years of study, astronomers still debate the identity of the
companion that eclipses Epsilon Aurigae every 27 years. By obtaining
and analyzing observations from the College of San Mateo (CSM) 8”
telescope, the Spitzer Space Telescope, and the Kitt Peak National
Observatory, our team hopes to shed light on this mystery. Using
spectra from CSM and Kitt Peak, students make equivalent width, relative
velocity, and full width half max measurements of prominent absorption
lines. Comparisons of these measurements combined with photometric
data from Spitzer should illuminate more details of the Epsilon Aurigae
dark companion. Data collection started in February 2009 (pre-eclipse)
and will continue throughout the two-year event. This study is part
of the NASA/IPAC Teacher Archive Research Project (NITARP).

---------------------------------------------------------
Title: Epsilon Aurigae in Total Eclipse, 2010 - A progress report
Authors: Stencel, Robert E.
2010SASS...29....7S Altcode: 2010arXiv1005.3738S
The enigmatic eclipsing binary, epsilon Aurigae, has once more entered
a rare eclipse phase, for the first time since 1983. A wonderful array
of photometric and spectroscopic observations is underway, thanks to
the eclipse observing campaign and its participants. In addition,
breakthrough results have emerged from infrared and ultraviolet
observations, and especially with interferometric imaging that revealed
the long suspected dark disk in transit, plus new optical spectra that
are revealing substructure inside the disk itself. Implications of many
of these observations are discussed, but as the eclipse data are still
being collected, I anticipate additional discoveries still to come,
throughout 2010, and beyond.

---------------------------------------------------------
Title: Epsilon Aurigae - Two-year Totality Transpiring
Authors: Kloppenborg, Brian K.; Stencel, R. E.; Hopkins, J. L.
2010AAS...21541938K Altcode: 2010BAAS...42R.282K
The 27 year period eclipsing binary, epsilon Aurigae, exhibits the
hallmarks of a classical Algol system, except that the companion to
the F supergiant primary star is surprisingly under-luminous for
its mass. Eclipse ingress appears to have begun shortly after the
predicted time in August 2009, near JD 2,455,065. At the University of
Denver, we have focused on near-infrared interferometry, spectroscopy,
and photometry with the superior instrumentation available today,
compared to that of the 1983 eclipse. Previously obtained interferometry
indicates that the source is asymmetric (Stencel, et. al. 2009 APLJ)
and initial CHARA+MIRC closure-phase imaging shows hints of resolved
structures. In parallel, we have pursued SPEX near-IR spectra at NASA
IRTF in order to confirm whether CO molecules only seen during the
second half of the 1983 eclipse will reappear on schedule. Additionally,
we have obtained J and H band photometry using an Optec SSP-4
photometer with a newly written control and analysis suite. Our goal
is to refine daytime photometric methods in order to provide coverage
of the anticipated mid-eclipse brightening during summer 2010, from our
high-altitude observatory atop Mt. Evans, Colorado. Also, many parallel
observations are ongoing as part of the epsilon Aurigae international
campaign (http://www.hposoft.com/Campaign09.html). In this report,
we describe the progress of the eclipse and ongoing observations. We
invite interested parties to get involved with the campaign for
coverage of the 2009-2011 eclipse via the campaign websites:
http://www.hposoft.com/Campaign09.html - and - http://www.du.edu/
rstencel/epsaur.htm - and - http://www.citizensky.org . This research
is supported in part by the bequest of William Herschel Womble to
the University of Denver. We are grateful to the participants in
the observing campaign and invite interested parties to join us in
monitoring the star for the balance of the eclipse.

---------------------------------------------------------
Title: Epsilon Aurigae Eclipse 2009 - Ingress
Authors: Hopkins, Jeffrey L.; Stencel, Robert E.; Leadbeater, Robin;
Beckmann, Paul J.; Buil, Christian; Collins, Donald; Colombo, Tiziano;
Garrel, Thierry; Gorodenski, Stanley; Gudmundsson, Snaevarr; Karlsson,
Mukund Kurtadikar; Lindberg, Hans-Goran; Loughney, Des; Mauclaire,
Benji; McCandless, Brian E.; Melillo, Frank J.; Miles, Richard;
Pearson, Robert T.; Samolyk, Gerard; Schanne, Lothar; Strikis,
Iakovos Marios; Teyssier, François; Thizy, Olivier
2010SASS...29...13H Altcode:
The mysterious star system epsilon Aurigae undergoes an eclipse every
27.1 years that lasts nearly two years. The most recent eclipse started
during the late summer of 2009. An international campaign for observing
this eclipse was created in 2006, with a web site for information and,
to-date, 17 periodic newsletters for details, as well as a Yahoo forum
List for immediate announcements and comments. Photometric data in
the UBVRIJH bands have been submitted. Ingress occurred with first
contact in the V band estimated at the second week of 2009 August and
second contact estimated at 2010 mid-January. Spectroscopic data were
also obtained during ingress. Spectroscopic data have been provided in
the potassium I region, hydrogen alpha and beta regions and sodium D
line region of the star system's spectrum. In this paper we describe
details of observations and preliminary analysis during ingress and
second contact. We introduce the observers and discuss plans for
observing throughout totality and the end of the eclipse in 2011.

---------------------------------------------------------
Title: Spitzer Reveals New Insights into Mass Loss History of
Evolved Stars
Authors: Geise, Kathleen M.; Ueta, T.; Speck, A. K.; Izumiura, H.;
Stencel, R. E.
2010AAS...21543114G Altcode: 2010BAAS...42..364G
We provide high-resolution maps of the circumstellar dust shells of
several dozen Asymptotic Giant Branch (AGB) stars using data from the
Spitzer space telescope Multiband Imaging Photometer (MIPS) imaged at
70um. AGB stars are the major contributors of chemical elements such
as carbon, oxygen and silicon, which are essential to the existence of
life in the universe, through mass loss processes that take place at the
surface of the star. We probe the spatial distribution of cold ( 40 K)
dust grains in order to trace the history of mass loss from the observed
radial density variation in these shells. Our high-resolution maps
indicate that the relative motion of the star and interstellar medium
(ISM) may be an important component of shell structure evolution. Our
images illustrate that different morphologies may evolve because AGB
stars interact with the ISM that surrounds them. This work is based on
observations made with the Spitzer Space Telescope, which is operated
by the Jet Propulsion Laboratory, California Institute of Technology
under a contract with NASA. Support for this work was provided by NASA
through an award issued by JPL/Caltech.

---------------------------------------------------------
Title: Distance Determination For High Luminosity Stars Using The
Extended Wilson-Bappu Effect.
Authors: Wall, Randall; Shetrone, M.; Stencel, R.
2010AAS...21541319W Altcode: 2010BAAS...42..253W
In 1957, Olin Wilson and Vainu Bappu published evidence for a direct
correlation between the width of the 3933A Ca K line emission core
seen in late type stars, and the stellar absolute magnitude, Mv. In
1977, the third author on this abstract published a spectroscopic
survey that showed the wing emission features seen in the broad
wings of the K line among higher luminosity late type stars share
a similar correlation of line width and Mv. Using a combination of
newer McDonald Observatory high dispersion spectra and the VLT UVES
spectral library, we have compiled new measurements including both core
and wing emissions correlations along with Hipparcos parallaxes. We
included different spectral type and luminosity subgroups, in order to
examine any temperature dependent correlations, as has been discussed
by Sid Parsons in a 2001 paper. We apply this method to new distance
determinations for the hypergiant rho Cas (F8Iap) and AGB star R Lyr
(M5 IIIe). We acknowledge partial support for this effort from the
University of Texas summer REU program.

---------------------------------------------------------
Title: Preliminary Study of Red Supergiant Star Membership in OB
Star Associations of the Milky Way
Authors: Stencel, R. E.; Ueta, T.; Wall, R. J.; Yamamura, I.
2009ASPC..418..459S Altcode:
Establishing a physical association of cooler, evolved stars with
hotter, upper main sequence, luminous blue variables and Wolf-Rayet
stars, can help provide constraints on high-mass loss cases of stellar
evolution, as well as clarify the formation history of the stellar OB
association. We are examining AKARI survey data in search of extended
circumstellar material of RSGs and evidence for interaction of said
material with ambient ISM connected with the high mass stars. In this
initial report, we confirm several cases where IRAS indicated that
an extended circumstellar shell was present, and identify candidates
where interaction with the ISM appears to be underway.

---------------------------------------------------------
Title: Mass Loss History of the AGB Star, R Cas
Authors: Ueta, T.; Stencel, R. E.; Yamamura, I.; Izumiura, H.; Nakada,
Y.; Matsuura, M.; Ita, Y.; Tanabé, T.; Fukushi, H.; Matsunaga, N.;
Mito, H.; Speck, A. K.
2009ASPC..418..463U Altcode: 2009arXiv0905.0750U
We report here on the discovery of an extended far-infrared shell around
the AGB star, R Cassiopeia, made by AKARI and Spitzer. The extended,
cold circumstellar shell of R Cas spans nearly 3’ and is probably
shaped by interaction with the interstellar medium. This report is one
of several studies of well-resolved mass loss histories of AGB stars
under AKARI and Spitzer observing programs labeled “Excavating Mass
Loss History in Extended Dust Shells of Evolved Stars (MLHES).”

---------------------------------------------------------
Title: 3-D Dynamics of Interactions between Stellar Winds and the
Interstellar Medium as Seen by AKARI and Spitzer
Authors: Ueta, T.; Izumiura, H.; Yamamura, I.; Stencel, R. E.; Nakada,
Y.; Matsuura, M.; Ita, Y.; Tanabé, T.; Fukushi, H.; Matsunaga, N.;
Mito, H.; Speck, A. K.
2009ASPC..418..117U Altcode: 2009arXiv0905.0756U
Recent far-infrared mapping of mass-losing stars by the AKARI Infrared
Astronomy Satellite and Spitzer Space Telescope have suggested that
far-infrared bow shock structures are probably ubiquitous around
these mass-losing stars, especially when these stars have high proper
motion. Higher spatial resolution data of such far-infrared bow shocks
now allow detailed fitting to yield the orientation of the bow shock
cone with respect to the heliocentric space motion vector of the central
star, using the analytical solution for these bow shocks under the
assumption of momentum conservation across a physically thin interface
between the stellar winds and interstellar medium (ISM). This fitting
analysis of the observed bow shock structure would enable determination
of the ambient ISM flow vector, founding a new technique to probe the
3-D ISM dynamics that are local to these interacting systems. In this
review, we will demonstrate this new technique for three particular
cases, Betelgeuse, R Hydrae, and R Cassiopeiae.

---------------------------------------------------------
Title: Eps Aurigae hydrogen-alpha emission line variation : the
horn dance.
Authors: Hopkins, J. L.; Stencel, R. E.
2009JAVSO..37..213H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Eps Aurigae, 2009 : the eclipse begins - observing campaign
status.
Authors: Stencel, R. E.; Hopkins, J. L.
2009JAVSO..37..212S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Biggest, Baddest, Coolest Stars
Authors: Luttermoser, D. G.; Smith, B. J.; Stencel, R. E.
2009ASPC..412.....L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Wilson-Bappu Effect - 50 Years Later
Authors: Stencel, R. E.
2009ASPC..412..251S Altcode:
Wilson and Bappu (1957) published an empirical correlation between the
FHWM of the emission core of the CaII K-Line at 3933A and the intrinsic
luminosity among late-type dwarf, giant, and supergiant stars. Later on,
Stencel (1977) extended this luminosity calibrator by using so-called
wing emission lines in the wings of the H and K lines. Efforts to
extend these techniques to the brightest supergiants in local group
galaxies were frustrated by the limits of photographic coude' spectra
even on 4-meter telescopes at the time. With the advent of CCD spectra
and S/N possible with 8-meter telescopes, we re-examine the potential
for extragalactic hypergiant star distance calibration.

---------------------------------------------------------
Title: The Circumstellar-Interstellar Boundary around Evolved Stars
- Revealed
Authors: Stencel, R. E.
2009ASPC..412..197S Altcode:
The mapping of a circumstellar-interstellar bow shock around the AGB
star R Hya using Spitzer MIPS 70 micron imaging (Ueta et al. 2006)
has transformed our perception of how shells merge with the galactic
environment. This helps place claims from the IRAS era in context with
exciting new far infrared images being collected with the AKARI all
sky survey and pointed observations. This paper reviews the past 20
years of efforts to map these phenomena.

---------------------------------------------------------
Title: Multiwavelength Study of Pulsation and Dust Production in
Mira Variables Using Optical Interferometry for Constraints
Authors: Creech-Eakman, M. J.; Hora, J.; Ivezic, Z.; Jurgenson, C.;
Luttermoser, D.; Marengo, M.; Speck, A.; Stencel, R.; Thompson, R. R.
2009AIPC.1170..137C Altcode:
Optical interferometry is a technique by which the diameters and
indeed the direct pulsations of stars are routinely being measured. As
a follow-on to a 7 year interferometric campaign to measure the
pulsations of over 100 mira variables, our team has been using the
Spitzer Space Telescope to obtain 95 mid-infrared spectra of 25
miras during their pulsations over one year while simultaneously
ascertaining their near-infrared diameters using the Palomar Testbed
Interferometer. These data will then be combined with modeling from
NLTE and radiative transfer codes to place hard constraints on our
understanding of these stars and their circumstellar environments. We
present some initial results from this work and discuss the next steps
toward fully characterizing the atmosphere, molecular photosphere and
dust production in mira variables.

---------------------------------------------------------
Title: Epsilon Aurigae Hydrogen Alpha Emission Line Variation:
The Horn Dance
Authors: Hopkins, Jeffrey L.; Stencel, Robert E.
2009SASS...28..157H Altcode:
The Hopkins Phoenix Observatory has been doing high resolution
spectroscopy on the 3rd magnitude long period (27.1 year) eclipsing
binary star system epsilon Aurigae since August 2008 using a Lhires
III spectrograph with a 2,400 line/mm grating mounted on a 12" Meade
LX200 GPS telescope. Observations have been in both the sodium D line
region of the spectrum and with near continuous observations of the
hydrogen alpha region. The out-of- eclipse hydrogen alpha spectrum
shows significant night-to-night variation. While many star systems
exhibit a strong hydrogen alpha absorption line, like Be stars. Epsilon
Aurigae also shows strong blue and red shifted emission components
sometimes called wings or horns bracketing the absorption line. Unlike
the Be stars where the blue and red horns remain relatively constant,
the hydrogen alpha horns of epsilon Aurigae seem to be in a wild dance
with continuous motion up and down. This paper will discuss techniques
and result of recent out-of-eclipse high-resolution spectroscopy of
epsilon Aurigae.

---------------------------------------------------------
Title: Pre-eclipse Observations, Epsilon Aurigae, 2009
Authors: Stencel, Robert E.; Hopkins, J. L.
2009AAS...21443102S Altcode:
The 27 year period eclipsing binary, epsilon Aurigae, exhibits the
hallmarks of a classical Algol system, except that the companion to
the F supergiant primary star is very sub-luminous. With the nearly
2 year long totality predicted to begin in mid-2009, we have been
amassing pre-eclipse observations to help characterize this system as
eclipse begins. Photometry has revealed that the characteristic period
of the long-known low-amplitude variability (0.1 magnitude at V), has
been decreasing decade to decade since last eclipse in the mid-1980s,
from nearly 100 days to under 65 days currently. Spectroscopy has begun
to show red-shifted components appearing that could be associated with
the fringes of the eclipsing secondary object, a putative dark disk,
encroaching on the F star during second half 2008, and consistent with
previous radial velocity studies. Polarimetry during the last eclipse
indicated a disk tilted relative to the orbital plane. Interferometry
is beginning to indicate measurable asymmetry in the orbital plane,
probably associated with the disk approaching conjunction. In this
report, we will describe the ongoing observations and invite interested
parties to get involved with the campaign for coverage of the 2009-11
eclipse. Campaign website: http://www.du.edu/ rstencel/epsaur.htm . This
research is supported in part by the bequest of William Herschel Womble
to the University of Denver.

---------------------------------------------------------
Title: Epsilon Aurigae, 2009: The Eclipse Begins - Observing
Campaign Status
Authors: Stencel, Robert E.; Hopkins, Jeffrey L.
2009SASS...28..149S Altcode:
The eclipse of 3rd magnitude epsilon Aurigae is forecast to begin during
August 2009, reaching totality by year's end, based on all fsix prior
eclipse events studied - 1982, 1955, 1930, 1902, 1874 and 1847. We
have organized a campaign during the past several years in order to
raise awareness about this rare opportunity, and to promote reporting
of observations of all kinds. We have 40 registered participants,
76 people signed up for alert notices, plus numerous informal
expressions of interest. Categories of observations being reported
in Campaign Newsletters (11 since 2006) which include Photometry,
Spectroscopy, Polarimetry, Interferometry and Citizen Science [website:
www.hposoft.com/Campaign09.html ]. In this presentation, we provide
a brief update on the optical and near-IR photometry obtained to
date. The nature of the short term light variations will be discussed
in the context of mapping the eclipse behavior. Spectroscopy benefits
from small telescope capabilities now widely available, along with
traditional large telescope, higher dispersion work. Examples of each
will be presented, along with the research objectives. Polarimetry
provided key insights during the last eclipse, and we continue to
promote the need for new data using this method. Finally, interferometry
has come of age since the last eclipse, and a status report on this
powerful method to directly detect the passing dark disk will be
provided. Along with these traditional measurements, we will briefly
discuss efforts to promote Citizen Science opportunities among the
public, in coordination with AAVSO and as part of the International
Year of Astronomy, IYA 2009.

---------------------------------------------------------
Title: The Very Long Mystery of Epsilon Aurigae
Authors: Stencel, Robert E.
2009S&T...117e..58S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Early Science - Epsilon Aurigae
Authors: Howell, Steve; Hoard, D. W.; Stencel, Robert; Rebull,
Luisa; Mighell, Ken; McCabe, Caer; Stanford, Darryl; Brumheller,
Dean; Seebode, Sally; Spuck, Tim; Johnson, Chelen H.
2009sptz.prop..535H Altcode:
Epsilon Aurigae is one of the most unusual and famous eclipsing binary
stars in all of astronomy, the subject of studies since 1824 but still
defying explanation. During Spitzer Cycle 6, Eps Aur will begin its
2-year eclipse. We propose a very modest 0.1 hour program to obtain
the first Spitzer IRAC observations of Eps Aur before eclipse.

---------------------------------------------------------
Title: Tie Breaking Spectra of the Dusty Bow Shock Near R Hya
Authors: Stencel, Robert; Matsuura, Mikako; Speck, Angela; Ueta,
Toshiya; Zijlstra, Albert
2009sptz.prop..532S Altcode:
We request 30 minutes of Director's Discretionary Time for an urgent,
tie-breaking IRS observation of the first-ever, Spitzer-MIPS discovered,
circumstellar-interstellar bow shock surrounding the AGB star, R Hydrae.

---------------------------------------------------------
Title: Spectro-Interferometrically Resolved Angular Diameters of
Giants and Supergiants
Authors: Hart, Alexa H.; van Belle, G. T.; Creech-Eakman, M. J.;
Stencel, R. E.
2009AAS...21349117H Altcode: 2009BAAS...41R.469H
We present narrow-band angular diameters of a set of Giants and
Supergiants from each of five K-band (2.0-2.4 µ) channels measured with
the Palomar Testbed Interferometer. Diameters measured in resolved
spectral channels containing absorption features (such as the CO
band and Br γ line) are compared with the diameters measured for
the continuum. White-light (wide band) diameters for these objects,
published in van Belle et al., 1999 and van Belle et al., 2008,
empirically determined the dependence of linear size on V-K color
for Luminosity Class I, II and III stars. This work expands on those
results by investigating the effects of metallicity on the measured
diameters. We discuss these results in the context of current stellar
evolution theory. Support provided by a bequest by William Herschel
Womble to the University of Denver Astronomy Program, and partial
support from the Rocky Mountain NASA Space Grant Consortium.

---------------------------------------------------------
Title: Citizen Science for the International Year of Astronomy
Authors: Price, Aaron; De Pree, C.; Fortson, L.; French, R.; Hartman,
M.; Jacoby, S.; Raddick, J.; Stencel, R.
2009AAS...21346501P Altcode: 2009BAAS...41..411P
The IYA 2009 working group on Research Experiences for Students,
Teachers, and Citizen-Scientists is planning a multi-year project
centering on the naked eye variable star Epsilon Aurigae. It begins
with a "Ten Star Training Program" of stars easy to observe from
suburban locations with the naked eye, which was launched in late
2008. Participants will be trained both in observing and also in
basic data analysis of photometric datasets (light curve and period
analysis). In the summer of IYA 2009, third-magnitude Eps Aur will
experience its next eclipse, which occurs every 27.1 years and lasts
714 days, nearly two years! However, the program is not limited to Eps
Aur and will likely include other occultation events such as monitoring
mutual eclipses of satellites of Jupiter and Saturn. Planning is
still underway and the scope of the project is dependent upon proper
funding. Results from a summer needs analysis workshop of citizen
science providers will be included. Advice and offers to help are
welcome. More info is at http://www.aavso.org/iya.

---------------------------------------------------------
Title: Interferometric Studies of the Extreme Binary epsilon Aurigae:
Pre-Eclipse Observations
Authors: Stencel, Robert E.; Creech-Eakman, Michelle; Hart, Alexa;
Hopkins, Jeffrey L.; Kloppenborg, Brian K.; Mais, Dale E.
2008ApJ...689L.137S Altcode: 2008arXiv0810.5382S
We report new and archival K-band interferometric uniform disk
diameters obtained with the Palomar Testbed Interferometer for the
eclipsing binary star epsilon Aurigae, in advance of the start of
its eclipse in 2009. The observations were intended to test whether
low-amplitude variations in the system are connected with the F
supergiant star (primary), or with the intersystem material connecting
the star with the enormous dark disk (secondary) inferred to cause the
eclipses. Cepheid-like radial pulsations of the F star are not detected,
nor do we find evidence for proposed 6% per decade shrinkage of the
F star. The measured 2.27 +/- 0.11 mas K-band diameter is consistent
with a 300 solar radius F supergiant star at the Hipparcos distance
of 625 pc. These results provide an improved context for observations
during the 2009-2011 eclipse.

---------------------------------------------------------
Title: Adventures in J- and H-Band Photometry of Evolved Stars
Authors: Bradley, A. J.; Stencel, R. E.
2008JAVSO..36..127B Altcode:
Among the classes of objects optimized for angular diameter measurements
by current generation astronomical interferometers are nearby red giant
stars. Precision diameters can help constrain atmospheric and evolution
models thereof, but many of these stars are intrinsically variable
and thus must be monitored during intervals when interferometry is
planned. Using an Optec SSP-4 photometer, we obtained the J- and
H-band magnitudes of a sample of such stars being studied by the
Palomar Testbed Interferometer, and report results here.

---------------------------------------------------------
Title: Gearing up for Epsilon Aurigae's First Eclipse of the
Millennium
Authors: Hopkins, Jeffery L.; Schanne, Lothar; Stencel, Robert E.
2008SASS...27...67H Altcode: 2008arXiv0807.2855H
The mysterious 3rd magnitude long period eclipsing binary star system,
epsilon Aurigae, is predicted to start its two-year eclipse in the
July 2009. This may be when the real excitement starts but much is
to be learned before first contact. This paper will discuss current
observational results that have accumulated data using photometry,
spectroscopy and other data sources. While the system is ideal for
single channel photometry, due to the system brightness and distant
comparison star, CCD photometry presents some interesting challenges. A
fairly simple way for amateur astronomers to do BVRI CCD photometry of
the system is using a 50 mm camera lens and DSI Pro camera is discussed.

---------------------------------------------------------
Title: Citizen Science for the International Year of Astronomy
Authors: Price, Aaron; De Pree, C.; Fortson, L.; Hartman, M.; Jacoby,
S.; Stencel, R.
2008AAS...212.3502P Altcode: 2008BAAS...40Q.234P
The IYA 2009 working group on Research Experience for Students,
Teachers, and Citizen-Scientists is planning a multi-year project
involving occulting systems. The project will include both observing
and data analysis components. It begins with training programs of
several types of binary and transient variable stars that are easy to
observe from suburban locations with the naked eye. Participants will be
trained both in observing and also in basic data analysis of photometric
datasets (light curve and period analysis). Eventually it will lead to a
capstone project: monitoring the rare and mysterious 2009-2011 eclipse
of Epsilon Aurigae. In the summer of IYA 2009, third-magnitude Eps Aur
will experience its next eclipse, which occurs every 27.1 years and
lasts 714 days, nearly two years! However, the program is not limited
to Eps Aur and will also include other occultation events such as
monitoring mutual eclipses of satellites of Jupiter and Saturn. Planning
is still underway; advice and offers to help are welcome.

---------------------------------------------------------
Title: Campaign Plans for, and Pre-eclipse Observations of the
Extreme Star, Epsilon Aurigae
Authors: Stencel, Robert E.
2008AAS...212.1403S Altcode: 2008BAAS...40..207S
Epsilon Aurigae is an F0 supergiant exhibiting Algol-like eclipses
on a 27 year period, last in 1982-84 -- see NASA Conf. Publication
2384 [available at http://www.du.edu/ rstencel/NASAcp2384.pdf
]. The problem is that despite the 0.8 mag total eclipse, which
lasts 2 years, the massive secondary object has proven difficult
to detect. Current models suggest that an enormous disk, stabilized
by an embedded binary, causes the eclipses. In preparation for the
predicted 2009-11 eclipse, an international observing campaign
again has been organized, via websites: http://www.du.edu/
rstencel/epsaur.htm and http://www.hposoft.com/Campaign09.html
- featuring current campaign newsletters. Recent optical
photometry has shown characteristics of a 67 day quasi-periodicity
[http://arxiv.org/ftp/arxiv/papers/0706/0706.0891.pdf ], which is
shorter than the 95 day quasi-periodicity noted after the last eclipse
[Nha, et al. 1993 http://adsabs.harvard.edu/full/1993ASPC...38..291N
]. Spectroscopic monitoring of H-alpha has shown rapid variation
[Schanne, 2007 http://www.konkoly.hu/cgi-bin/IBVS?5747]. Near
infrared efforts have involved spectroscopy [Clemens et al. 2008
PASP 119:1385 Fig.15] and K band interferometry at PTI [Stencel et
al., in preparation]. Spitzer infrared observations, with IRS and
MIPS, were obtained at a pair of epochs during Cycle 2 [Stencel 2007
http://adsabs.harvard.edu/abs/2007IAUS..240..202S ]. Additional effort
with polarimetry is solicited, and interested parties are invited to
contact this author to be added to the campaign notification lists. I
am delighted to acknowledge complicity in this campaign once again
with Jeff Hopkins, and the connection with the International Year
of Astronomy - Citizen Science effort and AAVSO. This research is
supported in part by Spitzer JPL Contract 1275955, and the bequest of
William Herschel Womble, to the University of Denver Astronomy Program.

---------------------------------------------------------
Title: Adventures in Interferometry
Authors: Mais, Dale E.; Kloppenborg, Brian; Stencel, Robert
2008SASS...27...77M Altcode:
While the Michelson Interferometer examined starlight atop the
Mt. Wilson 100-inch telescope nearly 100 years ago, it's taken decades
for interferometric instrumentation to begin to enter the mainstream of
astrophysics. We report on one application of these methods: measuring
the near-infrared angular diameter of the eclipsing binary star,
epsilon Aurigae, using the 100 meter Palomar Testbed Interferometer
located adjacent to the more famous 200-inch telescope atop Mt. Palomar.

---------------------------------------------------------
Title: An Interferometric Snapshot Survey to Constrain Mass-Loss
Dynamics and Physics in AGB Stars
Authors: Creech-Eakman, Michelle; Hora, Joseph; Ivezic, Zeljko;
Jurgenson, Colby; Luttermoser, Don; Marengo, Massimo; Stencel, Robert;
Thompson, Robert
2008sptz.prop50717C Altcode:
We propose Spitzer IRS observations of a unique sample of 25 AGB
(mira) variable stars with interferometrically determined K-band
angular diameters and spectrophotometry taken simultaneously using
the Palomar Testbed Interferometer. These high-resolution spectral
and spatial observations, in conjunction with amateur light-curves
(e.g. AAVSO), will be used together to place constraints on the
location of the IR stellar photosphere and the nature of the molecules
and dust in the circumstellar environment (CSE). We can then develop
complete models of the stars and CSE, using our state-of-the-art
hydrodynamic atmosphere codes (ATLAS/PANDORA) and radiative transfer
code (DUSTY). This will allow us to undertake the most accurate
modeling of these highly dynamic environments that has yet been done
for evolved stars. With results from these observations we will answer
several key questions about these stars including: 1) how important
are the roles of NLTE atmospheres in the formation of dust?; 2) what
dust species are relevant to a given AGB dust morphology and do these
change as a result of the pulsational cycle?; 3) is dust created or
destroyed during the pulsational cycle and how does this relate to
the abundances of other molecules in the CSE?; and finally, 4) what is
the physical location of the dust production around an AGB star which
acts to define the age-dependent spectral-energy distribution? These
types of observations require a high-level of spectroscopic fidelity,
repeatability and sensitivity which is unable to be executed under
conditions of telluric contamination. Therefore these types of
observations can only be performed with Spitzer's IRS instrument.

---------------------------------------------------------
Title: Observations of Broad Emission Lines in Wolf-Rayet Winds with
Long-Baseline Interferometry
Authors: Hart, Alexa H.; Jurgenson, C. A.; Creech-Eakman, M. J.;
Thompson, R. R.; Stencel, R. E.
2007AAS...211.5716H Altcode: 2007BAAS...39..832H
We present results of milli-arcsecond (mas) observations of six
Wolf-Rayet stars taken in 2003 with the Palomar Testbed Interferometer
(PTI) and the Keck Interferometer (KI) in the K band (2.0-2.4
microns). PTI has a nominal fringe spacing of 4 mas in the K band,
whereas KI has a fringe spacing of 5.2 mas. The purpose of these
observations was to exploit this high resolution to help determine
binarity, which is unknown for many Wolf-Rayet in systems. In addition,
we have resolved He emission lines in narrowband ( 0.1 micron
channel) measurements taken with both interferometers. Reduction of
the observations yield visibilities and derived angular sizes in 4
or 5 spectral channels across the K band, revealing stratification
of the stellar atmospheres. We have also recorded evolution in some
resolved spectral features, indicating structure in the winds; however,
follow-up interferometric observations are needed to better quantify
this phenomena. We present the observations, some of the narrow-band
data and initial conclusions based on our findings. We acknowledge
support from the Donald Menzel Memorial Fund and the Rocky Mountain
NASA Spacegrant Consortium at the University of Denver.

---------------------------------------------------------
Title: Citizen Science for the International Year of Astronomy
Authors: Jacoby, Suzanne H.; Fortson, L.; Hartman, M.; Lochner, J. C.;
Price, A.; Raddick, M. J.; Stencel, R. E.
2007AAS...21110608J Altcode: 2007BAAS...39..934J
The IYA 2009 working group on Research Experience for Students,
Teachers, and Citizen-Scientists is planning a multi-year project
involving variable stars. The project will begin with training programs
of several types of binary and transient variable stars that are easy to
observe from suburban locations with the naked eye. Eventually it will
lead to a capstone project: monitoring the rare and mysterious 2009-2010
eclipse of Epsilon Aurigae. In the summer of IYA 2009, third-magnitude
Eps Aur will experience its next eclipse, which occurs every 27.1 years
and lasts 714 days, nearly two years! Projects will be developed for
three audiences: amateurs, the general public and educators. Planning
is still underway; advice and offers to help are welcome.

---------------------------------------------------------
Title: Evidence for a Precessing Disk in the Extreme Binary Aurigae
Authors: Stencel, Robert E.
2007IAUS..240..202S Altcode: 2006IAUS..240E.112S
Among the longest known eclipse durations and binary periods is
that of the star epsilon Aurigae which exhibits 2 year long eclipses
every 27.1 years. Oddly, the nature of the secondary in the system
continues to elude ready identification. In 1965, Huang proposed a
massive disk as the eclipsing body, and study of the 1984 eclipse led
Lissauer and Backman to suggest an embedded B star binary in the disk
to maintain it. A collaboration of observers allows me to present
recent optical photometry and spectroscopy, near-IR spectroscopy
and Spitzer space telescope IRS and MIPS observations of epsilon
Aurigae as it approaches its next eclipse. These data argue for
current detectability of the embedded binary, and precession of
the disk axis, suggesting a radical change is possible for the next
mid-eclipse brightening. An international monitoring campaign for the
2009-2011 is being organized, and participation invited via website
http://www.du.edu/~rstencel/epsaur.htm.

---------------------------------------------------------
Title: Recent UBVJH Photometry of Epsilon Aurigae
Authors: Hopkins, Jeffrey L.; Stencel, Robert E.
2007arXiv0706.0891H Altcode:
Since first observed in the early 1980s, the Hopkins Phoenix Observatory
continues its UBV band observations of the long period (27.1 years)
eclipsing binary star system epsilon Aurigae. The UBV observations
routinely produce standard deviations or data spread better than 0.01
magnitudes many times approaching 0.001 magnitudes. A new infrared
photometer has allowed the addition of near-infrared observations
for the JH bands. Typical near-infrared observations approach a
standard deviation of data spread of 0.01 magnitudes. The 2003 -
2005 seasons (Fall through Spring) of epsilon Aurigae observations
showed a 66.2 day variation that gradually increases in average and
peak magnitude in the UBV bands. The 2006 season (Fall 2006 to Spring
2007) data show what appears to be a fall-back to a quiet period
near maximum amplitude of V= 3.00. This paper presents the data
and compares the current season to the past several seasons. The
next eclipse is predicted to begin in 2009 and an international
campaign has been organized to coordinate new observations. These
website links are: [http://www. hposoft.com/Campaign09.html ] and [
http://www.du.edu/~rstencel/epsaur.htm ] .

---------------------------------------------------------
Title: Spitzer Spectra of Epsilon Aurigae - As It Nears Eclipse
in 2009
Authors: Stencel, Robert E.
2007AAS...210.7504S Altcode: 2007BAAS...39Q.182S
The extremely long period eclipsing binary, epsilon Aurigae, is
approaching its next eclipse event [2009 Aug through 2011 May]. The
27.1 year binary features an otherwise normal enough F0 supergiant
but an optically invisible companion that causes the two year long
eclipse. Observations compiled during the 1982-1984 eclipse are
reported by Stencel (1985 NASA Conf. Publ. 2384 available on request)
and current interpretation was summarized by Carroll et al. (1991
Ap.J. 367: 278). In preparation for the next eclipse, UBVJH photometry
and H-alpha spectroscopy are being pursued by Jeff Hopkins (webpage
http://www.hposoft.com/Astro/PEP/EAURDATA.html ) and Lothar Schanne
(webpage http://www.konkoly.hu/cgi-bin/IBVS?5747 ). In collaboration
with Hopkins and Schanne, plus Tom Ake, Dana Backman, Dan Clemens,
Ed Guinan and Dale Mais, we have pursued additional data including
Mimir spectra and Spitzer IRS and MIPS observations. We report here
on the Spitzer IRS and MIPS SED data from Cycle 2 program 20058,
which reveal a bright continuum with weak emission lines at times of
observations. Line identifications and their diagnostics are consistent
with nebular emission associated with the F supergiant. Additional
epoch observations will help determine whether companion contributions
appear in the infrared. Persons interested in participating in the
multiwavelength campaign for the 2009 eclipse are invited to visit
webpage: http://www.du.edu/ rstencel/epsaur.htm for details. We are
grateful for partial support of this effort from JPL contract 1275955
to the University of Denver, and the estate of William Herschel Womble
in support of astronomy at the University of Denver.

---------------------------------------------------------
Title: Precision UBVJH Single Channel Photometry of Epsilon Aurigae
Authors: Hopkins, J. L.; Stencel, R. E.
2007SASS...26...37H Altcode:
First observed in the early 1980's the Hopkins Phoenix Observatory
continues its UBV band observations of the long period (27.1 years)
eclipsing binary star system Epsilon Aurigae. The UBV observations
routinely produce standard deviations or data spread better than 0.01
magnitudes many times approaching 0.001 magnitudes. A new infrared
detector has allowed the addition of precision infrared observations
for the JH bands. Typical infrared observations approach a standard
deviation of data spread of 0.01 magnitudes. The 2003 - 2005 seasons
(Fall through Spring) of Epsilon Aurigae observations showed a 66.2 day
variation that gradually increases in average and peak magnitude in the
UBV bands, The 2006 season (Fall 2006 to Spring 2007) data show what
appears to be a fall-back to a quiet period near maximum amplitude of V=
3.00. This paper presents the data and compares the current season to
the past several seasons. The next eclipse is scheduled to begin in
2009 and an international campaign has been organized to coordinate
new observations. [http://www.~hposoft.com/Campaign09.html].

---------------------------------------------------------
Title: The circumstellar - interstellar interface revealed
Authors: Stencel, Robert; Matsuura, Mikako; Speck, Angela; Ueta,
Toshiya; Wareing, Chris; Zijlstra, Albert
2007sptz.prop40166S Altcode:
With the discovery by Spitzer of a bow shock structure around the AGB
star, R Hydrae, a new class of circumstellar - interstellar interaction
physics is open to exploration. We propose IRS and MIPS-SED spectroscopy
of the bow shock structure around R Hya. The goal of the spectroscopy
is to provide temperature and density diagnostics for the material
in the shocked region. These measurements will provide context for
analysis of variation of mass loss and gas to dust ratio, as well
as exploration of the destruction of circumstellar dust at this
well-defined interstellar boundary.

---------------------------------------------------------
Title: Excavating the Mass Loss History in the Circumstellar Dust
Shells of Evolved Stars (Spitzer-MLHES)
Authors: Ueta, Toshiya; Izumiura, Hideyuki; Speck, Angela; Stencel,
Robert
2007sptz.prop40092U Altcode:
Using Spitzer/MIPS's unique observing capabilities, we propose to
observe the spatial distribution of the far-IR emission from extended
circumstellar dust shells (CDSs) of 37 asymptotic giant branch (AGB)
stars. Our sample is volume-limited (&lt; 500 pc) and includes all
known extended AGB CDSs whose internal structures can be resolved by
Spitzer at 70 microns. We will determine the dust distribution in these
shells and thus, (a) directly characterize AGB mass loss variations
in the CDSs; (b) confront our observational data with a range of
theoretical predictions to determine the effect of dust chemistry
on mass loss and the cause of the aspherical CDS structures; and
(c) constrain the masses of the progenitor stars. Most importantly,
we will achieve our science goals by deriving statistically sound
conclusions using a complete structure-resolvable sample in the solar
neighborhood. The mechanisms by which these evolved stars lose their
mass to the surrounding space are not well understood. The AGB CDSs
contain the fossil record of their mass loss, and therefore have
the potential to verify many aspects of stellar evolution. IRAS and
ISO data indicate that extended AGB CDSs exist showing evidence for
mass-loss variations that correlate with evolutionary changes in
the star itself. However, previous observations lacked both quantity
(data are scarce) and quality (sensitivity and spatial resolution) to
investigate the full extent and detailed structure of these large CDSs
in statistically meaningful ways. Hence, it is more than timely to apply
the powerful capabilities of Spitzer/MIPS to study the far-IR structure
and evolution of these extended CDSs at moderately high resolution and
sensitivity, for which there are presently no superior alternatives
to Spitzer. The AGB CDSs are being detected at a high rate (&gt; 60%)
in an on-going AKARI-MLHES study at lower resolution and sensitivity:
the likelihood for success of this proposed Spitzer-MLHES program at
higher resolution and sensitivity is therefore enhanced.

---------------------------------------------------------
Title: Three Years of Mira Variable CCD Photometry: What Has Been
Learned?
Authors: Mais, D. E.; Richards, D.; Stencel, R. E.
2007arXiv0704.2762M Altcode:
The subject of micro-variability among Mira stars has received increased
attention since DeLaverny et al. (1998) reported short-term brightness
variations in 15 percent of the 250 Mira or Long Period Variable stars
surveyed using the broadband 340 to 890 nm Hp filter on the HIPPARCOS
satellite. The abrupt variations reported ranged 0.2 to 1.1 magnitudes,
on time-scales between 2 to 100 hours, with a preponderance found
nearer Mira minimum light phases. However, the HIPPARCOS sampling
frequency was extremely sparse and required confirmation because of
potentially important atmospheric dynamics and dust-formation physics
that could be revealed. We report on Mira light curve sub-structure
based on new CCD V and R band data, augmenting the known light curves
of Hipparcos-selected long period variables [LPVs], and interpret same
in terms of [1] interior structure, [2] atmospheric structure change,
and/or [3] formation of circumstellar [CS] structure. We propose that
the alleged micro-variability among Miras is largely undersampled,
transient overtone pulsation structure in the light curves.

---------------------------------------------------------
Title: The Wilson-Bappu Effect Fifty Years Later
Authors: Matson, Rachel A.; Stencel, R. E.
2006AAS...209.9301M Altcode: 2006BAAS...38R1029M
Wilson and Bappu (1957 ApJ 125) published an empirical correlation
between the FHWM of the emission core of the CaII K-Line at 393nm and
the intrinsic luminosity among late-type dwarf, giant, and supergiant
stars. Later on, Stencel (1977 ApJ 215) extended this luminosity
calibrator by using so-called wing emission lines found in the wings of
the H and K lines. Efforts to extend these techniques to the brightest
supergiants in local group galaxies were frustrated by the limits of
photographic coude spectra at the time, even on 4-meter telescopes. With
the advent of CCD spectroscopy and S/N possible with 8-meter telescopes,
we here explore the potential for extragalactic hypergiant star
distance calibration. Using the Paranal Observatory library of
high-resolution spectra (http://www.sc.eso.org/santiago/uvespop/)
obtained from the UVES instrument at an ESO Very Large Telescope,
we measure the line widths of the CaII H and K lines and the wing
emission lines in late type stars. By plotting the measured FWHM
and absolute magnitude, we re-evaluate the Wilson-Bappu-Stencel
line-width-to-luminosity correlation for the K core emission and
H-K core wing emission lines. Because the H-K wing emission lines
remain visible in very luminous stars cooler than F1, whereas
circumstellar absorption obliterates the core emission, the wing
line-width-to-luminosity correlation may be useful in estimating
intrinsic luminosity for these stars. We are grateful to Dainis
Dravins for bringing our attention to the UVES altas, and for partial
support from the Geise Foundation and the estate of William Herschel
Womble for astronomy at the University of Denver.

---------------------------------------------------------
Title: Detached shells as tracers of asymptotic giant
branch-interstellar medium bow shocks
Authors: Wareing, C. J.; Zijlstra, Albert A.; Speck, Angela K.;
O'Brien, T. J.; Ueta, Toshiya; Elitzur, M.; Gehrz, R. D.; Herwig, F.;
Izumiura, H.; Matsuura, M.; Meixner, M.; Stencel, R. E.; Szczerba, R.
2006MNRAS.372L..63W Altcode: 2006MNRAS.tmpL..91W; 2006astro.ph..7500W
New Spitzer imaging observations have revealed the structure around the
Mira variable star R Hya to be a one-sided parabolic arc 100 arcsec
to the west, stretching from north to south. We successfully model
R Hya and its surroundings in terms of an interaction of the stellar
wind from an asymptotic giant branch (AGB) star with the interstellar
medium (ISM) the star moves through. Our three-dimensional hydrodynamic
simulation reproduces the structure as a bow shock into the oncoming
ISM. We propose this as another explanation of detached shells around
such stars, which should be considered alongside current theories of
internal origin. The simulation predicts the existence of a tail of
ram-pressure-stripped AGB material stretching downstream. Indications
for such a tail behind R Hya are seen in IRAS maps.

---------------------------------------------------------
Title: Detection of a Far-Infrared Bow Shock Nebula around R Hya:
The First MIRIAD Results
Authors: Ueta, T.; Speck, A. K.; Stencel, R. E.; Herwig, F.; Gehrz,
R. D.; Szczerba, R.; Izumiura, H.; Zijlstra, A. A.; Latter, W. B.;
Matsuura, M.; Meixner, M.; Steffen, M.; Elitzur, M.
2006ApJ...648L..39U Altcode: 2006astro.ph..7303U
We present the first results of the MIRIAD (MIPS InfraRed Imaging
of AGB Dust shells) project using the Spitzer Space Telescope. The
primary aim of the project is to probe the material distribution in the
extended circumstellar envelopes (CSEs) of evolved stars and recover
the fossil record of their mass-loss history. Hence, we must map the
whole of the CSEs plus the surrounding sky for background subtraction
while avoiding the central star that is brighter than the detector
saturation limit. With our unique mapping strategy, we have achieved
better than 1 MJy sr-1 sensitivity in 3 hr of integration
and successfully detected a faint (&lt;5 MJy sr-1), extended
(~400") far-infrared nebula around the asymptotic giant branch (AGB)
star R Hya. Based on the parabolic structure of the nebula, the
direction of the space motion of the star with respect to the nebula
shape, and the presence of extended Hα emission cospatial to the
nebula, we suggest that the detected far-IR nebula is due to a bow
shock at the interface of the interstellar medium and the AGB wind
of this moving star. This is the first detection of the stellar-wind
bow shock interaction for an AGB star and exemplifies the potential
of Spitzer as a tool to examine the detailed structure of extended
far-IR nebulae around bright central sources.

---------------------------------------------------------
Title: Educational Opportunities in Pro-Am Collaboration
Authors: Fienberg, R. T.; Stencel, R. E.
2006IAUSS...2E..83F Altcode:
While many backyard stargazers take up the hobby just for fun,
many others are attracted to it because of their keen interest in
learning more about the universe. The best way to learn science is
to do science. Happily, the technology available to today's amateur
astronomers — including computer-controlled telescopes, CCD cameras,
powerful astronomical software, and the Internet — gives them the
potential to make real contributions to scientific research and to
help support local educational objectives. Meanwhile, professional
astronomers are losing access to small telescopes as funding is shifted
to larger projects, including survey programs that will soon discover
countless interesting objects needing follow-up observations. Clearly
the field is ripe with opportunities for amateurs, professionals,
and educators to collaborate. Amateurs will benefit from mentoring by
expert professionals, pros will benefit from observations and data
processing by increasingly knowledgeable amateurs, and educators
will benefit from a larger pool of skilled talent to help them carry
out astronomy-education initiatives. We will look at some successful
pro-am collaborations that have already borne fruit and examine areas
where the need and/or potential for new partnerships is especially
large. In keeping with the theme of this special session, we will
focus on how pro-am collaborations in astronomy can contribute to
science education both inside and outside the classroom, not only for
students of school age but also for adults who may not have enjoyed
particularly good science education when they were younger. Because
nighttime observations with sophisticated equipment are not always
possible in formal educational settings, we will also mention other
types of pro-am partnerships, including those involving remote
observing, data mining, and/or distributed computing.

---------------------------------------------------------
Title: Three Years of Mira Photometry: What Has Been Learned?
Authors: Mais, D. E.; Richards, D.; Stencel, R. E.
2006SASS...25...31M Altcode:
The subject of micro-variability among Mira stars has received increased
attention since DeLaverny et al. (1998) reported short-term brightness
variations in 15 percent of the 250 Mira or Long Period Variable stars
surveyed using the broadband 340 to 890 nm "Hp" filter on the HIPPARCOS
satellite. The abrupt variations reported ranged 0.2 to 1.1 magnitudes,
on time-scales between 2 to 100 hours, with a preponderance found
nearer Mira minimum light phases. However, the HIPPARCOS sampling
frequency was extremely sparse and required confirmation because of
potentially important atmospheric dynamics and dust-formation physics
that could be revealed. We report on Mira light curve sub-structure
based on new CCD V and R band data, augmenting the known light curves
of Hipparcos-selected long period variables [LPVs], and interpret same
in terms of [1] interior structure, [2] at-mospheric structure change,
and/or [3] formation of circumstellar [CS] structure. We propose that
the alleged micro-variability among Miras is a largely undersampled,
transient overtone pulsation struc-ture in the light curves.

---------------------------------------------------------
Title: Single Channel UBV and JH Band Photometry of Epsilon Aurigae
Authors: Hopkins, J. L.; Stencel, R. E.
2006SASS...25...13H Altcode:
Epsilon Aurigae is the longest known eclipsing binary star system,
with a 27.1 year period. The next eclipse begins in 2009. While
many observatories make observations during the eclipse, few have
maintained an observing program between eclipses. As seen with the
last eclipse, there are some very interesting pre- and post-eclipse
light variations. There is evidence for periodic variations be-tween
eclipses, possibly pulsations of the primary F star. The Hopkins Phoenix
Observatory made single channel UBV photon counting observations
during the last eclipse and for several years there-after. In 2003
a concentrated observing effort was resumed and recently infrared
bands J and H have been added. The intent of these observations is
to provide out-of-eclipse data on the system in prepa-ration for
the 2009-2011 eclipse. This paper will summarize current activity,
present out-of-eclipse data, and provide analysis of the data.

---------------------------------------------------------
Title: Long-Period Eclipsing Binary System Epsilon Aurigae Eclipse
Campaign
Authors: Lucas, G. E.; Hopkins, J. L.; Stencel, R. E.
2006SASS...25...25L Altcode:
Epsilon Aurigae (Vmax = 2.99) is an eclipsing binary star system with
the longest orbital period known (27.1 years or 9,886 days). The next
eclipse of this unique object is due summer 2009. With such a long
orbital period, the actual eclipse might be expected to be short,
but is just the opposite, lasting nearly 2 years (ca. 714 days). To
a first approximation, this indicates the eclipsing body is of
gigantic proportions, on the order of 2,000 solar radii. The exact
nature of Eps Aur is still not fully resolved. A successful observing
campaign was organized during the last eclipse, 1982-1984. Amateur and
pro-fessional astronomers around the world contributed photometry,
polarimetry, and spectroscopy data. Despite the strong effort, some
questions still remain. Efforts have begun for a new eclipse campaign
in 2009-2011. Out-of-eclipse observations are being made. A dedicated
web site has been set up as a focal point.

---------------------------------------------------------
Title: Denver's great telescope : your guidebook to the University
of Denver's historic Chamberlin Observatory
Authors: Stencel, Claire M.; Stencel, Robert E.; Montgomery, Glenn E.
2006dasg.book.....S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Challenges and Opportunities in Operating a High-Altitude Site
Authors: Stencel, Robert E.
2006ASSL..335...97S Altcode: 2006osa6.book...97S
Observing stations at elevations in excess of 4000m are rare. This
report discusses the efforts to sustain and preserve one such site in
the Rocky Mountains of Colorado, in North America. The long-term value
of such sites can be measured in terms of their optical and infrared
characteristics, as well as their ability to inspire astronomers and
students to study the universe. The sustainability of this site is
yet to be determined.

---------------------------------------------------------
Title: SIFTIR: A Mid-IR Imaging Spectro-polarimeter
Authors: Jurgenson, C.; Stencel, R.
2005ASPC..343..280J Altcode:
We are currently developing an instrument that mates TNTCAM2 (Klebe et
al. 1998), an imaging polarimeter, with a Fourier transform spectrometer
(FTS), that operates from 2 to 15 micron. The FTS component enhances
TNTCAM2, giving the instrument a maximum resolution of 2000 at
10 micron, and 10^4 at 2 micron, while preserving the imaging
capabilities. This enables both moderately high resolution imaging
spectro-polarimetry of point sources, and the mapping of polarization
vectors over an extended nebulous region as well. Potential scientific
targets and discoveries will be discussed as well as the control
of the FTS moving mirror as related to waveplate rotation and the
observational technique of chopping &amp; nodding necessary for ground
based observations in the IR.

---------------------------------------------------------
Title: Spitzer/MIPS Infrared Imaging of the Extremely Extended
Circumstellar Dust Shell of HD 161796.
Authors: Speck, A. K.; Ueta, T.; Stencel, R.; MIRIAD Collaboration
2005AAS...20718215S Altcode: 2005BAAS...37.1465S
Evolved intermediate mass stars are major contributors to the
interstellar medium. However, the mechanisms by which they do this
are not well understood. Asymptotic giant branch (AGB) stars suffer
mass loss which leads to the formation of a circumstellar shell of
gas and dust. At the end of the AGB phase, mass loss stops and the
circumstellar shell begins to drift away from the star. If the velocity
of the AGB wind has been relatively constant, then dust furthest from
the star represents the oldest mass loss, while material closer to the
star represents more recent mass loss. Hence, circumstellar shells of
AGB and post-AGB stars contain the fossil record of their mass loss,
and therefore have the potential to verify many aspects of stellar
evolution. IRAS and ISO data indicate that huge dust shells exist
around many such objects, extending several parsecs from the central
star. Furthermore, some of these large dust shells show evidence for
mass-loss variations that correlate with evolutionary changes in the
star itself. Previous observations lacked the sensitivity and spatial
resolution to investigate the full extent and detailed structure of
these large dust shells. Using Spitzer/MIPS's unique sensitivity and
mapping capabilities, we have obtained a 160μ m image of the very
extended dust shell around post-AGB star HD161796, which confirms
that it exhibits weak extended emission out to a radius of several
hundred arcseconds. We present preliminary studies of this observation
and compare to previous FIR observations of this and other post-AGB
stars. From this study we will be able to (a) constrain the mass of the
progenitor star; (b) test theories of stellar evolution and mass-loss
mechanisms; (c) determine the effect of dust chemistry on mass loss
(and therefore on stellar evolution).

---------------------------------------------------------
Title: Search for transiting planets in NGC 6791 with milli-magnitude
V+R photometry
Authors: Dahl, M.; Stencel, R. E.; Howell, S.
2005AAS...207.6811D Altcode: 2005BAAS...37.1268D
With the discovery of an increasing number of planets around other
stars, it is expected that some fraction of these will produce
transit events. Open clusters provide a large sample of stars with
potential planets in a compact portion of sky, allowing for more
efficient monitoring. During 2005 summer, we began a series of
observations to search for transiting planets in open clusters,
specifically NGC 6791. Using the University of Denver's Mt. Evans
twin 0.72 meter telescopes, we obtained V+R band CCD data on several
nights during several months on this particular cluster. These data
were reduced for instrumental magnitudes using Source Extractor,
DAOPHOT/IRAF and IDL methods, and millimag precision achieved when
nights were photometric. We were able to confirm the short period and
low amplitude for previously described variable V522 Lyr, but find
variable V518 Lyr does not conform to previous description. We will
report on other low amplitude, transit-like variation among stars in
NGC 6791. We acknowledge the Marsico Initiative Visiting Scholar Fund
[SH]and the bequest of William Herschel Womble to the University of
Denver, for partial support of this research.

---------------------------------------------------------
Title: Epsilon Aurigae: a Laboratory for Understanding Circumstellar
Disk Physics
Authors: Stencel, Robert; Ake, Thomas; Backman, Dana; Guinan, Edward
2005sptz.prop20058S Altcode:
Circumstellar disks are now known to be common around young stellar
objects. However, their dimensions and compositions are measured
only with difficulty. Models suffer from lack of key constraints. The
disk around the secondary in the epsilon Aurigae binary, in contrast,
has some well-determined properties. A disk is inferred from eclipse
circumstances to be a 20 AU diameter, viewed edge-on &amp; partially
covers the F0 supergiant primary star for 2 full years during the 27
year binary period. This disk was discovered to be a strong thermal
IR source during the 1982-84 eclipse, in part by IRAS. We seek IRS
&amp; MIPS SED data to clarify the nature and evolutionary status of
this large protoplanetary-like disk &amp; help to better constrain a
class of disk models. This is among the most massive stellar systems
with a disk. Its dimensions are well-known from the eclipse light
curve. Temperature of the disk facing us during eclipse is known from
its IR SED; the composition &amp; velocities of gas from the secondary
are known from absorption lines detected in the last eclipse. The mass
of the system &amp; proximity of the disk to the luminous primary star
let us explore extremes of circumstellar disk physics. The secondary
now is near quadrature, the time of most rapidly changing geometric
aspect, so that measurements now give best resolution of temperature
versus azimuth angle around the disk. Our goals include: More precisely
defining temperature &amp; projected size of the disk-shaped IR-emitting
secondary object via IRS and MIPS measurements; Searching with IRS
for emission and absorption features, against the cool secondary;
Determining grain composition &amp; properties via the full range
of SST spectroscopy coverage [IRS &amp; MIPS SED]; Seeking evidence
for mass-loss history in extended material around the system [MIPS];
Establishing baselines of these &amp; other measures for comparison
during forthcoming eclipse campaigns (2009). It is only with SST that
these science goals can be accomplished.

---------------------------------------------------------
Title: MIPS Infrared Imaging of AGB Dustshells (MIRIAD): tracing
mass-loss histories in the extremely large shells around evolved stars
Authors: Speck, Angela; Elitzur, Moshe; Gehrz, Robert; Herwig, Falk;
Izumiura, Hideyuki; Latter, William; Matsuura, Mikako; Meixner,
Margaret; Steffen, Matthias; Stencel, Robert; Szczerba, Ryszard;
Ueta, Toshiya; Zijlstra, Albert
2005sptz.prop20258S Altcode:
Evolved intermediate mass stars are major contributors to the
interstellar medium. However, the mechanisms by which they do this
are not well understood. The circumstellar shells of evolved stars
(AGB and post-AGB stars) contain the fossil record of their mass
loss, and therefore have the potential to verify many aspects of
stellar evolution. IRAS and ISO data indicate that huge dust shells
exist around many such objects, extending several parsecs from the
central star. Furthermore, these large dust shells show evidence
for mass-loss variations that correlate with evolutionary changes
in the star itself. Previous observations lacked the sensitivity
and spatial resolution to investigate the full extent and detailed
structure of these large dust shells. Using Spitzer/MIPS's unique
sensitivity and mapping capabilities, we propose to produce far-IR
images of the parsec-sized dust shells around four carefully selected
evolved stars in order to determine the distribution of material in
these circumstellar envelopes. These maps will be the deepest yet
(sensitivity 1MJy/sr) and have the most complete spatial coverage to
date. Crucially, mapping in this level of detail will allow us to:
(a) constrain the masses of the progenitor stars; (b) test theories of
stellar evolution and mass-loss mechanisms; (c) determine the effect
of dust chemistry on mass loss (and therefore on stellar evolution);
(d) determine when the aspherical structures so prevalent in planetary
nebulae actually develop and thus constrain the cause.

---------------------------------------------------------
Title: Automated Photometry, Period Analysis and Flare-up Constraints
for Selected Mira Variable Stars
Authors: Mais, D. E.; Stencel, R. E.; Richards, D.
2005SASS...24...39M Altcode:
During the course of the past two years, 108 selected Mira-type program
stars have been monitored to address potential flare up episodes. These
include 34 M-type, 17-S type and 57 C-type Mira's. This paper will
describe the greater than 140,000 magnitude determinations that have
been obtained, many closely spaced in time, which are being used to
further constrain the potential occurrences of flare-up events. Random
reports in the literature suggest that some Mira variables may go
through flare up stages, which result in brightening on the order of
several tenths of a magnitude or more, and may last hours to days in
length. Very little is known about these events and their frequency,
indeed, it is not clear that these events are real or instrumental
phenomena. The light curves of many of the program stars show a
Cepheid like bump phenomenon, usually on the ascending part of the
light curve. In general, these bumps appear in longer period Mira's
(&gt;350 days) as pointed out by Melikian in 1999. Bumps are not obvious
or easily seen in visual data records, although slope changes during
rising phase are seen in some cases. In order to address the reality
of these events, we established an automated acquisition/analysis of
a group of 108 Mira variables [M(oxygen), S and C types] in order
to obtain the densest possible coverage of the periods, to better
constrain the character and frequency of flare-ups. Telescope control
scripts were put in place along with real time analysis. This allowed
for unattended acquisition of data on every clear night, all night long,
in the V, R and I photometric bands. In addition, during the course of
most nights, multiple determinations are often obtained for a given
star. We are grateful to the estate of William Herschel Womble for
partial support of these efforts.

---------------------------------------------------------
Title: SIFTIR: Spectro-Polarimetric Imaging Fourier Transform
Spectrometer for the InfraRed
Authors: Jurgenson, Colby; Stencel, Robert
2005hris.conf...92J Altcode:
Observations of evolved stars in the infrared are well suited for
studies of dusty environments, providing a wealth of absorption
and emission bands with which to diagnose grain characteristics. We
are currently developing an instrument that will employ a Fourier
transform spectrometer in conjunction with TNTCAM2 (Klebe et al. 1998),
an imaging polarimeter. The FTS component will enhance TNTCAM2,
giving the instrument a maximum resolution of 2000 at 10 μm. The
FTS is capable of operating between 2 15 μm, but polarimetry for the
instrument is limited to the 8 15 μm region due to waveplate/wiregrid
characteristics.

---------------------------------------------------------
Title: Monitoring of Mira Variable Stars
Authors: Mais, D. E.; Stencel, R. E.; Richards, D.
2004JAVSO..33...48M Altcode:
We have begun intensive V- and R-band CCD monitoring of Mira variable
stars since early in 2003. This project was initiated in the hopes
of improving the statistics of putative flaring phenomena among these
stars. This paper will give an update of the project and describe the
strategies being employed.

---------------------------------------------------------
Title: Imaging Fourier Transform Spectro-polarimetry in the Infrared
Authors: Jurgenson, C. A.; Stencel, R. E.; Stout, J.
2004AAS...205.4914J Altcode: 2004BAAS...36.1420J
Imaging spectro-polarimetry has the capability to trace polarization
changes in dust grains throughout an extended region of interest. An
instrument that has the capability to achieve moderately high resolution
(R = 2000 at 10 microns) via a stepping Fourier transform spectrometer,
while preserving imaging polarimetry capabilities (TNTCAM2, Jurgenson
et al. 2003), is set to achieve first light during early 2005. Motion
control of the interferometer, as well as array control/readout
is accomplished via an FPGA card programmed in LabVIEW(c). Mid-IR
polarization studies are useful in approximating grain shapes and
sizes in dusty environments. Correlation studies between mid and
near-IR features can be used to test the core-mantle arrangement
of grain growth. Polarization analysis is currently only possible
between 8-13 microns, but the interferometer, as well as TNTCAM2, can
operate at selected bandpasses in the near-IR region. A wire grid and
waveplate would need to be purchased for work in the near-IR. Laboratory
calibration results, both spectral and polarization, are reported. We
are seeking collaborators in shared-risk science with this instrument,
so please contact the authors if interested. Sigma Xi Grants In Aid
of Research as well as the estate of William Herschel Womble provided
funding for this endeavor.

---------------------------------------------------------
Title: Out-of Eclipse UBV Variations of epsilon Aurigae [F0Iap]
Authors: Hopkins, J.; Stencel, R. E.
2004AAS...20510705H Altcode: 2004BAAS...36Q1525H
Epsilon Aurigae is a binary star system that eclipses once every
27.1 years. The next eclipse is predicted to begin in 2009. The
eclipse is flat-bottomed and lasts nearly two years. In the high
mass model, the primary star is an F supergiant, but the nature of
the eclipsing object is poorly determined. During the 1982 - 1984
eclipse, a world-wide monitoring campaign was formed to observe
the system with modern equipment. Despite a wealth of photometric,
spectroscopic and polarimetric data, the nature of the eclipsing body
is still debatable. To make matters more interesting, a mid-eclipse
brightening was seen by several observers, including observations from
space, discounting an earthly atmospheric extinction effect. Previous
eclipse data also shows a mid-eclipse brightening. The primary F star
appears to have pulsations, but most of the published data for the
star system has been taken during eclipses. There are few data taken
between eclipses. The Hopkins Phoenix Observatory has been obtaining
UBV data of the star system out-of-eclipse since 1984. This paper
examines the out-of-eclipse data and light curves to date, and presents
possible pulsation periods with amplitudes. These data should provide
a better baseline for the next eclipse, including any pulsation role
in mid-eclipse brightening. Persons interested in participating in
the upcoming eclipse campaign can contact co-author Stencel for a
reference copy of the 1985 workshop on the eclipse of epsilon Aurigae.

---------------------------------------------------------
Title: Automated photometry, period analysis and flare-up constraints
for selected Mira Variable Stars
Authors: Mais, D. E.; Stencel, R. E.; Richards, D.
2004AAS...205.5406M Altcode: 2004BAAS...36Q1428M
During the course of the past two years, 108 selected Mira-type program
stars have been monitored to address potential flare up episodes. These
include 34 M-type, 17-S type and 57 C-type Mira's. This poster will
describe the greater than 100,000 magnitude determinations that have
been obtained, many closely spaced in time, which are being used to
further constrain the potential occurrences of flare-up events. Random
reports in the literature suggest that some Mira variables may go
through flare up stages, which result in brightening on the order of
several tenths of a magnitude or more, and may last hours to days in
length. Very little is known about these events and their frequency,
indeed, it is not clear that these events are real or instrumental
phenomena. The light curves of many of the program stars show a
Cepheid like bump phenomenon, usually on the ascending part of the
light curve. In general, these bumps appear in longer period Mira's
(&gt;350 days) as pointed out by Melikian in 1999. Bumps are not obvious
or easily seen in visual data records, although slope changes during
rising phase are seen in some cases. In order to address the reality
of these events, we established an automated acquisition/analysis of
a group of 108 Mira variables [M(oxygen), S and C types] in order
to obtain the densest possible coverage of the periods, to better
constrain the character and frequency of flare-ups. Telescope control
scripts were put in place along with real time analysis. This allowed
for unattended acquisition of data on every clear night, all night long,
in the V, R and I photometric bands. In addition, during the course of
most nights, multiple determinations are often obtained for a given
star. We are grateful to the estate of William Herschel Womble for
partial support of these efforts.

---------------------------------------------------------
Title: Discrete Fourier Analysis of the Light Curve of S Persei
Authors: Chipps, K. A.; Stencel, R. E.; Mattei, J. A.
2004JAVSO..32....1C Altcode:
A discrete Fourier analysis was performed on the validated S Persei
visual light curve data as obtained from the American Association of
Variable Star Observers (AAVSO). These observations span just over a
century, from February of 1903 to July of 2003. This analysis was an
attempt to find the fundamental periods of the variability of the red
supergiant S Persei. Inspection of the S Per light curve indicates a
likely complex combination of sinusoids of differing periods. Using
Fourier analysis, four periods of various relative strengths were
extracted from these data: 745, 797, 952, and 2857 days. Although some
of these periods are similar to earlier results, they seem to indicate
a more complex result than has previously been determined.

---------------------------------------------------------
Title: Amateur Spectroscopy: What is Achievable from the Backyard?
Authors: Mais, D. E.; Stencel, R. E.
2004AAS...204.3504M Altcode: 2004BAAS...36..705M
Recent advances in technology have opened the doors for amateurs
to potentially contribute in the area of spectroscopy. This is due
to both a shift in the use of more sensitive CCD detectors and the
recent availability of powerful and versatile spectrometers aimed at
the amateur community. We will focus on the instrument produced by
Santa Barbara Instrument Group (SBIG), the Self-Guided Spectrometer
(SGS). This instrument appeared on the market about four years
ago aimed at a sub group of amateurs. In conjunction with SBIG CCD
cameras, the SGS is self-guiding in that it keeps the image of an
object locked onto the entrance slit, which allows for long exposures
to be taken. The SGS allows spectra to be obtained with only modest
aperture instruments of stars down to 10-12 magnitude. In addition,
the SGS features a dual grating carousal which, with the flip of a
lever, allows you to obtain dispersions in the low-resolution mode (
4 Angstroms/pixel) or higher resolution mode ( 1 Angstrom/pixel). In
the low-resolution mode, about 3000 Angstrom coverage is obtained
whereas in the high-resolution mode, about 750 Angstroms. The area
of the visible and near infrared part of the spectrum you decide to
obtain a spectrum is dialed in by the user. More recently, swappable
grating carousals have allowed for gratings with even higher dispersions
(0.5 -0.3 Angstroms/pixel). The lower resolution mode is useful for
stellar classification and obtaining spectra of planetary nebula. In
the high-resolution modes, many absorption lines are visible of atoms,
ions and simple molecules. In addition, one can measure the Doppler
shift of absorption and emission lines to determine velocities of
approach or recession of objects along with rotation velocities of
stars and planets. Our particular interests have focused on identifying
chemical elements/ions and compounds in the atmospheres of stars and
nebulae. The resolution and sensitivity of the instrument is such
that we have been able to identify the unstable element technetium
in certain S and C type stars along with anomalous 12C/13C ratios as
measured by absorption bands of diatomic carbon (C2). Measurements
of certain line intensity ratios in planetary nebula allows for the
calculation of both the nebula temperature and electron density. Our
presentation will go into detail on the use of the SGS, its calibration
and some of the kinds of measurements that can be made with an amateur
sized telescope equipped with such "off the shelf" instrument.

---------------------------------------------------------
Title: Precision Photometry of Long Period Variable Stars
Authors: Mais, D. E.; Bhatia, A.; Stencel, R. E.; Richards, D.
2004AAS...204.0709M Altcode: 2004BAAS...36..786M
Recently, evidence has been accumulating to suggest that Mira variables
may go through flare up stages which result in brightening on the
order of several tenths of a magnitude or more, and may last hours to
days in length (Schaefer 1991, Maffei and Tosti 1995 and de Laverny
1998). Very little is known about these events, indeed it is not clear
that these events are real. If they are real events, the spectroscopic
changes, which occur during these flare-up episodes, remain relatively
unexplored. This project was initiated in order to monitor a group of
program stars of these classes in the V and R photometric bands in
the hopes of "catching" some of these stars during these flare ups,
thus offering confirmation to their reality and to be able to conduct
spectral analysis of the flare-ups in real time and compare these
spectra to the non-flare spectra. During the course of the past year,
nearly 98 program stars have been monitored to address the potential
flare up episodes. These include 25 M-type, 16-S type and 57 C-type
Mira's. However, this more careful monitoring appears to not detect
comparable behavior in similar stars near their minimum light, but
rather exhibits a "Cepheid bump-like" phenomenon in several cases
after minimum light, typically around phase 0.6-0.8 (cf. Melikian,
1999). Interpretation as an intermittent overtone pulsation is provided,
and its effect on dust production discussed. We acknowledge support
from the estate of William Herschel Womble, for the University of
Denver astronomers participating in this effort.

---------------------------------------------------------
Title: Mira Variable Stars: Spectroscopic and Photometric Monitoring
of this broad class of Long Term Variable and Highly Evolved Stars.
Authors: Mais, D. E.; Stencel, R. E.; Richards, D.
2004AAS...204.8502M Altcode: 2004BAAS...36R.817M
Mira variable stars are a broad class long period variable stars,
which encompass spectroscopic classes of type M, S and C. Recently,
evidence has accumulated to suggest that Mira variables may go through
flare up stages which result in brightening on the order of several
tenths of a magnitude or more and may last hours to days in length
(Schaefer, B., 1991, Maffei, P., and Tosti, G., 1995 and de Laverny,
P., et. al., 1998). Very little is known about these events, indeed
it is not clear that these events are real. If they are real events,
the spectroscopic changes, which occur during these flare-up episodes,
remain relatively unexplored. This project was initiated in order
to monitor a group of program stars of these classes in the V and R
photometric bands in the hopes of "catching" some of these stars during
one of these flare ups, thus offering confirmation to their reality
and to be able to conduct spectral analysis of the flare-ups in real
time and compare these spectra to the non-flare spectra. Monitoring
of a group of these stars was carried out using equipment readily
available to amateurs, both in the way of telescopes, CCD cameras and
software. Commercially available software was used to control telescope
pointing and image acquisition with different filters. In addition, in
order to make analysis as real time as possible, scripts for reduction
of images were created to automatically perform astrometric solutions
and determine magnitudes of the variables from standard stars in the
field. During the course of the past year, nearly 98 program stars
have been monitored to address the potential flare up episodes. These
include 25 M-type, 16-S type and 57 C-type Mira's. Precision of these
measurements are in the milli-magnitude regime. This talk will describe
the results obtained so far.

---------------------------------------------------------
Title: NASA's High Energy Vision: Chandra and the X-Ray Universe
Authors: Mais, D. E.; Stencel, R. E.; Richards, D.
2004SASS...23...81M Altcode:
The Chandra X-Ray Observatory is the most sophisticated X-ray
observatory launched by NASA. Chandra is designed to observe X-rays
from high-energy regions of the universe, such as the remnants of
supernovae explosions, col- liding galaxies, black holes, pulsars,
neutron stars, quasars, and X-ray bi- nary stars. The spectacular
results from the first five years of Chandra ob- servations are changing
and redefining theories with each observation. Every exciting new image
shows glimpses of such exotic phenomena as super-massive black holes,
surprising black hole activity in old galaxies, rivers of grav- ity
that define the cosmic landscape, unexpected x-ray activity in proto-
stars and failed stars, puzzling distributions of elements in supernovae
remnants, the sound waves from a super-massive black hole, and the
even the tantalizing possibility of an entirely new form of matter -
the strange quark star. On September 14, 2000, triggered by alerts from
amateur astron- omers worldwide, Chandra observed the outburst of the
brightest northern dwarf nova SS Cygni. The cooperation of hundreds
of amateur variable star astronomers and the Chandra X-Ray scientists
and spacecraft specialists pro- vided proof that the collaboration
of amateur and professional astronomers is a powerful tool to study
cosmic phenomena.

---------------------------------------------------------
Title: Mira Variable Stars: Spectroscopic and Photometric Monitoring
of this Broad Class of Long Term Variable and Highly Evolved Stars-II
Authors: Mais, D. E.; Stencel, R. E.; Richards, D.
2004SASS...23...71M Altcode:
We have been monitoring Mira variable stars, which encompass
spectroscopic classes of type M, S and C during the past year and a
half. These stars are closely related in terms of their long term
variability, position on the Hertzsprung-Russell diagram their
intermediate mass (from ~0.8 to ~8 solar mass) and the fact that
class M evolves into the S and C type stars. These stars are very
interesting from the stand point that they can produce heavy elements
beyond iron and also carbon which can appear at the surface of these
stars during periods in their evolution. In addition, it is suspected
that these type stars, in particular, the M type Mira's can flare
up over periods of hours to days by several tenths of a magnitude
or more. The spectroscopic changes, which occur during these flare
episodes, ultimately driven by core burning evolution, remain relatively
unexplored. This project was initiated in order to monitor a group of
program stars of these classes in the V and R photometric bands in
the hopes of catching some of these stars during one of these flare
ups and thus to be able to conduct spectral analysis of the flare-ups
in real time and compare these spectra to the non-flare spectra. This
paper will give an update of the project and describe the strategies
being employed to monitor these stars.

---------------------------------------------------------
Title: Nineteenth Century Origins of Denver Astronomy
Authors: Winter, B.; Howe, H. J.; Stencel, R. E.
2004AAS...204.5702W Altcode: 2004BAAS...36..763W
During the past decade, new light has been shed on the origins of
Chamberlin Observatory, located in south Denver, and its 0.5 meter
aperture Clark-Saegmuller refractor. The new information derives from a
set of daily diaries maintained by Herbert Alonzo Howe 1880-1926. He was
the first astronomer at the University of Denver. Having examined this
new historic record, we have compiled the life and times of Professor
Howe and the -then new- observatory into a biography entitled "Denver's
Pioneer Astronomer" and will present vignettes from the book in this
poster paper. We are grateful to the estate of William Herschel Womble
for support of Astronomy efforts at the University of Denver.

---------------------------------------------------------
Title: 2MASS and IRAS Discovery of Red Supergiant Stars in OB Star
Associations
Authors: McNabb, I. A.; Stencel, R. E.
2004AAS...204.4502M Altcode: 2004BAAS...36..734M
In 1992, Garmany and Stencel published a survey of northern Milky Way OB
star associations spanning galactic longitudes 55 to 150 degrees, based
on visual and IRAS data sources [A&amp;AS 94: 211]. This compilation
introduced a number of candidate red supergiant star members to these
groups. Subsequently, 2MASS and reprocessed IRAS datasets have become
available, making re-evaluation of these preliminary results timely. We
report here the beginning of the efforts to confirm membership of
candidate evolved stars in these groups, as well as examine facets
of the structure and evolutionary record seen in these data. We
acknowledge the estate of William Herschel Womble for partial support
of this effort.

---------------------------------------------------------
Title: Instrumentation Development for Mid-IR Imaging
Spectro-polarimetry
Authors: Jurgenson, C. A.; Stencel, R. E.
2004AAS...204.1005J Altcode: 2004BAAS...36..673J
SIFTIR, the Spectro-polarimetric Imaging Fourier Transform spectrometer
for the InfraRed, is currently being developed at the University
of Denver for studies on the atmospheres of evolved stars. With
a maximum resolution of 2000 at 10 μ m, SIFTIR will be able to
resolve, specifically, the 9.7 μ m silicate feature, and the 11.2
μ m crystalline olivine feature. To accomplish this, an FTS will
be used with TNTCAM2, an imaging polarimeter. The full spectral
range of the instrument will be between 2-15 μ m, with selectable
bandpass filters and polarimetry only available between 8-15 μ m
due to waveplate/wiregrid characteristics. Control and calibration
of SIFTIR will be discussed, as well as preliminary results with the
FTS component. We acknowledge the estate of William Herschel Womble,
Sigma Xi grants in aid of research, and NASA's Rocky Mountain Space
Grant for support of this endeavor.

---------------------------------------------------------
Title: Progress Report on the Student Astronomy Lab telescope at
the University of Denver
Authors: Mellon, R. R.; Scheld, D. L.; Stencel, R. E.
2004AAS...204.1002M Altcode: 2004BAAS...36..672M
Integration and test activities associated with a new telescope for
the Student Astronomy Laboratory (SAL) at the University of Denver are
currently nearing completion on the main Denver campus. The 76.2-cm
aperture SAL telescope incorporates novel design features, enabling it
to operate as the first professional astronomical teaching and research
telescope expressly designed to include use by wheelchair accommodated
observers. The telescope is located 23-m above ground level on the fifth
floor roof of the Space Sciences Laboratory building and is supported
by a steel tower structure from the fourth floor support beams in the NW
corner of the building. An afocal Mersenne optical configuration is used
to send a collimated beam through the RA and DEC axes of the mounting,
through a figure-4 mirror set, and thence vertically downward into a
periscope, where condensing optics form an image plane accessible to
visible band and IR detectors. A technical description of the telescope
installation is provided, along with photographs illustrating key design
features. Wheelchair-bound observers can enter the fourth floor lab
and make use of an eye-level eyepiece when suitable periscope optics
are installed. The SAL installation will be accessible to visitors by
pre-arrangement with DU Observatories during the Denver AAS meeting
[#204]. We are grateful to Glenn Montgpomery, Sarah Nelson and the
estate of William Herschel Womble for their support of this University
of Denver astronomy project.

---------------------------------------------------------
Title: Interferometric Studies of Dust Formation in the Red Supergiant
Star S Persei
Authors: Stencel, R. E.; Jurgenson, C. A.; Ostrowski-Fukuda, T. A.
2004IAUS..219..925S Altcode: 2003IAUS..219E.124S
Few methods are as effective as interferometry for probing the dust
formation regions around evolved stars at high spatial scales. Using
multi-epoch VLBA monitoring observations of 43 GHz SiO (v=1J=1-0)
maser emission Ostrowski-Fukuda et al.(2003 AAS meeting 201 poster
115) found that the red supergiant S Persei exhibits clumpy and
variable SiO maser spots in a broken elongated (elliptical) ring
approximately 23 by 16 milli-arcsec with the semi-major axis oriented
in the northeast-southwest (NE-SW) direction. Independent K band
interferometry (PTI group Creech-Eakman and Thompson) obtained a
limb darkened diameter for S Per of 5 mas similarly oriented. These
facts combined suggest that the masers constitute a standing wave
phenomenon associated with rapid particle formation at ~2 stellar
radii. We present these results and a model for this phenomenon.

---------------------------------------------------------
Title: Microvariability and Long-Term Variability of Four Blazars
Authors: Howard, Emily S.; Webb, James R.; Pollock, Joseph T.; Stencel,
Robert E.
2004AJ....127...17H Altcode:
Long-term light curves of four blazars, Mrk 421, Mrk 501, 3C 345, and
BL Lacertae were constructed using archival data and supplemented
with new observations. The occurrences of microvariability are
correlated temporally with long-term optical activity in the light
curves. Although the statistics are not conclusive, we find evidence
that microvariability is correlated with rapid flux changes rather
than specific flux levels. We discuss the implications of these results
for quasar variability models.

---------------------------------------------------------
Title: Metallicity and Infrared Debris disks: ISO Evidence for
Anti-correlation
Authors: Edwards, M. L.; Stencel, R. E.
2003csss...12..754E Altcode:
University of Denver (DU) executed a NASA key project that acquired a
magnitude limited sample of 66 stars from the Infrared Space Observatory
(ISO) mission, looking for infrared signatures indicative of planet
formation around nearby stars. Age and abundance data has been obtained
from the literature to supplement the infrared photometry performed
by the ISO satellite in the interest of discovering correlations
between infrared excesses, ages, and chemical abundances. There are
two possible scenarios other than the null possibility where disk
stars are identical chemically to non-disk stars. Either the disk
will enhance the metal content of the star through accretion or it
will lower the metalicity of the parent star by acting as a sink for
iron and other heavy elements. The most likely scenario is that young
stars with disks will show evidence of a low abundance pattern as the
heavy elements in the protostellar cloud form regions of higher density,
thus making their own regions of gravitational collapse independent of
the main stellar mass. Then as these planetesimals collapse into the
parent star the abundances return to more normal levels as time passes,
perhaps even increasing the abundances to unusually high levels. The
strongest conclusion from the University of Denver ISO sample is
that infrared excesses decrease slowly over time regardless of sample
choice. This means that dust disks are persistent features of a star,
so persistent that a mechanism for replenishing the dust is necessary
in order to explain the strength of dust found around older stars.

---------------------------------------------------------
Title: Microvariability among Selected Long Period Variables
Authors: Stencel, R. E.; Ostrowski-Fukuda, T. A.; Jurgenson, C. A.;
Phillips, A.
2003csss...12.1074S Altcode:
DeLaverny et al. (1998) reported short-term brightness variations in
15 percent of the 250 Mira or Long Period Variable stars surveyed using
the HIPPARCOS satellite, with the broadband 340 to 890 nm Hp filter. The
abrupt variations ranged 0.2 to 1.1 magnitudes, on time-scales between
2 to 100 hours, with a preponderance found nearer Mira minimum light
phases. However, the sampling frequency was extremely sparse and
requires confirmation because of potentially important dust-formation
physics that can be revealed. We report here ground-based photometric
observations of several of these objects that support and tend to
confirm, the deLaverny et al. findings. In our observations, four out
of five Miras sampled (XZ Her, HO Lyr, AU Cyg and AM Cyg) were found
to have significant fluctuations over these same short time-scales
(at 95% confidence level and higher), based on analysis of photometric
variance, and F-tests. Interpretation of this micro-variation is offered
in terms of dust formation episodes in the upper atmosphere of the star,
and tests using interferometric visibility curves are proposed.

---------------------------------------------------------
Title: Mira Variable Stars: Spectroscopic and Photometric Monitoring
of this Broad Class of Long Term Variable and Highly Evolved Stars
Authors: Mais, D. E.; Stencel, R. E.; Richards, D.
2003SASS...22...55M Altcode:
Mira variable stars are a broad class of stars, which encompass
spectroscopic classes of type M, S and C. These stars are closely
related in terms of their long term variability, position on the
Hertzsprung-Russell diagram their intermediate mass (from ~0.8 to
~8 solar mass) and the fact that class M evolves into the S and
C type stars as certain stages of shell burning around the core
proceeds. These shell burning episodes produce heavy elements beyond
iron and also carbon which can appear at the surface of these stars
during periods of convective instability resulting in greatly enhanced
abundances of elements beyond the iron group and an increase in the
carbon/oxygen ratio. In addition, it is suspected that these type
stars, in particular, the M type Mira's can flare up over periods
of hours to days by several tenths of a mag- nitude or more. The
spectroscopic changes, which occur during these flare ep- isodes,
ultimately driven by core burning evolution, remain relatively un-
explored. This project was initiated in order to monitor a group of
program stars of these classes in the V and R photometric bands in the
hopes of "catching" some of these stars during one of these flare ups
and thus to be able to conduct spectral analysis of the flare-ups in
real time and compare these spectra to the non-flare spectra. This talk
will describe the back- ground of these type stars, in particular, their
evolutionary history and their spectroscopic differences. In addition,
the strategies and initiation of this project will be described.

---------------------------------------------------------
Title: Teaching a College Course on Light Pollution
Authors: Stencel, R. E.
2003AAS...202.1014S Altcode: 2003BAAS...35..713S
Most introductory astronomy classes mention light pollution as a problem
for observers of the night sky. Cursory coverage leaves students with
an acquaintance of the problem, but they are rarely taught to recognize
and deal with the practical aspects of energy waste, glare, trespass
and choice of alternative lighting fixtures. Recently, I ran a 10 week
Honors seminar at the University of Denver entitled "Environmental
and Social Consequences of Artificial Light" during winter term,
2003, which attracted a variety of arts, humanities and business
majors. The course was facilitated greatly by the suite of online
materials available at the International Darksky Association [IDA]
website [www.darksky.org/resources/library.html], including the Lighting
Code Handbook plus access to international, national and local lighting
regulations and legislation. The students were assigned to review and
summarize self-selected items by state, and present written summaries
for in-class discussion purposes. We also had a guest lecture by a local
IDA activist, Nancy Clanton, and considered involving other speakers
from local CPTED and Planning departments. Slide mounted transparent
diffraction gratings were distributed to help students observe spectra
from different types of lights at night. After the students learned
what the problems are, and the basic remedies, student-driven inquiry
lead to a number of fascinating questions that I hope will help them
to remain aware and active in this arena. Details are posted at my
website [www.du.edu/ rstencel] but some of the key points include: (1)
To whom does the night sky belong? Are economic interests sufficient
to justify invasion of one's dark space? (2) Do we accept disruption
of our circadian rhythms in the name of "progress", even if research
now suggests linkage between melatonin problems and excessive levels
of artificial lighting at night? (3) Does the loss of access to viewing
the Milky Way pose risks to the imagination of younger generations? (4)
Just because lighting is amenable to engineering solutions, does it
merit attention in comparison with other pressing problems of our
time? In my opinion, the recent flurry of better lighting regulation
is not enough, and dark skies will continue to be degraded, if we
cannot convince our younger citizens of the need for vigilance and
activism on this issue. Please contact the author for any assistance
needed in starting, or experiences related to, similar classes. My
thanks to the estate of William Herschel Womble, IDA and Ms. Clanton,
for support that made this class possible.

---------------------------------------------------------
Title: Mid-infrared polarimetry of axi-symmetric mass loss and the
shaping of NGC 7027
Authors: Jurgenson, Colby A.; Stencel, Robert E.
2003ASSL..283..253J Altcode: 2003mlps.work..253J
We obtained the first ever mid-IR polarimetry maps of the
axi-symmetric planetary nebula NGC 7027. The observations were
taken with the University of Denver's TNTCAM2 at the Wyoming Infrared
Observatory's (WIRO) 2.3 m aperture telescope, providing 0.78 arcsecond
resolution. Polarization maps in the mid-IR can help constrain
the properties and alignment of dust grains in the circumstellar
environment.

---------------------------------------------------------
Title: Afocal Mersenne telescope for teaching and research
Authors: Mellon, Russell R.; Scheld, Daniel L.; Stencel, Robert E.
2003SPIE.4837...51M Altcode:
A new 76.2-cm aperture handicapped accessible telescope exhibiting novel
design features is nearing completion for installation within the Space
Sciences Laboratory building on the main campus of the University of
Denver. This Student Astronomy Laboratory (SAL) instrument incorporates
a Coude" optical path working in combination with a vertical periscope
to bring the optical beam to a location inside a 4th floor
laboratory room, where visible and IR observations can be made. The
primary and secondary mirrors are arranged in the afocal Mersenne
configuration to provide a collimated, compacted beam that is folded
through the rotating Right Ascension and Declination axes of the
telescope mounting. A pair of optical flats then directs the compacted
beam downward into the indoor laboratory, through visible or IR band
auxiliary condensing telescopes, to locations where visual observers
(including those in wheelchairs) or visible or IR instruments can be
accommodated. The mounting uses large inner race diameter preloaded
turntable bearings in each axis and provides a rotary stage at the
payload flange to cancel image rotation associated with the Coude"
configuration. Long baseline interferometry is planned between the
SAL and the DU Meyer-Womble Observatory on Mt. Evans, Colorado.

---------------------------------------------------------
Title: The Student Telescope Network (STN) experiment
Authors: Hannahoe, Ryan M.; Stencel, Robert E.; Bisque, Steve;
Rice, Mike
2003SPIE.4796..255H Altcode:
Several factors make observational astronomy difficult for pre-college
students and teachers. (1) not many schools have teachers trained
to use and maintain astronomy equipment; (2) school usually happens
during the day and observing normally is a night-time activity; (3)
the scourge of light pollution has hidden the stars from many students
living in or near cities; (4) there is a general lack of access to
expertise when needed. In addition, physically disabled students cannot
climb ladders, to access the telescope eyepiece. Internet access to
computer-controlled telescopes equipped with digital cameras can solve
many of these difficulties. This enables students and their teachers
to access well-maintained, robust Internet-controllable telescopes in
dark-site locations and to consult more readily with experts. We present
the results of technical solutions to Internet-control of telescopes,
by Software Bisque, the New Mexico Skies Guest Observatory and the Youth
Activities Committee of the Astronomical League in collaboration with
Denver University Astronomy. We jointly submitted a funding proposal
to the Institute for Connecting Science Research to the Classroom,
and conducted a pilot program allowing high school students to access a
CCD-equipped, accurately-pointing and tracking telescope, controllable
over the Web, with a user-friendly skymap browser tool. With suitably
placed telescopes worldwide, observing from the classroom in daylight
will become feasible, as we have demonstrated with Australian and
Eurasian student users of the New Mexico Skies Internet telescope. We
report here on a three-month pilot project exploring this solution,
conducted Feb-May 2002. User interest proved phenomenal, while user
statistics proved diverse and there were distinct lessons learned about
how to enhance student participation in the research process. We thank
the Institute for Connecting Science Research to the Classroom for a
grant to the University of Denver in partial support of this effort,
and acknowleedge in-kind support from the estate of William Herschel
Womble. Details at website www.du.edu/~rstencel/stn.htm.

---------------------------------------------------------
Title: Mid-Infrared Imaging Polarimetry of NGC 7027
Authors: Jurgenson, C. A.; Stencel, R. E.; Theil, D. S.; Klebe, D. I.;
Ueta, T.
2003ApJ...582L..35J Altcode:
We present mid-infrared imaging polarization vector diagrams of the
young planetary nebula NGC 7027. The observations were taken with the
University of Denver's Ten and Twenty μm Camera at the Wyoming Infrared
Observatory. Individual wave plate position images have been deconvolved
to remove the instrument point-spread function. The deconvolved 9-13 μm
intensity images, in 1 μm wide bandpasses, show a bright ellipsoidal
double-peaked core surrounded by a region of fainter emission,
consistent with recent continuum images in the near-infrared. The
vector diagrams show significant changes in polarization position
angle with wavelength, suggesting scattering from large grains.

---------------------------------------------------------
Title: Teaching with Internet Telescopes: Some Lessons Learned
Authors: Stencel, Robert
2003IAUSS...4E..42S Altcode:
Observational astronomy is often difficult for pre-college students and
teachers because: (1) school occurs in daytime and visual observing
at night; (2) light pollution hides the stars from students living
in cities; (3) few schools have teachers trained to use and maintain
astronomy equipment; (4) there is lack of access to expertise when
needed; (5) physically disabled students cannot easily access a
telescope eypiece. Internet access to computer controlled telescopes
with digital cameras can solve many of these difficulties. The
Web enables students and teachers to access well-maintained
internet-controllable telescopes at dark-site locations and to consult
more readily with experts. This paper reports on a three-month pilot
project exploring this situation conducted Feb-May 2002 which allowed
high school students to access a CCD-equipped accurately-pointing and
tracking telescope located in New Mexico controllable over the Web with
a user-friendly skymap browser tool. User interest proved phenomenal
and user statistics proved diverse. There were distinct lessons
learned about how to enhance student participation in the research
process. Details available at website www.du.edu/~rstencel/stn.htm. We
thank the ICSRC for a grant to Denver University and acknowledge
in-kind support from the estate of William Herschel Womble.

---------------------------------------------------------
Title: Circumstellar Aerosols: Interferometry and Spectro-polarimetry
Authors: Stencel, Robert; Jurgenson, Colby
2003asdu.confE.104S Altcode:
Analysis of the production and dispersal of solids in the atmospheres
of evolved stars benefits from high spatial, spectral and polarimetric
resolution. We present recent results [S Persei and NGC 7027] and
outline instrumentation opportunities in spectro-polarimetry. The red
supergiant, S Persei, has been shown to exhibit a clumped outflow at
the 8 milli-arcsec scale, via VLBA monitoring observations in 43GHz
SiO (v = 1,J = 1-0) maser emission (Ostrowski-Fukuda et al. 2003 AAS
meeting 201, poster 115). Independent K band interferometry (PTI group,
Creech-Eakman and Thompson, private comm.) obtained a limb darkened
diameter for S Per of 5 mas. These facts combined suggest that the
masers constitute a standing wave phenomenon associated with rapid
particle formation at 2 stellar radii. Furthermore, the planetary
nebula, NGC 7027, is composed of a spheroidal core ionized region,
surrounded by a ring-like photo-dissociation region, and extended
hourglass nebulosity. Recently, Jurgenson et al (2003 ApJ) obtained
mid-infrared narrow band polarimetry, revealing systematic differences
between PAH emission and dust continuum behavior, varying spatially
across the nebula. These differences are suggestive of changes in
particle size and orientation. To exploit the ensemble of discovery
made possible with these methods, we are designing and plan to build
a mid-infrared spectro-polarimeter [Spectro-polarimetric Imaging -
Fourier Transforms for the InfraRed, SIFTIR].

---------------------------------------------------------
Title: Movie and Description of the 43-GHz SiO Masers in S Per
Authors: Ostrowski-Fukuda, T. A.; Stencel, R. E.; Kemball, A.; Harper,
G.; Diamond, P. J.
2002AAS...20111509O Altcode: 2002BAAS...34.1291O
The Very Long Baseline Array (VLBA) has been used to monitor the 43 GHz
SiO (v=1,J=1-0) maser emission in the red supergiant star, S Persei,
monthly since 1999. SiO masers act as probes of the gas motions and
magnetic fields of this star allowing us to investigate its extended
atmosphere. Here we report the preliminary results of this on-going
project. Many epochs of data have been reduced and pieced together
in a time-lapse movie fashion, allowing us to follow the motions
of the individual maser regions. The motion of twenty-three maser
spots are followed through the selected epochs, revealing velocity
and ring structure information. Proper motions are detected by using
a pairwise separation test and the average expansion velocity will be
discussed. Finally, the relation between the pulsational phase of the
star and the SiO maser emission will be discussed. The results of this
study provide the first SiO maser movie of a red supergiant star and
allow us to make a comparison between S Per, and Mira-type red giant
stars, such as TX Cam. This work is supported by the University of
Denver's Menzel Scholarship Fund and in conjunction with the National
Radio Astronomy Observatory, Socorro, NM.

---------------------------------------------------------
Title: SiO Maser Emission in S Per - The Movie
Authors: Ostrowski-Fukuda, T. A.; Stencel, R. E.; Kemball, A.; Diamond,
P. J.
2002AAS...200.7409O Altcode: 2002BAAS...34..771O
The Very Long Baseline Array (VLBA) has been used to monitor the
43-GHz SiO (v=1, J=1-0) maser emission in the supergiant star S Persei
monthly since 1999. SiO masers act as probes of the gas motions and
magnetic fields of this star allowing us to investigate its extended
atmosphere. Here we report the continuing results of this on-going
project. Many epochs of data have been reduced and pieced together in
a time-lapse movie fashion, allowing us to follow the motions of the
individual maser regions. The trajectories and velocities of the SiO
masers are investigated. Our findings from S Per are compared to TX Cam,
which has been studied in the same fashion. We are most interested in
learning out about the structure, time evolution, mass-loss process,
magnetic field structure, and the physical conditions in the inner
regions of these types of stars. Just as in the case of TX Cam, we
have found that our images reveal that the mass loss may not be the
same for all regions of the star's surface. This work is supported
by the Menzel Scholarship Fund at the University of Denver, and in
conjunction with the National Radio Astronomy Observatory, Socorro, NM.

---------------------------------------------------------
Title: Hosting the Student Telescope Network First Site
Authors: Rice, M.; Bisque, S. T. M. D.; Stencel, R. E.
2002AAS...200.4704R Altcode: 2002BAAS...34..718R
The demonstration site for the Student Telescope Network, and for
the first practical public-use Internet observatory, as powered
by iBisque software, is at New Mexico Skies in southern New Mexico
(www.nmskies.com). The observatory site, located approximately 14
miles northeast of the Apache Point Observatory and the Sunspot
National Solar Observatory, is at 2,225 meters elevation in the
southern Sacramento Mountains of New Mexico. It has very dark
transparent skies, excellent weather conditions, good seeing and a
high proportion of clear photometric nights. The Internet observatory
pod concept includes placing multiple telescopes (as many as twelve),
in each of several 32-foot roll-off roof observatories. The 14 to 16
inch aperture telescopes, mounted on accurately pointing and tracking
Bisque "Paramounts" (www.bisque.com), plus KAF-1001E CCD cameras,
are controlled with a browser-based sky-map GUI (patent pending)
control system also developed by Software Bisque. We provide detail
on the concept and its implementation. As of mid-March, 2002, the
first demonstration telescope has been operating nightly for about
60 days. Over 420 users have registered on the telescope server, more
than 2,000 images have been taken and their FITS files downloaded to
users' computers all over the world. In this and the companion poster,
we report our experiences over the period of the February-May (2002)
trial period, including technical challenges and performance measures on
the Internet observatory's operations. We further detail lessons learned
for future development of browser-based Internet observatories for high
school/college level instructional use, and lessons applicable to the
use of Internet-based telescopes for serious astronomical research as
well. We thank the Institute for Connecting Science Research to the
Classroom for a grant to the University of Denver in support of this
Internet telescope services pilot project.

---------------------------------------------------------
Title: The Student Telescope Network (STN) Experiment
Authors: Stencel, R. E.; Harland, H. A.; Hannahoe, R.; Bisque,
S. T. M. D.; Rice, M.
2002AAS...200.4705S Altcode: 2002BAAS...34..719S
Several factors make observational astronomy difficult for pre-college
students and teachers: (1) school happens during the day and observing
is normally a night-time activity; (2) not many schools have teachers
comfortable with astronomy equipment; (3) the scourge of light pollution
has hidden the stars from many students living in or near cities; (4)
there is a general lack of access to expertise when needed. Electronic
access to computer-controlled telescopes equipped with digital cameras
can solve some these difficulties by enabling students and their
teachers to access internet-controllable telescopes, and consult more
readily with experts. We report on a happy convergence of technical
solutions to internet-control of telescopes by Software Bisque
(www.bisque.com), the opening of New Mexico Skies guest observatory
(www.nmskies.com) and outreach by the Youth Astronomy Committee of the
Astronomical League. Recognizing the opportunity, we jointly proposed
to the Institute for Connecting Science Research to the Classroom,
to conduct a pilot program allowing high school students to access a
CCD-equipped, accurately pointing and tracking telescope, controllable
over the web, with a user-friendly sky-map browser tool. As we have
demonstrated with Australian and Eurasian student participants, that
suitably placed telescopes worldwide can make observing from the
classroom/home in daylight feasible. In this and a related poster,
we report on a three month pilot project conducted Feb-May 2002,
including user interest and statistics, lessons learned, and ideas on
how to enhance student participation in the research process. We thank
the Institute for Connecting Science Research to the Classroom for a
grant to the University of Denver in partial support of this effort.

---------------------------------------------------------
Title: Paramount Tracking and Pointing Accuracy Plus Browser Control:
As Applied in the Student Telescope Network and Beyond
Authors: Bisque, S.; Rice, M.; Stencel, R. E.
2002AAS...200.4706B Altcode: 2002BAAS...34..719B
Reducing the complexities of research grade CCD imaging to a
few simple mouse clicks required the convergence of numerous
technologies that been in development for over a decade. The
operational site "iBisque at New Mexico Skies" demonstrates the
convergence of various telescope technologies resulting in multiple
remotely accessible research grade systems, accessible via a web
browser. Pointing a telescope with sufficient accuracy to place the
target object accurately on the CCD array requires a precision robotic
telescope mount coupled with telescope pointing software (TPoint:
www.tpsoft.demon.co.uk). Maintaining accurate tracking during several
minute unguided exposures is accomplished by manufacturing precision
worm/gears sets that exhibit less than 5 arc-seconds of periodic
error peak-to-peak. Again TPoint software is employed for providing
information on the telescope errors and dynamics during the exposure
(i.e. tube flexure, refraction, polar misalignment etc.). Finally, the
remotely capable robotic telescope system is made accessible via any
web browser using Browser Astronomy Software (www.bisque.com). In this
and the companion posters, we further describe the software technologies
and off-the-shelf instrumentation used to create the first interactive,
browser-controlled observatory. Experience gained and lessons learned
with the Student Telescope Network (STN) pilot project now enable this
internet telescope service to be available to interested astronomy
researchers and educators.

---------------------------------------------------------
Title: Mid-IR Polarimetry of Axi-Symmetric Mass Loss in the Shaping
of Planetary Nebula NGC 7027
Authors: Jurgenson, C. A.; Stencel, R. E.; Ueta, T.
2002AAS...200.1512J Altcode: 2002BAAS...34..666J
We present the first ever mid-IR imaging polarimetry maps of the
axi-symmetric planetary nebula NGC 7027. The observations were taken
with the University of Denver's TNTCAM II at the Wyoming Infrared
Observatory's 2.3-meter aperture telescope during June 2001. The
polarimetry maps were produced in one micron wide band passes
centered at 9.756, 10.598, 11.658 and 12.598 microns. An HST/WFPC2
image of NGC 7027 shows an ionized elliptical ring surrounded by an
extended region of lower surface brightness whose radial profiles
are suggestive of the presence of blow out regions. While HST/NICMOS
images have suggested that emission from this region is not only in
the form of scattered light, but possibly due to thermal dust emission
(Latter et al. 2000). Polarization maps in the mid-IR present unique
opportunities to reveal the properties and alignment of dust grains in
the circumstellar environment. We compare our polariztion maps with
those produced by theoretical models in which grain alignment occurs
due to various magnetic field configurations. Our models are based
on work done by Aitken et al. (2002). We acknowledge partial support
from NSF grant AST-9724506 to build the mid-IR imaging polarimeter,
and the estate of William Herschel Womble.

---------------------------------------------------------
Title: Deep Inside OMC2
Authors: Jones, T. J.; Kelbe, D. I.; Creech-Eakman, M. J.; Stencel, R.
2001AAS...199.0405J Altcode: 2001BAAS...33.1306J
We present deep 10 micron imaging and near IR imaging polarimetry of the
inner core of OMC2. We find no evidence for new sources at 10 microns
not found at shorter wavelengths. The faintest stars, none of which
have yet reached the main sequence, have all been detected. Imaging
polarimetry shows significant departure from centrosymmetric scattering
about IRS1 along a narrow cone extending from the star.

---------------------------------------------------------
Title: Efforts to Verify Micro-variability among HIPPARCOS-selected
AGB Stars
Authors: Stencel, R. E.; Phillips, A.; Jurgenson, C.; Ostrowski-Fukuda,
T.
2001AAS...199.9219S Altcode: 2001BAAS...33R1443S
De Laverny et al. (1998 A&amp; A) reported short-term brightness
variations in 15 percent of the 250 Mira or Long Period Variable stars
surveyed using the HIPPARCOS satellite, with the broadband 340 to 890
nm Hp filter. The abrupt variations ranged 0.2 to 1.1 magnitudes,
on time-scales between 2 to 100 hours, with a preponderance found
nearer Mira minimum light phases. However, the sampling frequency
was extremely sparse and requires confirmation because of potentially
important dust-formation physics that can be revealed. We report here
ground-based photometric observations of several of these objects that
support and tend to confirm, the de Laverny et al. findings. Initially,
our observations indicated that four out of five Miras sampled (XZ Her,
HO Lyr, AU Cyg and AM Cyg) were found to have low level but significant
fluctuations over these same short time-scales (at 95% confidence level
and higher), based on analysis of photometric variance, and F-tests
(see Stencel et al. 2001 in Proceedings of Cool Stars 12). However,
more careful observations at Mt. Evans observatory during summer 2001
failed to detect comparable behavior in similar stars near minimum
light. Further observations are needed to confirm and delineate this
effect among long period variables. Interpretation of micro-variation
is offered in terms of dust formation episodes in the upper atmosphere
of the star, and tests using interferometric visibility curves are
proposed. We are pleased to acknowledge support for this work from
the estate of William Herschel Womble and the University of Denver.

---------------------------------------------------------
Title: Detailed Monitoring of the 43-GHz SiO Maser Emission in S Per
Authors: Ostrowski-Fukuda, T. A.; Kemball, A. J.; Stencel, R. E.
2001AAS...199.9211O Altcode: 2001BAAS...33.1442O
We report the preliminary results of a 3 year project to investigate
the processes of SiO masers (v=1, J=1-0) in the extended atmosphere
of S Per. Using the Very Long Baseline Array (VLBA) at 43-GHz the SiO
masers act as probes of the gas motions and magnetic fields surrounding
this late-type supergiant. Several epochs have been reduced and pieced
together in a time-lapse movie fashion. This "preview" of the full
movie already allows us to follow the motions of the individual maser
regions. One of our main goals is to compare and contrast our findings
from S Per to other similar stars. We are most interested in learning
out about the structure, time evolution, mass-loss process, magnetic
field structure, and the physical conditions in the inner regions of
these types of stars. Just as in the case of TX Cam, (Diamond &amp;
Kemball, 1999), we have also found that our time-lapse images show
that the gas motions of S Per are not uniform around the star. This
allows us to also speculate that the rate of mass loss may not be the
same for all regions of the star's surface. This work is supported by
the University of Denver's Menzel Scholarship Fund and in conjunction
with the National Radio Astronomy Observatory, Socorro, NM.

---------------------------------------------------------
Title: Mid-IR Imaging and Polarimetry of Highly Evolved Objects
Authors: Jurgenson, C. A.; Stencel, R. E.; Theil, D. S.
2001AAS...19913701J Altcode: 2001BAAS...33.1511J
We present imaging and polarimetry observation results at selected
mid-IR wavelengths taken with the University of Denver's TNTCAM2 at
the Wyoming Infrared Observatory's 2.3 m aperture telescope. Post
AGB objects include the luminous blue variable AFGL 2298, CW Leo and
R CrB. Planetary Nebulae include the Butterfly Nebula M 2-9 and NGC
7027. The characteristics of spectral emission distribution, dust
emissivity and magnetic field orientation based on spatial intensity
distribution and polarization will be discussed. The objects were
chosen for their advanced state of stellar evolution and evidence of
resolved nebular structure. In reconstructing our chopped and nodded
images, we used a constrained least squares technique called the
projected Landweber Method based on work done by Bertero et al. PASP
(2000) 112;1121-1137 and the adaptation of the technique by Linz et
al. A&amp;A 2002 (in preparation). We acknowledge helpful conversations
with Craig Smith, and support for this work from NSF grant AST 9724506,
and from the estate of William Herschel Womble.

---------------------------------------------------------
Title: Early Results from TNTCAM2, a Mid-IR Imaging Polarimeter,
and Remote Internet Observing
Authors: Theil, D. S.; Edwards, M. E.; Jurgenson, C. A.; Klebe, D. I.;
Stencel, R. E.; Cash, J. L.; Martin, R. T.; Johnson, P. E.; Weger,
J. S.
2001AAS...198.0506T Altcode: 2001BAAS...33..791T
We present new science results from TNTCAM2 obtained at the WIRO 2.3
meter telescope. These include: (1) polarization maps of the BN object
and a section of M42 around the Trapezium that shows bow shocks; (2)
imaging and polarimetry of selected circumstellar shells of evolved
stars and planetary nebulae; (3) new mid-IR photometry of ISO selected
Vega-type stars showing a mid-infrared spectral energy excess, and (4)
attempts to detect proplyds in Orion. The photometry and polarimetry
of bright sources allows us to characterize the system performance in
terms of throughput of the optics and net system sensitivity, which
we compare to the sensitivity of TNTCAM1 at WIRO (S/N = 5 on an 8.0
magnitude 11.5μ m source (20 mJy) over a 30 minutes of coadded .03s
integrations). We also present the efficiency of the polarization
analyzer and a comparison of our polarization measurments of selected
bright objects with previous measurements in the mid-IR. We discuss
and demonstrate the remote use of TNTCAM2 on the Wyoming Infra-Red
Observatory (WIRO) telescope. The remote observer can connect to
the observatory computers from a variety of operating systems using
AT&amp;T's Virtual Network Computing software. Remote real-time
control of the telescope and TNTCAM2 have already been achieved from
the University of Denver over a standard ethernet connection through
WIRO's 10.5 Mbps microwave link. We thank Craig Smith for invaluable
suggestions and guidance in collecting and reducing polarimetry data in
the mid-IR. We acknowledge support under NSF grant AST-9724506 to the
University of Denver and NASA EPSCoR grant #NCC5-414 to the University
of Wyoming.

---------------------------------------------------------
Title: Ages and Abundances Among β Pictoris Stars
Authors: Edwards, Michael L.; Stencel, Robert E.
2001ASPC..245..133E Altcode: 2001aats.conf..133E
No abstract at ADS

---------------------------------------------------------
Title: ISOPHOT Mapping of Vega-type Circumstellar Dust
Authors: Fajardo-Acosta, S. B.; Backman, D. E.; Stencel, R. E.
2000ESASP.455...73F Altcode: 2000ibps.conf...73F
We searched for far-infrared (60 microns) extended emission, in the
form of circumstellar dust disks, in the maps of seven main-sequence
stars. Direct detection of circumstellar disks in these systems can
advance our understanding of the Vega phenomenon. We obtained 60 micron
maps with the PHOT C100 3 × 3-pixel far-infrared camera on-board
the Infrared Space Observatory (ISO), in the PHT32 microscanning
dedicated mapping mode. The spatial resolution of the maps is ≅
30”. The Vega-type stars we observed are γ Oph, α PsA, γ Tri, 61
Cyg A, τ1 Eri, τ Cet, and ɛ Eri. We compared the maps
of these systems with similar maps of the stars α Boo and α Aql,
which do not possess circumstellar dust. We discuss techniques to model
point-spread functions (PSFs) from the latter, and their subtraction
from our Vega-type stellar maps. We did not spatially resolve extended
emission in the maps of γ Oph, γ Tri, 61 Cyg A, τ1 Eri,
ɛ Eri, and τ Cet. The map of &amp;alpha, PsA definitely shows extended
emission as far as ~700 AU from the star, when compared with model PSFs.

---------------------------------------------------------
Title: Mid-Infrared Silicate Variation in Long-Period, Oxygen-Rich
Variable Stars
Authors: Creech-Eakman, M. J.; Stencel, R. E.
2000IAUS..177..527C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Prospects for Mid-infrared Imaging and Polarimetry with
Denver's TNTCAM2
Authors: Stencel, Robert E.
2000ASPC..199..101S Altcode: 2000apn..conf..101S
Structural detail of asymmetric planetary nebulae is conditioned by
the mass loss history of central stars (and their planets?). Much of
this outlying structure can be mapped with thermal infrared imaging and
polarimetry - both of which are capabilities designed into our second
generation, NSF-sponsored Ten and Twenty micron CAMera, featuring
collaborative access to the community of interested researchers. The
University of Denver is now completing construction of a mid-infrared
imaging polarimeter dubbed TNTCAM Mark II. The instrument will be the
only one of its kind capable of attaining polarimetric accuracy of 0.2
&amp;#37 across the 5 - 25 micron spectral interval. This sensitivity is
only attainable by cooling the transmissive polarizing optics to liquid
helium (LHe) temperatures. A major technical challenge in the design
of this instrument has been finding a way to modulate the polarization
signature of the incoming beam at a rate sufficient to combat the
degrading effects of the atmosphere. Our group has chosen to quickly
rotate a half-waveplate situated on the cold (i.e. 4 degrees Kelvin)
work-surface. The waveplate is rotated between two fixed positions
separated by 45 degrees at a rate of 1 Hz to obtain one of the two
Stoke's parameters required to measure linear polarization. The
waveplate is then offset by 22.5 degrees and then rotated again at
1 Hz between two positions separated by 45 degrees to obtain the
other Stoke's parameter. In addition to rotating the waveplate, the
waveplate itself must be moved out of the beam during normal imaging
applications. This instrument is being developed under NSF grant
AST-9724506 to the University of Denver and is slated for community
access after January 2000.

---------------------------------------------------------
Title: AGB Star Polar Breakout and the Origin of Aspherical Planetary
Nebulae
Authors: Stencel, Robert E.
2000ASPC..199...99S Altcode: 2000apn..conf...99S
The problem of the transition between presumed spherical configuration
of AGB stars, and manifestly aspherical shapes of proto- planetary
nebula, is addressed with an hypothesis that features selective removal
of high latitude stellar layers near the end of AGB phase of evolution,
during thermal pulses. As deeper, hotter layers of the atmosphere and
envelope are exposed, an instability related to increasing radiative
forces at the poles could be triggered, promoting a bipolar flow.

---------------------------------------------------------
Title: Hipparcos and Microvariability in Mira Variables: An
Observational Attempt to Confirm Same.
Authors: Stencel, R. E.; et al.
2000IAUJD..13E..40S Altcode:
DeLaverny et al.(1998 Astron.Astrophys.330:169) reported detection with
Hipparcos photometry, of broadband fluctuations measuring several tenths
of a magnitude, on timescales of a few to hundreds of hours, among 15
percent of 250 Mira and long period variables surveyed. With the help of
students, we have begun a CCD monitoring campaign for several of these
and will report on attempts to verify some of the Hipparcos report. Such
fluctuations, if verified, would be highly interesting in the context
of catastrophic models for dust formation in the extended atmospheres of
such stars, cf.Stencel et al.1990 Astrophys.Journ. 350:L45). Statistical
techniques, such as the analysis of the variance, will be applied to
the light curves to evaluate the reliability of small amplitude, short
term changes in aperiodically sampled BVRI data, following the approach
of Howell et al.1988 Astron.Journ.95:247. I am grateful to the estate
of William Herschel Womble for support of these activities at Denver.

---------------------------------------------------------
Title: TNTCAM MARK II: First light Mid-IR Images
Authors: Stencel, R. E.; Theil, D.; Klebe, D.
1999AAS...195.8716S Altcode: 1999BAAS...31R1504S
First light observations were achieved with our redesigned mid-infrared
array camera, TNTCAM2 at NASA's Infrared Telescope Facility (IRTF)
atop Mauna Kea on May 2-5, 1999. Collaborative observations were
made of Jupiter, in support of a Galileo spacecraft encounter (Glenn
Orton et al. JPL), Mars at opposition (Terry Martin, JPL), Nova Sgr
(Robert Gehrz et al. U.Minnesota), plus YSOs, star forming regions and
planetary nebulae, using intermediate and narrow band filters from 5 to
24 microns. TNTCAM2 (Ten and Twenty μ m Camera Mark II) represents an
improvement over the original optical and cryostat design described by
(Klebe et al., 1996, ASP Conf. Series, v97, p.79). Image quality and
cryostat hold time objectives were met (see Theil et al. 1999 SPIE
Proceedings, vol.3786C Conference on Optomechanical Engineering). The
complete system will also include an upgrade from the current Rockwell
HF16 128x128 Si:As array, and polarimetry across these mid-infrared
filter regions as well, with sensitivities as small as 0.4% (at 6.0
mag/sq.arcsec on a 2.4m telescope in 4 hours). Frequent use of the
instrument is planned as part of a cooperative access agreement with
the University of Wyoming's Infrared Observatory (WIRO), and is offered
for collaborative community access beginning this year. We are happy
to acknowledge support via NSF grant AST-9724506.

---------------------------------------------------------
Title: Stepper motors at LHe temperatures in astronomical mid-infrared
instrumentation
Authors: Theil, David S.; Stencel, Robert E.; Klebe, Dimitri I.;
Flaming, Dale; Belgum, Jack
1999SPIE.3786..376T Altcode:
The University of Denver is now completing construction of a
mid-infrared imaging polarimeter dubbed TNTCAM Mark II. The instrument
will be the only one of its kind capable of attaining polarimetric
accuracy of 0.2 % across the 5 -- 25 micron spectral interval. This
sensitivity is only attainable by cooling the transmissive polarizing
optics to liquid helium (LHe) temperatures. A major technical challenge
in the design of this instrument has been finding a way to modulate
the polarization signature of the incoming beam at a rate sufficient to
combat the degrading effects of the atmosphere. Our group has chosen to
quickly rotate a half-waveplate situated on the cold (i.e. 4 degrees
Kelvin) work-surface. The waveplate is rotated between two fixed
positions separated by 45 degrees at a rate of 1 Hz to obtain one of
the two Stoke's parameters required to measure linear polarization. The
waveplate is then offset by 22.5 degrees and then rotated again at
1 Hz between two positions separated by 45 degrees to obtain the
other Stoke's parameter. In addition to rotating the waveplate, the
waveplate itself must be moved out of the beam during normal imaging
applications. The camera can contribute to the understanding of YSOs
and evolved stars, obtaining high resolution mid-IR observations of
dusty environments immediately surrounding these objects. In imaging
mode mosaics of extended objects can be made in 2'x2' sub-fields. In
polarimetry mode, B-fields in YSOs can be probed by dust emission
from hot cores, incidentally constraining grain alignment scenarios
in young stellar environments. In this paper we present the design
and the results of our moving optical componenets susbsytem. Five
cryo-stepper motors drive these mechanisms. This instrument is being
developed under NSF grant AST-9724506 and is slated for community
access in January 2000.

---------------------------------------------------------
Title: Infrared Space Observatory (ISO) Key Project: the Birth and
Death of Planets
Authors: Stencel, Robert E.; Creech-Eakman, Michelle; Fajardo-Acosta,
Sergio; Backman, Dana
1999STIN...9916782S Altcode:
This program was designed to continue to analyze observations of stars
thought to be forming protoplanets, using the European Space Agency's
Infrared Space Observatory, ISO, as one of NASA Key Projects with ISO. A
particular class of Infrared Astronomy Satellite (IRAS) discovered
stars, known after the prototype, Vega, are principal targets for these
observations aimed at examining the evidence for processes involved in
forming, or failing to form, planetary systems around other stars. In
addition, this program continued to provide partial support for related
science in the WIRE, SOFIA and Space Infrared Telescope Facility (SIRTF)
projects, plus approved ISO supplementary time observations under
programs MCREE1 29 and VEGADMAP. Their goals include time dependent
changes in SWS spectra of Long Period Variable stars and PHOT P32
mapping experiments of recognized protoplanetary disk candidate stars.

---------------------------------------------------------
Title: Infrared Space Observatory Photometric Search of Main-Sequence
Stars for Vega-Type Systems
Authors: Fajardo-Acosta, S. B.; Stencel, R. E.; Backman, D. E.;
Thakur, N.
1999ApJ...520..215F Altcode:
We obtained 3.6-20 μm photometry of 38 bright [IRAS Fν(12
μm)&gt;0.7 Jy] main-sequence stars with the Infrared Space Observatory
(ISO). Observations were conducted with the ISOPHOT instrument, in
the single-pointing photometry mode, through filters at 3.6, 11.5,
and 20.0 μm. We searched for excess (Vega-type) emission from dust
at temperatures &gt;~100 K, located at ~1-60 AU from the stars. We
thus sampled dust at warm, terrestrial material temperatures and at
cool (~100 K) temperatures of possible Kuiper Belt-type regions in
these systems. We detected 20 μm excesses from ~14% of our sources,
but we did not detect 11.5 μm excesses from any of them. We present
single-temperature blackbody models of the location and density of
dust emission around 10 stars, two of them (29 Cyg and Gl 816) with
excesses newly reported here. We make a thorough comparison of ISO and
IRAS data on our target stars and propose a new calibration procedure
for ISOPHOT staring measurements at 3.6, 11.5, and 20 μm. Based
on observations with ISO, an ESA project with instruments funded by
ESA member states, with the participation of ISAS and NASA.

---------------------------------------------------------
Title: Photometry of Hipparcos Variable Stars
Authors: Ostrowski, Therese A.; Stencel, Robert E.
1999JAVSO..27...37O Altcode:
Among the discoveries reported by the Hipparcos team was the detection
of short-term photometric fluctuations in several long period, or Mira,
variables (de Laverny et al. 1998). Nearly 15 percent of the 250 Miras
surveyed in the broadband 380 to 800 nm filter showed variation of 0.2
to 1.1 magnitudes on timescales of 2 to 100 hours, preferentially around
minimum light phases. We have begun an observational effort to confirm
these variations. We seek to correlate the behavior with ancillary
information, such as optical and infrared spectra plus maser data,
to determine whether the fluctuations can be understood as thermal
instabilities or so-called molecular catastrophe (cf. Muchmore et al
1987; Stencel et al. 1990). A progress report and call for observation
coordination are given.

---------------------------------------------------------
Title: First Light at the New Mt. Evans Observatory
Authors: Stencel, Robert E.
1999JAVSO..27...61S Altcode:
The new Mt. Evans Meyer-Womble Observatory may be one of a few
professional-grade facilities with a strong orientation to the work
of the American Association of Variable Star Observers. Some details
of its construction and its telescopic capabilities are given here.

---------------------------------------------------------
Title: Denver's Pioneer Astronomer: Herbert Alonso Howe (1858-1926)
Authors: Howe, H. J.; Stencel, R. E.; Fisher, S.
1999AAS...194.1003H Altcode: 1999BAAS...31..840H
Herbert A. Howe arrived at Denver University (DU) to teach autumn 1880
classes, in math, astronomy and surveying. Howe established himself
with clever solutions to the Kepler problem for orbit determinations in
thesis work at Cincinnati Observatory. Riding the economic expansion
of Colorado gold and silver mining in 1888, the University accepted a
proposed gift of a major observatory, offered by Denver real estate
baron, Humphrey Chamberlin. The result features a 20 inch aperture
Alvan Clark refractor, which still ranks among the largest telescopes
of the era. With the observatory building ready, the Silver Panic of
1893 -- when the US Congress dropped silver reserves from the currency
basis -- burst the Denver economic bubble. Chamberlin was unable
to complete payments on the balances due. Clark and G.N.Saegmuller
(Fauth and Co.) at personal expense, delivered on the optics and
telescope assemblies in 1894, but would wait for repayment. Sadly,
this fiscal crisis affected DU for over a decade. Professor Howe,
while observatory director, found himself consumed as Dean and Acting
Chancellor for a young, struggling university, at the expense of
the astronomy future that had looked so bright in 1892. Absent the
Silver Panic, Howe would have probably been given an endowed chair
in astronomy, as promised by Chamberlin. The complexion of American
astronomy at the time of the birth of the American Astronomical Society
in 1899 might have been different, in terms of US observing sites,
etc. We are fortunate to have extensive Prof.Howe's daily diaries now
in the University archives. These describe Howe's view of progress on
the observatory, meetings with astronomy notables, plus vignettes of
the life and times of Denver and the nation. Grandson, Herbert Julian
Howe rediscovered their existence and is summarizing them in the form
of a biography entitled: The Pioneer Astronomer. DU archival records
contain numerous original letters from late 19th century astronomy
luminaries like Hale, Barnard, Pickering, Clark, Saegmuller, etc and
may constitute an important historical resource. Contact University
Archivist, Steven Fisher, sfisher@du.edu for access. We remain grateful
to the estate of William Herschel Womble for helping to fulfill the
dream that partially eluded Mr.Chamberlin.

---------------------------------------------------------
Title: The Search for Astronomical Alignments in the Seventh Century
A.D. Silla Capital at Kyongju, Korea
Authors: Nelson, S. M.; Stencel, R. E.
1999AAS...194.1002N Altcode: 1999BAAS...31..840N
In the center of the modern Korean city of Kyongju stands a modest
structure dating from the 7th century AD, known as Chomsongdae, or the
Star Observatory. Known locally as the oldest observatory in Asia,
details of its precise use are lost, but its construction coincided
with the height of Silla culture and its dominance over the Korean
peninsula. Radially from the structure are located the so-called
Moon Fortress, numerous large tombsites for elite of the culture,
plus hillside fortresses and elaborate Buddhist temples. During 1999,
we've conducted a course at Denver as part of our Core Curriculum
program for The Women's College, that has examined the astronomical
and cultural aspects of the Kyongju site, to attempt to determine
whether the architects may have included astronomical alignments
into the “Feng Shui" of their city planning, spanning centuries. The
preliminary result of our studies suggests that east and west of Star
Observatory lay fortress and wall features that may have been useful
for equinox determination. A discussion of ethnographic supporting
evidence will be provided, but additional on-site observations will
be needed to confirm the idea.

---------------------------------------------------------
Title: Performance of The Meyer Binocular Telescope at Mt.Evans
Observatory
Authors: Stencel, R. E.; Meyer, E. T.
1999AAS...194.0910S Altcode: 1999BAAS...31..838S
An unusual dual-aperture 28.5-inch, f/21 Ritchey-Chretien telescope
has been installed in the recently upgraded University of Denver
extreme high altitude observatory facility, atop 14,268 ft. Mount
Evans in Colorado -- see 1994 BAAS 26:895 &amp; 26:1321; 1998 BAAS
29:1272 &amp; 30:1293; www.du.edu/ rstencel/MtEvans. Designed to
optimize high spatial resolution imaging, the Meyer Binocular Telescope
incorporates active thermal management of the telescope structure. The
secondary mirror support elements are fabricated from INVAR and permit
active tip-tilt and focusing capability. The optics were fabricated
from Zerodur by Contraves USA, and each system has a measured total
wavefront error less than 0.050 at 633nm. All optical surfaces are
coated with a multi-layer dielectric enhanced silver, providing high
reflectance from below 350nm to beyond 26 microns. During 1998, the
first operational phases revealed that uncorrected image performance
met image quality expectations. The dual Ritchey-Chretien optical
systems were fabricated by Contraves USA. They incorporate a 0.7m F3
primary mirror and a 12cm, 7 power secondary mirror for a combined
focal length of 14.92 meters. The Strehl ratio for both systems is
approximately 94 noteworthy that these two telescopes are nearly
identical in focal length and aperture thus simplifying the exchange
of instrumentation between, and comparison of data obtained at, the
two telescopes. All four mirrors are coated with a multilayer enhanced
(protected) silver FSS 99 from Denton Vacuum. The low emissivity of
this coating in the thermal infrared complement the low precipitable
H2O levels measured at the Mount Evans site. The telescope control
system has been designed to allow initial operation from an insulated
control room. Long-term plans call for attended and remote operation
from the University of Denver campus via direct microwave radio link,
over a 35 mile direct line of sight. The University of Denver astronomy
program is grateful to the Meyer Foundation and the estate of William
Herschel Womble for support to Denver University for these endeavors. A
CDROM is available including 1998 observing results, plus ancillary
and site survey data. Persons with serious student projects and/or
optical/infrared focal plane instruments to test at our site are
encouraged to contact us directly (rstencel@du.edu).

---------------------------------------------------------
Title: Mid-Infrared Visibility Measurements of Evolved Stars
Authors: Sudol, J. J.; Dyck, H. M.; Stencel, R. E.; Klebe, D. I.;
Creech-Eakman, M. J.
1999AJ....117.1609S Altcode:
We have used Denver University's Ten-and-Twenty Micron Camera at the
Wyoming Infrared Observatory to image 12 evolved stars at 11.5 mum. We
have obtained both visibility data and photometric magnitudes from
these images. We have partially resolved the circumstellar dust shell
for eight of these 12 stars: alpha Ori, VY CMa, IRC +10216, chi Cyg, IK
Tau, NML Cyg, mu Cep, and IRC +10420. We compare our data to published
data and to visibility curves predicted by radiative transfer models
in the literature.

---------------------------------------------------------
Title: ISOSWS Spectral Variations of Oxygen-Rich Miras
Authors: Creech-Eakman, M. J.; Stencel, R. E.
1999IAUS..191..245C Altcode:
In conjunction with an extensive ground-based monitoring program of 32
oxygen-rich Mira variables, a subset of this sample has been monitored
with phase using ISO's Short Wavelength Spectrometer (ISOSWS) and
ground-based mid-infrared spectrometers. Some of the six sources will be
presented here in 2.5--45 microns ISOSWS spectra and 7.5--13.5 microns
ground-based spectra using CGS3. Discussion of the spectral features of
SiO, CO, H2O, and silicates will be presented. These data
are considered in the context of recent demonstrations of variations
in the spectral features with phase of the Miras.

---------------------------------------------------------
Title: Toward Precision Photometry of Red Variable Stars
Authors: Ostrowski, T. A.; Stencel, R. E.
1999ASPC..189..207O Altcode: 1999pcp..conf..207O
No abstract at ADS

---------------------------------------------------------
Title: Daytime Polar Alignment of Telescope Mountings Using GPS and
Internal Reference Optics
Authors: Mellon, R. R.; Scheld, D.; Stencel, R. E.
1998AAS...193.1104M Altcode: 1998BAAS...30.1264M
A technique is presented for performing polar alignment of astronomical
telescope mountings to high precision during daylight hours. This work
originated in the requirement to erect a truck mounted astronomical
telescope at multiple locations during the day in order to measure the
atmospheric convective turbulence Fried Parameter r0 by tracking stars
at various zenith angles. The custom equatorial mounting built for this
project incorporates a surveyor's theodolite, which is used to establish
an optical line of sight to the North Celestial Pole (NCP). The
elevation angle of this line of sight is set directly by adjusting
the theodolite tube elevation angle to that of the local geographic
latitude obtained from a Global Positioning System (GPS) receiver. The
theodolite is set into the azimuth of the Pole by observing an object
on the horizon of known bearing angle or by observing the Sun=92s
known azimuth at a specified time. Once the theodolite line of sight
to the NCP is established, an optical target projector contained
within and aligned with the polar axis provides an illuminated
pattern, which is viewed by the theodolite. Subsequent adjustments
of the elevation and azimuth of the polar axis bring the projected
pattern onto the intersection of the crosshairs in the theodolite
reticule, thereby bringing the polar axis into close coincidence
with the NCP. Denver University astronomers are interested in this
application for their proposed Fully Adaptive Segmented Telescope
(FAST) instrument, a meter-class instrument which can be transported
among high altitude sites (see www. adaptive-optics.com). Equinox
Interscience (303-843-0313) can provide this daytime polar alignment
capability to interested users for equatorial mountings.

---------------------------------------------------------
Title: ISO and Sub-mm Imaging of Dusty Disks Around Vega-type Stars
Authors: Fajardo-Acosta, S. B.; Stencel, R. E.; Backman, D. E.
1998AAS...193.6907F Altcode: 1998BAAS...30R1350F
We present a comparison of far-infrared (60 mu m) and sub-millimeter
(850 mu m) images of circumstellar dust of the Vega-type stars alpha
PsA (A3 V) and epsilon Eri (K2 V). The 60 mu m images were obtained
with the Infrared Space Observatory (ISO), using the PHOT C-100 array
camera in its dedicated micromapping mode. The 60 mu m image of alpha
PsA was measured by Fajardo-Acosta et al. (1997, ApJ, 487, L151; 1998,
ApJ, 503, L193); that of epsilon Eri is reported for the first time
here. The 850 mu m images were obtained with the sub-millimeter camera
SCUBA at the James Clerk Maxwell Telescope (JCMT). The 850 mu m image
of alpha PsA was measured by Holland et al. (1998, Nature, 392, 788);
that of epsilon Eri was measured by Greaves et al. (1998, ApJ, 506,
L133). The comparison of the far-infrared and sub-millimeter images
aims at confirming the reality of the reported morphology of the dust
regions around these sources. These observations were conducted with
very different methods and instrumentation. However, both the ISO PHOT
and JCMT SCUBA images of alpha PsA show a nearly edge-on disk around
it, oriented nearly north-south. Also, both observations of epsilon Eri
resolved extended dust around it. The SCUBA image shows a ring of dust
around epsilon Eri. The PHOT image of epsilon Eri also shows similarly
extended dust emission, but we also detected a central condensation
of dust at the star position. We compared the spatial scales of the
reported dust structures in these objects. We comment on plausible
grain size distributions implied by these comparisons.

---------------------------------------------------------
Title: TNTCAM MARK II: A New Mid-IR Array Imager and Polarimeter
Authors: Theil, D. S.; Klebe, D. I.; Stencel, R. E.
1998AAS...193.1203T Altcode: 1998BAAS...30.1268T
Building on our success with TNTCAM (Klebe et al., 1996, ASP
Conf. Series, v97, p79) we present progress on a new mid-IR (5-25mu
m) imaging polarimeter, TNTCAM (Ten and Twenty mu m Camera) MARK
II. With a Boeing 256x256 Si:As BIB array, the camera will surpass
any instrument currently in use at these wavelengths as an imager and
polarimeter. All optics are chilled to liquid helium temperatures,
excluding the entrance window; there are currently no mid-IR array
polarimeters with all cold optics. In polarimetry mode TNTCAM II will be
sensitive to linear polarizations as small as 0.4% (at 6.0 magnitudes
arcsec(-2) on a 2.4m telescope in four hours). Our current schedule
achieves first light during 1999. Community access is planned as part
of the funding agreement under a NSF Major Research Infrastructure
grant. To measure polarimetry the camera images one polarization
state at a time. Modulating the polarization faster than atmospheric
and system noise fluctuations requires rotating waveplates rapidly at
LHe temperatures. We present details of our mechanical design showing
how this is accomplished. We also present a rotating window assembly
allowing on-the-fly f-ratio adjustment and observation across the entire
5-25mu m band. This camera will contribute to the understanding of
YSOs and evolved stars, obtaining high resolution mid-IR observations
of dusty environments surrounding these objects. Mosaics of extended
objects can be made with 2(') x 2(') sub-fields. In polarimetry mode,
assuming adequate grain alignment timescales, magnetic fields in
YSOs can be probed by dust emission from hot cores. The camera will
constrain grain alignment scenarios in young stellar environments and
around evolved stars, and will be useful for exploring the magnetic
fields of external galaxies. We acknowledge support under NSF grant
AST-9724506 to the University of Denver.

---------------------------------------------------------
Title: High Altitude Observing: Some Lessons Learned
Authors: Stencel, R. E.
1998AAS...193.3403S Altcode: 1998BAAS...30.1293S
After achieving first light in late summer 1997, Denver University
astronomers, Students and volunteers enjoyed our first summer of full-up
operations in 1998, at the new Meyer-Womble Observatory -- located
near the summit of 14,268 ft Mt.Evans, 35 miles west of Denver. The
facility features twin 0.72 meter f/21 telescopes, excellent seeing
and outstanding infrared transparency (1994 BAAS 26:895 &amp; 26:1321;
1998 BAAS 29:1272; www.du.edu/ rstencel/MtEvans). Experiences gained
during a week-long intensive undergraduate course in CCD astr onomy held
at the observatory will be shared. We also report here on progress in
the areas of (1) solar photovoltaic power for this off-grid location;
(2) wireless modem microwave communication for email and internet
connections miles away from hard phonelines, and prospects for eventual
remote operations using similar links; (3) successful application
of new intensified eyepiece technology from Collins Electro-Optics
(www.ceoptics.com) to achieve 17th magnitude at video frame rates
(1/60th sec), and (4) utilization of T-points software to model polar
alignment, gearing and other flexure parameters to achieve improved
pointing (www.bisque.com). These improvements pave the way for planned
use of new infrared array cameras at this location during future
observing seasons. I am grateful to the estate of William Herschel
Womble for support to Denver University for these endeavors. A CDROM
of 1998 observing results and ancillary data is available. Persons
with serious student projects and/or focal plane instruments to test
at our site are encouraged to contact me directly (rstencel@du.edu).

---------------------------------------------------------
Title: How to get 17th Magnitude at Video Frame Rates
Authors: Collins, W.; Stencel, R. E.
1998AAS...193.3409C Altcode: 1998BAAS...30Q1294C
We would like to alert college astronomy instructors to a significant
new instrument that can greatly improve student experiences with modest
aperture telescopes. The I3Piece is made by Collins Electro-Optics of
Denver, CO and includes an ITT image intensifier and S-20 photocathode,
capable of 50,000 amplification, 60 lines/mm resolution and only uses a
few kV versus classical intensifiers that required many kV. The unit
is ruggedly packaged with 1.25 and 2 inch barrel options, and can
mate with an eyepiece, video camera or CCD camera easily, with total
lengths under 12 inches. We report here on application of this device
in astronomy instruction at the Denver University Observatories. When
coupled with a typical video camera and monitor, one can readily deliver
a better than visual limiting magnitude view of stars, clusters and
galaxies. For reference, according to Roy Garstang at a recent AAVSO
meeting, the limiting visual magnitude for a telescope of aperture d
(cm) is 7.6 + 5 log d. The I3Piece is too sensitive to look at planets
or the moon, but usually these bright object can be viewed without
difficulty, by students. The real advantage of the device is how it
can surmount the "fuzzy blob" view usually experienced by first-time
telescope users, and deliver literally picture book quality views, even
from light polluted sites. The I3Piece works best under clear skies,
as it amplifies haze and clouds, as well as stars. When coupled to
our 0.7 meter at Mt.Evans Observatory, we were able to identify 17th
magnitude stars in real-time on the monitor, viewing the calibrated
cluster, NGC7006. Comparably outstanding views were obtained when used
with our 20-inch Clark refractor at DU's Chamberlin Observatory in
central Denver. The key point is that in either eyeball or video mode,
the I3Piece will insure students won't leave the telescope session
disappointed, because they will easily see the physical principles
illustrated when we share with them views of self-gravitating systems
of stars or star forming nebulae. We invite instructors investigate
the website www.ceoptics.com, phone 303-889-5910, billc@creek.net,
and/or rstencel@du.edu, 303-871-2135.

---------------------------------------------------------
Title: CCD Photometry of Hipparacos Variable Stars
Authors: Ostrowski, T. A.; Stencel, R. E.
1998AAS...193.4608O Altcode: 1998BAAS...30.1321O
Among the discoveries reported by the Hipparcos team, was the detection
of short term photometric fluctuations in several long period or Mira
variables (de Laverny et al. 1998 Astron. Astrophys. 330: 169). Nearly
15 percent of the 250 Miras surveyed in the broadband 380 to 800 nm
filter showed variation of 0.2 to 1.1 magnitude on timescales of 2
to 100 hours, preferentially around minimum light phases. We have
begun an undergraduate thesis project to confirm these variations,
using the 72cm/AP7 MBT at Mt.Evans, and 20cm/ST5 "Roboscope" at
Chamberlin Observatory (www.du.edu/ rstencel). These new data will
be used to correlate the behavior with ancillary information, such as
optical and infrared spectra plus maser data, to determine whether the
fluctuations can be understood as thermal instabilities or so-called
molecular catastrophe (Muchmore, Nuth and Stencel 1987 ApJ 315:L141;
Stencel et al. 1990 ApJ 350: L45). A progress report and call for
observation coordination will be given.

---------------------------------------------------------
Title: Infrared Space Observatory Mapping of 60 Micron Dust Emission
around Vega-Type Systems: Erratum
Authors: Fajardo-Acosta, S. B.; Stencel, R. E.; Backman, D. E.
1998ApJ...503L.193F Altcode:
In the Letter “Infrared Space Observatory Mapping of 60 Micron
Dust Emission around Vega-type Systems” by S. B. Fajardo-Acosta,
R. E. Stencel, and D. E. Backman (ApJ, 487, L151 [1997]), there is an
error in the equatorial coordinates that we assigned to our maps. Using
preliminary versions of the PHOT Interactive Analysis (PIA) program, we
incorrectly labeled the PHOT C-100 array axes as if they were aligned
with equatorial coordinates. We rereduced our PHOT maps with a more
recent version of PIA, version 6.3. The orientation of the C-100 array
relative to equatorial coordinates, unique to each mapping observation,
is now properly taken into account. This orientation is indicated by the
scan direction vector plotted in Figures 2a (α PsA) and 2b (α Boo)
of our Letter. The scan direction of the map of γ Oph, in which
we found hints of extended emission (Figs. 1c and 1d of our Letter),
is along P.A. 184°, very close to the scan direction of the map of α
Boo (P.A. 186°). Therefore, the one-dimensional profile cuts in these
maps should be reinterpreted as hinting at extended emission being
present north and south of γ Oph. Below we show a corrected
version of Figure 2 of our Letter. The maps of α PsA (Fig. 2a)
and α Boo (Fig. 2b) are now properly rotated relative to equatorial
coordinates. The morphology of these maps is slightly different from
that of our Letter. The reason is that the point-spread function
model from α Boo is now rotated relative to the map of α PsA by the
difference in the scan directions of these two maps (29° clockwise). Corrected Figure 2a shows that the inferred disk around α PsA is
aligned nearly north-south, or 12deg+/-13deg
west of north. This orientation is consistent with previous inferences
from 60 μm IRAS scans by F. C. Gillett (in Light on Dark Matter,
ed. F. P. Israel [Dordrecht: Reidel], 61 [1986]), which suggested that
extended emission was present along 29° west of north. A recent 850
μm image of α PsA by W. S. Holland et al. (Nature, 392, 788 [1998])
shows extended emission along 18deg+/-4deg
west of north, thus also consistent with our corrected measurement.

---------------------------------------------------------
Title: TNTCAM MARK II: a new mid-IR array imager/polarimeter
Authors: Klebe, Dimitri I.; Stencel, Robert E.; Theil, David S.
1998SPIE.3354..853K Altcode:
We present design considerations for a mid-IR imaging polarimeter,
TNTCAM2. Using a 256 by 256 Si:As BIB array, the camera will be
unparalleled as an polarimeter/imager by any instrument currently
in use at these wavelengths. Thanks to NSF support, access by the
general astronomical community will be arranged. In polarimetry mode,
TNTCAM II will be sensitive to linear polarizations as small as 0.2
percent. Polarized emission from cosmic sources will be modulated
at a frequency high enough to remove atmospheric and system noise
fluctuations. Dewar design and the optical system are discussed,
including CCD assisted digital shift and ad tip- tilt correction
and use of a rotating entrance window assembly allowing on-the-fly
f-ratio adjustment and optimal throughput across the entire 5-25 $mu@m
band. The camera can contribute to the understanding of YSOs(Young
Stellar Objects) and evolved stars, obtaining high resolution mid-IR
observations of dusty environments immediately surrounding these
objects. In imaging mode mosaics of extended objects can be made in 2'
by 2' sub-fields. In polarimetry mode, B-fields in YSOs can be probed by
dust emission from hot cores, incidentally constraining grain alignment
scenarios in young stellar environments.

---------------------------------------------------------
Title: Infrared space observatory photometry of circumstellar dust
in Vega-type systems
Authors: Fajardo-Acosta, S. B.; Stencel, R. E.; Backman, D. E.;
Thakur, N.
1998exdu.work..265F Altcode:
The ISOPHOT (Infrared Space Observatory Photometry) instrument onboard
the Infrared Space Observatory (ISO) was used to obtain 3.6-90 micron
photometry of Vega-type systems. Photometric data were calibrated with
the ISOPHOT fine calibration source 1 (FCS1). Linear regression was
used to derive transformations to make comparisons to ground-based and
IRAS photometry systems possible. These transformations were applied
to the photometry of 14 main-sequence stars. Details of these results
are reported on.

---------------------------------------------------------
Title: Dust Disks around Main Sequence Stars
Authors: Backman, D. E.; Fajardo-Acosta, S. B.; Stencel, R. E.;
Stauffer, J. R.
1998Ap&SS.255...91B Altcode: 1997Ap&SS.255...91B
Many nearby main sequence stars are surrounded by cool dust radiating
strongly in the far-IR. The characteristics of some of the prototype
systems will be discussed. The dust is understood to represent debris
related to planet formation, and the known disk systems may be dense
analogs of the Kuiper Belt structure in our outer solar system. ISO
observing programs plan to address questions regarding how common
planetary material is around normal stars and how its amount and
location depend on system age. These questions are central to an
understanding of the place of the "Vega/β Pic" disks in stellar
evolution. Preliminary results from the first year of ISO operation
will be reported.

---------------------------------------------------------
Title: Astronomical Alignments in a Neolithic Chinese Site?
Authors: Nelson, S.; Stencel, R. E.
1997AAS...191.3803N Altcode: 1997BAAS...29.1264N
In the Manchurian province of Liaoning, near 41N19' and 119E30',
exist ruins of a middle Neolithic society (2500 to 4000 BC) known as
the Hongshan culture. This location, called Niuheliang, is comprised
of 16 locations with monumental structures scattered over 80 square
kilometers of hills. Most are stone burial structures that contain
jade artifacts implying wealth and power. One structure is unique in
being unusually shaped and containing oversized effigies of goddess
figures. This structure also has a commanding view of the surrounding
landscape. The presence of decorated pottery, jade and worked copper
suggests the Hongshan people were sophisticated artisans and engaged in
long-distance trading. During 1997, we've conducted a course at Denver
as part of our Core Curriculum program for upper division students, that
has examined the astronomical and cultural aspects of the Niuheliang
site, to attempt to determine whether these contemporaries of the
builders of Stonehenge may have included astronomical alignments into
their constructions. The preliminary result of our studies suggests
that certain monuments have potential for lunar standstill observation
from the "goddess temple". For updates on these results, please see
our website: www.du.edu/ rstencel/core2103.html.

---------------------------------------------------------
Title: First Light Achieved at the new Mt.Evans High Altitude
Observatory
Authors: Stencel, R. E.
1997AAS...191.4117S Altcode: 1997BAAS...29.1272S
During August 1997, first light images were obtained with the new Meyer
Binocular Telescope, a twin 0.72 meter RC system, located at the Meyer-
Womble Observatory atop 14,268 ft Mt.Evans, Colorado. The site is along
a treeless high ridge which frequently enjoys laminar airflow and good
seeing. The telescope and building also include thermal and airflow
management systems for seeing optimization. Finally, a 5 element
adaptive optics system that is being tested at Yerkes Observatory,
should be able to correct the native seeing to nearly the limit of
optical performance. For details on all of the above, please refer
to my website: www.du.edu/ rstencel. The high altitude of Mt.Evans
makes it ideal for mid-infrared studies, and we anticipate pursuing
mid-IR imaging and spectroscopy from this site. Mark 2 of our TNTCAM
(Klebe et al.-this meeting) is now in design stage, thanks to an NSF
MRI grant. The spectrometer, TGIRS (Creech-Eakman et al. 1996 BAAS 28:
1372) has also achieved first light in the lab. We plan to use both at
the new mountaintop facility. Another interesting feature of the new
observatory is its photovoltaic energy supply for continuous power,
sponsored in part by the Renewable Energy Trust, National Renewable
Energy Lab and the Colorado Office of Energy Conservation. Denver
University is interested in forming partnerships with other programs in
order to make best use of this new resource for educational research in
astronomy and astrophysics. This can include REU-style student summer
visits, instrument testing and/or observational studies. I am pleased
to acknowledge sponsorship by the Estate of William Herschel Womble,
and the Meyer Foundation.

---------------------------------------------------------
Title: TNTCAM MARK II: A New Mid-IR Array Imager/Polarimeter
Authors: Klebe, D. I.; Stencel, R. E.; Theil, D.
1997AAS...191.0909K Altcode: 1997BAAS...29.1224K
We present design considerations for a new mid-IR (5-25mu m)
imaging polarimeter, TNTCAM II. Built around a 256x256 Si:As BIB
array from Boeing, as an imager the camera will be unparalleled by
any instrument currently in use at these wavelengths. Access to this
instrument is planned as part of the funding agreement under the NSF
Major Research Infrastructure grant supporting its development. This
camera can contribute to the understanding of YSOs and evolved stars,
obtaining high resolution mid-IR observations of dusty environments
immediately surrounding these objects. In ordinary imaging mode mosaics
of extended objects can be made in 2x2 arcmin intervals. In polarimetry
mode, assuming adequate grain alignment timescales, magnetic fields
in YSOs can be probed by dust emission from hot cores. The camera
can better constrain grain alignment scenarios in young stellar
environments. Emission (rather than scattering) dominates signal
at mid-IR wavelengths, allowing determination of grain alignment
in a source. This enables distinction between models explaining
near-IR polarization seen in dust shells surrounding late red giants,
i.e. scattering from asymmetric shells or aligned grains. There are
no mid-IR array polarimeters in operation. In polarimetry mode, TNTCAM
II will be sensitive to linear polarizations as small as 0.2%. We have
chosen the simple approach of imaging one state at a time and modulating
polarization at a frequency high enough to remove atmospheric and
system noise fluctuations. Dewar design and the optical system are
discussed, including the pros and cons of rotating waveplates or an
Abbe-Konig "K"-mirror to modulate the polarization, and the use of a
rotating window assembly allowing on-the-fly f-ratio adjustment and
observation across the entire 5-25mu m band. We acknowledge support
under NSF grant AST-9724506 to the University of Denver.

---------------------------------------------------------
Title: ISO Spectral Energy Distributions for Vega-type Stars
Authors: Thakur, N.; Fajardo-Acosta, S. B.; Stencel, R. E.; Backman,
D. E.
1997AAS...191.4713T Altcode: 1997BAAS...29Q1287T
We present new infrared photometry of main-sequence stars in order
to determine the frequency of mid- and far-infrared excesses in their
spectral energy distributions. These observations constitute NASA Key
Project VEGADISK (Stencel &amp; Backman 1994, Ap&amp;SS, 212, 417). We
used the Infrared Space Observatory's (ISO) ISOPHOT instrument at
wavelengths of 3.6, 11.5, 20, 60, and for some stars, 90 mu m, with
a uniform 52 arcsec aperture. Final calibration of ISOPHOT data is
not available from the ISO Project, so we have compared the fluxes
obtained from ISO, IRAS, and ground-based observations to standardize
our preliminary flux values. On this basis, nearly 25% of our stars
show infrared excesses in our sample. We will report on the correlation
of these excesses with stellar age.

---------------------------------------------------------
Title: Infrared Space Observatory Mapping of 60 Micron Dust Emission
around Vega-Type Systems
Authors: Fajardo-Acosta, S. B.; Stencel, R. E.; Backman, D. E.
1997ApJ...487L.151F Altcode:
We mapped 60 μm emission around five Vega-type systems. We utilized
the PHOT-C100 far-infrared array camera on board the Infrared Space
Observatory. The spatial resolution of the maps is ~30". The maps of
three sources (α CrB, σ Her, and α Cen) do not show any evidence of
extended emission. The map of γ Oph shows marginal hints of extended
emission ~30" (800 AU) from the star. The map of α PsA shows extended
emission ~30"-80" (~210-560 AU) from the star. This location, together
with α PsA's characteristic IRAS temperature of 58-75 K, suggest
the observed dust grains around α PsA are up to ~10 μm in size. We
estimate the mass of dust grains emitting the IRAS 60 μm excess of
α PsA to be ~(2-6) ×10-3 M⊕. Based on
observations with ISO, an ESA project with instruments funded by ESA
member states, with the participation of ISAS and NASA.

---------------------------------------------------------
Title: A survey of lunar domes.
Authors: Ross, R. W.; Stencel, R. E.
1997JALPO..39..172R Altcode: 1997StAst..39..172R
A visual survey of selected lunar domes was undertaken with the 20-inch
Clark refractor at the University of Denver's historic Chamberlin
Observatory for the purpose of augmenting existing catalogs and
providing new estimates for feature heights. Twenty-three relative
elevations ranging from 27 to 412 meters are reported.

---------------------------------------------------------
Title: Variation of Silicate Dust Features with Phase Mid-IR
Monitoring of Oxygen-Rich Mira Variable Stars
Authors: Creech-Eakman, Michelle J.; Stencel, Robert E.
1997Ap&SS.251..157C Altcode:
We present photometric and spectroscopic data on a subset of over
30 oxygen-rich Long Period Variable (LPV) stars which we have been
monitoring between 8/95 &amp; 4/97. With these data, we are attempting
to ascertain the relationship of dust formation to optical period. Our
ultimate goal is to determine what conditions lead to dust formation and
destruction in these environments, and whether or not an evolutionary
sequence can be inferred for AGB stars also based on their spectra
and dust formation.

---------------------------------------------------------
Title: The UV/X-ray emission of the symbiotic star AG Draconis during
quiescence and the 1994/1995 outbursts.
Authors: Greiner, J.; Bickert, K.; Luthardt, R.; Viotti, R.; Altamore,
A.; Gonzalez-Riestra, R.; Stencel, R. E.
1997A&A...322..576G Altcode: 1996astro.ph.12035G
We present the results of an extensive campaign of coordinated X-ray
(ROSAT) and UV (IUE) observations of the symbiotic star AG Dra during
a long period of quiescence followed recently by a remarkable phase
of activity characterized by two optical outbursts. The major optical
outburst in June 1994 and the secondary outburst in July 1995 were
covered by a number of target of opportunity observations (TOO)
with both satellites. Optical photometry is used to establish the
state of evolution along the outburst. Our outburst observations
are supplemented by a substantial number of X-ray observations of AG
Dra during its quiescent phase between 1990-1993. Near-simultaneous
IUE observations at the end of 1992 are used to derive the spectral
energy distribution from the optical to the X-ray range. The X-ray
flux remained constant over this three year quiescent phase. The hot
component (i.e. X-ray emitting compact object) turns out to be very
luminous: a blackbody fit to the X-ray data in quiescence with an
absorbing column equal to the total galactic N_H_ in this direction
gives (9.5+/-1.5)x10^36^(D/2.5 kpc)^2^erg/s. This suggests that
the compact object is burning hydrogen-rich matter on its surface
even in the quiescent (as defined optically) state at a rate of
(3.2+/-0.5)x10^-8^(D/2.5 kpc)^2^Msun_/yr. Assuming a steady
state, i.e. burning at precisely the accretion supply rate, this high
rate suggests a Roche lobe filling cool companion though Bondi-Hoyle
accretion from the companion wind cannot be excluded. With ROSAT
observations we have discovered a remarkable decrease of the X-ray
flux during both optical maxima, followed by a gradual recovering to
the pre-outburst flux. In the UV these events were characterized by a
large increase of the emission line and continuum fluxes, comparable
to the behaviour of AG Dra during the 1980-81 active phase. The
anticorrelation of X-ray/UV flux and optical brightness evolution is
very likely due to a temperature decrease of the hot component. Such a
temperature decrease could be the result of an increased mass transfer
to the burning compact object, causing it to slowly expand to about
twice its original size during each optical outburst.

---------------------------------------------------------
Title: Silicate Feature Variation in Long-period Variable
Stars. I. Initial Observations
Authors: Creech-Eakman, Michelle J.; Stencel, Robert E.; Williams,
W. John; Klebe, Dimitri I.
1997ApJ...477..825C Altcode:
We report new mid-infrared spectra of five bright, long-period variable
(LPV) stars, as well as related objects, obtained at the Wyoming
Infrared Observatory with Denver University's medium-resolution CAESR
instrument. The data, when combined with low-resolution spectrometer
spectra from IRAS, show variation of the silicate feature with phase
of the LPV. We perform a calculation for impingement time of the shock
on the circumstellar dust shell to demonstrate that this variation
could be the result of a shock-shell interaction.

---------------------------------------------------------
Title: Preliminary results from ISO: US guaranteed time projects
Authors: Helou, G.; Becklin, E. E.; Stencel, R. E.; Wilkes, B. J.
1997ASPC..124..393H Altcode: 1997diri.conf..393H
No abstract at ADS

---------------------------------------------------------
Title: Infrared Space Observatory mapping of 60 μm dust emission
around Vega-type systems.
Authors: Fajardo-Acosta, S. B.; Stencel, R. E.; Backman, D. E.
1996BAAS...28.1300F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Internet as a Tool for Astronomy Homework - Conucopia
or Curse?
Authors: Creech-Eakman, M. J.; Stencel, R. E.
1996AAS...189.3003C Altcode: 1996BAAS...28.1311C
We explore methods by which entry level college astronomy classes can
utilize the internet as a part of the curriculum. There are several
ways the internet can be used by beginning students: a. finding a
specific fact (What does Titan look like, its diameter?) b. finding
explanations for theories (What is the hot big bang model? What is
light pollution?) c. delving into topics in more depth than textbooks
can cover (HST instruments) d. making "connections" in astronomy (Is
there an astronomy club in Podunk?) We will present prototype homework
assignments based on these categories and show the performance on these
assignments by undergraduate test subjects. Successes and pitfalls
will be discussed.

---------------------------------------------------------
Title: Infrared Space Observatory Mapping of 60 MU M Dust Emission
Around Vega-type Systems
Authors: Fajardo-Acosta, S. B.; Stencel, R. E.; Backman, D. E.
1996AAS...189.1910F Altcode: 1996BAAS...28V1300F
We mapped 60 mu m emission around 5 Vega-type systems. We utilized
the PHT-C100 3x3-pixel far-infrared camera on-board ISO, in the P32
microscanning dedicated mapping mode. The maps are centered on the
stars and span 6'15”x5'45” (RAxDEC), at a spatial resolution of
15”. The maps of 3 sources (alpha CrB, sigma Her, and alpha CenB) do
not show any evidence of extended emission when compared to a model
point-spread function obtained from a similar map of alpha Boo. The
map of gamma Oph possibly shows extended emission ~ 30” from the star,
slightly above the background noise ( ~ 4 MJy/sr). The map of alpha PsA
shows extended emission features ~ 30--80” from the star. The extended
emission peak brightness in alpha PsA, after background subtraction,
is ~ 13 MJy/sr, or ~ 4sigma , above the background noise. The S/N of
our mapping observations is not high but as a preliminary result we
estimate some physical parameters of the 60 mu m emitting dust around
alpha PsA. The innermost ~ 30” or ~ 210 AU from the star are relatively
dust-depleted. The dust is found between ~ 210 AU and ~ 560 AU from
the star, with peak 60 mu m emission located at ~ 320 AU. We take the
latter as a characteristic location of the emitting dust. This location,
together with a characteristic IRAS temperature of 72 K (Backman &amp;
Paresce 1993, Protostars and Planets III, ed. Levy &amp; Lunine, 1253),
suggests the observed dust grains are ~ 1.5 mu m in size. The mass of
these grains emitting the total extended emission of ~ 11.9 Jy across ~
3.4 x 10(3) arcsec(2) is ~ 3 x 10(-3) M_⊕.

---------------------------------------------------------
Title: First Light Report on TGIRS - DU's New mid-IR Spectrometer
Authors: Stencel, R. E.; Creech-Eakman, M. J.; Klebe, D. I.; Williams,
W. J.
1996AAS...189.7505S Altcode: 1996BAAS...28.1370S
We present a first light report on TGIRS, Denver University Astronomy
Program's new Two Grating mid-InfraRed Spectrometer. The instrument
was designed and assembled in a little over a year, has been tested in
the lab and will be acquiring data at a telescope. This spectrometer
was built specifically to study mid-IR silicate features of Long
Period Variable stars. We plan to present alignment and throughput
test results, along with sample spectra over its bandpass of 7 to 14
microns, at a resolution of about 750. A novel feature of TGIRS is its
use of a mechanical cryocooling system that utilizes a Gifford-McMahon
cryocooler. We will report on the success of vibrational isolation
of the detector and optics from the piston action. The design and
construction of this instrument forms the basis for a PhD thesis
by graduate student M. Creech-Eakman. We plan for TGIRS to become a
facility instrument at our newly built Meyer-Womble Observatory, one
of the highest observatories in the world, at an elevation of 14,148
feet, atop Mt. Evans near Denver. From this vantage, above 90 percent
of the telluric water vapor, we anticipate that substantial quantities
of high-quality spectra can be obtained for monitoring studies.

---------------------------------------------------------
Title: Monitoring of the Mid-Infrared Silicate Features of Long
Period Variable Stars
Authors: Creech-Eakman, M. J.; Stencel, R. E.
1996AAS...189.6303C Altcode: 1996BAAS...28.1352C
We present photometric and some spectroscopic data on over thirty
oxygen-rich Long Period Variable stars which we have been monitoring
from 8/95 to 12/96. The photometric data was taken with Denver
University's TNTCAM (Ten and Twenty Micron Camera -- Klebe, Dahm
and Stencel, 1995) using narrow band filters over the wavelength
region from 4.8 to 24 microns on 8 separate monitoring campaigns,
mostly at the Wyoming Infrared Observatory. Wavelengths were selected
to help characterize the silicate emission profile and to detect
changes therein. The spectroscopic data was obtained using CGS3
in two wavebands, from 7-14 and 16-24 microns, at UKIRT during 3
different service observing campaigns. Our results are presented
along with the rationale for our long term observing campaign and
modelling/explanations for the variability we have observed to date. We
would like to thank WIRO for their support of our observing runs and
UKIRT for support via their service observing programs. We would also
like to acknowledge the partial support of M. Creech-Eakman by NASA
under grant NGT-51290.

---------------------------------------------------------
Title: New dual-aperture telescope for the Mt. Evans observatory
Authors: Meyer, Eric T.; Stencel, Robert E.; Bruns, Donald G.
1996SPIE.2828..463M Altcode:
An unusual dual-aperture 28.5-inch, f/21 Ritchey-Chretien telescope
has been completed and will be installed in the recently upgraded
University of Denver extreme high altitude observatory facility, atop
14,268 ft. Mount Evans in Colorado. Designed to optimize high spatial
resolution imaging, the Meyer binocular telescope incorporates active
thermal management of the telescope structure. The secondary mirror
support elements are fabricated from INVAR and permit active tip-tilt
and focusing capability. The optics were fabricated from Zerodur
by Contraves USA, and each system has a measured total wavefront
error less than 0.050 lambda at 633 nm. All optical surfaces are
coated with a multi- layer dielectric enhanced silver, providing high
reflectance from below 350 nm to beyond 26 micrometer. The telescope
control system has been designed to allow initial operation from
an insulated control room. Long-term plans call for totally remote
operation from the University of Denver campus via direct microwave
radio link. Instrumentation planned for the telescope at first light
includes: (1) a low order 400 nm to 1,000 nm band adaptive optics
system (AO5: adaptive optics, 5 mode) equipped with a large format
CCD camera; (2) a mid-infrared array camera (TNTCAM: ten and twenty
micron camera); and (3) a mid-IR moderate dispersion spectrometer
(TGIRS: two grating IR spectrometer). Some of the science problems
the dual aperture telescope is uniquely situated to tackle include the
study of planetary atmosphere, detection of planetary systems around
nearby stars and the analysis of evolutionary changes in stars. The
Mount Evans site (at 4,303 meters elevation, the highest operating
astronomical facility in the world) is located 70 km west of Denver
and can be reached via a paved state highway which extends all the
way to the summit. The observatory is currently under construction
with installation of the telescope planned for late summer 1996.

---------------------------------------------------------
Title: TGIRS: a two-grating (mid) infrared spectrometer
Authors: Creech-Eakman, Michelle J.; Klebe, Dimitri I.; Stencel,
Robert E.; Williams, W. John
1996SPIE.2814..115C Altcode:
We present a brief overview of the design and construction of two
grating infrared spectrometer, a new 2D array, dual grating spectrometer
for the 7.0 to 13.8 micron region, built at the University of Denver
(DU). This instrument has been designed to fulfill specific scientific
goals in astronomy while utilizing the array to its fullest extent. The
instrument uses diamond-turned aluminum optics to allow warm optical
alignment and eliminate differential contraction of the optics
while operating at cryogenic temperatures. Two gratings are used in
the optical design to provide a resolution of about 800. The entire
assembly is cooled with a Gifford-McMahon refrigerator so that it
may later be adapted for use during remote observing. The array is
a Rockwell 128 by 128 Si:As BIB hybrid focal plane array sensitive
from optical to 26 microns. The electronics package and software for
readout were developed by Wallace Instruments and are already in use
on our TNTCAM at DU. 'First light' is scheduled for late summer 1996.

---------------------------------------------------------
Title: Characterization of Jupiter's Atmosphere from Galileo and
Earth-Based Observations During the Ganymede-1 and Ganymede-2 Orbit
Encounters
Authors: Orton, G.; Fisher, B.; Ortiz, J. L.; Yanamandra-Fisher,
P.; Rages, K.; Howell, R.; Klebe, D.; Stencel, R.; Drossart, P.;
Lecacheux, J.; Colas, F.; Frappa, E.; Hernandez, C.; Parker, D.;
Miyazaki, I.; Stewart, S.; Stansberry, J.; Spencer, J.; Golisch, W.;
Griep, D.; Hainaut, M. -C.; Joseph, R.; Kaminski, C.; Banjevic, M.;
Connor, C.; Hinkley, S.; Marinova, M.; Marriage, B.; Dobrea, E. Noe
1996DPS....28.2118O Altcode: 1996BAAS...28.1137O
Galileo remote sensing data are examined in the context of an extensive
set of earth-based observations supporting the Ganymede-1 and Ganymede-2
encounters. Movies of the Great Red Spot (GRS) in reflected sunlight,
show large-scale flow; for example, the circular feature northwest
of the GRS during G1 was one of several high-altitude systems moving
westward with respect to the GRS. The southern part of the clear band
surrounding the GRS was narrower at 5 mu m than 8.57 mu m, suggesting
more cloud cover at depth than at the NH_3 condensation level; this
region was also warmer in the troposphere. High-altitude particles
were found in the flow pattern “trailing” the GRS. The real-time
NIMS G1 spectra sampled a region only moderately bright at 5-mu m,
not a classical “hot spot”. Synoptic middle-infrared spectra of this
region complement NIMS spectra of the deep troposphere by constraining
abundances of NH_3 and PH_3 at higher altitudes. The southern part
of the North Equatorial Belt, observed by both NIMS spectra and PPR
radiometry, was very active, generating classical bright “plumes”
and dark ovals (“barges”) for the first time in many months. A
long-term program will continue to observe potential targets for the
Galileo's atmospheric investigation.

---------------------------------------------------------
Title: Ground-based 10-mu M Observations of Hotspots on Io
Authors: Howell, R. R.; Klassen, D. R.; Klebe, D.; Stencel, R. E.;
Creech-Eakman, M. J.
1996DPS....28.2304H Altcode: 1996BAAS...28.1152H
The availability of mid-infrared array cameras makes it possible
to apply at longer wavelengths some of the techniques for measuring
individual hotspots which up to now have only been used in the 1 to
5-mu m region. At the longer wavelengths the limited spatial resolution
available with most telescopes prevents the application of direct
imaging to detecting hotspots, but the cameras should make it possible
to apply the Jupiter occultation technique. That should in turn make
it possible to monitor the activity of the cooler hotspots which are
not apparent in the existing data sets, but which may dominate the
energy output of Io. Analysis of those occultation light curves will
provide mid-IR photometry of discrete hotspots with a spatial resolution
unmatched at this wavelength except by the occasional satellite mutual
occultations. Using Denver University's 128x128 mid-IR camera “TNTCAM”
and the University of Wyoming 2.3-m telescope we have obtained images of
Io during eclipse and also during Jupiter occultation at a wavelength
of 10 mu m. The preliminary photometry shows that half the total
Io flux is from volcanic hot spots and Io remains easily detectable
immediately up to the time of its occultation by Jupiter. We are still
developing the techniques to properly subtract the Jupiter light, but
are confident this is possible. Although in a relative sense Jupiter is
much brighter at this wavelength than in the 3.4-mu m band typically
used for occultations, the hotspots are also much brighter. We expect
to present occultation light curves from several events during 1996,
and weather permitting will obtain additional observations during the
upcoming G2 and C3 Galileo encounters.

---------------------------------------------------------
Title: Variable Dust Features in Infrared Spectra of AU Cygni
Authors: Little-Marenin, I. R.; Stencel, R. E.; Staley, S. B.
1996ApJ...467..806L Altcode:
We report the first clear evidence for variation in the infrared
spectral features due to silicates in the circumstellar shell of
the oxygen-rich Mira variable AU Cygni, based on individual scans
obtained with the IRAS low-resolution spectrometer, during the 1983
IRAS mission. For the optically thin shell of AU Cyg, the contrast of
the silicate feature is stronger near optical maximum and weaker near
optical minimum. We propose that circumstellar dust has a significant
population of small grains. This population may get enhanced near
maximum, probably due to evaporation of larger grains, increasing the
amount of 10 μm band emission relative to continuum emission. The
shape of the emission feature does not vary measurably from maximum
to minimum brightness.

---------------------------------------------------------
Title: Short-Term Chromospheric Variability in alpha Tauri (K5 III):
Results from IUE Time Series Observations
Authors: Cuntz, Manfred; Deeney, Bryan D.; Brown, Alexander; Stencel,
Robert E.
1996ApJ...464..426C Altcode:
We evaluate time series observations of chromospheric lines (Mg II, Mg
I, and C II) for the K giant α Tau obtained using the IUE LWP camera at
high dispersion. These observations cover a time span of about 2 weeks
in 1994 February-March and were designed to resolve variations occurring
within hours, days, and weeks. We consider the observational results in
relation to theoretical acoustic heating models, motivated by the fact
that αTau may exhibit a basal (i.e., minimum) level of chromospheric
activity. The data reveal flux variations between the extremes of 8%
in Mg II h + k and 15% in each emission component. These variations
occur on timescales as short as 8 hr but not on timescales longer than
∼3 days. For the h and k components, flux variations occurring on a
timescale as short as 1.5 hr are also found. These changes are often
not correlated (and are sometimes even anticorrelated), leading to
remarkable differences in the h/k ratios. We argue that these results
are consistent with the presence of strong acoustic shocks, which
can lead to variable Mg II line emission when only a small number of
strong shocks are propagating through the atmosphere. We deduce the
electron density in the C II] λ2325 line formation region to be log
Ne ≃ 9.0, in agreement with previous studies. Our data
provide evidence that the Mg II basal flux limit for K giants might
be a factor of 4 higher than suggested by Rutten et al.

---------------------------------------------------------
Title: TGIRS - A New Two-Grating Mid-Infrared Spectrometer
Authors: Creech-Eakman, M. J.; Klebe, D. I.; Stencel, R. E.; Williams,
W. J.
1996AAS...188.8506C Altcode: 1996BAAS...28..962C
We present a brief overview of the design and construction of a
Two Grating Infrared Spectrometer (TGIRS), a new mid-IR array,
dual grating spectrometer for the 7.0-13.8 mu m region built at
the University of Denver (DU). This instrument has been designed to
monitor silicate features in evolved stars, but is flexible enough to
accomodate a variety of astrophysical investigations. The instrument
uses diamond-turned aluminum optics to allow warm optical alignment and
eliminate differential contraction of the optics while operating at 6.5
K. Two gratings are used in the optical design to provide a resolution
of about 800. The first grating cross disperses the flux into several
orders, 8-14. The second grating is the high resolution grating which
disperses the flux into each of the above orders over the wavelength
range of the instrument. This second grating has two position settings
controlled by a swing arm device to allow for both maximum spectral
coverage and efficient use of the array detector with the least amount
of moving hardware. The entire assembly is cooled with a Gifford-McMahon
refrigerator so that it may later be adapted for use during remote
observing. The array is a Rockwell 128X128 Si:As BIB Hybrid Focal
Plane Array sensitive to 26 mu m. The dewar is being custom built
by J. K. Henricksen and Assoc. in Vista, CA. Short wavelength IR and
optical radiation is blocked with a long pass filter. The slit of the
instrument is 1"X 4" allowing for both spectral and spatial coverage
of the objects being studied. The electronics package and software
for readout were developed by Wallace Instruments and are already in
use on our TNTCAM at DU. With "first light" scheduled for summer '96,
we expect to have photographs of the instrument for display and data by
year's end. We acknowledge partial support under NASA grant NGT-51290.

---------------------------------------------------------
Title: The Birth and Death of Planetary Systems
Authors: Stencel, R. E.; Backman, D. E.
1996AAS...188.5209S Altcode: 1996BAAS...28..902S
Within the 35 hours allocated for ISO observations under this NASA Key
Project, we planned to examine a sample of normal and evolved stars,
to shed light on the general question of planetary system development
and evolution. Three main observational efforts include: (a) sampling
A, F, G, K and M main sequence stars, defined to have photospheres
detectable in the far-IR, with ISO's 10-30X IRAS sensitivity, to
determine the statistical frequency of mid-IR excesses characteristic
of the Vega-disk phenomenon; (b) mapping the dust disk extensions in
a sample of twelve bright sources with infrared excesses, using ISO's
oversampled mapping mode, and (c) surveying small portions of potential
Kuiper Belt material for parallactic shifts over several months of
time, in regions identified from analysis of far-IR COBE DIRBE data
by Backman, Dasgupta and Stencel (1995). As of this writing (3/96),
only a few percent of our observations have been completed by ISO,
and first release data products are expected in a timely fashion.

---------------------------------------------------------
Title: Mid-Infrared Silicate Variation in Long Period Variable Stars
Authors: Stencel, R. E.; Creech-Eakman, M. J.
1996AAS...188.7202S Altcode: 1996BAAS...28..943S
We present preliminary results of our ongoing monitoring campaign of a
selected group of more than 30 Long Period Variable (LPV) stars at 10,
11 and 18 mu m. Our stars were chosen from a list by Little-Marenin
&amp; Little (1990) based upon a classification scheme of silicate
features of oxygen rich LPV stars. We are monitoring these LPV's for
changes in their silicate features at 10 and 18 mu m with respect to
IR continuum and optical phase. We are attempting to ascertain the
relationship of dust formation to optical period, and any shell-shock
interactions from the acoustic shocks, originating in the photosphere
of the stars and later impinging on these dust forming areas. The
ultimate goal is to determine what conditions lead to dust formation and
destruction in these environments, and whether or not an evolutionary
sequence can be inferred for AGB objects based on their spectra and dust
formation. The instrument being used is Denver Univ.'s (DU) TNTCAM (Ten
aNd Twenty micron CAMera), a liquid Helium cooled, mid-IR camera using
a Rockwell 128x128 Si:As BIB Hybrid Focal Plane Array, sensitive to 26
microns, and housing 7 filters on an externally driven filter wheel
(Klebe et al. 1995). A portion of this list of stars was chosen for
our initial campaign at Wyoming Infrared Observatory (WIRO) in 1993,
including the brightest of our objects with a range of periods and
LML types (Creech-Eakman et al. 1996). The rest of our list consists
of a sample of LML types with periods of 300-400 days and fluxes of
25 +/- 5 Jy at 8 mu m chosen for one of our ISO proposals. Ancillary
mid-IR spectra, exists from LRS on IRAS in '83, our CAESR data from
'93, and CGS-3 data from UKIRT service time in '95. We hope to obtain
photometric data with TNTCAM and spectral data using ISO's SWS, and
TGIRS, DU's new Two Grating mid-IR Spectrometer (Creech-Eakman et al.,
this meeting). We would like to thank the Univ. of Wyoming for time
at WIRO and M. Dahm, T. Eakman, M. Jalakas, D. Klebe &amp; B. Lepore
for assistance in observing. We also acknowledge the partial support
under NASA grant NGT-51290.

---------------------------------------------------------
Title: IUE Monitoring of Long Period Eclipsing Systems, and
Intersystem C2 Lines as Shock Diagnostics in Stellar Chromospheres
Authors: Stencel, Robert E.
1996denv.rept.....S Altcode:
Activities under this grant include: 19th Episode Observing time;
18th Episode Observing time; 16th/17th Episode Observing time; Long
Period Eclipsing Systems; and Intersystem C 2 lines and Shocks in
Stellar Chromospheres.

---------------------------------------------------------
Title: ROSAT Observations of Symbiotic Binaries and Related Objects
Authors: Bickert, K. F.; Greiner, J.; Stencel, R. E.
1996LNP...472..225B Altcode: 1996LNP96.472..225B; 1996sxrs.conf..225B
We present X-ray observations of 217 confirmed or suspected symbiotic
binaries with the ROSAT PSPC during the all-sky survey and 129 archived
pointings. A table lists 3σ upper limits or detected count rates for
survey and pointing observations (available for 46 objects) plus a
collection of UBVJHK brightnesses, stellar types, outburst status, and
structure (jets, ejecta, winds, clouds). The detection of 28 symbiotics
(21 in survey) will be handled in greater detail in a forthcoming paper.

---------------------------------------------------------
Title: Optical, UV and X-ray observations of the symbiotic star AG
Draconis during quiescence and the 1994/1995 outburst
Authors: Greiner, J.; Bickert, K.; Luthardt, R.; Viotti, R.; Altamore,
A.; Gonzales-Riestra, R.; Stencel, R. E.
1996OAP.....9...26G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: HAO II - a large telescope for the extreme high altitude site
at Mt. Evans, Colorado.
Authors: Montgomery, G. E.; Stencel, R. E.
1996BAAS...28.1194M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Model of a Kuiper Belt Small Grain Population and Resulting
Far-Infrared Emission
Authors: Backman, D. E.; Dasgupta, A.; Stencel, R. E.
1995ApJ...450L..35B Altcode:
We have calculated a simple model of the expected Kuiper Belt (KB)
small grain population and the thermal emission that would arise from
such grains. We have also sought observational evidence for this
emission. The model assumed equilibrium between grain creation by
collisional fragmentation of comets and removal by Poynting-Robertson
radiation drag, radiation pressure--driven ejection, mutual collisions,
and sublimation. The model far-IR intensity scales as the square
of total KB mass. Comparison of our model with observations of the
zodiacal dust rules out emission from trans-Neptunian dust representing
more than about 0.3 M_⊕ of KB comets. This agrees with recent HST
reports of a population of comet-sized bodies in the KB which has
a minimum mass of about 0.04 M_⊕ , although that population can
be extrapolated to include as much as 1 M_⊕ in the volume of our
model. The model KB dust fractional bolometric luminosity (Ldust/Lstar)
would have about 10-2 and 10-4 of the values for the grain disks around
Vega and beta Pic, respectively. A preliminary search in COBE DIRBE
data reveals nonuniform bands near the ecliptic of cold (T = 20--30 K)
emission prominent at wavelengths of 140 and 240 mu m but not prominent
relative to zodiacal emission at shorter (IRAS) wavelengths. Most of
this emission is probably not from solar system material.

---------------------------------------------------------
Title: The Infrared Colors of Main Sequence Stars: How Much
Circumstellar Debris is Normal?
Authors: Stencel, Robert E.; Backman, Dana E.
1995Ap&SS.224..401S Altcode:
We have been awarded NASA Key Project observing time on ISO, in
order to establish the true frequency of far-infrared excesses in a
volume-limited sample of main sequence and related stars, and address
the relative success or failure of single stars in processes related
to the forming of planetary systems. For a volume-limited subset of
main sequence and related stars, PHT03 measurements at 3.6, 11.5, 20
and 60 micron will be obtained, using a 120 arsec aperture in all cases
to eliminate possible companion confusion with differing apertures, to
ascertain spectral energy distributions. For the M dwarfs, 100 micron
observations will also be obtained. For some, brighter sources, more
extensive wavelength coverage and improved spatial resolution will be
attempted, using CAM and SWS. Spatially over-sampled PHOT observations
will be made at 60 micron of the brightest and nearest Vega-like sources
to measure the characteristic sizes of the emitting regions and obtain
some information regarding their shapes and orientations. The goal
is not a map, but scan profiles along 3 position angles which can be
deconvolved to find the intrinsic size and shape of the half-maximum
contour of the emitting region. Photometry of selected lines of
sight through the zodiacal dust will also be carried out to look for
outer solar system (Kuiper Belt) material. Observation at a range
of wavelengths, ecliptic latitudes and at 2 epochs is designed to
help untangle foreground Zodiacal from background Kuiper flux, not
necessarily to look for individual macroscopic objects.

---------------------------------------------------------
Title: Silicates in Evolved Stars: The LRS-Maser Chronology Revisited
Authors: Stencel, Robert E.
1995Ap&SS.224..563S Altcode:
Since the publication of our correlation (1990 Ap.J. 350, L45)
suggesting a temporal relationship among: (a) shapes of 10 micron
silicates seen in IRAS Low Resolution Spectra (LRS); (b) IRAS broad
band colors; (c) light curve asymmetries, and (d) the types of masers
associated with various Mira variable stars, the question has arisen
whether the implied chronology refelcts the interval between thermal
pulses, or the more lengthy ascent of the AGB. There is evidence
in favor of the former interpretation. A strong implication of
this idea is that variability among pre-silicate spectra should be
significant. Several examples of this have been found in the extended
LRS database, and are presented. Finally, plans are presented to
continue monitoring of selected variables in the 10 micron region, to
verify the variability suggested in the limited phase coverage provided
in the LRS database. Monitoring will include use of our facilities
at the Mt.Evans-Womble Observatory — highest in the world at 4313
meters altitude.

---------------------------------------------------------
Title: Short-term Mg II flux variations in α Tauri (K5 III):
results from recent IUE data sets
Authors: Cuntz, M.; Deeney, B. D.; Brown, A.; Stencel, R. E.
1995IAUS..176P.162C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Nineteenth Episode Monitoring of Long Period Eclipsing Systems
Authors: Stencel, Robert E.
1995iue..prop.5115S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: GHRS and IUE Observations of the Symbiotic Binary CI Cygni
Authors: Jalakas, M.; Stencel, R. E.; Carpenter, K. G.; Robinson, R. D.
1994AAS...185.2111J Altcode: 1994BAAS...26.1345J
The interacting symbiotic binary star, CI Cygni, is a system
which consists of a hot star orbiting a red giant. Matter from
the larger star is being transfered to the smaller one. Both IUE
and more recently, the Goddard High Resolution Spectrograph on HST
have detected variable ultraviolet emission lines produced by this
transfer. Phase-dependent changes to the doppler velocity of the
matter allow us to map the direction of the flow. Using the HST
snd IUE spectrometers, we re-examined two different types of lines
(resonance and intercombination) which had been reported to show
velocity differences. We will present an analysis of these data showing
the relative locations of high and low density features in the matter
transfer in this system. The lead authors are pleased to acknowledge
partial support for this effort through NASA grant NAG5-2368 to the
University of Denver.

---------------------------------------------------------
Title: Sky Brightness &amp; Acoustic Soundings, Mt.Evans Observatory
Authors: Stencel, R. E.; Dahm, M. A.; Jalakas, M.; Klebe, D.; Emerson,
G.; Butenhoff, C.; Gehrz, R. D.
1994AAS...185.1004S Altcode: 1994BAAS...26.1321S
As a part of the site survey for future telescope construction at
the Mt. Evans Womble Observatory, Colorado [elev.4,303 meters], sky
brightness and acoustic sounding measurements are underway. V band
CCD observations of the photometrically calibrated cluster, NGC 7790
(Odewahn et al, 1992 PASP) were obtained during 1994 Aug/Sept. These
measurements were then compared to a new sky brightness model, based
on methods developed by Garstang (1989, 1991 PASP), which agreed with
other observatory numbers and predicted a zenith sky brightness for
Mt.Evans of 21.65 magnitudes/arcsec(2) . The CCD data, taken during a
period marked by forest fires in the Western U.S. indicate a near-zenith
sky brightness observed of no brighter than 19.5 mag/arcsec(2) . We
plan to obtain additional observations to determine whether seasonal
differences occur. Acoustic sounding observations of airflow over the
Observatory were obtained during 1994 Sept, using the method outlined
by Forbes et al. (1985 Apr. SPIE Symposium 551-34), as applied at Mauna
Kea and other sites. Mt.Evans values for the atmospheric refractive
index structure parameter, C_n(2) , were found to be of order 10(-16)
to 10(-18) m(-2/3) . These values are indicative of an atmospheric
correlation length of a few meters, and a long exposure seeing disk
of theta_ {FWHM}(V) &lt; 1 arcsec. Concurrent, in-dome seeing tests
with the antique 0.6m Ealing-Beck R-C on site, indicate times of
sub-arcsecond seeing, but further statistics are being developed. At
the time of this writing, negotiations with the US Forest Service for
permission to build a 4 meter class optical-IR telescope are proceeding
well, and we would like to contact additional potential collaborators
for said project. We are please to acknowledge the help of Fred Forbes
(NOAO), the Radian Corp. and William Herschel Womble for assistance
with the acoustic soundings.

---------------------------------------------------------
Title: Rapid Line Profile Variations in the Long-Period Interacting
Binary VV Cephei
Authors: Bauer, W. H.; Grenfell, T. G.; Taylor, D. M.; Stencel, R. E.
1994AAS...185.8511B Altcode: 1994BAAS...26Q1461H
Significant variations have been seen on time scales as short as
two weeks in the ultraviolet line profiles of the 20-year period
eclipsing binary system VV Cephei. VV Cep consists of an M supergiant
primary which fills its Roche lobe at periastron and a hot, probably
main-sequence companion surrounded by a disk. Both the primary and
secondary are 20 M_⊙ objects. Stencel et al. (PASP 105, 45) monitored
VV Cep in the ultraviolet every two weeks from 1991 June - Oct. They
integrated the 1200 - 2000 Angstroms and 2000 - 3200 Angstroms fluxes,
finding these wavelength regions to vary together for the most part,
with larger variation seen in the short-wavelength region. Over some
of these two-week intervals, the integrated short-wavelength flux
varied by nearly a factor of two. The high-resolution IUE spectra of
VV Cep are very complex. Numerous emission features (mostly Fe II)
are superimposed on an absorption spectrum similar to those seen
during chromospheric eclipse in the zeta Aur binaries. A few regions
of spectrum which probably represent a continuum from the B star
and/or its accretion disk can be identified. At some times the line
profiles in the chromosphere-like absorption spectrum are symmetric,
but more often, many of them have additional broad absorption features
superimposed on them, which may be either red- or blue-shifted. Over
the 1991 monitoring period, the high-resolution spectra have shown at
least some degree of this additional redshifting. The strength and
velocity distribution within these additional redshifted components
frequently varied significantly over the two-week intervals. Over
the 1991 monitoring period, the highest integrated flux levels seen
corresponded to spectra in which the continuum regions were seen
to be higher and which had minimal additional redshifts. The lowest
integrated flux levels corresponded to spectra with reduced continuum,
and signficant extra redshifts.

---------------------------------------------------------
Title: Extended 60 micron Emission From Nearby Mira Variables
Authors: Hagen Bauer, Wendy; Stencel, Robert E.
1994AJ....107.2233H Altcode: 1994AJ....107.2233B
The Infrared Astronomy Satellite (IRAS) has detected extended emission
around a number of evolved stars. Individual IRAS scans of nearby
Mira variables which showed emission from circumstellar dust and
for which distance estimates were available were examined. Extended
emission at 60 micrometers was detected for R Cas, o Cet, R Leo,
U Ori, and possibly for R Hor. The Leung code for the calculation of
radiative transfer in a circumstellar dust shell was used to calculate
the emission from model dust shells composed of silicate grains. The
output was convolved with the IRAS beam profile to determine whether
steady mass loss could explain the observed extension. The observed
extensions for o Cet, R Hor and U Ori could be due to steady mass loss,
while the model calculations do not produce enough extension to explain
the observations of R Cas and R Leo.

---------------------------------------------------------
Title: 10 Micron Spectra of Long Period Variables
Authors: Creech-Eakman, M.; Stencel, R. E.; Klebe, D.; Williams, J.
1994AAS...184.5501C Altcode: 1994BAAS...26..948C
The University of Denver's Cold Atmospheric Emission Spectral Radiometer
(CAESR) is a cryogenically cooled low resolution grating spectrometer
which scans the 7.4 to 12.8 mu region. It has been adapted from its
balloon flight capabilities for use with a telescope. Over 70 scans of
about 30 different variable and calibration stars were obtained from
1993, Aug. 20 - 24 at the Wyoming Infrared Observatory (WIRO). The
data is read from binary form to an ASCII record of on and off-source
chops and time signatures at a chop frequency of 10 Hz for scans
lasting about 7 minutes. The data, which is recorded in dimensionless
counts of grating position and flux intensity, is then calibrated
in wavelength and flux space with blackbody curves obtained in the
lab. Subtraction of the off-source from on-source chop for each star
yields the stellar and dust feature signatures. This subtracted form
is then noise-filtered with a Fast Fourier Transform technique on a
SPARCstation using IDL software. The resulting signature is then divided
by a similarily processed calibration star signature to obtain the
silicate signature. A comparison of our results with IRAS Low Resolution
Spectrometer data will be presented. We are seeking to establish good
evidence with these and future observations to support the theory that
the silicate signature varies periodically with the variable star's
phase. More observations are needed to ascertain the exact nature of
the silicate and variable star phase variability. We plan to upgrade
to an array spectrometer to continue this investigation. We thank
WIRO and Tracy Hodge for use of the telescope and assistance in its
operation. We also thank Charles Dirks for the initial software to
read the spectral scans and blackbody calibration data. This research
was made possible in part by the generous bequest of William Herschel
Womble to the University of Denver, and NASA Space Grant NGT 40014.

---------------------------------------------------------
Title: ROSAT Detections of Symbiotic Binaries
Authors: Bickert, K.; Stencel, R. E.
1994AAS...184.4509B Altcode: 1994BAAS...26..935B
This poster reports on the results of survey and pointed observations
of symbiotic binaries made with the Roentgen Satellite [ROSAT] during
the sky-survey phase and AOs 2 and 3. Among the goals of the study were
to determine the frequency of xray emission among symbiotics as a class
of astronomical objects, and to determine, insofar as possible, their
high energy variability and spectral characteristics. The symbiotic
star, AG Draconis, known to exhibit optical flare-like events every
few years, was re-observed several times. The initial analysis of
the pointed observations suggests that only a minority of all known
symbiotics were detected at the level of the ROSAT sky survey limit
(f_x \le 10(-12) erg cm(-2) s(-1) ). Further, among those objects
detected, a majority showed evidence in the ROSAT observations for xray
variability. Relatively few showed evidence for photons harder than
about 1 keV. AG Dra may have exhibited a small flare-like event between
1992 June and September. We are pleased to acknowledge assistance by
Tom Fleming and Jurgen Schmitt, as well as partial support for this
effort through NASA ROSAT grant NAG5-2094 to the University of Denver.

---------------------------------------------------------
Title: The Mount Evans Observatory -- Site Survey Update
Authors: Mack, J.; Stencel, R. E.; Klebe, D.; Sullivan, P.; Dirks,
C.; Williams, J.; Emerson, G.; Meyer, E.
1994AAS...184.2607M Altcode: 1994BAAS...26..895M
The Astronomical Almanac lists Mt.Evans Observatory as the world's
highest (Georgetown, Colorado, elev. 4,313 meters). We report
on site observations conducted since our initial report (1993
Bull.A.A.S. 24:1240). Evidence will be provided that the site is
competitive with the best, currently operational optical-infrared
sites. The elevation difference between Denver and the summit is
9,000 feet, which strongly reduces the scattered light contribution to
sky brightness. Astronomical seeing tests, as well as regional cloud
cover statistics will be presented. The mid-continental location and
elevation are responsible for minimal amounts of precipital water
vapor (directly measured at 0.8mm in 1993 Sept. and estimated from
observed temperature, pressure and relative humidity at the site to
be even lower in winter months), giving the Mt.Evans site excellent
infrared transparency. Three years of automated weather station data
from the summit show the daily and annual temperature variations to
be far from extreme, and the average wind field peaks daily at 20
knots out of the west. The treeless summit topography is favorable for
laminar flow, which enhances optical/infrared image quality. Because
Mt. Evans offers a potentially superior observatory site, we will also
address the possiblities for future telescope development. The summit
is easily accessible via a paved State Highway, and the unobstructed
line of sight to the DU campus enhances the possibilities for remote
operations. We are grateful to the estate of William Herschel Womble
for providing funds in support of this investigation.

---------------------------------------------------------
Title: ISO-NASA Key Project: The Birth and Death of Planetary Systems
Authors: Stencel, R. E.; Backman, D. E.
1994AAS...184.1609S Altcode: 1994BAAS...26..884S
The aim of this Infrared Space Observatory [ISO], NASA-selected
Guaranteed Time observing program is to establish the true frequency
for far-infrared excesses in a volume-limited sample of main sequence
and related stars, in order to address the relative success or failure
of single stars in processes related to the forming of planetary
systems. For a volume-limited subset of main sequence and related stars,
PHT03 measurements at 3.6, 11.5, 20 and 60 microns will be obtained,
using a 120 arcsec aperture in all cases to eliminate possible
companion confusion with differing apertures. For the M dwarfs, 100
micron observations will also be obtained. For some, brighter sources,
more extensive wavelength coverage and improved spatial resolution will
be attempted, using CAM and SWS. We also plan PHOT micro-scanning 60
micron observations of the brightest and nearest Vega-like sources to
measure the characteristic sizes of the emitting regions and obtain
some information regarding their shapes and orientations. The goal
is to derive the intrinsic size and shape of the FWHM contour of the
emitting region. We also plan photometry of selected lines of sight
through the zodiacal dust into possible outer solar system (Kuiper Belt)
material. Observations at a range of wavelengths, ecliptic latitudes and
at 2 epochs are designed to help untangle foreground from background
flux, not necessarily to look for individual macroscopic objects. We
are pleased to acknowledge partial support for this effort through
NASA grant NAGW-3680 to the University of Denver.

---------------------------------------------------------
Title: Planetary System Evolution and the VEGA Stars: The Potential
for ESA's Infrared Space Observatory
Authors: Stencel, Robert E.; Backman, Dana E.
1994Ap&SS.212..417S Altcode:
ESA's Infrared Space Observatory [ISO], scheduled for launch within the
next 2 3 years, will place a complement of powerful infrared imagers and
spectrometers into high orbit, with an operational life anticipated to
be about 18 months. During this time, numerous scientific investigations
of every conceivable astrophysical target will be made. The purpose
of this paper is to consider the instrumental complement in terms of
specific observations of Vega-like systems with cold, infrared excesses,
in order to investigate problems relating to the evolution of planetary
systems, and to optimize the scientific results possible with ISO on
such topics.

---------------------------------------------------------
Title: Eighteenth Episode Monitoring of Long Period Eclipsing Systems
Authors: Stencel, Robert E.
1994iue..prop.4841S Altcode:
We propose to obtain fiducial observations of a series of long period
eclipsing binaries, scheduled to eclipse during the next one to 20 year
period. Because IUE has investigated many of these binaries previously,
but cannot be expected to follow them indefinitely, we request that
a program of regular monitoring begin as soon as possible to insure
that as complete a record as possible be acquired. Motivations for
this effort include recent recognition of rapid mass loss transients
from such systems, along with new possibilities to deduce density and
velocity structure in component atmospheres.

---------------------------------------------------------
Title: IUE Observations of the 1993 Eclipse of Zeta Aurigae
Authors: Stencel, R. E.; Potter, D. E.; Stencel, R. E.; Potter, D. E.
1993AAS...183.5405S Altcode: 1993BAAS...25.1377S
Ultraviolet Spectra of Zeta Aurigae, obtained with the IUE satellite
observatory prior to and through mid eclipse(phase .8-.05) are
presented and interpreted according to the model proposed by Stencel
and Chapman 1981. The profiles of various emission lines as a function
of orbital phase through the eclipse are used to infer the conditions
of the extended atmosphere and wind region of the K2II supergiant and
the shocks resulting from the interaction of the B8V and K winds. The
abundant profiles of Fe II are used to interpret the relatively cooler
regions of the K star atmosphere while the profiles of C IV, Si IV and
Fe III are used to reveal the structure of the hotter shock regions. The
complex P Cygni profile of the Mg II resonance lines are identified
as having components produced in the circumstellar, interstellar, and
emission regions of the system. Ultraviolet Spectra of Zeta Aurigae,
obtained with the IUE satellite observatory prior to and through mid
eclipse(phase .8-.05) are presented and interpreted according to the
model proposed by Stencel and Chapman 1981. The profiles of various
emission lines as a function of orbital phase through the eclipse are
used to infer the conditions of the extended atmosphere and wind region
of the K2II supergiant and the shocks resulting from the interaction
of the B8V and K winds. The abundant profiles of Fe II are used to
interpret the relatively cooler regions of the K star atmosphere while
the profiles of C IV, Si IV and Fe III are used to reveal the structure
of the hotter shock regions. The complex P Cygni profile of the Mg II
resonance lines are identified as having components produced in the
circumstellar, interstellar, and emission regions of the system.

---------------------------------------------------------
Title: ROSAT-IUE observations of symbiotic stars. The X ray morphology
of high latitude associations
Authors: Stencel, Robert E.
1993colo.reptQ....S Altcode:
The purposes of this grant included: to provide for continuing
investigations of the x-ray properties of a class of interacting
binaries known as symbiotic stars through analysis of their
detection statistics in the ROSAT All-Sky Survey and simultaneous IUE
observations; and to obtain and analyze ROSAT images of selected high
latitude OB star associations, in order to permit multi-wavelength
dissection of their contents and energetics. The first study is
expected to result in enhanced information on mass transfer and
accretion in such systems, and provide a more quantitative basis
for interpretation of the spectra of these and similar stellar and
extragalactic systems. This particular effort represents NASA support
for an approved collaboration between the PI and the ROSAT Team at
MPE Garching. In the second study, we seek to correlate the strength
with which the diffuse clouds have been shocked and the recent star
formation triggered, namely, the O and B stars of the Association,
as well as nearby T Tauri stars. The large scale X-ray emission in
deep ROSAT PSPC images will be compared with the optical, infrared,
and radio topology of nearby supernova remnants, molecular clouds, and
the distribution of massive stars in the regions. This should enable
us to test whether the star formation triggering shocks originate
from in the galactic plane (nearby supernovae) or from the collision
of infalling matter with the disk material (galactic fountain dynamics).

---------------------------------------------------------
Title: Line Profile Variations in M Giants: Clues to Mass-Loss and
Chromospheric Heating Mechanisms
Authors: Judge, P. G.; Luttermoser, D. G.; Neff, D. H.; Cuntz, M.;
Stencel, R. E.
1993AJ....105.1973J Altcode:
Analysis is presented of time-series, high dispersion spectra of
the Mg II, k, Ca II H, and K lines of the semiregular giants Rho Per
(M4 II-III, periodicity of about 50 days), R Lyr (M5 III, period of
about 46 days), and g Her (M6 III, period of about 90 days). The fine
error sensor on the IUE satellite and ground based UBV photometry was
used to relate line profile variations to photospheric variations. The
above mentioned stars were selected to study the relative importance
of convective motions and global stellar pulsations in determining
the structure of the outer atmospheres. Small amplitude changes, but
substantial changes in the profiles of Mg II and Ca II lines were
detected. It is contended that the observed variability is due to
changes in chromospheric conditions and not variations within the
circumstellar shell. The picture of a steady state chromosphere,
which is modulated on long time scales, is corroborated by these
observations. Localized heating is found in g Her.

---------------------------------------------------------
Title: Sixteenth Episode Monitoring of Long Period Eclipsing Systems
Authors: Stencel, Robert E.
1993iue..prop.4587S Altcode:
We propose to obtain fiducial observations of a series of long period
eclipsing binaries, scheduled to eclipse during the next one to 20 year
period. Because IUE has investigated many of these binaries previously,
but cannot be expected to follow them indefinitely, we request that
a program of regular monitoring begin as soon as possible to insure
that as complete a record as possible be acquired. Motivations for
this effort include recent recognition of rapid mass loss transients
from such systems, along with new possibilities to deduce density and
velocity structure in component atmospheres.

---------------------------------------------------------
Title: Additional Spectroscopic Discoveries Possible Among Late Type,
Evolved Stars with ISO
Authors: Stencel, Robert E.
1993ASPC...41..113S Altcode: 1993ais..conf..113S
No abstract at ADS

---------------------------------------------------------
Title: Does the Ten Micron Dust Feature Vary in Miras? A Survey of
LRS Spectra
Authors: Little-Marenin, Irene R.; Staley, Stephanine B.; Stencel,
Robert
1993ASPC...41..117L Altcode: 1993ais..conf..117L
No abstract at ADS

---------------------------------------------------------
Title: Extended 60 μm Emission from Nearby Mira Variables
Authors: Bauer, W. H.; Stencel, R. E.
1993AAS...18111912B Altcode: 1993BAAS...25..743B
Circumstellar dust envelopes around some optically visible late-type
stars are so extensive that they are detectable as extended at an
arc-minute scale by the IRAS survey observations (Stencel, Pesce
and Bauer 1988, Astron. J 95, 141; Hawkins 1990, Astron. Ap. 229,
L8). The width of the IRAS scan profiles at 10% of peak intensity is an
indicator of source extension. Wyatt and Cahn (1983, Ap. J. 275, 225)
presented a sample of 124 Mira variables in the solar neighborhood. Of
this sample, 11 Miras which show silicate emission are bright enough
at 60 microns for a significant determination of the width of a scan
at 10% of peak flux. Individual scans and maps were examined in order
to determine whether any observed extension was associated with the
central star. Five stars showed significant extension apparently due
to mass loss from the central star: R Leo, o Cet, U Ori, R Cas and
R Hor. IRAS LRS spectra, point source fluxes and observed extensions
of these sources are compared to the predictions of model dust shells
which assume steady mass loss. This work was supported in part by NASA
grant NAG 5-1213 to Wellesley College.

---------------------------------------------------------
Title: Rapid Mass-Loss Transients in VV Cephei
Authors: Stencel, Robert E.; Potter, Daniel E.; Bauer, Wendy H.
1993PASP..105...45S Altcode:
Biweekly ultraviolet observations of the red supergiant-hot dwarf
binary, VV Cephei during 1991, obtained near third quadrature, have
revealed the existence of short-term continuum variations. We infer
these are superposed on an underlying emission-line spectrum. The
viewing geometry of this long period system suggests we are seeing
a process associated with non-uniform mass transfer to an accretion
disk. This rapid variability can be related to global instabilities in
the stellar wind and mass loss from the red supergiant. (SECTION: Stars)

---------------------------------------------------------
Title: ROSAT Observations of Symbiotic Stars
Authors: Bickert, K. F.; Stencel, R. E.; Luthardt, R.
1993IAUS..155..405B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Molecular catastrophes and circumstellar SiO masers
Authors: Stencel, Robert E.
1993LNP...412..449S Altcode: 1993asma.conf..449S
Understanding the complex SiO maser regions of highly evolved stars
can be improved through multiwavelength studies of 'premaser' stars,
such as M0-M4 giants and semiregular variables, which can be placed
on normal H-R diagrams unlike most of the OH-IR stars. I argue that
SiO masers are a key part of the transformation of hot stellar plasma
into cold circumstellar silicate dust, in the outflows from evolved,
oxygen rich stars. Evidence for this statement rests on the following:
(1) red giant mass loss originates in a stochastic, amsotropic manner;
(2) SiO maser maps of Miras and red supergiants show numerous maser
spots within a few stellar radii; (3) molecules and dust naturally form
in a cooling outflow; (4) the IRAS Low Resolution Spectrometer provided
evidence for diverse and variable 10 micron silicate features in Miras,
and these shapes correlate well with the proposed maser chronology,
suggesting a formation and annealing sequence. The theory for the
occurrence of SiO masers involving thermal instability, related 'new'
physics, recent calculations and a prediction are discussed.

---------------------------------------------------------
Title: VVNRS: Variable phenomena in VV Cephei
Authors: Stencel, Robert E.
1993colo.reptR....S Altcode:
The current research project (VVNRS) involves VV Cephei, which is
a binary system in which a 20 solar mass main sequence star orbits
within the extended atmosphere of the 40 solar mass M-type supergiant
primary. Although the period of the system is 20.3 years, the components
are close enough for a stream of matter from the primary to form an
accretion disk around the hot secondary. We had previously completed
an ADP-sponsored study of twelve years of archival spectra of this
system and were surprised to find intermittent changes in the line
profiles of the chromosphere-like absorption spectrum. This we think
may be related to the accretion process. The previously existing
spectra were not closely spaced enough in time to clearly delineate
the nature of these changes. Therefore, we proposed and were granted
eleven half-shifts to obtain closely spaced IUE spectra during IUE's
14th year of operations (1991/1992).

---------------------------------------------------------
Title: Mount Evans Observatory: Infrared Spectroradiometric
Observations and Site Survey Results
Authors: Klebe, D.; Mack, J.; Wiese, K.; Williams, J.; Stencel, R.
1992AAS...181.7411K Altcode: 1992BAAS...24.1240K
The 24 inch Cassegrain at U of Denver's Mount Evans Observatory
(elev. 14,154 feet) is being renovated and utilized to measure
selected bright infrared objects in the 16 to 28 micron infrared
spectral region. The mirrors have been refurbished and the telescope
drive upgraded with a PC-controlled microstepper system. Software and
hardware are now in place to control the sky chop and nod functions
required for operating our infrared spectral radiometer. A small
observing room facility adjacent to the dome has been added. Spectral
radiometric observations and associated analysis of CW Leo, Mars and
selected lunar surface regions, covering the 16 to 28 micron spectral
interval will be presented, and compared with available IRAS LRS data
(8--23 microns). The transparency in the atmospheric windows will be
discussed quantitatively. In parallel, the results of ongoing site
survey studies of water vapor column and meteorological conditions will
be presented, including estimates for the number of days per year with
total water vapor &lt;2 pr mm and &lt;1 precipitable millimeters. We
are grateful to the estate of William Herschel Womble for providing
funds to support these activities.

---------------------------------------------------------
Title: The Search for Acoustically-Driven Mass-Loss in Evolved Stars
Authors: Stencel, R. E.; Brown, A.; Carpenter, K. G.; Cuntz, M.;
Judge, P.
1992AAS...181.3603S Altcode: 1992BAAS...24.1175S
Recent ab-initio calculations of stochastic stellar wind models by
Cuntz (1992 in Cool Stars VII, ASP Conf. Ser. 26, p.383) have proven
remarkably robust in predicting observed chromospheric flow patterns
including possible variabilities with time in selected cool, evolved
stars. The calculations solve the equations of hydrodynamics using
the method of characteristics and assume: (i) saw-tooth shock wave
profiles, and (ii) wave periods were changed stochastically while
keeping the wave amplitudes constant (see Cuntz 1990 Ap.J. 349,
p.141). Among the results of fitting chromospheric flow velocities is
the implication that the permitted range of acoustic wave periods for
a given star is constrained. We made use of the IUE satellite during
August and September 1992 to repeatedly observe two stars, the yellow
giant Aldebaran (K5 III) and the red supergiant, Betelgeuse (M2 Iab),
in order to sample variations in their atmospheres on timescales of ~
10(4) to ~ 10(6) seconds, which bracket the predicted mean acoustic wave
periods for these objects. In particular, we obtained deep exposures
in order to measure density-sensitive line ratios within the C II]
intercombination features near 2325A (cf. Lennon et al. 1985 Ap.J. 294,
p.200) to test the hypothesis that density fluctuations could be
measured as a consequence of these acoustic waves. The results of
these observations will be presented and discussed in terms of the
number and amplitude of acoustic waves contributing to chromospheric
heating and mass loss from these stars, as well as the wave origins in
the evolving oscillatory structure of these stellar interiors. We are
pleased to acknowledge IUE--NASA grant NAG5-2103 for partial support
of this effort.

---------------------------------------------------------
Title: To vary or not to vary: SiC Dust Emission from Circumstellar
Shells
Authors: Little, S. J.; Little-Marenin, I. R.; Staley, S. B.; Stencel,
R. E.
1992AAS...181.5011L Altcode: 1992BAAS...24Q1205L
Analysis of the low resolution spectra obtained by IRAS has shown that
the 10 microns silicate dust grain emission feature varies in M type
Mira variables in phase with their optical light curves (Little-Marenin
and Stencel, 1992, ASP Conf. Ser. vol 26, 591). Both the strength of
the emission feature and the the 12 microns PSCII fluxes show the same
dependence on time. The magnitude difference between maximum and minimum
for those Miras is between 1-2 magnitudes, similar to their K magnitude
variation. The strength of the emission feature varies by 20-30% during
the same time interval. Of the 22 carbon star Miras with LRS spectra,
16 (70%) are listed in the point source catalog with a variability
index greater than 7 indicating that the individual point source fluxes
showed variablity. Among the M star Miras we also found that about 70%
of the stars showed variablity. However, unlike the 10 microns silicate
feature in M Miras, the strength of the SiC dust emission feature in C
stars shows little if any variation in strength with time despite the
variations in the 12 microns broadband fluxes of up to one magnitude,
reflecting differences in the formation mechanisms between the silicate
and SiC dust grains. The optical depths of the circumstellar shell
in the 8-22 microns region for C stars with SiC dust grain features
is usually small since this part of the spectrum can be matched with
blackbody energy distributions close to the effective temperature
of the star. We find that M stars with silicate features have larger
optical depths since their black body temperature obtained by fitting
the 8-22 microns region is typically around 600-800K.

---------------------------------------------------------
Title: On the Interaction between Dust and Gas in Late-Type Stellar
Atmospheres and Winds
Authors: MacGregor, K. B.; Stencel, R. E.
1992ApJ...397..644M Altcode:
An assumption inherent to most models of dust-driven winds from cool,
evolved stars is that the radiative and collisional drag forces acting
on an individual dust grain are in balance throughout the flow. We have
checked the validity of this supposition of 'complete momentum coupling'
by comparing the grain motion obtained from such a model with that
derived from solution of the full grain equation of motion. For physical
conditions typical of the circumstellar envelopes of oxygen-rich red
giants, we find that silicate grains with initial radii smaller than
about 5 x 10 exp -6 cm decouple from the ambient gas near the base of
the outflow. The implications of these results for models of dust-driven
mass loss from late-type giants and supergiants are discussed.

---------------------------------------------------------
Title: Rapid Mass-Loss Transients in VV Cephei
Authors: Potter, D.; Stencel, R. E.; Bauer, W. H.
1992AAS...181.6613P Altcode: 1992BAAS...24.1226P
No abstract at ADS

---------------------------------------------------------
Title: Galactic OB associations in the Northern Milky Way
Galaxy. I. Longitudes 55 to 150.
Authors: Garmany, C. D.; Stencel, R. E.
1992A&AS...94..211G Altcode:
The literature on all OB associations was reviewed, and their
IRAS point source content was studied, between galactic longitude
55 and 150 deg. Only one third of the 24 associations listed by
Ruprecht et al. (1981) have been the subject of individual studies
designed to identify the brightest stars. Distances to all of
these were recomputed using the method of cluster fitting of the
B main sequence stars, which makes it poossible to reexamine the
absolute magnitude calibration of the O stars, as well as for the
red supergiant candidate stars. Also examined was the composite HR
diagram for these associations. Associations with the best defined
main sequences, which also tend to contain very young clusters,
referred to here as OB clusters, have extremely few evolved B and A
or red supergiants. Associations with poorly defined main sequences
and few OB clusters have many more evolved stars. They also show an
effect in the upper HR diagram referred to as a ledge by Fitzpatrick
and Garmany (1990) in similar data for the Large Magellanic Cloud. It
is suggested that the differences in the associations are not just
observational selection effects but represent real differences in age
and formation history.

---------------------------------------------------------
Title: Wind-Driven Dust: The Interaction Between Dust; Gas in
Late-Type Stellar Atmospheres; Winds
Authors: MacGregor, K. B.; Stencel, R. E.
1992ASPC...26..484M Altcode: 1992csss....7..484M
No abstract at ADS

---------------------------------------------------------
Title: LUE; ROSAT Survey Observations of Symbiotic Stars
Authors: Stencel, R. E.; Brugel, E. W.; Kenyon, S. J.; Bickert, K. F.;
Fleming, T. A.; Schmitt, J. H. M. M.
1992ASPC...26...46S Altcode: 1992csss....7...46S
No abstract at ADS

---------------------------------------------------------
Title: Extended 60-m Emission from Nearby Mira Variables
Authors: Bauer, W. H.; Stencel, R. E.
1992ASPC...26..478B Altcode: 1992csss....7..478B
No abstract at ADS

---------------------------------------------------------
Title: A stellar evolution paradigm based on specific mass loss and
feedback modes.
Authors: Cuntz, Manfred; Stencel, Robert E.
1992ASPC...26..451C Altcode: 1992csss....7..451C
The authors present a new paradigm for stellar evolution which deals
with a detailed treatment of mass loss and feedback modes. The
paradigm is presented as a logical diagram which describes the
respective dependencies of atmospheric properties relevant to mass
loss generation. (orig.)

---------------------------------------------------------
Title: Do Dust Grain Signatures Vary During the Light Cycle of A Mira?
Authors: Little-Marenin, I. R.; Stencel, R. E.
1992ASPC...26..591L Altcode: 1992csss....7..591L
No abstract at ADS

---------------------------------------------------------
Title: A new paradigm of stellar evolution including detailed mass
loss processes
Authors: Cuntz, M.; Stencel, R. E.
1992iesh.conf..182C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Four Years of Monitoring a Orionis with the VLA: Where have
all the Flares Gone?
Authors: Drake, S. A.; Bookbinder, J. A.; Florkowski, D. R.; Linsky,
J. L.; Simon, T.; Stencel, R. E.
1992ASPC...26..455D Altcode: 1992csss....7..455D
No abstract at ADS

---------------------------------------------------------
Title: Intersystem C II Lines as Shock Diagnositics in Stellar
Chromospheres
Authors: Stencel, Robert E.
1992iue..prop.4307S Altcode:
The mid-UV intersystem lines of C II near 2325A have been demonstrated
to provide a useful diagnostic for stellar chromospheres, through
density sensitive variations of the multiplet line ratios. Recent
HST/GHRS observations of the K5 III star Alpha Tau surprised
investigators in revealing unexpectedly large line widths of near 25
km/sec. These widths are thought to arise from either high levels
of turbulence or some other new line broadening mechanism. If the
turbulence arises from stochastic acoustic waves, as theorized
by Cuntz and others, variations in the C II] line strengths and
density-sensitive line ratios are anticipated. We propose to survey
a sample of non-coronal giant and supergiant stars to look for this
variation on timescales of days and months, and in combination with
the limited archival data, years.

---------------------------------------------------------
Title: Fifteenth Episode Monitoring of Long Period Eclipsing Systems
Authors: Stencel, Robert E.
1992iue..prop.4302S Altcode:
We propose to obtain fiducial observations of a series of long period
eclipsing binaries, scheduled to eclipse during the next one to 20 year
period. Because IUE has investigated many of these binaries previously,
but cannot be expected to follow them indefinitely, we request that
a program of regular monitoring begin as soon as possible to insure
that as complete a record as possible be acquired. Motivations for
this effort include recent recognition of rapid mass loss transients
from such systems, along with new possibilities to deduce density and
velocity structure in component atmospheres.

---------------------------------------------------------
Title: New Low-Resolution Spectrometer Spectra for IRAS Sources
Authors: Volk, Kevin; Kwok, Sun; Stencel, R. E.; Brugel, E.
1991ApJS...77..607V Altcode:
Low-resolution spectra of 486 IRAS point sources with Fnu(12
microns) in the range 20-40 Jy are presented. This is part of an effort
to extract and classify spectra that were not included in the Atlas
of Low-Resolution Spectra and represents an extension of the earlier
work by Volk and Cohen which covers sources with Fnu(12
microns) greater than 40 Jy. The spectra have been examined by eye and
classified into nine groups based on the spectral morphology. This new
classification scheme is compared with the mechanical classification
of the Atlas, and the differences are noted. Oxygen-rich stars of the
asymptotic giant branch make up 33 percent of the sample. Solid state
features dominate the spectra of most sources. It is found that the
nature of the sources as implied by the present spectral classification
is consistent with the classifications based on broad-band colors of
the sources.

---------------------------------------------------------
Title: Twelve years of IUE spectra of the interacting binary VV
Cephei.
Authors: Bauer, W. H.; Stencel, R. E.; Neff, D. H.
1991A&AS...90..175B Altcode: 1991A&AS...90..175H
All well-exposed high-resolution IUE spectra obtained of the eclipsing
binary system VV Cephei (M2Iabep + B) are examined. High-temperature
absorption features attributable to the hot companion were detected,
indicating that the companion (or the inner regions of its accretion
disk) are not as hot as a B1-B2 star. Doubling of Fe II (UV 1) lines,
with an additional narrow component redshifted by about 60 km/sec,
occurs only when the B star is behind the plane of the sky containing
the M supergiant, suggesting the existence of mass transfer from the
red to the blue star. Absorption features from neutral elements weaken
dramatically during egress, while those from ionized elements remain
at nearly constant strength. During egress from primary eclipse,
the Mg II resonance doublet shows asymmetric double-peaked emission
indicative of formation in an expanding chromosphere. It is concluded
that the outer atmosphere of the M supergiant is highly clumped.

---------------------------------------------------------
Title: S Persei : optical and water maser variability - 1984 to 1990.
Authors: Little-Marenin, I. R.; Benson, P. J.; McConahay, M. M.;
Cadmus, R. R., Jr.; Stencel, R. E.; Eriksson, K.
1991A&A...249..465L Altcode:
The M supergiant S Persei was monitored since 1984 optically and
since 1987 for water maser emission at 22 GHz. The dozen H2O maser
features show complex variations in intensity with many of the features
varying independently of one another. Some of the water maser features
brightened dramatically at the time of the bright optical maximum
observed in 1988 August and again 10 weeks later. It is possible the
increase in water maser intensity is related to the ejection of a dust
shell near the time of the preceding optical minimum. The intensity
variations of the maser spectrum as being produced by an asymmetric
distribution of maser spots are interpreted. A double shell of maser
spots may be present on the near side of the shell, but appears to be
lacking or be occulted on the far side. No chromospheric activity was
detected about 10 weeks after optical maximum. A well developed shock
is seen in a near-infrared spectrum obtained in 1988 October.

---------------------------------------------------------
Title: Evolution of the Chromospheres and Winds of Low- and
Intermediate-Mass Giant Stars
Authors: Judge, P. G.; Stencel, R. E.
1991ApJ...371..357J Altcode:
Results are presented of an empirical analysis of the global
thermodynamical requirements of the winds in the outer atmospheres of a
representative sample of red giant stars of low- and intermediate-mass
range. Results indicate that the mass-loss rates in these stars are
not strongly dependent on the actual physical processes driving the
winds. It is suggested that nonlinear processes act to regulate wind
energy fluxes. Possible mechanisms responsible for the chromospheric
heating and the mass loss in the low- and intermediate-mass giant
stars are discussed.

---------------------------------------------------------
Title: Galactic OB Associations in the Northern Milky Way Galaxy
Authors: Garmany, C. D.; Stencel, R. E.
1991BAAS...23..909G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Survey for Infrared Excesses among High Galactic Latitude
SAO Stars
Authors: Stencel, Robert E.; Backman, Dana E.
1991ApJS...75..905S Altcode:
This project involves extending the previous analysis of infrared
excesses among a volume-limited sample of 134 nearby A-K main-sequence
stars to a magnitude-limited sample of stars, culled from the SAO
Catalog, with excesses determined from the IRAS Point Source Catalog
flux density ratios. This new sample includes 5706 B-M type stars,
379 of which have infrared excesses. The objective involved use of a
statistically complete survey of objects in a standard catalog in order
to assess the frequency with which different physical processes can
affect the infrared output of stars. These processes include, but are
not limited to, orbiting cold particle clouds and the onset of rapid
mass loss. It is concluded that cold disks are consistent with the
infrared excesses found among A-G dwarfs and G-K giants in the sample.

---------------------------------------------------------
Title: On the Nature of the Symbiotic Binary CI Cygni
Authors: Kenyon, S. J.; Oliversen, N. A.; Mikolajewska, J.;
Mikolajewski, M.; Stencel, R. E.; Garcia, M. R.; Anderson, C. M.
1991AJ....101..637K Altcode:
An analysis of ultraviolet and optical spectroscopy is presented for
the symbiotic binary CI Cyg. This system contains an M5 II asymptotic
branch giant Mg of about 1.5 solar mass, transfering material at a few
times 0.00001 solar mass/yr into a large accretion disk surrounding a
main-sequence star with Mh of about 0.5 solar mass. A boundary layer at
the inner edge of the disk photoionizes a small nebula approximately
confined to the Roche volume of the accreting star. An extended,
more highly ionized region forms when material ejected from the disk
interacts with the red giant wind.

---------------------------------------------------------
Title: Cometary clouds and other circumstellar shells.
Authors: Stencel, R. E.
1991ASPC...14..158S Altcode: 1990ASPC...14..158S
The proposed compound paradigm for the analysis of evolved stars
is based upon not only evidence for dust driven mass loss in a
circumstellar shell, but also the existence of residual material left
over from the star's formation era. Direct evidence for both types of
circumstellar matter has been provided by IRAS and related studies. New
observational opportunities are outlined.

---------------------------------------------------------
Title: A search for red supergiant stars in the northern Milky Way.
Authors: Stencel, R.; Overgard, E.; Garmany, K.; Casa, J. P.; Wing, R.
1991ASPC...20..621S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: What Can Observations of Giants and Supergiant Stars Tell Us
About Chromospheric and Coronal Heating?
Authors: Cuntz, M.; Stencel, R. E.
1991mcch.conf..206C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Ultraviolet Monitoring of VV Cephei
Authors: Stencel, Robert E.
1991iue..prop.4041S Altcode:
VV Cephei, like alpha Ori, is a well studied M supergiant. However,
VV Cep also is a binary system in which a 20 solar mass main sequence
star orbits within the extended atmosphere of the M supergiant
primary. Although the period of the system is 20.3 years, the components
are relatively close enough for a stream of matter from the primary
to form an accretion disk around the hot secondary. We have recently
completed a study of 12 years of archival IUE spectra of this system
and were surprised to find frequent, intermittent changes in the line
profiles of the chromosphere-like absorption spectrum. We believe
these changes may be related to the non-steady mass loss from the
red supergiant, feeding the accretion process. Existing spectra are
not closely enough spaced in time to delineate the nature of these
changes. Therefore, we request 8 half-shifts in order to observe
VV Cephei every two weeks during a 2-1/2 month period in summer '91
as well as a 6 week period in winter '92 during which the system is
optimally accessible to IUE.

---------------------------------------------------------
Title: Workstation-based preprocessing of IRAS sky-flux images
Authors: Domik, Gitta; Brugel, Edward W.; Stencel, Robert E.; Pang,
Jinzhong; Vasudevan, Subramanian
1990PASP..102.1167D Altcode:
Computer algorithms to remove two types of degradations in IRAS sky-flux
images, namely slowly varying background illumination (strongly
effected by the presence of zodiacal light) and periodic stripes,
are presented. This paper discusses both algorithms in detail and
shows results of its use on various sky-flux images. Focus of the work
was on the implementation within a workstation environment, and its
value as a preprocessing tool for researchers. Speed of the process,
usability of the programs, and correctness of the results were the
main goals in developing these tools.

---------------------------------------------------------
Title: Spatial Segregation of Red Supergiant Star Members in
Certifiable OB Associations
Authors: Stencel, R. E.; Garmany, C. D.; Overgard, E.
1990BAAS...22..797S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Applications of IRAS Preprocessing at the Workstation
Authors: Domik, G. O.; Brugel, E. W.; Stencel, R. E.; Vasudevan, S.;
Pang, J.
1990BAAS...22..828D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Twelve Years of IUE Spectra of the Interacting Binary VV Cephei
Authors: Bauer, W. H.; Stencel, R. E.; Neff, D. H.
1990BAAS...22..830B Altcode: 1990BAAS...22..830H
No abstract at ADS

---------------------------------------------------------
Title: The Formation and Annealing of Circumstellar Dust, as Gauged
by IRAS Low-Resolution Spectra and the Microwave Maser Chronology
Authors: Stencel, Robert E.; Nuth, Joseph A., III; Little-Marenin,
Irene R.; Little, Stephen J.
1990ApJ...350L..45S Altcode:
By comparing IRAS mean colors and LRS spectral differences in a large
sample of Mira variables with the chronological sequence for development
of microwave maser emission among such stars, it appears possible to
describe a dust grain formation and annealing sequence. The early time
spectra are dominated by aluminum oxides, which are then overrun by
the emergence of silicates. Rather than the growth of silicate mantles
on aluminate cores, this sequence is interpreted as a simple result
of the higher electron affinity of aluminum for oxygen, resulting in
an initial abundance of AlO bonds in the underoxidized grains. Once
all the Al becomes fully oxidized, the relative abundances of Al and
Si dictate that the AlO signature will be swamped by the growth of
the SiO stretching fundamental. The correlations among the proposed
dust chronology, the increasingly thick circumstellar envelopes,
and the light curve asymmetries of Mira variables are instructive for
understanding the evolutionary changes occurring in such stars.

---------------------------------------------------------
Title: Toward Mapping the Ultraviolet Circumstellar Shells of
Late-Type Stars
Authors: Stencel, Robert E.; Judge, Philip G.; Carpenter, Kenneth G.
1990ASPC....9..467S Altcode: 1990csss....6..467S
Detection of spatially resolved circumstellar matter surrounding
selected cool stars, using off-source observations made with the
International Ultraviolet Explorer satellite, is reported. The data
demonstrate that: (1) the instrumental scattered light profile of
IUE appears to depend on the ultraviolet color temperature of the
star observed, and (2) certain red stars show signal in excess of the
instrumental levels, at spatial offsets of 10 to 20 arc-seconds from
the star.

---------------------------------------------------------
Title: The Evolution of Chromospheres and Winds of Low and
Intermediate Mass Giant Stars
Authors: Judge, P. G.; Stencel, R. E.
1990ASPC....9..411J Altcode: 1990csss....6..411J
No abstract at ADS

---------------------------------------------------------
Title: Mapping the UV Circumstellar Nebulae of Cool Stars
Authors: Stencel, Robert E.
1990iue..prop.3752S Altcode:
We propose to continue experimentation with a promising technique of
offsource observing with IUE, to pursue direct detection and analysis
of reflection nebulae surrounding cool, evolved stars. With CMKRS
observing time in 1988 and some Discretionary time in 1989, we have
demonstrated that: (a) the instrumental scattered light profile of
IUE depends on the effective temperature of the star in question,
and (b) that red supergiants like Antares and Betelgeuse show signal
well in excess of the instrumental levels, at distances of 10 to 20
arc-seconds from the star. This signal is circumstellar in origin,
and will permit new estimates of density and temperature structure in
the circumstellar nebula.. However, to secure these results, additional
calibration and circumstellar sources need to be observed.

---------------------------------------------------------
Title: IRAS Low Resolution Spectra of 26 Symbiotic Stars
Authors: Stencel, Robert E.; Brugel, Edward W.; Goodwill, Michael E.
1990ASPC....9..217S Altcode: 1990csss....6..217S
Data related to the spectral scans for 26 symbiotic stars are described
which were extracted from the IRAS low resolution database. Data from
the 8-15- and 15-23-micron bands are merged in a program that scales
the longer wavelength and produces a weighted average of the spectral
scans for each source. The survey shows that active dust producers
can probably be isolated and some theories related to the presence of
dust emission features are discussed in terms of source variability
for measurements made with low resolution spectra.

---------------------------------------------------------
Title: The Formation and Anneling of Circumstellar Dust, as Gauged
by IRAS LRS Spectra
Authors: Little-Marenin, I. R.; Little, S. J.; Stencel, R. E.; Nuth,
J. A., III
1989BAAS...21.1118L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Far-Infrared Properties of Flare Stars and dM Stars
Authors: Mullan, D. J.; Stencel, R. E.; Backman, D. E.
1989ApJ...343..400M Altcode:
Results are reported from a search of the IRAS data base for flare
stars and for a control sample of dM stars. At 12 microns, 70-80
percent of both samples have been detected. The K-12 colors of flare
stars are significantly different from those of dM stars: for a given
K magnitude, a flare star is about 70 percent brighter at 12 microns
than a dM star. At 100 microns, 27 percent of the flare stars which are
sources at 12 microns have been detected, while none of the comparable
dM stars has been detected. Implications for microflaring are discussed.

---------------------------------------------------------
Title: Infrared Circumstellar Shells: Origins, and Clues to the
Evolution of Massive Stars
Authors: Stencel, Robert E.; Pesce, Joseph E.; Bauer, Wendy Hagen
1989AJ.....97.1120S Altcode:
The infrared fluxes, spatial and spectral characteristics for a
sample of 111 supergiant stars of spectral types F0 through M5 are
tabulated, and correlations examined with respect to the nature of their
circumstellar envelopes. One-fourth of these objects were spatialy
resolved by IRAS at 60 microns and possess extended circumstellar
shell material, with implied expansion ages of about 10 to the 5th
yr. Inferences about the production of dust, mass loss, and the
relation of these characteristics of the evolution of massive stars,
are discussed.

---------------------------------------------------------
Title: On the Luminosities and CN Strengths of Stars with Dust Shells
in a Region in Monoceros
Authors: Wing, R. F.; Stencel, R. E.
1989BAAS...21..790W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Line Identifications in the Ultraviolet Spectrum of 31 Cygni
Authors: Bauer, Wendy Hagen; Stencel, Robert E.
1989ApJS...69..667B Altcode: 1989ApJS...69..667H
Line identifications are presented for the Zeta Aur-type eclipsing
binary system 31 Cyg (K4 Ib + B4 V). The rich absorption spectrum
observed during chromospheric eclipse has been nearly completely
identified. This list will be useful in analyzing spectra of
related binaries, such as 32 Cyg and VV Cep. The large number of line
transitions contributing to many of the observed features indicates that
spectrum synthesis methods for determining chromospheric properties will
be more useful than curve-of-growth analyses of individual lines. The
emission spectrum seen during primary eclipse has also been described
and identified.

---------------------------------------------------------
Title: A Search for Red Supergiant Stars in the Northern Milky Way
Authors: Stencel, R.; Overgard, E.; Garmany, K.; Pesce, J.; Wing, R.
1989BAAS...21..790S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Oxygen-rich mass loss from carbon-rich stars-some implications
Authors: Stencel, Robert E.; Pesce, Joseph E.
1989AIPC..183..416S Altcode: 1989cam..conf..416S
We have evaluated the degree of dust to gas coupling in the atmospheres
of red giant stars, and find non-zero drift velocities. Chemical
fractionation of the stellar atmosphere on an evolutionary timescale
is implied.

---------------------------------------------------------
Title: Book-Review - Cool Stars Stellar System and the Sun - 5TH
Cambridge Workshop
Authors: Linsky, J. L.; Stencel, R. E.; Rudiger, G.
1989AN....310..374L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Production of Low Mass Carbon Stars: Carbon-Rich Dredge
up or Oxygen-Rich Mass Loss?
Authors: Stencel, R. E.; Pesce, J. E.; MacGregor, K. M.
1989eprg.proc..229S Altcode: 1989IAUCo.106..229S
Conventional theory explains the origin of carbon stars as due to
dredge up of carbon enriched material from the stellar core during
helium flash events late in the life of solar mass AGB stars. This
relatively efficient process, however, seems to produce a larger C/O
ratio than observed (Lambert et al., 1987). A secondary effect which
could contribute to the appearance of carbon stars, is the selective
removal of oxygen from the atmosphere by radiative force expulsion of
oxygen-rich dust grains. Calculations for this scenario are presented,
which evaluate the degree of momentum coupling between the grains and
gas under the thermodynamical conditions of AGB star atmospheres.

---------------------------------------------------------
Title: Multi-Wavelength Observations of the Peculiar Red Giant HR 3126
Authors: Pesce, J. E.; Stencel, R. E.; Doggett, J.; Walter, F. M.;
Whitelock, P. A.; Dachs, J.
1989eprg.proc...55P Altcode: 1989IAUCo.106...55P
No abstract at ADS

---------------------------------------------------------
Title: Far-Infrared Circumstellar Debris Shells: Clues to the
Evolution of Massive Stars?
Authors: Stencel, R. E.; Garmany, C. D.
1989ASSL..157..293S Altcode: 1989plbv.coll..293S; 1989IAUCo.113..293S
No abstract at ADS

---------------------------------------------------------
Title: The winds of high luminosity late-type bright stars
Authors: Stencel, Robert E.; Carpenter, K. G.
1989gsfc.reptQ....S Altcode:
The occurrence and characteristics of the Fe II line asymmetries
were studied to determine the radial dependence of the wind velocity
for each star. The dependence of the Fe II profiles on spectral type
and luminosity class and thus the variation of the velocity fields
with stellar type was also investigated. This allows the generality
of the results reported for alpha Ori by Carpenter (1984b) to be
judged. In addition, new atomic data was used along with observations
of the C II (UV 0.01) multiplet to estimate Ne in the
stellar winds. Measures of relative Fe II fluxes can be used in a
probability-of-escape model to determine the opacity and hydrogen
column density versus height in the chromosphere of each star. Finally,
analysis of the fluorescent Fe II lines (pumped by Ly alpha) near 2507
A will yield estimates of the intrinsic stellar Ly alpha flux that
cannot be measured directly because of interstellar and circumstellar
absorption. One important goal of the effort was to acquire high
resolution spectra of the whole 2300 to 3200 A region of 13 luminous
K and M stars as a data base that will be enormously valuable in
planning observations with the Hubble Space Telescope High Resolution
Spectrograph. It is also proposed to follow up the recent discovery
of significant variations in the Fe II chromospheric emission line
profiles from the M-giant Gamma Cru for the purpose of determining
the underlying cause of the variations.

---------------------------------------------------------
Title: Book-Review - Cool Stars Stellar Systems and the Sun / 5TH
Cambridge Workshop / Boulder, Colorado 1987JUL
Authors: Linsky, J. L.; Stencel, R. E.; Venkatakrishnan, P.
1988BASI...16..248L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - Cool Stars Stellar Systems and the Sun -
Cambridge - 1987JULY
Authors: Linsky, J. L.; Stencel, R. E.
1988S&T....76..639L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Ultraviolet Spectrum of Noncoronal Late-Type Stars:
The Gamma Crucis (M3.4 III) Reference Spectrum
Authors: Carpenter, Kenneth G.; Pesce, Joseph E.; Stencel, Robert E.;
Brown, Alexander; Johansson, Sveneric; Wing, Robert F.
1988ApJS...68..345C Altcode:
A guide is presented to the UV spectrum of M-type giants and supergiants
whose outer atmospheres contain warm chromospheres but not coronae. The
M3 giant Gamma Crucis is taken as the archetype of the cooler,
oxygen-rich, noncoronal stars. Line identifications and integrated
line flux measurements of the chromospheric emission features seen in
the 1200-3200 A range of IUE high-resolution spectra are presented. The
major fluorescence processes operating in the outer atmosphere of Gamma
Crucis, including eight previously unknown pumping processes and 21
new fluorescent line products, are summarized, and the enhancements
of selected line strengths by 'line leakage' is discussed. A set of
absorption features toward the longer wavelength end of this range
is identified which can be used to characterize the radial velocity
of the stellar photospheres. The applicability of the results to the
spectra of noncoronal stars with different effective temperatures and
gravities is discussed.

---------------------------------------------------------
Title: Late Type SAO Stars With Infrared Excesses
Authors: Backman, D. E.; Stencel, R. E.; Holtrop, K.
1988BAAS...20Q.959B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - Cool Stars Stellar Systems and the Sun -
Workshop / Boulder, Colo / 1987JUL
Authors: Linsky, J. L.; Stencel, R. E.
1988Sci...241..991L Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Stellar Wind Velocity Function for Red Supergiants
Determined in Eclipsing Binaries
Authors: Ahmad, Imad A.; Stencel, Robert E.
1988ApJ...329..797A Altcode:
The potential for direct measurement of the acceleration of stellar
winds from the supergiant component of Zeta Aurigae-type binary
stars is discussed. The aberration angle of the interaction shock cone
centered on the hot star provides a measure of the velocity of the cool
star wind at the orbit of the secondary. This is confirmed by direct
observations of stellar wind (P Cygni) line profile variations. This
velocity is generally smaller than the final (terminal) velocity of
the wind, deduced from the P Cygni line profiles. The contrast between
these results and previously published supergiant wind models is
discussed. The implication on the physics of energy source dissipation
predicted in the theoretical models is considered.

---------------------------------------------------------
Title: Direct UV observations of the circumstellar envelope of
alpha Orionis.
Authors: Stencel, R. E.; Carpenter, K. G.; Pesce, J. E.; Skinner,
S.; Brown, A.; Judge, P.
1988ESASP.281a.249S Altcode: 1988uvai....1..249S; 1988IUE88...1..249S
Observations were made in the IUE LWP camera, low dispersion mode, with
alpha Ori being offset various distances from the center of the Long
Wavelength Large Aperture along its major axis. Signal was acquired
at all offset positions and is comprised of unequal components of
background/dark counts, telescope-scattered light, and scattered light
emanating from the extended circumstellar shell. The star is known from
optical and infrared observations to possess an extended, arc-minute
sized, shell of cool material. Attempts to observe this shell with the
IUE are described, although the deconvolution of the stellar signal
from the telescope scattered light requires further calibration effort.

---------------------------------------------------------
Title: Multi-wavelength observations of the peculiar red giant
HR 3126.
Authors: Pesce, Joseph E.; Stencel, Robert E.; Walter, Frederick M.;
Doggett, Jesse; Dachs, Joachim; Whitelock, Patricia A.; Mundt, Reinhard
1988ESASP.281a.253P Altcode: 1988uvai....1..253P; 1988IUE88...1..253P
Ultraviolet observations of the red giant HR 3126 are combined with
multi-wavelength data in order to provide a firmer basis for explaining
the arc-minute sized nebula surrounding the object. Possibilities as
to the location of HR 3126 on the Hertzsprung-Russel diagram, and to
the formation mechanisms of the reflection nebula IC 2220 associated
with it, are summarized.

---------------------------------------------------------
Title: Far-Infrared Data for Symbiotic Stars. II. The IRAS Survey
Observations
Authors: Kenyon, S. J.; Fernandez-Castro, T.; Stencel, R. E.
1988AJ.....95.1817K Altcode:
IRAS survey data for all known symbiotic binaries are reported. S type
systems have 25 micron excesses much larger than those of single red
giant stars, suggesting that these objects lose mass more rapidly than
do normal giants. D type objects have far-IR colors similar to those of
Mira variables, implying mass-loss rate of about 10 to the -6th solar
masses/yr. The near-IR extinctions of the D types indicate that their
Mira components are enshrouded in optically thick dust shells, while
their hot companions lie outside the shells. If this interpretation
of the data is correct, then the very red near-IR colors of D type
symbiotic stars are caused by extreme amounts of dust absorption rather
than dust emission. The small group of D prime objects possesses far-IR
colors resembling those of compact planetary nebulae or extreme OH/IR
stars. It is speculated that these binaries are not symbiotic stars at
all, but contain a hot compact star and an exasymptotic branch giant
which is in the process of ejecting a planetary nebula shell.

---------------------------------------------------------
Title: S Persei
Authors: Skiff, B. A.; Stencel, R.
1988IAUC.4577....2S Altcode: 1988IAUC.4577....0S
B. A. Skiff, Lowell Observatory, reports that the steady rise in
brightness noted by R. Stencel (IAUC 4556) has slowed considerably in
the last several weeks, from about 0.010 mag/day in February to near
constancy at the end of March. This is apparent from the following
representative differential measurements (uncertainty 0.005 mag)
relative to HD 14415, obtained with the Lowell 0.53-m telescope and
a Stromgren y filter: Feb. 8.14 UT, 0.934; 20.13, 0.804; Mar. 1.10,
0.722; 8.13, 0.694; 18.13, 0.678; 27.12, 0.656.

---------------------------------------------------------
Title: S Persei
Authors: Stencel, R. E.; Street, D.; Keen, R.; Sapp, J.
1988IAUC.4556....1S Altcode: 1988IAUC.4556....0S
R. E. Stencel, Center for Astrophysics and Space Astronomy, University
of Colorado, writes that this red supergiant variable and maser source
has brightened by 1.5 mag in the past two months, after many months
near visual mag 11, as indicated by the following visual magnitude
estimates reported to D. Street and Stencel, who have been coordinating
a monitoring campaign: 1987 Nov. 9, 10.7 (R. Keen, Mt. Thorodin,
CO); Nov. 25, 10.8 (J. Sapp, Boulder, CO); 1988 Feb. 13, 9.2 (Sapp);
Feb. 22, 9.2 (Keen). A similar rapid rise was observed in late 1981,
when the star brightened from 11.5 to 8.5 in 150 days. Spectroscopic
observations are encouraged.

---------------------------------------------------------
Title: VY Cma
Authors: Stencel, Robert E.
1988iue..prop.3240S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: S Per
Authors: Stencel, Robert E.
1988iue..prop.3256S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Summary of Final Discussion
Authors: Stencel, R. E.
1988ASSL..145..347S Altcode: 1988IAUCo.103..347S; 1988syph.book..347S
No abstract at ADS

---------------------------------------------------------
Title: Mapping Circumstellar Shells of Red Supergiant Stars
Authors: Stencel, Robert E.
1988iue..prop.3169S Altcode:
We propose to obtain off source observations of a variety of sources
which are currently undergoing substantial mass loss or have in
their recent history shown such evidence. Detection of signal in a
majority species like Mg+ by means of emission near 2800A (among cool
stars) will be crucial in establishing the existence, density and
ionization state of material at large distances from the stars under
consideration. Recent observational experience with the red supergiant,
alpha Ori has shown that it is possible to obtain, at distances of 10
to 30+ arc sec from the star, circumstellar signal in excess of the
background produced by scattered light in the telescope optics. This
success implies the utility of this technique for a number of related,
bright sources.

---------------------------------------------------------
Title: Far-Infrared Circumstellar "Debris" Shells of Red Supergiant
Stars
Authors: Stencel, Robert E.; Pesce, Joseph E.; Hagen Bauer, Wendy
1988AJ.....95..141S Altcode:
An examination of IRAS data of red supergiant stars in the field and in
galactic OB star associations indicates the presence of substantial
amounts of 60 μm emitting material extending several arcminutes
around many such sources. The characteristics of these large shells
are discussed in terms of remnants of ongoing mass loss, and a simple
model developed for the case of α Orionis, in particular.

---------------------------------------------------------
Title: The Environments of Cool Stars
Authors: Stencel, Robert E.
1988ASSL..145...57S Altcode: 1988IAUCo.103...57S; 1988syph.book...57S
This review describes recent conclusions about the physical environment
of red giant and supergiant stars. This includes coronae, chromospheres,
dust formation and stellar winds. This knowledge can provide the
boundary conditions for considering what role such objects play as
members of binary star systems, where tidal forces and companion
behavior alter observed characteristics.

---------------------------------------------------------
Title: The Search for the Elusive Companion of EG Andromedae
Authors: Pesce, J. E.; Stencel, R. E.; Oliversen, N. A.
1988ASSL..145..291P Altcode: 1988IAUCo.103..291P; 1988syph.book..291P
The authors report observations at opposite quadratures of the
interacting symbiotic binary EG Andromedae (HD 4174, period =
470d). Correcting for absolute motion at the system, it
appears that many of the nebular lines arise from material that moves
with the red giant star. The He II feature appears to track the hot
component. It may be possible to use this feature in other, similar
systems in order to "pin-down" the mass ratio.

---------------------------------------------------------
Title: Alpha-Ori Shell
Authors: Stencel, Robert E.
1988iue..prop.3247S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The search for the elusive companion of EG Andromedae.
Authors: Pesce, Joseph E.; Stencel, Robert E.; Oliversen, Nancy A.
1987PASP...99.1178P Altcode:
The authors report observations at opposite quadratures of
the interacting symbiotic binary EG And (HD 4174, Period =
470d). After correcting for absolute motion at the system,
it appears, surprisingly, that many of the nebular lines arise from
material that moves with the red giant star. This fact is used to
interpret the observed complex line profiles of C IV and He II in
the object.

---------------------------------------------------------
Title: Observaciones con IUE e IRAS de gigantes y supergigantes rojas.
Authors: Hagen, W.; Carpenter, K. G.; Stencel, R. E.
1987RMxAA..14..380H Altcode:
. Previous observations of M giants and supergiants have indicated
that chromospheric Ca II,H and K emission is lacking in stars with high
circumstellar dust-to-gas ratios (Hagen, Stencel, and Dickinson 1983,
Ap. J., 274, 286). Observations with lUE detected other chromospheric
lines (e.g., Mg II, Al II, Fe II) in stars without Ca II emission,
indicating that the dust does not completely quench the . However,
line intensities in dusty stars were reduced. (Carpenter, Stencel, and
Hagen 1986, Ap. J., 308, 859). IRAS observations of visually bright
M giants and supergiants and simple dust shell models indicate that
the 60 and lO0 m excesses can be satisfactorily explained by silicate
grains. Examination of individual IRAS scans indicates spatially
extended emission for the stars R Dor,aOri, W Hya, a Sco, AH Sco, R
Lyr, Cep, PZ Cas and L2 Pup at 60 m. Kay : STARS-CIRCUMSTELLAR SHELLS
- STARS-CHROMOSPHERES

---------------------------------------------------------
Title: SiO Cooling Instability in the Envelopes of Cool Giant Stars
Authors: Muchmore, David O.; Nuth, Joseph A., III; Stencel, Robert E.
1987ApJ...315L.141M Altcode:
In the outer atmospheres of oxygen-rich giant and supergiant stars,
the formation of the silicon monoxide molecule not only represents
a first step toward the production of dust but may also produce an
efficient radiative cooling agent. Molecular cooling occurs as a
thermal instability in many cases with an onset at 2000 to 3500 K,
rapidly reducing the temperature by as much as 1000 K. This process
may occur in the upper photosphere-lower chromosphere of such stars
and can have profound dynamical consequences. The process occurs far
from LTE, on a time scale controlled by the reaction rates for SiO
formation. SiO masers may be indicative of this process. The molecule
CS which may play a similar role in carbon stars and serve as the
basis for carbonaceous dust production.

---------------------------------------------------------
Title: Red Supergiant Infrared Shells and the Galactic Metallicity
Gradient
Authors: Pesce, J. E.; Stencel, R. E.; Hagen Bauer, W.
1987BAAS...19..724P Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Roadmap to the Ultraviolet Spectrum of Cool, Non-Coronal
Stars
Authors: Carpenter, K. G.; Peace, J.; Stencel, R. E.; Brown, A.
1987BAAS...19..705C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: VLA Observations of Rapid 6 cm Flux Variations in α Ori
Authors: Stencel, R. E.; Bookbinder, J.; Drake, S. A.; Simon, T.;
Linsky, J. L.; Florkowski, D.
1987BAAS...19..706S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: VLA Observations of Rapid 6 cm Flux Variations in α Ori
Authors: Bookbinder, J. A.; Stencel, R. E.; Drake, S. A.; Simon, T.;
Linsky, J. L.; Florkowski, D.
1987LNP...291..337B Altcode: 1987csss....5..337B; 1987LNP87.291..337B
We present a series of VLA observations designed to monitor the
6 cm flux density variations of α Ori. Our results indicate that
variability is present at the 30% - 40% level on timescales of several
weeks. These timescales are probably inconsistent with any global or
large-scale processes.

---------------------------------------------------------
Title: Molecular catastrophes and the formation of circumstellar dust.
Authors: Stencel, R. E.
1987IAUS..122..529S Altcode:
Radiative instabilities due to simple molecules may convert
chromospheric material into masering molecules and dust capable of
being removed from the star by radiation pressure.

---------------------------------------------------------
Title: Alpha-Ori Scattered Light
Authors: Stencel, Robert E.
1987iue..prop.2899S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: UV Observations of the Southern Star HR 3126
Authors: Stencel, Robert
1987iue..prop.2860S Altcode:
The M-type bright giant star HR 3126, which lies at the center of
the butterfly-shaped reflection nebula, IC2220, is an unusual object
by any measure. At present, we have only optical and near infrared
observations. Based on these alone, it seems just as likely that HR3126
is an evolved red star with bipolar mass ejecta, or an R Aquarii-like
symbiotic binary with extended interaction effluent. If HR 3126 is
indeed an evolved red star inside a planetary nebula, it contradicts
our normal understanding of stellar evolution at the planetary nebula
ejection phase, because the central star hardly looks like a hot
subdwarf. If indeed a binary, this object, like R Aqr, would be one
of the very rare instances where the spatially extended source could
be studied in detail, including mapping of its jets. In either event,
we feel that observations in the ultra-violet by the IUE satellite
will prove to be extremely important in our understanding of this
enigmatic object. Note that no UV observations of this source have
been made thus far.

---------------------------------------------------------
Title: The Ultraviolet Circumstellar Shell of Alpha Ori
Authors: Stencel, Robert E.
1987iue..prop.2848S Altcode:
We propose off-source observations of the circumstellar shell of
a Orionis to attempt to detect resonantly scattered chromospheric
emission in the Mg II h and k lines at 2800A, as well as the Mg I
resonance line at 2852A and the S I resonance features at 1820A. We
estimate that moderate duration exposures with the LWP camera at
low resolution, with the aperture offset 10 arcsec from the star,
should yield detectable flux. This is based on chromospheric models and
previous optical observations of the K I resonance line (7699 Angstroms)
which is known to extend 50 arcsec from the star. These observations
should enable the first direct measurement of the column densities
of majority species in the CS shell of alpha Ori at large distances,
and will result in much tighter constraints on current stellar mass
loss and wind models than are available at present. To the best of
our ability to judge, all previous exposures with IUE, except for one
in 1978, have been made "on-source". This important early experiment
deserves follow-up.

---------------------------------------------------------
Title: Cool Stars, Stellar Systems, and the Sun
Authors: Linsky, J. L.; Stencel, R. E.
1987LNP...291.....L Altcode: 1987csss....5.....L
No abstract at ADS

---------------------------------------------------------
Title: Symbiotic Stars
Authors: Nussbaumer, Harry; Stencel, Robert E.
1987ASSL..129..203N Altcode: 1987euwi.book..203N
Observations of symbiotic stars (SSs) obtained with the IUE satellite
since its launch in 1978 are reviewed. The general features of SS
spectra are discussed (IR emission from a cool highly evolved star
and UV emission from a nebula ionized by a source of 100,000 K or
hotter), and the astrophysical interest of SSs is indicated. Particular
attention is given to the S-type SSs AG Peg, AR Pav, Z And, HBV 475,
AG Dra, and CH Cyg; the D-type SSs R Aqr, V 1016 Cyg, and RR Tel; SSs in
other galaxies; the UV continuum, emisssion lines, abundances, electron
temperatures, Doppler shifts, and Doppler broadening and line profiles;
and theoretical models based on multispectral information. Sample
spectra, graphs, and tables listing SS parameter values are provided.

---------------------------------------------------------
Title: Red supergiant infrared shells and the galactic metallicity
gradient.
Authors: Stencel, R. E.; Pesce, J. E.; Bauer, W. H.
1987PASP...99Q1150S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Mg II Emission Lines in the Spectra of Cool, High Luminosity
Stars
Authors: Carpenter, Kenneth G.; Stencel, Robert E.; Pesce, Joseph E.
1987LNP...291..164C Altcode: 1987LNP87.291..164C; 1987csss....5..164C
We present the initial results of a survey of the Mg II emission
lines in the spectra of K and M giants, bright giants, and
supergiants. Profiles of the Mg II h and k lines in 12 such stars are
shown in a relative spectral type/luminosity class grid. Plots based
on the h-line data illustrate the existence of a Wilson-Bappu. effect
in these lines and of a slight dependence of the line asymmetry on V-R
color. A time series of Mg II profiles for the M3 giant Gamma Cru show
that the Mg II profiles have not undergone the profile shape changes
seen in the Fe II lines from this star over the same time period.

---------------------------------------------------------
Title: Remarks on Red Giant and Supergiant Stars
Authors: Stencel, Robert E.
1987LNP...291..409S Altcode: 1987csss....5..409S; 1987LNP87.291..409S
The preceeding review paper by Hollis Johnson and these remarks
summarize portions of a half-day meeting held immediately prior
to the Fifth Cool Stars Workshop. This special session was held in
order to allow the astronomers interested in problems related to the
atmospheres and evolution of red giant and supergiant stars to share
ideas on selected current topics and to obtain previews of some of the
papers presented during the Workshop. Many of the talks presented are
published in these Proceedings.

---------------------------------------------------------
Title: Far infrared circumstellar “Debris” shells of red supergiant
stars
Authors: Stencel, Robert E.; Pesce, Joseph E.; Hagen Bauer, Wendy
1987LNP...291..380S Altcode: 1987LNP87.291..380S; 1987csss....5..380S
Examination of IRAS data on late type evolved stars suggests that
there is yet another transition line, between chromospheres and dust,
which lies above and to the right of corona-wind transitions in the HR
Diagram. The IRAS 60 µm data also appears to indicate the existence
of very cool material extending tens of thousands of stellar radii
around red supergiant stars. These circumstellar debris shells may
prove useful in the analysis of the history of mass loss in given
objects and larger scale galactic trends, such as metallicity.

---------------------------------------------------------
Title: NASA plans relevant to the study of circumstellar matter.
Authors: Stencel, Robert E.
1987IAUS..122..563S Altcode:
The Astrophysics program of the National Aeronautics and Space
Administration of the United States emphasizes use of vehicles to obtain
above-the-atmosphere observational advantages, including expanded
electromagnetic frequency access, enhanced sensitivity resulting
from reduced or eliminated atmospheric absorption of light and image
smearing. Space technology provides a superior means for astrophysical
inquiry, particularly in the case of circumstellar material. Much of
the flight program is undergoing intensive review following the Space
Shuttle disaster of January 1986.

---------------------------------------------------------
Title: Far-infrared data for symbiotic stars. I. The IRAS pointed
observations.
Authors: Kenyon, Scott J.; Fernandez-Castro, Telmo; Stencel, Robert E.
1986AJ.....92.1118K Altcode:
The authors present IRAS pointed observations of eight symbiotic
stars. Five S-type symbiotics (EG And, T CrB, RS Oph, AR Pav, and
AX Per) have IR energy distributions that are very similar to those
of normal M giants. Free-free emission may supply a fraction of the
observed 12 and 25 μm flux in RS Oph, AR Pav, and AX Per. Three D-type
symbiotics (RX Pup, HM Sge, and RR Tel) have IR energy distributions
that are consistent with those of Mira variables only if the giants
are heavily reddened (AK ≡ 1-2). The hot components in
these binaries appear to lie outside the dust shell that enshrouds
their Mira companions.

---------------------------------------------------------
Title: Molecular catastrophes and the formation of circumstellar dust
Authors: Stencel, R. E.
1986inpr.conf..147S Altcode:
Interstellar dust grains are presumed in part to have their origins in
the outer atmospheres of red giant and supergiant stars because, despite
the efficiency of shock destruction of grains in the interstellar
medium (ISM), meteoritic samples possess isotopic signatures that
are consistent with nucleosynthetic origin in the interior of evolved
stars. There is ample evidence to suggest that once dust grains form
near red giants and supergiants, radiation pressure is sufficient to
drive them to infinity. The molecular catastrophe description for the
conversion of chromospheric gas into molecular masers and circumstellar
dust holds promise for a coherent explanation of the formation of these
entities and the process of mas loss from cool, high luminosity objects.

---------------------------------------------------------
Title: Ultraviolet and Infrared Observations of Stars with
“Quenched” Chromospheres and the Nature of Mass Loss
Authors: Stencel, R. E.; Carpenter, K. G.; Hagen, W.
1986ApJ...308..859S Altcode:
Previous observational evidence implies that the presence of Ca II
emission, a chromospheric indicator, is correlated with the gas/dust
ratio in the envelopes of red giant and supergiant stars. An attempt
is made to determine whether this correlation can be generalized to
all chromospheric activity indicators and the gas/dust ratio. New
ultraviolet observations address the strength of UV emission features
and the fraction of the total chromospheric flux emitted in various
lines. Evidence is found that chromospheres are not completely quenched
in the presence of dust, but that significant alteration of relative
radiative loss patterns may occur. These observations are interpreted
in terms of an instability that converts warm, chromospheric gas into
near-surface dust grains and cool gas capable of supporting molecular
masing. This supports the dust-driven mass loss scenario for red
giant winds.

---------------------------------------------------------
Title: Scattered light in the IUE spectra of epsilon Aurigae.
Authors: Altner, B.; Chapman, R. D.; Kondo, Y.; Stencel, R. E.
1986A&AS...65..199A Altcode:
Recent infrared photometry indicates that the alleged disk of
particulate matter surrounding the mysterious secondary object in the
Epsilon Aur system is cold, around 500 K. IUE spectra, on the other
hand, contain significant flux in excess of that expected from an F0
Ia star in the far UV, which if interpreted as a hot secondary star
leads to a possible contradiction with the IR data. Other models of the
UV excess have been proposed, including the idea that the bulk of the
short-wavelength flux is light scattered into the SWP camera from longer
wavelengths. With the recent availability of a detailed generalized
IUE descattering algorithm it is possible to thoroughly investigate
the scattered-light contribution to the short-wavelength continuum. It
is found that the IUE spectra are indeed partially contaminated by
scattered light, but that even after correction for this instrumental
effect a significant time-dependent UV excess is still present.

---------------------------------------------------------
Title: Current NASA Plans for Future Space Astrophysics Experiments
Authors: Stencel, R. E.
1986IrAJ...17..353S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Chromospheric Dust Formation, Stellar Masers and Mass Loss
Authors: Stencel, R. E.
1986IrAJ...17..336S Altcode:
Among the non-pulsating, cool, evolved stars, the author proposes that
the outer atmosphere is best described by a quasistatic but extended
chromosphere. This structure is prone to thermal instabilities and can
produce mass loss. Specifically, the mechanism involves condensation
instability in extended chromospheres, converting warm, diffuse gas into
cool, dense clouds which are conducive to the formation of molecules
and dust grains. The newly formed dust can be driven away from the
star by radiation pressure.

---------------------------------------------------------
Title: Acceleration of Supergiant Stellar Winds
Authors: Ahmad, I. A.; Stencel, R. E.
1986LNP...254..430A Altcode: 1986csss....4..430A
No abstract at ADS

---------------------------------------------------------
Title: Photometry of the recent eclipse of Epsilon Aurigae.
Authors: Stencel, R. E.
1986HiA.....7..143S Altcode:
New observations of the long period eclipsing system Epsilon Aurigae
are discussed, including optical and infrared photometry, ultraviolet
spectrophotometry and optical polarization. Trends are noted in the
light curves and compared to previous eclipses. Comments regarding
interpretation are also provided.

---------------------------------------------------------
Title: Interrelationships among circumstellar, interstellar,
and interplanetary dust : proceedings of a workshop held at the
Aspen Institute's Wye Plantation Conference Center, Wye, Maryland,
February 27-March 1, 1985
Authors: Nuth, J. A., III; Stencel, R. E.
1986NASCP2403.....N Altcode: 1986icii.conf.....N; 1986QB791.I565.....
No abstract at ADS

---------------------------------------------------------
Title: IUE and IRAS observations of luminous M stars with varying
gas-to-dust ratios.
Authors: Hagen, W.; Carpenter, K. G.; Stencel, R. E.
1986NASCP2403A...8H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Chromospheric dust formation, stellar masers and mass loss.
Authors: Stencel, R. E.
1986NASCP2403A..29S Altcode:
The author outlines a multi-step scenario which describes a plausible
mass loss mechanism associated with red giant and related stars. The
process involves triggering a condensation instability in an extended
chromosphere, leading to the formation of cool, dense clouds which
are conducive to the formation of molecules and dust grains. Once
formed, the dust can be driven away from the star by radiation
pressure. Consistency with various observed phenomena is discussed.

---------------------------------------------------------
Title: Epsilon Aurigae.
Authors: Hopkins, J. L.; Stencel, R. E.
1986Ast....14b...6H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Effect of Dust on the Chromospheres of Cool, Luminous Stars
Authors: Carpenter, K. G.; Stencel, R. E.; Hagen, W.
1985BAAS...17..876C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Scattered light in the IUE spectra of Epsilon Aurigae
Authors: Aitner, B.; Chapman, R. D.; Kondo, Y.; Stencel, R. E.
1985eepa.rept...81A Altcode:
As a result of this work it was found that light scattered from the
longer wavelengths constitutes a small but non-negligible, wavelength
and time dependent fraction of the measured flux in the far UV. The
reality of the UV excess has not been unambigiously ruled out. However,
it is noted that there are still uncertainties in the assumed scattering
profile. New measurements of the scattering properties of the cross
disperser grating are planned in order to verify the results of Mount
and Fastie and extend the wavelength coverage into the far wings of
the profile. The results of these measurements will no doubt reduce
some of these uncertainties. For the present, it is felt that the
BCH approach is a significant improvement over the methods heretofore
available for the treatment of scattered light in IUE spectra.

---------------------------------------------------------
Title: Observational studies of the symbiotic
stars. III. High-dispersion IUE and H alpha observations of EG
Andromedae.
Authors: Oliversen, N. A.; Anderson, C. M.; Stencel, R. E.; Slovak,
M. H.
1985ApJ...295..620O Altcode:
High-dispersion IUE and optical spectra are presented for the symbiotic
star EG Andromedae (HD 4174). Remarkable emission-line strength and
profile variations are confirmed for the S IV, O IV, C IV, and He
II ultraviolet lines as well as H-alpha. Accurate cross-correlation
absorption-line velocities determined from Ti I, Ca I, and Fe I features
convincingly demonstrate that EG And is a single-lined spectroscopic
binary. The velocity curve suggests that the photometric ephemeris
reported by Smith in 1980 should be revised by a redefinition of
zero phase by about 0.08 of a period. The primary of the system may
be similar to the central star of a planetary nebula embedded in a
dense nebula with a mild stellar wind. The behavior of the emission
lines is interpreted to indicate that the primary and its surrounding
nebula suffer a partial eclipse by the cool giant secondary.

---------------------------------------------------------
Title: Densities, Temperatures and Geometric Extents of C II Emitting
Regions in the Winds of Luminous, Late-Type Stars
Authors: Carpenter, K. G.; Brown, A.; Stencel, R. E.
1985mlrg.proc...55C Altcode:
The authors summarize techniques for using IUE observations of the
C II UV 0.01 and UV 1 emission line multiplets at 2325 Å and 1335
Å to estimate the electron density (Ne) and temperature
(Te) in, and the geometric extent of, the chromospheres of
late-type stars. The results of applying these techniques to a sample
of 15 stars observed with the IUE satellite are discussed.

---------------------------------------------------------
Title: Contact Times for the 1982-4 Eclipse of epsilon Aur
Authors: Schmidtke, P. C.; Hopkins, J. L.; Ingvarsson, S. I.; Stencel,
R. E.
1985IBVS.2748....1S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Chromospheric Dust Formation and Mass Loss
Authors: Stencel, R. E.
1985BAAS...17R.569S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Binary Nature of the Symbiotic Star EG Andromedae
Authors: Oliversen, N. A.; Anderson, C. M.; Slovak, M.; Stencel, R. E.
1985BAAS...17..552O Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Line identifications, line strengths and continuum flux
measurements in the ultraviolet spectrum of Arcturus.
Authors: Carpenter, K. G.; Wing, R. F.; Stencel, R. E.
1985ApJS...57..405C Altcode:
The ultraviolet spectrum of Arcturus has been observed at high
resolution with the IUE satellite. Line identifications, mean absolute
'continuum' flux measurements, integrated absolute emission-line
fluxes, and measurements of selected absorption line strengths are
presented for the 2250-2930 A region. In the 1150-2000 A region,
identifications are given primarily on the basis of low-resolution
spectra. Chromospheric emission lines have been identified with
low-excitation species including H I, C I, C II, O I, Mg I, Mg II,
Al II, Si I, Si II, S I, and Fe II; there is no evidence for lines of
C IV, N V, or other species requiring high temperatures. A search for
molecular absorption features in the 2500-2930 A interval has led to
several tentative identifications, but only OH could be established as
definitely present. Iron lines strongly dominate the identifications
in the 2250-2930 A region, Fe II accounting for about 86 percent
of the emission features and Fe I for 43 percent of the identified
absorption features.

---------------------------------------------------------
Title: The geometric extent of C II (UV 0.01) emitting regions around
luminous, late-type stars
Authors: Carpenter, K. G.; Brown, A.; Stencel, R. E.
1985ApJ...289..676C Altcode:
A method is presented by which the geometric extent of the chromospheres
around late-type stars can be estimated from measurements of the
total emission-line flux and line ratios within the C II (UV 0.01)
multiplet. Application of this technique to a sample of 15 late-type
stars indicates a clear difference in the radial extent of the
chromospheres around coronal and noncoronal stars. The former stars
appear to have very thin chromospheres (of no more than 0.1 percent of
the photospheric radius), while the latter stars have chromospheres
extending, on average, out to 2.5 photospheric radii. This, in
principle, provides information for understanding structural differences
between late-type giant and supergiant stars with and without coronae,
and could lead to an understanding of the mass-loss mechanisms involved.

---------------------------------------------------------
Title: Scattered light in the IUE spectra of ɛ Aurigae.
Authors: Altner, B.; Chapman, R. D.; Kondo, Y.; Stencel, R. E.
1985NASCP2384...81A Altcode:
The authors have found that the IUE spectra vary on timescales
comparable to the optical photometry (Schmidtke 1985) in agreement
with Ake (1985) and that they are indeed partially contaminated by
scattered light. Even after correction for this instrumental effect,
however, a significant, time dependent UV excess is still present.

---------------------------------------------------------
Title: Rotational modulation of chromospheric emission in cool giants
and "hybrid" stars.
Authors: Brosius, J. W.; Mullan, D. J.; Stencel, R. E.
1985ApJ...288..310B Altcode:
Archival data from the International Ultraviolet Explorer have been
used to study temporal variations of the Mg II h and k emission lines
in eight late-type giants. Evidence is presented that the variations
are periodic in nature. It is argued that the periodicities can be
interpreted in terms of rotation. It is found that the four fastest
rotators in the sample are 'hybrid' stars.

---------------------------------------------------------
Title: 1982 - 1984 eclipse of Epsilon Aurigae. Summary of a working
meeting held in Tucson, Arizona, 16 - 17 January 1985.
Authors: Stencel, R. E.
1985eea..book.....S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: 1982-1984 eclipse of Epsilon Aurigae : summary of a working
meeting held in Tucson, Arizona, January 16-17, 1985
Authors: Stencel, R. E.
1985eepa.rept.....S Altcode: 1985QB823.A17......
No abstract at ADS

---------------------------------------------------------
Title: Eg And
Authors: Stencel, Robert E.
1985iue..prop.2282S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: On the rarity of FK COM stars.
Authors: Hagen, W.; Stencel, R. E.
1985AJ.....90..120H Altcode:
Very high-dispersion spectra (2.5 Å mm-1) were obtained
of 31 southern late-type stars, predominantly early G giants, in an
effort to find new rapidly rotating, active stars which would be FK
Com-like. Measurements of linewidths and the strength of chromospheric
Ca II K-line emission are presented, but no new star could be added
to the class of "rapid rotators". Space densities and evolutionary
lifetimes for FK Com stars are discussed.

---------------------------------------------------------
Title: UV observations of Epsilon Aurigae during ingress and totality.
Authors: Altner, B. M.; Chapman, R. D.; Kondo, Y.; Stencel, R. E.
1984NASCP2349..365A Altcode: 1984fiue.rept..365A; 1984IUE84......365A
Analysis of short wavelength prime camera (SWP) and long wavelength
redundant camera (LWR) spectra of Epsilon Aurigae taken during
the preeclipse, ingress and total phases of the present eclipse has
provided further constraints on models of this enigmatic system. High
dispersion images show no significant change in the strength of the Mg
II emission lines during the course of the eclipse. Both high and low
dispersion spectra indicate that the eclipse starts earlier, ends later
and is deeper in the UV compared to visual wqvelengths. The earlier
observation that the eclipse depth is wavelength dependent shortward
of 2400 A is confirmed. Abrupt changes in the light curve appear at
all wavelengths, suggestive of discontinuities in the opacity of a
ring of material surrounding the secondary object.

---------------------------------------------------------
Title: Accretion in the Zeta Aurigae and 32 Cygni shock cones.
Authors: Ahmad, I. A.; Chapman, R. D.; Stencel, R. E.; Kondo, Y.
1984NASCP2349..357A Altcode: 1984fiue.rept..357A; 1984IUE84......357A
Zeta Aurigae and 32 Cygni are binary stars consisting of a cool
supergiant primary and a hot dwarf secondary. Variations in the Mg
II 2800 A and C IV 1550 A doublets of these stars near the time and
secondary minimum were observed. Longward-shifted absorption is seen in
the Mg II lines of both stars which may be due to material accreting
onto the B star behind the shock front. A reverse P-Cygni profile in
the C IV lines at some phases of zeta Aur was observed. This phenomenon
seems transient and recurrent, and may suggest streaming. An abrupt
strengthening and broadening of the absorption-especially at higher
positive radial velocities-manifested in the CIV lines coincides with
the onset and termination of the Mg II accretion absorption. It is
suggested that this is the effect of the abrupt increase in optical
depth as the line of sight aligns with the shock front. For 32 Cygni
the observed aberration angle is similar to that of zeta Aur, but
the system seems more diffucult to model. For zeta Aur the angle of
aberration of the accreting material from the radial direction is about
38 deg. and the half width of the shock cone is about 11 deg. For 32
Cygni the aberration angle is about 44 deg.

---------------------------------------------------------
Title: Rotational modulation of chromospheric emission in cool giants
and "hybrid" stars.
Authors: Brosius, J. W.; Mullan, D. J.; Stencel, R. E.
1984NASCP2349..476B Altcode: 1984fiue.rept..476B; 1984IUE84......476B
The authors have used IUE archival data to study temporal variations of
the Mg II h and k emission lines in 8 late-type giants. They present
evidence that the variations are periodic in nature. They argue that
the periodicities can be interpreted in terms of rotation and find
that the four fastest rotators in their sample are "hybrid" stars.

---------------------------------------------------------
Title: Observations of Mg I and Mg II in the local ISM.
Authors: Bruhweiler, F. C.; Oegerle, W.; Weiler, E.; Stencel, R. E.;
Kondo, Y.
1984NASCP2349..200B Altcode: 1984IUE84......200B; 1984fiue.rept..200B
High quality IUE data combined with that acquired by Copernicus
were used to study the Mg II/MG I ionization balance in the local
interstellar medium within 50 pc of the Sun. The high resolution,
high signal to noise Copernicus data reveal, in three stars,
weak interstellar Mg I features at 2852. High quality IUE data for
interstellar Mg II near 2800 A were acquired by coadding high dispersion
estimates and incorporating an observing technique that minimized the
effects of camera fixed-pattern noise. The results are in agreement
with the local cloud model as presented previously by Bruhweiler. The
Mg I and Mg II column densities are used to place constraints on the
physical conditions of the interstellar gas near the Sun.

---------------------------------------------------------
Title: Multi-year &amp; possibly periodic variations in the UV
spectrum of 56 Pegasi.
Authors: Stencel, R. E.; Neff, J. E.; McClure, R. D.
1984NASCP2349..400S Altcode: 1984IUE84......400S; 1984fiue.rept..400S
Radical variations in the Mg II emission profile of the late type
supergiant 56 Peg have been observed to occur during the course of five
years of IUE operations. Pronounced and possibly periodic changes in
asymmetry, emission relative velocity and photospheric radial velocity
are reported. The data can be viewed as either reflecting binary motion,
or a strong enhancement (flare?) in the Mg II forming region, on a 4
to 5 year timescale.

---------------------------------------------------------
Title: Observations of Local Interstellar MG i and MG II
Authors: Bruhweiler, F. C.; Oegerle, W.; Weiler, E.; Stencel, R. E.;
Kondo, Y.
1984NASCP2345...64B Altcode: 1984lism.rept...64B; 1984IAUCo..81...64B
The authors have combined Copernicus and IUE observations of 5 stars
within 50 pc of the Sun to study the ionization of magnesium in the
local interstellar medium (LISM). The high resolution Copernicus
spectrometer was used to detect interstellar Mg I 2852 in the spectra
of α Gru, α Eri, and α Lyr, while placing upper limits on Mg I
in the spectra of α CMa and α PsA. Observations of Mg II 2795,
2802 for these stars were also obtained with IUE and Copernicus. The
column densities of Mg I and Mg II are used to place constraints on
the temperature of the LISM.

---------------------------------------------------------
Title: IUE and IRAS Observations of Luminous M Stars with Varying
Gas-to-Dust Ratios
Authors: Hagen, W.; Carpenter, K. G.; Stencel, R. E.
1984BAAS...16..895H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Capabilities of Proposed NASA Missions to Observe Below
Lyman Alpha
Authors: Weiler, E. J.; Stencel, R. E.
1984BAAS...16..984W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Epsilon Aurigae 1982-1984 Eclipse Campaign Report
Authors: Hopkins, J. L.; Stencel, R. E.
1984BAAS...16..910H Altcode: 1984BAAS...16Q.910H
No abstract at ADS

---------------------------------------------------------
Title: High-resolution, far-ultraviolet study of beta Draconis
(G2 Ib-II) : transition region structure and energy balance.
Authors: Brown, A.; Jordan, C.; Stencel, R. E.; Linsky, J. L.; Ayres,
T. R.
1984ApJ...283..731B Altcode:
High-resolution far ultraviolet spectra of the star Beta Draconis have
been obtained with the IUE satellite. The observations and emission
line data from the spectra are presented, the interpretation of the
emission line widths and shifts is discussed, and the implications
are given in terms of atmospheric properties. The emission measure
distribution is derived, and density diagnostics involving both line
ratios and line opacity arguments is investigated. The methods for
calculating spherically symmetric models of the atmospheric structure
are outlined, and several such models are presented. The extension of
these models to log T(e) greater than 5.3 using the observed X-ray flux
is addressed, the energy balance of an 'optimum' model is investigated,
and possible models of energy transport and deposition are discussed.

---------------------------------------------------------
Title: Ultraviolet Observations of 56 Pegasi
Authors: Stencel, Robert E.
1984iue..prop.1955S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The 1982 eclipse of 31 Cygni.
Authors: Stencel, R. E.; Hopkins, J. L.; Hagen, W.; Fried, R.;
Schmidtke, P. C.; Kondo, Y.; Chapman, R. D.
1984ApJ...281..751S Altcode:
UBV photometry and optical-UV spectroscopy of the primary eclipse of the
long period ζ Aurigae-like system 31 Cygni are reported. The precise
timings made possible by the photometry imply that the spectral features
could be due to an accretion shock associated with a hot star embedded
in an extended chromosphere surrounding the red supergiant. The data
also suggest an extended clumpy structure to the atmosphere of the
late-type supergiant in the binary.

---------------------------------------------------------
Title: Changes in the ultraviolet spectrum of EG Andromedae.
Authors: Stencel, R. E.
1984ApJ...281L..75S Altcode:
Ultraviolet observations of EG Andromedae, a symbiotic star, are
reported which clearly show pronounced eclipse-like effects on
the high-temperature far-UV continuum. Continuum and emission-line
variations with phase are reported and related to synoptic hydrogen
alpha data. System parameters are characterized.

---------------------------------------------------------
Title: Winds in collision. II. an analysis of the X-ray emission
from the eruptive symbiotic HM Sge.
Authors: Willson, L. A.; Wallerstein, G.; Brugel, E. W.; Stencel, R. E.
1984A&A...133..154W Altcode:
X-ray emissions from HM Sge obtained in 1981 from the HEAO-2 satellite
are analyzed and compared quantitatively with observations of HM Sge
made in 1980 and of HM Sge, V 1016 Cyg, and RR Tel made in 1979. The
change in the X-ray emission from HM Sge between 1979 and 1981 is
found to be consistent with the X-ray luminosity and/or temperature
of the emitting region declining with an e-folding timescale of the
order of one to several decades. Comparison with X-ray data from V
1016 Cyg and RR Tel gives a composite X-ray light curve that is also
consistent with such a decline. A comparison of the X-ray observation
with spectroscopic information makes it possible to constrain the
properties of the X-ray emitting region: the result is consistent
with emission from an optically thin region between the two stars in
the system where their winds collide head on. It is also shown that
the observations are inconsistent with a stellar (blackbody) source,
with emission from an accretion disk around a white dwarf or a neutron
star, and with emission from a single star wind from either a white
dwarf or a neutron star.

---------------------------------------------------------
Title: Optical and Ultraviolet Observations of the Spectral Variations
of the Symbiotic Star AZ Persie
Authors: Anderson, C. M.; Oliversen, N. A.; Stencel, R. E.
1984BAAS...16..506A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Rotational Modulation of Chromospheric Emission in Cool Giants
and `Hybrid' Stars
Authors: Brosius, J. W.; Mullan, D. J.; Stencel, R. E.
1984BAAS...16..491B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Rotational Modulation and High Speed Streams in FK Comae
Berenices: Evidence for a Massive, Highly Evolved Binary System
Authors: Walter, F. M.; Neff, J. E.; Bopp, B. W.; Stencel, R. E.
1984LNP...193..279W Altcode: 1984csss....3..279W
No abstract at ADS

---------------------------------------------------------
Title: Preliminary Results from Studies of High Resolution Line
Spectra in Late-type Giant and Supergiant Stars
Authors: Engvold, O.; Kjeldseth Moe, O.; Jensen, E.; Jordan, C.;
Stencel, R.; Linsky, J.
1984LNP...193..359E Altcode: 1984csss....3..359E
No abstract at ADS

---------------------------------------------------------
Title: Observations of two peculiar emission objects in the Large
MagellanicCloud.
Authors: Kafatos, M.; Michalitsianos, A. G.; Allen, D. A.; Stencel,
R. E.
1983ApJ...275..584K Altcode:
Ultraviolet and visual wavelength spectra were obtained of two
peculiar emission objects, Henize S63 and Sanduleak's star in the
Large Magellanic Cloud. Previously not observed in the near- or
far-ultraviolet, both objects exhibit strong permitted and semiforbidden
line emissions. Estimates based on the absolute continuum flux of the
hot companion star in Hen S63 indicate that it rivals the luminosity
of the carbon star primary. The emission-line profile structure in
both objects does not suggest Wolf-Rayet type emission. Carbon in
Sanduleak's star (LMC anonymous) is conspicuously absent, while
N V, semiforbidden N IV, and semiforbidden N III dominate the UV
emission-line spectrum. Nitrogen is overabundant with respect to carbon
and oxygen in both objects. The large overabundance of nitrogen in
Sanduleak's star suggests evidence for CNO processes material similar
to that seen in Nu Car.

---------------------------------------------------------
Title: Observations of active chromosphere stars.
Authors: Bopp, B. W.; Africano, J. L.; Stencel, R. E.; Noah, P. V.;
Klimke, A.
1983ApJ...275..691B Altcode:
It is pointed out that spectroscopic signatures of stellar chromospheric
activity are readily observable. The present study is concerned with
new photometric and spectroscopic observations of active-chromosphere
RS CVn, BY Dra, and FK Com stars. Attention is given to the first
results of a synoptic monitoring program of many active chromosphere
stars. During the time from 1980 to 1982, photometric and spectroscopic
observations of 10 known or suspected active-chromosphere objects were
made. The results regarding the individual stars are discussed. Seven
stars observed with the International Ultraviolet Explorer (IUE)
are all spectroscopic binaries.

---------------------------------------------------------
Title: Spectrophotometric observations of symbiotic stars and
related objects.
Authors: Blair, W. P.; Stencel, R. E.; Feibelman, W. A.;
Michalitisianos, A. G.
1983ApJS...53..573B Altcode:
Calibrated optical spectrophotometric observations of 16 symbiotic
and symbiotic-like objects are presented. The objects observed
include Z And, T CrB, CH Cyg, CI Cyg, V1016 Cyg, V1329 Cyg, AG Dra,
YY Her, RS Oph, XX Oph, AG Peg, AX Per, CL Sco, HM Sge, AS 289,
and M1-2. Integrated emission-line intensities are tabulated for
comparison with ultraviolet and infrared data, as well as with
previous optical studies. The reddening to each of the objects is
derived by assuming that Balmer lines are emitted in their case
B recombination ratios. However, the values so derived are often
systematically higher than reddening estimates from the ultraviolet 2200
A feature. Comparisons with the available data from other wavelength
ranges are noted.

---------------------------------------------------------
Title: The circumstellar envelopes and chromospheres of cool giants
and supergiants.
Authors: Hagen, W.; Stencel, R. E.; Dickinson, D. F.
1983ApJ...274..286H Altcode:
A survey of the circumstellar (CS) envelopes of cool giants and
supergiants shows no correlation between the quantities of CS gas
and dust, indicating that radiation pressure on dust grains is not
the principal mechanism of mass loss. The observed quantity of dust
is not sufficient to drive the observed mass loss. Stars with high
dust-to-gas ratios were also seen to show a high proportion of neutral
to ionized gas and a lack of Ca II H and K emission, and in many cases,
Balmer emission, and/or molecular masing. It is argued that shock
waves may be linked to dust formation. Mass loss rates were derived
for the program stars and found to correlate with K4 absorption width,
indicating that the mass loss mechanism may be coupled to turbulence.

---------------------------------------------------------
Title: Redshifts of high-temperature emission lines in the
far-ultraviolet spectra of late-type stars.
Authors: Ayres, T. R.; Stencel, R. E.; Linsky, J. L.; Simon, T.;
Jordan, C.; Brown, A.; Engvold, O.
1983ApJ...274..801A Altcode:
High-dispersion IUE spectra of six late-type stars exhibit small but
statistically significant differential redshifts of high-temperature
emission lines, like Si IV and C IV, with respect to low-temperature
lines like S I and O I. A well-exposed, small-aperture spectrum of
the active chromosphere binary Capella (Alpha Aurigae A: G6 II+F9
III) establishes that the high-temperature lines are redshifted in an
absolute sense with respect to the accurately determined photospheric
velocity of the system at single-line phase 0.50. Several possible
explanations for the stellar redshifts are discused, including a warm
wind (100,000 K) in which aparent redshifts are produced in optically
thick lines by an accelerating outfow, and the downflowing component
of a vertical circulation system for which the up-leg portion of the
flow is too cool, too hot, or too tenuous to be visible in Si IV and C
IV. If the second scenario is true, the stellar redshifts may provide
an important phenomenological link to the downflows observed in 100,000
K species over magnetic active regions in the sun.

---------------------------------------------------------
Title: Evidence for a warm wind from the red star in symbiotic
binaries.
Authors: Friedjung, M.; Stencel, R. E.; Viotti, R.
1983A&A...126..407F Altcode:
A systematic redshift of the high ionization resonance emission lines
with respect to the intercombination lines is found from an examination
of the ultraviolet spectra of symbiotic stars obtained with IUE. After
consideration of other possibilities, this is most probably explained
by photon scattering in an expanding envelope optically thick to the
resonance lines. Line formation in a wind, or at the base of a wind is
therefore suggested. Reasons are also given indicating line formation
of the most ionized species in a region with an electron temperature of
the order of 100,000 K, probably around the cool star. The behavior of
the emission line width with ionization energy seems to support this
model. The cool components of symbiotic stars appear to differ from
normal red giants, which do not have winds of this temperature. An
explanation in terms of a higher rotation velocity due to the binary
nature of these stars is suggested.

---------------------------------------------------------
Title: Observations of the 1982 Eclipse of 31 Cyg.
Authors: Hagen, W.; Stencel, R. E.; Hopkins, J. L.; Fried, R.;
Schmidtke, P. C.; Kondo, Y.; Chapman, R. D.
1983BAAS...15..925H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Eclipse-like Changes in the Far UV Spectrum of the Symbiotic
Star EG And (HD 4174)
Authors: Stencel, R. E.
1983BAAS...15..927S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: High Dispersion Observations of the Eclipse of EG Andromedae
Authors: Oliversen, N. A.; Stencel, R. E.; Anderson, C. M.; Slovak,
M. H.
1983BAAS...15..927O Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Eclipse Timings of 31 Cygni
Authors: Schmidtke, P. C.; Fried, R. E.; Hopkins, J. L.; Stencel, R. E.
1983IBVS.2392....1S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The narrow ultraviolet emission lines of the red dwarf AU
Microscopii(dM1.6e).
Authors: Ayres, T. R.; Eriksson, K.; Linsky, J. L.; Stencel, R. E.
1983ApJ...270L..17A Altcode:
It is pointed out that the red dwarfs are the smallest, coolest,
faintest, least massive, but most common of normal main-sequence
stars. The dMe (H-alpha emission) subclass of the red dwarfs
exhibits the largest median soft X-ray to bolometric luminosity
ratio of any group of late-type stars. In connection with the present
investigation, attention is given to the first high-dispersion spectra
of the chromospheric (6000 K) and higher temperature (up to 100,000
K) emissions of a dMe star, AU Microscopii in the far-ultraviolet
(1150-2000 A) and middle-ultraviolet (2000-3000 A) bands accessible to
the International Ultraviolet Explorer (IUE). AU Mic is one of the most
luminous of lower main-sequence stars in C IV and soft X-ray emission.

---------------------------------------------------------
Title: The partial phase of the eclipse of Epsilon Aurigae.
Authors: Chapman, R. D.; Kondo, Y.; Stencel, R. E.
1983ApJ...269L..17C Altcode:
Ultraviolet spectra of the peculiar eclipsing binary Epsilon Aurigae
(FO Ia + ?) were obtained with the International Ultraviolet Explorer at
pre-eclipse and ingress partial phases. The results show a wavelength
dependence of the eclipse in contrast to the grayness (non-wavelength
dependence) of the eclipse observed in visible light. From the current
results, incorporating previous observations, it is suggested that:
(1) the obscuration of the light of the F supergiant by the disk
proposed by Huang (1965) is the result of electron scattering in
visible light; (2) the increase in the eclipse depths toward shorter
wavelengths observed in the ultraviolet is caused by dust; and (3)
the temperature of the disk is in the range from 1000 to 2000 K.

---------------------------------------------------------
Title: Coordinated Einstein and IUE observations of a disparitions
brusques type flare event and quiescent emission from Proxima
Centauri.
Authors: Haisch, B. M.; Linsky, J. L.; Bornmann, P. L.; Stencel,
R. E.; Antiochos, S. K.; Golub, L.; Vaiana, G. S.
1983ApJ...267..280H Altcode:
The Einstein Imaging Particle Counter observed a major X-ray flare
in its entirety during a 5-hr period of simultaneous observations,
with the IUE, of the dM5e flare star Proxima Centauri in August,
1980. The detailed X-ray light curve, temperature determinations
during various intervals, and UV line fluxes obtained before, during,
and after the flare indirectly indicate a 'two-ribbon flare' prominence
eruption. The calculated ratio of coronal to bolometric luminosity for
the event is about 100 times the solar ratio. The Proxima Cen corona
is analyzed in the context of static loop models, in light of which
it is concluded that less than 6% of the stellar surface seems to be
covered by X-ray emitting active regions.

---------------------------------------------------------
Title: The Gas-to-Dust Ratio in M Giants and Supergiants
Authors: Hagen, W.; Stencel, R. E.; Dickinson, D. F.
1983BAAS...15..652H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Epsilon-Aurigae Report and Analysis Program
Authors: Stencel, R. E.
1983mca..symp..238S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Flare-like activity of red giant stars
Authors: Stencel, R. E.
1983ASSL..102..251S Altcode: 1983IAUCo..71..251S; 1983ards.proc..251S
The present investigation is concerned with the evidence for flare-like
activity among higher luminosity cool stars, taking into account red
giants and supergiants. In a Mg II study, Mullan and Stencel (1982)
have observed several cool giants and supergiants repeatedly. The
observations showed a variation in total emission strength, or
strength/velocity of circumstellar Mg II absorption. A radio flare on
the red giant Alpha Ceti was reported by Boice et al. (1981). Goldberg
et al. (1982) have reported the measurement of polarization changes in
the red supergiant Alpha Ori which were correlated with changes in the
brightness distribution of the extended chromosphere revealed in narrow
band (H-alpha) speckle interferometry. The available limited synoptic
data suggest that among red giants and supergiants, flare-like events
occur on timescales in the range from 10,000 to 10 million seconds.

---------------------------------------------------------
Title: NASA astrophysics: optical systems to explore the Universe.
Authors: Pellerin, C. J., Jr.; Stencel, R. E.
1983SPIE..380..344P Altcode:
Major and minor NASA astrophysical research efforts in the near-term
are outlined, together with projections of direction for future
projects. The Space Telescope is being readied for a 1986 launch
and will feature an f/24, 2.4 m aperture, an MgF2 mirror with better
than 1/60 wavelength accuracy and will be diffraction-limited in the
UV. Pointing accuracy is designed to be 0.007 arcsec for 24 hr. Optical,
spectrometric, and photometric equipment will be included. Around 1990,
Shuttle-based missions will include an IR telescope and a subarcsec
solar surface imaging device. A free-flying X-ray observatory
(AXAF) is planned and will include a sensitivity that exceeds that
of the HEAO-2 spacecraft by two orders of magnitude. Instruments
are under development for higher resolution UV, gamma-ray, and IR
studies. In-orbit interferometry is being studied and will depend on
in-orbit assembly and servicing of stable structures with segmented
optics.

---------------------------------------------------------
Title: Erratum: "IUE observations of gas stream effects in the
ultraviolet spectrum of U Cephei" [Astrophys. J., Vol. 233, 906 -
912 (1979)].
Authors: Kondo, Y.; McCluskey, G. E.; Stencel, R. E.
1983ApJ...264..746K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Measurements of chromospheric densities and geometrical
extensions of late-type giant and super-giant stars
Authors: Wing, R. F.; Carpenter, K. G.; Stencel, R. E.; Linsky, J. L.
1983osuc.rept.....W Altcode:
The density sensitivity of the emission lines within the UV 0.01
multiplet of C II near 2325 A was examined in additional late type
giants and supergiants with deep LWR high dispersion exposures. The
new data support the original contention based on these lines that
noncoronal red giants possess geometrically extended chromospheres.

---------------------------------------------------------
Title: Magnetic topology and the heating of extended chromospheres
Authors: Stencel, R. E.
1983IAUS..102..445S Altcode:
New data indicate that red giants are surrounded by geometrically thick
chromospheres of several stellar radii extent. Such chromospheres occur
among stars which apparently lack coronae. Maintenance of this extended
warm region may require non-compressional wave heating of a magnetic
character, and this may provide a crucial clue to the mechanism of
rapid mass loss from red giant stars.

---------------------------------------------------------
Title: Mg II Variations in 56 Pegasi
Authors: Stencel, Robert E.
1983iue..prop.1581S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Ultraviolet and X-ray detection of the 56 Peg system (K0
II p+WD) : evidence for accretion of a cool stellar wind onto a
white dwarf.
Authors: Schindler, M.; Stencel, R. E.; Linsky, J. L.; Basri, G. S.;
Helfand, D. J.
1982ApJ...263..269S Altcode:
IUE spectra of the slowly rotating mild barium star 56 Peg (HD 218356;
K0 IIp) show excess continuum emission from 1300 to 2000 Å, a broad
Lyα absorption feature, and emission lines usually associated with a
l04-(2 × l05) K plasma. The best fit blackbody
curve to the dereddened continuum gives a temperature of 32000 ± 4000
K and a radius for the object of (2.7 ± 1.0) × l09 cm,
consistent with that of a white dwarf. Einstein IPC observations of this
system yield Lx ≍ 3 × 1O31 ergs s-1,
which is as bright as the RS CVn binary systems. The X-rays can be
fitted to a bremsstrahlung spectrum with kT = 0.45 ± 0.3 keV, or a
blackbody spectrum with kT ≍ 0.2 keV. Since bright X-ray and high
temperature emission lines are unusual for single stars in this region
of the H-R diagram, we do not believe that the 56 Peg primary has a
hot corona and transition region. Instead, we propose that the observed
X-ray luminosity is due to accretion onto the white dwarf of ∼0.1% of
the wind from the primary, which we assume has a reasonable mass loss
rate of 2 × 10-7 to 4 × l0-9 Msun
yr-1. The ultraviolet emission lines likely result from
reprocessed X-radiation absorbed by the wind. The Mg II K line exhibits
a time-varying emission core, that may be explained by ionization of
Mg+ in the wind by X-rays from the white dwarf.

---------------------------------------------------------
Title: Eclipsing Symbiotic Stars
Authors: Stencel, R. E.
1982BAAS...14..979S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Far Ultraviolet Spectroscopy Explorer (FUSE)
Authors: Weiler, E. J.; Stencel, R. E.
1982BAAS...14..883W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Narrow Ultraviolet Emission Lines of the Red Dwarf AU
Microscopii (dM1.6e)
Authors: Ayres, T. R.; Eriksson, K.; Gustafsson, B.; Linsky, J. L.;
Saxner, M.; Stencel, R. E.
1982BAAS...14Q.865A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Outer atmospheric properties of beta Draconis (G2 Ib-II)
Authors: Brown, A.; Jordan, C.; Ayres, T. R.; Linsky, J. L.; Stencel,
R. E.
1982ESASP.176..142B Altcode: 1982IUE3r......142B; 1982iue..conf..142B
Observations of the supergiant Beta Draconis made by IUE are
discussed. Electron pressure is comparable with that found in the quiet
solar atmosphere. The X-ray fluxes from previous observations suggest
T = 10 to 20 million k, when combined with the analysis of the IUE
spectra; this would be greater than the proton escape velocity. The
radiation losses between 10,000 and 100,000 K exceed those from the
Sun by an order of magnitude, but in the absence of a stellar wind the
energy losses from the corona would be lower than in the Sun. The line
profile widths indicate substantial (M=2) nonthermal broadening. If
interpreted as energy associated with a wave flux, they would imply
more coronal energy than required by radiation and conduction losses,
suggesting an energetic mass loss. However, line asymmetries can also
be interpreted as motions within the atmosphere.

---------------------------------------------------------
Title: On the reality of a boundary in the H-R diagram between
late-type stars with and without high temperature outer atmospheres.
Authors: Simon, T.; Linsky, J. L.; Stencel, R. E.
1982ApJ...257..225S Altcode:
The Linsky-Haisch hypothesis (1979) that a boundary exists in the H-R
diagram separating yellow giants from red giants and supergiants is
tested. IUE 1150-2000 A low-resolution spectra of 10 stars chosen to
constitute a reverse bias sample are presented and discussed. Despite
the bias, weak C IV emission indicative of high-temperature plasma was
observed in four of the six stars chosen to be probable red stars,
while no C IV emission was detected in the four stars chosen to be
yellows. In a second test using the entire sample of 39 stars, nearly
all of the yellow giants and supergiants were found to have an emission
feature at 1549 A, which is attributed to C IV. The large magnitude
dispersion could be attributed to temporal or spatial variability,
differing magnetic field strengths and geometries, or age-related
effects during post-main-sequence evolution. It is concluded that the
Linsky-Haisch transition region boundary is a real phenomenon.

---------------------------------------------------------
Title: High resolution EUV spectroscopy of 56 Pegasi (K0II P + wd).
Authors: Jordan, C.; Brown, A.; Ayres, T. R.; Linsky, J. L.; Stencel,
R. E.
1982ESASP.176..161J Altcode: 1982iue..conf..161J; 1982IUE3r......161J
The hypothesis that X-ray and UV emission by 56 Pegasi (K0II p + wd)
originates in a conventional chromosphere, transition region and corona,
as opposed to Schindler's hypothesis of accretion of the cool stellar
wind onto the white dwarf companion, is discussed. Analysis of IUE data
indicates that within the uncertainties associated with determining the
stellar radius and abundances, the chromosphere, transition region, and
corona of 56 Peg are similar to that of Beta Draconis both in structure
and energy balance. The accretion hypothesis is not a unique explanation
of the observed spectral properties and the white dwarf companion may
not play a direct role. Furthermore, 56 Peg, according to current
values of V-R and luminosity class, is on the nonsolar side of the
Linsky-Haisch dividing line whereas Beta Draconis is on the solar side.

---------------------------------------------------------
Title: Outer atmospheres of cool stars. XI. High-dispersion IUE
spectra of five late-type dwarfs and giants.
Authors: Ayres, T. R.; Linsky, J. L.; Basri, G. S.; Landsman, W.;
Henry, R. C.; Moos, H. W.; Stencel, R. E.
1982ApJ...256..550A Altcode:
We present high-dispersion, far-ultraviolet (1150-2000 Å) spectra
of five late-type dwarfs and giants obtained with the International
Ultraviolet Explorer. The chromospheric (T ≲104K)
emission lines in the giants tend to be about twice as broad as
the corresponding features of the dwarf star spectra, suggesting a
width-luminosity relation similar to the Wilson-Bappu effect for Ca
II H and K. The Si III λ1892 and C III λ1909 intercombination lines
formed in hotter layers (T ≍ 5 × 104K) also broaden
by a factor of 2 from the main-sequence stars to the evolved stars,
and the permitted resonance doublets of C II(3 × 104
K), Si IV (6 × 104 K), and C IV (105 K) are as much as
a factor of 4 broader in the giants than in the dwarfs. However, we
find no evidence for asymmetric or shifted emission profiles that
might indicate the presence of warm (T≪105K) stellar
winds. We conclude that broad C iv profiles, in particular, are typical
of active chromosphere giant stars and are unlikely to be a unique
signature of an extended, expanding warm wind. Since the resonance
lines tend to be wider than the intersystem lines formed at similar
temperatures in the chromosphere and in hotter layers, we conclude
that opacity must be an important broadening enhancement mechanism in
active chromosphere giant stars. Nevertheless, the intercombination
line widths do indicate a general increase in the outer atmosphere
Doppler motions from the dwarfs to the giants. Application of
the density sensitive line ratio C III λ1909/Si III λ1892 suggests
that the outer atmosphere pressures (T ≍ 5 × 104K)
are similar in the active chromosphere subgiant λ And and the quiet
chromosphere dwarfs, α Cen A and B. However, the pressures derived
for the Capella secondary and β Dra are factors of 3 or more lower
than the dwarfs, suggesting geometrically extended, low-density outer
atmosphere structures qualitatively different from the high-pressure,
compact structures typical of solar magnetic active regions. Finally, we have isolated the He II λ1640 emission component
from contaminant blends, and we find that the line strength is well
correlated with soft X-ray fluxes of the sample stars, as predicted
by photoionization-recombination models of the He II Bα formation.

---------------------------------------------------------
Title: Fluorescence in Stellar Chromospheres
Authors: Carpenter, K. G.; Wing, R. F.; Stencel, R. E.
1982BAAS...14..614C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A High Resolution EUV Spectrum of α Ori
Authors: Engvold, O.; Kjeldseth Moe, O.; Jensen, E.; Linsky, J. L.;
Stencel, R. E.
1982BAAS...14..651E Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Gas Flow in the Chromosphere of α Ori
Authors: Kjeldseth Moe, O.; Engvold, O.; Jensen, E.; Linsky, J. L.;
Stencel, R. E.
1982BAAS...14..651K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Ultraviolet observations of the 1980 eclipse of the symbiotic
star CICyg.
Authors: Stencel, R. E.; Boiarchuk, A. A.; Michalitsianos, A. G.;
Kafatos, M.
1982ApJ...253L..77S Altcode:
The paper presents secular and eclipse variations of ultraviolet
lines and continua in the course of nearly a complete orbit of
CI Cygni. High-excitation resonance lines show minimal effects of
eclipse, while intercombination lines have faded and show pronounced
but nontotal eclipse effects. The observations are examined in terms
of mass transfer from the extended cool envelope of the red giant to a
compact secondary. The formation of an accretion disk is a transitory
phenomenon in which viscosity eventually dissipates the disk over
orbital time scales. The intercombination line emission is explained by
a large-scale low-density nebula, and it is found that the resonance
line emission apparently arises in a large volume emitting region,
possibly formed through shock collision from interacting stellar winds
from the primary and secondary.

---------------------------------------------------------
Title: Evidence for extended chromospheres surrounding red giant
stars.
Authors: Stencel, R. E.
1982SAOSR.392A.137S Altcode: 1982csss....2..137S
There is now an increasing amount of both observational evidence
and theoretical arguments that regions of partially ionized hydrogen
extending several stellar radii are an important feature of red giant
and supergiant stars. This evidence is discussed and the implications
of the existence of extended chromospheres in terms of the nature of
the outer atmospheres of, and mass loss from, cool stars are examined.

---------------------------------------------------------
Title: Magnesium emission variability among late-type giant stars.
Authors: Mullan, D. J.; Stencel, R. E.
1982ApJ...253..716M Altcode:
Profiles of the Mg II h and k emission features in the spectra of 21
late-type giant stars were obtained. Emission strengths were separately
measured in the shortward (S) and longward (L) components. Variations
in total emission intensity (S + L) can be interpreted as evidence
for variations in the rate of mechanical energy deposition in the
chromosphere. Mass loss processes in the corona/outer atmosphere may
be strong enough to affect the ratio of S/L: thus, rapid mass loss
causes S/L to be less than unity. Rapid mass loss is likely caused by
deposition of mechanical energy by stellar wind. Variations in S/L are
a measure of variations in the rate of mechanical energy deposition
in the corona/outer atmosphere. The stellar sample variations were
divided into four classes: (1) variations in S/L; (2) variations in the
circumstellar absorption components; (3) variations in the total flux;
and (4) no evidence for variations found on the time scales used.

---------------------------------------------------------
Title: Ultraviolet and X-ray detection of the 56 Peg system (K0 IIp
+ WD).
Authors: Schindler, M.; Stencel, R. E.; Linsky, J. L.; Basri, G.;
Helfand, D.
1982SAOSR.392B.125S Altcode: 1982STIN...8234317S
Both IUE short and long wavelength exposures of the 56 Peg system are
discussed. This mild barium star has an X-ray luminosity of 3 x 10 to
the 31st power ergs/1, comparable to the rapidly rotating RS CVn binary
systems, yet lies in a region of the HR diagram where stellar X-rays
are generally not observed. This cool, bright giant is not a rapid
rotator and the key to understanding its emission lies in the recent
discovery of its white dwarf companion. Accretion onto the white dwarf
of approximately 0.1% of the stellar wind of the primary is sufficient
to power an X-ray source of the observed luminosity. Reprocessing of
the X-rays in the cool dense stellar wind explains the origin of the
UV emission line spectrum, and may explain the time varying asymmetry
of the Mg 2 kappa line profile that is observed. Graphs which show
observed fluxes and wavelengths are discussed.

---------------------------------------------------------
Title: A comparison of circumstellar gas and dust in M giants and
supergiants.
Authors: Hagen, W.; Dickinson, D. F.; Humphreys, R. M.; Stencel, R. E.
1982SAOSR.392A.231H Altcode: 1982csss....2..231H
This paper presents the results of a study of circumstellar gas and dust
in a larger sample of stars than that of Hagen (1978). The gas-to-dust
ratio varies considerably from star to star. The observations were
obtained at Cerro Tololo Interamerican Observatory and Kitt Peak
National Observatory. CS gas was observed with 2.5 and 5.1 A/mm
echelle spectra obtained with the 4-meter telescopes. CS dust was
observed through infrared photometry done with the CTIO 60 and KPNO
50 telescopes.

---------------------------------------------------------
Title: Changes in the UV spectrum of HD 4174.
Authors: Stencel, R. E.
1982NASCP2238..219S Altcode: 1982IUE82......219S; 1982NASCP2338..219S; 1982auva.nasa..219S
It is noted that the symbiotic-like object HD 4174 (EG And) exhibits
the optical spectrum of an M2 giant star, but also shows Balmer and
nebular line emission. The first UV spectrum showed an intense far
UV emission line spectrum typical of many symbiotic stars. A 470 day
binary or pulsation period for this system, based on the changing
strength and velocity of the H alpha emission. Preliminary indications
are that the H alpha and far UV continuum are eclipsed near phase 0.6
(at maximum H alpha redshift), but that the correlation for the emission
lines remains unclear and requires additional observations.

---------------------------------------------------------
Title: High resolution observations of magnesium II 2800 angstrom in
alf CenA : the density of interstellar magnesium II and the stellar
chromospheric profiles.
Authors: Oegerle, W. R.; Kondo, Y.; Stencel, R. E.; Weiler, E. J.
1982ApJ...252..302O Altcode:
The profiles are virtually identical with the solar profiles except
for the presence of an absorption feature near line center in the
h and k lines of Alpha Centauri A. It is found that this absorption
feature can be explained by interstellar absorption of Mg II along
the line of sight. The average density of Mg II is found to be 2.75
plus or minus 0.7 x 10 to the -7th/cu cm, in good agreement with the
previously determined values in the solar vicinity in the direction
of Alpha CMa and Alpha Lyr.

---------------------------------------------------------
Title: UV observations of the 1981 eclipse of 32 Cygni.
Authors: Stencel, R. E.; Chapman, R. D.; Kondo, Y.; Wing, R. F.
1982NASCP2238..497S Altcode: 1982auva.nasa..497S; 1982IUE82......497S; 1982NASCP2338..497S
Preliminary results of an extensive set of high dispersion UV spectra
of the supergiant eclipsing system 32 Cyg are detailed and contrasted
with spectroscopic studies of other Zeta Aur systems.

---------------------------------------------------------
Title: Evidence for extended chromospheres surrounding red giant stars
Authors: Stencel, R. E.
1982STIN...8234316S Altcode:
Observational evidence and theoretical arguments are summarized which
indicate that regions of partially ionized hydrogen extending several
stellar radii are an important feature of red giant and supergiant
stars. The implications of the existence of extended chromospheres are
examined in terms of the nature of the other atmospheres of, and mass
loss from cool stars.

---------------------------------------------------------
Title: HD4174
Authors: Stencel, Robert E.
1982iue..prop.1245S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: UV eclipse observations of CI Cyg.
Authors: Michalitsianos, A. G.; Kafatos, M.; Stencel, R. E.; Boiarchuk,
A. A.
1982ASSL...95..141M Altcode: 1982IAUCo..70..141M; 1982nss..coll..141M
Low spectral resolution observations were obtained with the IUE during
the eclipse phase. Additional data obtained by other IUE groups have
been included in the eclipse observations, making it possible to
examine the UV spectral properties of CI Cyg over nearly an entire
orbit which spans early 1979 through mid 1981. Data obtained over this
period suggest an overall decline in UV emission, consistent with
the decline of optical emission following the outburst of 1975. The
short-wavelength spectrum 1200-2000 A is characterized by numerous
intense high-excitation emission lines which become more prominent out
of eclipse. The LWR wavelength range 2000-3200 A exhibits a few more
additional lines of O III, Mg II, and He II which are superimposed
on continuum that rises gradually with increasing wavelength. The
observations are consistent with a binary star model which involves
mass transfer from the extended cool envelope of the primary to the
compact secondary.

---------------------------------------------------------
Title: High dispersion far ultraviolet spectra of cool stars.
Authors: Stencel, R. E.; Linsky, J. L.; Ayres, T. R.; Jordan, C.;
Brown, A.; Engvold, O.
1982NASCP2238..259S Altcode: 1982auva.nasa..259S; 1982IUE82......259S; 1982NASCP2338..259S
Recent far ultraviolet high dispersion spectra of two cool supergiant
stars, Beta Dra (G2 Ib) and Alpha Ori (M2 Iab) are examined in the
context of current questions regarding stellar chromospheres, coronae
and mass loss. These stars show very different outer atmosphere
structure. Beta Dra has a geometrically thin transition region with
bright emission lines of 100,000 K plasma that are red-shifted,
indicating downflow in magnetic flux tubes. By contrast, Alpha Ori
has a cool extended chromosphere and circumstellar envelope with large
mass loss.

---------------------------------------------------------
Title: Density sensitive C II lines in cool giant stars.
Authors: Stencel, R. E.; Carpenter, K. G.
1982NASCP2238..243S Altcode: 1982NASCP2338..243S; 1982auva.nasa..243S; 1982IUE82......243S
The density sensitivity of the emission lines within the ultraviolet
0.01 multiplet of C II near 2325 A was examined in additional late type
giants and supergiants with deep LWR high dispersion exposures. The
new data support the original contention based on these lines that
noncoronal red giants posses geometrically extended chromospheres.

---------------------------------------------------------
Title: Pre-eclipse ultraviolet spectra of Epsilon Aurigae.
Authors: Chapman, R. D.; Kondo, Y.; Stencel, R. E.
1982NASCP2238..505C Altcode: 1982NASCP2338..505C; 1982IUE82......505C; 1982auva.nasa..505C
Existing high dispersion, long wavelength IUE, high dispersion
long and short wavelength, and Balloon borne ultraviolet stellar
spectrograph (BUSS) spectra providing a baseline measurement of the
ultraviolet spectrum of the Epsilon Aurigae system before eclipse are
reviewed. Plans for ultraviolet spectrum IUE observations during the
1982 to 1984 eclipse of Epsilon Aurigae are presented.

---------------------------------------------------------
Title: "Discrepant asymmetry" stars: the role of unsteady magnetic
flux loops in the atmospheres of late-type giant stars.
Authors: Mullan, D. J.; Stencel, R. E.
1982NASCP2238..235M Altcode: 1982auva.nasa..235M; 1982IUE82......235M; 1982NASCP2338..235M
A number of spectroscopic peculiarities of K giants and other
stars which lie in a wedge in the HR diagram are discussed. These
peculiarities can be understood in terms of unsteady magnetic flux
loops emerging into the stellar atmosphere from beneath the surface.

---------------------------------------------------------
Title: CI Cygni since the 1980 eclipse.
Authors: Stencel, R. E.; Michalitsianos, A. G.; Kafatos, M.
1982NASCP2238..509S Altcode: 1982IUE82......509S; 1982auva.nasa..509S; 1982NASCP2338..509S
During the 1980 eclipse of the 855 day period symbiotic binary CI Cyg,
a data set showing high excitation resonance lines which were largely
uneclipsed but brightening on an orbital timescale, and intercombination
lines exhibiting pronounced but nontotal eclipses and which were
fading on an orbital timescale were obtained. A model invoking a low
density dissipating nebula surrounding the hot companion to explain the
intercombination lines, and a shock between stellar winds to interpret
the resonance lines, is described. Subsequent synoptic observations
revealed continuing changes in the UV emission line fluxes consistent
with those described above, except for the brightening of Mg II and the
emergence of strong, not previously seen Mg V emission. Post-outburst
and phase dependent changes must be included in any interpretation
of this system as the archetypal symbiotic binary. Observations to be
made during the 1982 October eclipse are summarized.

---------------------------------------------------------
Title: CI Cygni
Authors: Stencel, Robert E.
1982iue..prop.1261S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The 1979-1980 eclipse of ZET Aur. II. The emission spectrum.
Authors: Stencel, R. E.; Chapman, R. D.
1981ApJ...251..597S Altcode:
UV observations using the IUE are employed to discuss the strength and
changes of Zeta Aur between a second contact and mid-eclipse in 1979,
the relative visibility of the supergiant's chromosphere as compared
with the circumstellar (CS) nebular scattering of the B star photons,
and the origin of the high speed CS components observed at all orbital
phases. Agreement has been found for a spectoscopic radius of 200
solar radii and a 400 pc distance, and eclipse emission lines were
recorded from 1238.9-2802.7 microns. An asymmetry in the Fe III lines
at 46 plus or minus 15 km/sec was seen during eclipse and is taken to
indicate downflowing material. The high speed wind flowing from the
K supergiant is thought to expand homogeneously until encountering
the B type main sequence star, where an accretion bow shock forms,
and the smaller star's passage near the K star at periastron may cause
local surface heating and subsequent high speed flows.

---------------------------------------------------------
Title: Las envolturas circunestelares de las supergiantes del tipo
F Y G EN la NUBE Mayor de Magallanes.
Authors: Hagen, W.; Humphreys, R. M.; Stencel, R. E.
1981RMxAA...6...59H Altcode:
The outer atmospheres of four F- and G-type supergiants in the LMC are
compared with those of their Milky Way counterparts by means of 2.5 and
5.1 A/mm high dispersion Echelle spectra. Na I D line doubling indicates
extensive circumstellar envelopes, mass loss rates greater than 0.00001
solar masses/year, and outflow velocities of 10-60 km/sec. The Ca II
H and K lines yield new data on extragalactic star chromospheres.

---------------------------------------------------------
Title: High-dispersion spectroscopy of the most luminous F-and G-
type supergiants in the Large Magellanic Cloud and the milky way.
Authors: Hagen, W.; Humphreys, R. M.; Stencel, R. E.
1981PASP...93..567H Altcode:
High-resolution spectroscopic observations of the most luminous F- and
G-type supergiant stars in the Large Magellanic Cloud and in the Galaxy
are compared. High-dispersion echelle spectrograms, at dispersions
of 2.5 and 5.1 A/mm, were obtained together with optical and infrared
photometry for the four brightest LMC supergiants and seven Galactic
supergiants of comparable spectral types and luminosities. The LMC
supergiants are all observed to exhibit line doubling in the Na I D
lines, while no evidence for circumstellar line cores or line doubling
is seen in either Ca I 4226 A or Sr II 4077 A. The galactic yellow
supergiants also show evidence for broad diffuse or doubled lines. The
Ca II H and K core emission profiles along with the doubled lines
indicate extensive circumstellar envelopes, and lead to estimates of
mass-loss rates in excess of 0.0001 solar mass/year. It is suggested
that this mass loss rate may be explained by an outer atmospheric
structure consisting of an inner shell in which material circulates
between an extended atmosphere and the photosphere, and an outer shell
from which matter outflow takes place.

---------------------------------------------------------
Title: The FK COM stars.
Authors: Bopp, B. W.; Stencel, R. E.
1981ApJ...247L.131B Altcode:
The paper presents IUE observations of three very rapidly rotating G-K
giants (v sin i = 100 km/s). The UV spectra show strong chromospheric
and transition region emission lines similar to (and in excess of)
the RS CVn binaries. These stars show no evidence for radial velocity
variations in excess of plus or minus 3 to plus or minus 20 km/s,
arguing against duplicity. As a class, they lend support to the
rotation-activity hypothesis. Coalesced W UMa binaries, rather than
single stars, are the possible progenitors for these FK Com variables.

---------------------------------------------------------
Title: Density sensitive C II lines in cool stars of low gravity.
Authors: Stencel, R. E.; Linsky, J. L.; Brown, A.; Jordan, C.;
Carpenter, K. G.; Wing, R. F.; Czyzak, S.
1981MNRAS.196P..47S Altcode:
It is shown that the relative intensities of emission lines within the
multiplet UV 0.01 of C II, around 2325 A, are sensitive to electron
density in the range 10 to the 9th to 10 to the 7th per cu cm. The lines
therefore offer a valuable method for measuring electron densities in
the chromospheres of late-type giants and supergiants. Calculated line
ratios are compared with those observed in a range of objects.

---------------------------------------------------------
Title: HM Sge : Symbiotic cousin of the RS CVn stars ?
Authors: Blair, W. P.; Stencel, R. E.; Shaviv, G.; Feibelman, W. A.
1981A&A....99...73B Altcode:
In the brief time since its brightening in 1975, the optical
spectrum of HM Sagittae has shown considerable variation in both
its general characteristics and relative line intensity ratios. The
observations place HM Sagittae in a small class of objects which are
thought to be proto-planetary nebulae, of which V 1016 Cygni is the
prototype. Attention is given to derived density and temperature,
helium abundance and nebular mass, and an evolutionary scenario. The
considered observations show a decrease in the intensity of the
continuum and a continuation of the trend toward higher excitation
in the spectrum of HM Sagittae. Parallels are seen in the development
of this object and V 1016 Cygni, with the implication that the trend
toward higher excitation is expected to continue.

---------------------------------------------------------
Title: High-resolution spectra of five late-type dwarfs and giants
obtained with the IUE satellite.
Authors: Ayres, T. R.; Basri, G. S.; Henry, R. C.; Landsman, W.;
Linsky, J. L.; Moos, H. W.; Stencel, R. E.
1981BAAS...13..546A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The unusual outer atmosphere of 56 Pegasi (K0 IIp).
Authors: Schindler, M.; Stencel, R. E.; Linsky, J. L.; Helfand, D. J.;
Basri, G.
1981BAAS...13..547S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Are Discrepant Asymmetry Red Giants Necessarily Hybrid Stars?
Authors: Mullan, D. J.; Stencel, R. E.
1981BAAS...13..886M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Boundary in the H-R Diagram between Late-Type Stars with
and without High Temperature Outer Atmospheres
Authors: Simon, T.; Linsky, J. L.; Stencel, R. E.
1981BAAS...13..885S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Coordinated Ultraviolet-Optical-Infrared Observing Campaign
for the 1982-84 Eclipse of Epsilon Aurigae
Authors: Genet, R. M.; Stencel, R. E.
1981BAAS...13..804G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Variable mass loss and magnetic topology in cool giant stars.
Authors: Mullan, D. J.; Stencel, R. E.
1981BAAS...13..547M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Ultraviolet Spectroscopy of the 1981 Eclipse of 32 Cygni
Authors: Stencel, R. E.; Chapman, R. D.; Kondo, Y.; Wing, R. F.
1981BAAS...13R.830S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: IUE Echelle Mode Observations Contrasting Coronal and
Non-Coronal Late Type Giant and Supergiant Stars
Authors: Brown, A.; Stencel, R. E.; Linsky, J. L.; Jordan, C.;
Engvold, O.
1981BAAS...13..885B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Unusual Outer Atmosphere of 56 Pegasi (KO IIp)
Authors: Schindler, M.; Stencel, R.; Linsky, J.; Helfand, D.; Basri, G.
1981BAAS...13Q.545S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: High-Resolution Spectra of Five Late-Type Dwarfs and Giants
Obtained with the IUE Satellite
Authors: Ayres, T. R.; Basri, G. S.; Henry, R. C.; Landsman, W.;
Linsky, J. L.; Moos, H. W.; Stencel, R. E.
1981BAAS...13R.545A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: CH Cygni
Authors: Kafatos, M.; Michalitsianos, A. G.; Feibelman, W. A.; Hobbs,
R. W.; Stencel, R. E.
1981IAUC.3570....1K Altcode:
M. Kafatos, A. G. Michalitsianos, W. A. Feibelman and R. W. Hobbs,
Goddard Space Flight Center; and R. E. Stencel, Joint Institute for
Laboratory Astrophysics, report: "IUE observations of the symbiotic
star CH Cyg were made on 1980 Dec. 23.3 UT, and the fine-error-sensor
indicated V = 5.9. High-dispersion spectrograms showed He II 164.0 nm,
Si III 189.2 nm and C III 190.6 and 190.9 nm in emission; there was
also complex emission and absorption of Mg II 279.6 and 280.3 nm. The
continuum had a strong discontinuity at 172.0 nm in low dispersion,
consistent with a star having a temperature near 7000 K."

---------------------------------------------------------
Title: Other Late-Type Binaries with Symbiotic Characteristics
Authors: Stencel, R.
1981syst.work...25S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Chromospheric Densities &amp; Geometrical Extensions of
Late-Type Giant &amp; Supergiants
Authors: Stencel, Robert E.
1981iue..prop..820S Altcode:
There is now considerable evidence, on the basis of IUE spectra and
Einstein X-ray fluxes, that the cool half of the HR diagram can be
divided into two regions. The first region, including the dwarfs
and yellow giants, contains stars with weak winds and hot outer
atmospheres (containing transition regions and coronae). The second
region, including the red giants and supergiants, contains stars with
strong winds and cool plasma. These two regions have a boundary in
which stars with both characteristics occur. We have recently found
that ratios among the five lines in the C II 2325 A multiplet and the
ratio of the integrated fluxes in the C II 2325 A and 1335 A multiplets
are powerful diagnostics of electron densities, temperatures, and
geometrical extent (atmospheric extension) of chromospheres in the
yellow giants and red giants and supergiants. The few IUE LWR high
dispersion exposures with sufficient integration time to date have been
used to suggest that cool star chromospheres may be extremely thick,
and their dimensions correlated with dominant magnetic topology in
the outer atmosphere. We propose (a) to verify the use of the C II
2325 A lines as density diagnostics with long exposures of additional
bright cool stars, and (b) to investigate the correlation of inferred
chromospheric thickness with location in the HR diagram, relative to the
coronal/wind dividing line which occurs along a locus between K1 III
and G5 Ib in the HR diagram. With properties thereby calibrated among
cool stars, we can use LWR low dispersion observations to obtain C II
2325 A total fluxes to constrain chromospheric thickness among a wider
sample of cool giants and supergiants with more extreme properties,
and to thereby evaluate temperature and luminosity variations.

---------------------------------------------------------
Title: A Study of the MG II Profiles in the UV Spectra of Symbiotic
Stars
Authors: Stencel, Robert E.
1981iue..prop..839S Altcode:
We wish to undertake an exploration of the circumstellar and nebular
environment of symbiotic binaries via LWR high dispersion mode Mg
II region exposures to distinguish the nature and degree of binary
interaction. The observed structure of the Mg II 2800A resonance doublet
bears a striking generic similarity to those seen in the binary Zeta Aur
during its recent eclipse. In addition to this multiple peaked emission
structure, the total flux in Mg II for symbiotics greatly exceeds any
normal single cool star of giant or supergiant type, as is also the
case for Zeta Aur. The synoptic coverage of Zeta Aur systems in and out
of eclipse suggests that the nebular and circumstellar phenomena seen
therein, find their extreme expression among the symbiotic stars. We
wish to explore this similarity, and in view of the surprising lack of
LWR high dispersion observations of symbiotics, request IUE observing
time for the purpose. Previously observed and published IUE data will
be drawn upon to complement the new observations in the search for
binary variations.

---------------------------------------------------------
Title: Ultraviolet Eclipse Observations of Ci-Cygni
Authors: Stencel, R.; Kafatos, M.; Michalitsianos, A. G.; Boyarchuk,
N. A.
1981syst.work....5S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: MGII Profiles of Symbiotic Stars
Authors: Stencel, R.; Michalitsianos, A. G.; Kafatos, M.
1981syst.work...30S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: An Emission Measure Analysis of the High Dispersion SWP Spectra
Authors: Stencel, Robert E.
1981iue..prop..833S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: High resolution flux profiles of the Mg II h &amp; k lines
in evolved F8 to M5 stars.
Authors: Stencel, R. E.; Mullan, D. J.; Basri, G. S.; Linsky, J. L.
1981NASCP2171..317S Altcode: 1980IUE80......317S; 1981uviu.nasa..317S; 1981NASCP3171..317S
The central results of a survey of the Mg II resonance line
emission in a sample of over 50 evolved late type stars, including
spectral-luminosity type F8 to M5 and La to IV are presented. Observed
and surface fluxes are derived and correlations noted. The major
findings include: (1) Mg II k emission core asymmetry transition near
K1 III, analogous to that known for Ca II K; (2) a small gravity and
temperature dependence of the Mg II chromospheric radiative loss rate.

---------------------------------------------------------
Title: UV chromospheric and circumstellar diagnostic features among
F supergiant stars.
Authors: Stencel, R. E.; Worden, S. P.; Giampapa, M. S.
1981NASCP2171..311S Altcode: 1981NASCP3171..311S; 1980IUE80......311S; 1981uviu.nasa..311S
A survey of F supergiant stars to evaluate the extension of
chromospheric and circumstellar characteristics commonly observed
in the slightly cooler G, K, and M supergiant is discussed. An
ultraviolet survey was elected since UV features of Mg II and Fe II
might persist in revealing outer atmosphere phenomena even among F
supergiants. The encompassed spectral types F0 to G0, and luminosity
classes Ib, Ia, and Ia-0. In addition, the usefulness of the emission
line width-to-luminosity correlation for the G-M stars in both the Ca
II and Mg II lines is examined.

---------------------------------------------------------
Title: 32 Cygni
Authors: Stencel, Robert E.
1981iue..prop..865S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: SWP High Resolution Spectra &amp; Emission Measure Analysis
of Yellow Bright Giants with Coronae
Authors: Stencel, Robert E.
1981iue..prop..822S Altcode:
There is now considerable evidence, on the basis of IUE spectra and
Einstein X-ray fluxes, that the cool half of the HR diagram can be
divided into two regions. The first region, including the dwarfs and
yellow giants, contains stars with weak winds and hot outer atmospheres
(containing transition regions and coronae). The second region,
including the red giants and supergiants, contains stars with strong
winds and cool plasma. These two regions have a boundary in which stars
with both characteristics occur. We propose to study in detail 4 yellow
bright giants and supergiants that have hot outer atmospheres and lie
close to or on the dividing line separating these two regions. These
stars (Beta Dra, 56 Peg, alpha Aqr, and Beta Cam) were chosen because
of their intrinsic interest, previous extensive studies, and because
they are bright enough that 15 hour SWP-HI exposures should produce
good quality line profiles for a number of important transition region
and chromosphere lines. Our objectives are to compute detailed models
for the chromospheres and transition regions of these stars using the
strengths and profiles of lines of Mg II, C II, Si II, Si III, C III,
C IV, and N V, using density-sensitive line ratios, and an emission
measure analysis that incorporates information on line opacities and
widths in addition to their fluxes. The aim of this analysis is to
determine the energy balance as a function of height in these stars
and to compare the derived pressures to those of other stars studied
that lie further away from the boundary of these two regions of the
HR diagram.

---------------------------------------------------------
Title: Ingress observations of the 1980 eclipse of the symbiotic
star CI Cygni.
Authors: Stencel, R. E.; Michalitsianos, A. G.; Kafatos, M.; Boyarchuk,
A. A.
1981NASCP2171..459S Altcode: 1981NASCP3171..459S; 1981uviu.nasa..459S; 1980IUE80......459S
One of the major results from the IUE may prove to be the
knowledge gained by studies of the ultraviolet spectra of symbiotic
stars. Symbiotics combine spectral features of a cool M giant like
photosphere with strong high excitation emission lines of nebular
origin, superposed. The UV spectra are dominated by intense permitted
and semiforbidden emission lines and weak continua indicative of hot
compact objects and accretion disks. Two symbiotics, AR Pav and CI
Cyg are thought to be eclipsing binaries and IUE observations during
the 1980 eclipse of CI Cygni are discussed.

---------------------------------------------------------
Title: North American Workshop on Symbiotic Stars
Authors: Stencel, R. E.
1981syst.work.....S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The outher atmospheres of cool stars. VII. High resolution,
absolute flux profiles of the MG II H and K lines in stars of spectral
types F8 to M5.
Authors: Stencel, R. E.; Mullan, D. J.; Linsky, J. L.; Basri, G. S.;
Worden, S. P.
1980ApJS...44..383S Altcode:
We present high-resolution lUE spectra of the emission cores of the
Mg II resonance doublet at 280 nm in a selection of 54 stars covering
a range of spectral type from F8 to MS and of luminosity class from
supergiant (Ia) to subgiant (IV). These spectra were obtained with the
LWR echelle system onboard the IUE satellite, and have been calibrated
in absolute flux units using OAO 2 photometry of Eta UMa as a standard,
plus the Barnes and Evans relations for stellar angular diameters. The
uncertainty in flux is probably of order 20%. We discuss the qualitative
line profile groupings, as determined by Basri and Linsky, and derive
chromospheric radiative losses in the h and k lines; we discuss
these loss rates as functions of effective temperature and luminosity
class. We make further comparisons of these rates with rates derived
for the Ca II H and K lines by Linsky and his colleagues. Chromospheric
velocity fields and indicators of circumstellar envelopes are discussed
in terms of profile asymmetries and other diagnostics. Line width
measures and velocity shifts of the central reversals are tabulated,
among other quantities, and several correlations noted. Finally, we
discuss the relation of the Wilson K index and stellar coronae to Mg
II emission, and note the occurrence of Fe II emission lines in the
middle range of the UV of late-type stars.

---------------------------------------------------------
Title: Moderate Resolution McGraw-Hill Scanner Observations of
Symbiotic and Related Stars
Authors: Blair, W.; Stencel, R.; Feibelman, W.; Michalitsianos, A.
1980BAAS...12..869B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Solar and Stellar Resonance Line Emission Cores and Inferred
Magnetic Topology
Authors: Stencel, R. E.
1980BAAS...12..913S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Chromospheric Densities and Geometrical Extensions of Red
Giants and Supergiants using C II Lines as Diagnostics
Authors: Stencel, R. E.; Jordan, C.; Wing, R. F.; Linsky, J. L.;
Carpenter, K. G.; Brown, A.; Czyzak, S. J.
1980BAAS...12..806S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Addendum - Detection of Mass Loss in Stellar Chromospheres
Authors: Stencel, R. E.; Mullan, D. J.
1980ApJ...240..718S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Synoptic UV Observations of the Zeta Aurigae Binaries
Authors: Kondo, Y.; Chapman, R.; Stencel, R. E.; Wing, R.
1980BAAS...12..868K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: High Resolution Spectroscopy and Mass Loss Rates for LMC
Yellow Supergiants
Authors: Hagen, W.; Humphreys, R.; Stencel, R.
1980BAAS...12..801H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Onset of Mass-Loss Among G Supergiants
Authors: Basri, G. S.; Stencel, R. E.; Linsky, J. L.
1980BAAS...12R.805B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: UV Observations of the 1980 Eclipse of the Symbiotic Star
CI Cygni
Authors: Boyarchuk, A.; Stencel, R.; Michalitsianos, A.; Kafatos, M.
1980BAAS...12..868B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Search for Mg II Asymmetry Variations Among Cool Evolved
Stars
Authors: Mullan, D.; Stencel, R.
1980BAAS...12..801M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Radial velocity study of four southern RS CVn candidates and
related field stars.
Authors: Stacy, J. G.; Stencel, R. E.; Weiler, E. J.
1980AJ.....85..858S Altcode:
Radial velocity variations are demonstrated for four southern RS CVn
candidates: HD 39937, 101379, 155555, and 174429. The period of HD
155555 appears to have decreased by about one part in 100,000 over the
past 18 yr. In addition, high-resolution observations of the Ca II H and
K profiles and the Mg II 2800-A emission doublet are presented. These
enhance the likelihood of these being RS CVn objects. Radial velocity
data for 15 other late-type bright field stars are presented. Some of
these were observed by Copernicus and may exhibit unusual chromospheres,
while the rest lack radial velocity information as tabulated in the
Bright Star Catalog. All velocity measures have been corrected to the
IAU heliocentric system.

---------------------------------------------------------
Title: IUE observations of the peculiar M giant HD 4174.
Authors: Stencel, R. E.; Sahade, J.
1980ApJ...238..929S Altcode:
Ultraviolet spectra of the peculiar M giant HD 4174, which may
possess a significant magnetic field, are shown to exhibit numerous
high-excitation emission lines and no background continuum. Ionization
equilibrium temperatures for species observed range from 6000 K
(Mg II) up to 200,000 K (N v). Density diagnostics using line ratios
indicate electron density of 3 x 10 to the 9th power per cu cm in the
emission-line-forming region, which favorably compares with coronal
model parameters previously suggested for this star. High-resolution
Ca II and Mg II profiles suggest an enhanced chromospheric temperature
rise. Comparison with symbiotic objects and a high-excitation planetary
nebula reveals similarities among these objects.

---------------------------------------------------------
Title: Detection of mass loss in stellar chromospheres.
Authors: Stencel, R. E.; Mullan, D. J.
1980ApJ...238..221S Altcode:
IUE observations of 47 cool giants have been made in a search for
the onset of expansion in the Mg II h and k emission cores. It
is found that, in a statistical sense, the longward emission peak
becomes dominant above a velocity dividing line in the H-R diagram,
which lies close to a temperature dividing line reported by Linsky
and Haisch (1979). Also discussed are asymmetries in emission cores,
collected asymmetry data including the evaluation of absolute visual
magnitude by MK classification, Ca K emission width, and Mg k emission
width, and evolutionary implications for the hypothesized supersonic
transition locus (Mullan, 1978).

---------------------------------------------------------
Title: Solar limb emission lines near CA II H &amp; K and their
spatial intensity variations
Authors: Rutten, R. J.; Stencel, R. E.
1980A&AS...39..415R Altcode:
The paper employs solar observations of high spatial and spectral
resolution to identify emission lines seen in the extended wings of Ca
II H &amp; K near the solar limb. Emission lines in the wings of H &amp;
K represent valuable diagnostics of the atmospheres of cool stars,
with a varying information content which depends on their particular
formation mechanism. In solar spectrograms different emission line
formation mechanisms can be distinguished by the character of the
spatial intensity variation (SIV) apparent in the lines. Various classes
of H &amp; K emission features, their spatial intensity variations and
their formation mechanisms (of which some pose further problems) are
discussed. A new extended list of line identifications is compiled based
on their formation class and compared with other line lists. Evidence
is found that stellar luminosity-sensitive lines tend to show large
spatial intensity variation on the sun.

---------------------------------------------------------
Title: Extension of Line Identifications in Arcturus Shortward
to 2250A
Authors: Carpenter, K. G.; Stencel, R. E.; Wing, R. F.
1980BAAS...12..529C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Ultraviolet observations of 31 and 32 Cygni.
Authors: Stencel, R. E.; Kondo, Y.; Bernat, A. P.; McCluskey, G.
1980IAUS...88..555S Altcode:
Some observations of 31 and 32 Cygni, started in September 1978, at
phases 0.62 and 0.17, respectively, are presented. The UV spectrum of
32 Cyg is described both qualitatively and quantitatively. Numerous
lines of Si II, O I, C II, Al II and III and Fe II appear with P
Cygni characteristics. The LWR-2275 image is dominated by the Mg II
2800 A resonance doublet and numerous Fe II lines in the 2200 - 2700 A
region, all showing P Cygni profiles. More quantitatively, ionization
modeling for the B star environs was made by comparing observed and
computed equivalent widths to deduce density, temperature and turbulence
values. At the projected separation between the stars, the log particle
density obtained was 7.2, neglecting dust and molecule formation.

---------------------------------------------------------
Title: Stellar Wind Energetics and Mass Loss in Late-Type Supergiant
Stars
Authors: Stencel, R. E.
1980SAOSR.389..183S Altcode: 1980csss....1..183S
No abstract at ADS

---------------------------------------------------------
Title: Depth-dependence of turbulence in stellar atmospheres
Authors: Stencel, R. E.
1980LNP...114..136S Altcode: 1980IAUCo..51..136S; 1980sttu.coll..136S
Recent observations concerning the depth dependence of motions in
stellar atmospheres are reviewed. With regard to turbulence in stellar
photospheres, attention is given to evidence from the sun and Arcturus
for an increase in the total micro- plus macro-velocities with height,
starting at mid-photospheric levels. Concerning stellar chromospheric
velocity fields, it is noted that Mg II data point to changes in
the hydrodynamic structure of the upper atmosphere. Ca II and Mg II
asymmetry observations and other studies are used to describe the upper
atmospheric structure of cool evolved stars, particularly coronae and
circumstellar envelopes, revealing a depth dependent effect of velocity
fields among a wide range of such stars.

---------------------------------------------------------
Title: Observations of the Eclipse of the Symbiotic Star Ci Cygni
Authors: Stencel, Robert E.
1980iue..prop..515S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: IUE Ultraviolet Spectra of the Interacting Binary U-Cephei
Authors: Kondo, Y.; McCluskey, G. E.; Stencel, R. E.
1980IAUS...88..237K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Study of Chromospheres and Circumstellar Envelopes in G, K,
M Supergiants
Authors: Stencel, Robert E.
1980iue..prop..502S Altcode:
We propose to continue work begun this summer with IUE 2nd year
observations of cool supergiants. With the initial data, we have
begun to derive physical models for chromospheres and circumstellar
envelopes of cool supergiants of spectral types G, K and M. Emission
lines with complex profile structure appear throughout the LWR region,
including the Mg II resonance lines at 2800 the Mg I resonance line at
2852 A and a large number of Fe I and Fe II lines spanning the 2200
to 3000 A region. These lines show chromospheric emission components
and blue-shifted circumstellar absorption components. We have started
the process of modeling these profiles using a sphericalgeometry,
partial-redistribution computer code which simultaneously solves the
coupled equations of statistical equilibrium and radiative transfer
in the co-moving frame of the absorbing atoms and ions. As we are
particularly interested in the dynamics of the mass loss processes
in these stars and the extent to which the outer atmospheres are
inhomogeneous, additional IUE spectra for supergiants over the full
range in effective temperature, gravity and strength of C IF 1549 A are
needed to complete the physical analysis just begun by the limited IUE
observing time provided during its second year. Results of the analysis
to date include physical models for the supergiants Beta Draconis and
Alpha Ori which match their observed Mg II and Ca II emission profiles,
along with the discovery of unexpected effects in line formation which
imply "thin" chromospheres for supergiants of late-type.

---------------------------------------------------------
Title: Transition region chromospheric models of 24 UMa based on
IUE ultraviolet spectrograms.
Authors: Simon, T.; Stencel, R. E.; Lites, B. W.
1980PASP...92R.550S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A search for the reported TI II lam 3080 multiplet emission
in late-type stars.
Authors: Oegerle, W. R.; Stencel, R. E.; Weiler, E. J.
1979PASP...91..781O Altcode:
Gurzadyan (1975), using a low-resolution objective-prism spectrograph,
has reported the presence of both the multiplet Ti II 3080 and the
doublet Mg II 2800 simultaneously either in emission or in absorption
in late-type stars. Using the high-resolution spectrometers onboard
Copernicus and BUSS, it is found that stars which display Mg II 2800
strongly in emission do not have a corresponding emission feature
at 3080.

---------------------------------------------------------
Title: IUE observations of gas stream effects in the ultraviolet
spectrum of U Cephei.
Authors: Kondo, Y.; McCluskey, G. E.; Stencel, R. E.
1979ApJ...233..906K Altcode:
The eclipsing binary U Cephei has been observed with the International
Ultraviolet Explorer (IUE) satellite. Nine high-resolution spectra in
the mid-ultraviolet (1900-3200 A) and one high-resolution spectrum in
the far-ultraviolet (1200-1900 A) were obtained. The effects of gas
streaming are clearly seen in the mid-ultraviolet resonance lines of
Fe II (2599 A) and Mg II (2795 and 2802 A). The data indicate that much
of the gas leaving the G star circles behind the B star and leaves the
system. It is suggested that g-mode oscillations in the G star supply
part of the energy required to drive the gas out of the system.

---------------------------------------------------------
Title: IUE observations of 32 Cygni: the effects of the B star within
the upper chromosphere of a late-type supergiant.
Authors: Stencel, R. E.; Kondo, Y.; Bernat, A. P.; McCluskey, G. E.
1979ApJ...233..621S Altcode:
The object 32 Cygni is a Aurigae-type system, comprised of a KS
supergiant and a dwarf, which undergoes atmospheric eclipses. We have
obtained high-resolution ultraviolet spectra of this system with IUEnear
orbital phase 0.2, covering the 1175-3000 A region. The UV spectrum is
striking, since all resonance and other strong lines exhibit marked P
Cygni characteristics. Further, the absorption portion of these lines
is generally complex, revealing multiple absorption components at high
velocities (-400 km s -1) which have not previously been seen with such
strength or so far from primary eclipse. The origin of the excess UV
flux seen in OA 0 2 observations is explained by strong chromospheric
line emission during primary eclipse. The spectral type of the B star is
reevaluated from its photospheric line strengths. Earlier hypotheses of
multiple condensations in the supergiant chromosphere are discussed in
light of overionization effects and Saito's hypothesis of Lyman photon
driven shocks. Ionization modeling supports the hypothesis that the
B star resides within the upper chromosphere of the K supergiant. We
determine a line-of-sight density of 1.6 x 10 cm -3 at 4 K star radii,
which coupled with measured velocities leads to a mass loss rate of
4 x 10- M0 yr -1, consistent with previous investigations. Finally,
the effect of the B star on the K supergiant atmosphere is reviewed
in light of the small separation between the stars compared with the
Str6mgren ionization radius of the B star. Subject headings: line
identifications - stars: chromospheres - stars: eclipsing binaries -
stars: individual - ultraviolet: spectra

---------------------------------------------------------
Title: Zodiacal Light Surface Brightness Measurements by Atmosphere
Explorer-C
Authors: Torr, M. R.; Torr, D. G.; Stencel, R.
1979Icar...40...49T Altcode:
Using the visible airglow photometer on the Atmosphere Explorer-C
satellite, we have mapped the zodiacal light surface brightness at
the wavelengths monitored by the instrument: 3371, 4278, 5200, 5577,
6300, and 7319 Å. The study constitutes a survey over this wavelength
range, covering most of the celestial sphere, from altitudes above
the atmospheric emissions, and free from atmospheric scattering
and attenuation. The intensity variations reveal enhancements near
elongations of 130°, and possibly near 60°, at all wavelengths. The
intensity of the zodiacal light near the ecliptic pole is found to
be ∼30 S 10. The color ratio with respect to the Sun is
found to be redder than the Sun (0.7) at all elongations.

---------------------------------------------------------
Title: Southern RS CVn systems. Candidate list.
Authors: Weiler, E. J.; Stencel, R. E.
1979AJ.....84.1372W Altcode:
A list of 43 candidate RS CVn binary systems in the far southern
hemisphere of the sky (south of -40 deg declination) is presented. The
candidate systems were selected from the first two volumes of
the Michigan Spectral Catalog (1975, 1978), which provides MK
classifications for southern HD stars and identifies any unusual
characteristics noted for individual stellar spectra. The selection
criteria used were: (1) the occurrence of Ca II H and K emission;
(2) known or suspected binary nature; (3) regular light variations
of zero to one magnitude; and (4) spectral type between F0 and K2 and
luminosity less than bright giant (II).

---------------------------------------------------------
Title: Stellar magnetic fields: the role of a magnetic field in the
peculiar M giant, HD 4174.
Authors: Stencel, R. E.; Ionson, J. A.
1979PASP...91..452S Altcode: 1979STIN...7923863S
Principles of coronal heating via basic electrodynamic effects,
viz., resonant absorption of Alfven surface waves (quiescent) and
magnetic tearing instabilities (impulsive), are detailed to argue
three principles which may have application to late-type evolved
stars. First, if one observes that B-squared/8 pi is much greater
than rho times v-squared in a stellar atmosphere, then the observed
magnetic field must originate in an interior dynamo. Second, low
mass-loss rates could imply the presence of closed magnetic flux loops
within the outer atmosphere, which constrain hydrodynamic flows when
the magnetic body forces exceed the driving forces. Third, given that
such magnetic loops effect an enhancement of the local heating rate,
a positive correlation is predicted between the existence of a corona
and low mass-loss rates. Application of these principles is made in
the case of the peculiar M giant star HD 4174, which is purported
to have a kilogauss magnetic field. Several of its spectroscopic
peculiarities are shown to be consistent with the above principles,
and further observational checks are suggested. Possible application
to dMe and RS CVn objects is sketched.

---------------------------------------------------------
Title: A comparison of emission lines in the ultraviolet spectra
of alpha Boo (K2 IIIp), alpha Tau (K5 III), alpha Ori (M1-2 Ia-b)
and alpha Sco (M1.5 Iab+B2.5 V).
Authors: van der Hucht, K. A.; Stencel, R. E.; Haisch, B. M.; Kondo, Y.
1979A&AS...36..377V Altcode:
Observations and identifications are presented of 45 emission lines in
the near-ultraviolet spectra of Boo (K2 IIIp), x Tau (KS III), z Ori
(M1-2 Ia-b) and 1 +2 Sco (M1.5 Iab+ B2.5 V). The useful wavelength
ranges, A for Boo, 28( A for Tau, A for Ori and 2()()( 2400 A, 27O(
3200 A for 1+2 Sco are covered with a resolution of 0.1 A. We have
identified emission lines of Mg I, Fe I, Fe II, Fe III and a possible
Si I emission line, in addition to the strong chromospheric Mg II h
and k resonance emission lines. Several Fe I and Fe II fluorescence
emission lines are identified, which may originate through pumping by
the Mg II X2795 k line. Because of the lack of an intensity calibration
only a qualitative description of the data is possible. Where possible
we have established radial velocities for the various regions in the
chromospheres and circumstellar envelopes of the stars. The emission
lines of x Ori show an outflow of material from both the chromospheric
and circumstellar regions, in contrast to a previously determined
inflow as measured by Boesgaard and Magnan (1975). We conclude
that we are seeing a different phase of an apparently variable mass
motion phenomenon. We suggest an interpretation in terms of very large
convective elements as hypothesized by Schwarzschild (1975). The other
three stars show a blue shifted absorption component in the Mg II lines
on top of the overall redshifted emission. The Fe III emission lines in
the spectrum of 1 +2 Sco are due to the presence of the B star within
the circumstellar envelope of the M star. Key words: chromosphere -
circumstellar envelope - stars: individual - spectra: ultraviolet

---------------------------------------------------------
Title: Gas stream observed in the ultraviolet spectrum of U Cephei.
Authors: Kondo, Y.; Stencel, R. E.; McCluskey, G. E.
1979BAAS...11..422K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Upper Chromosphere of the Late-Type Supergiant 32 Cygni
Observed in the Ultraviolet
Authors: Stencel, R. E.; Kondo, Y.; Bernat, A. P.; McCluskey, G. E.
1979BAAS...11R.449S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Gas Stream Observed in the Ultraviolet Spectrum of U Cephei
Authors: Kondo, Y.; Stencel, R. E.; McCluskey, G. E.
1979BAAS...11..423K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Handbook of Unusual Natural Phenomena %a William R. Corliss
Authors: Stencel, Robert E.
1979Arch....2c..23S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Natural Solar Architecture: A Passive Primer %a David Wright
Authors: Stencel, Robert E.
1979Arch....2b..22S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Study of Chromospheres and Circumstellar Envelopes in G,K,
and M Supergiants by Obtaining and Analyzing IUE Profiles
Authors: Stencel, Robert E.
1979iue..prop..247S Altcode:
We propose to derive physical models of chromospheres and circumstellar
envelopes of cool supergiants for spectral types G0 through mid-M and
covering luminosity classes II through Ia-0. To derive these models
we request IUE time to observe the target stars at high dispersion
with the LWR camera. The lines of interest are MgII 2798, 2803,
MgI 2852, and a number of Fe I and Fe II lines at 2400-3200 A,
especially the Fe II lines near 2500 A. We expect these lines to
have chromospheric emission components and blue-shifted circumstellar
absorption components. These complex line profiles will be modelled
using a spherical geometry partial redistribution computer code which
solves the transfer equation in the comoving frame of the absorbing
atoms. We are especially interested in the dynamics of the mass loss
processes in these stars and the extent to which the outer atmospheres
are inhomogeneous.

---------------------------------------------------------
Title: Lines in the 2736 - 3303 Å spectrum of Arcturus.
Authors: Stencel, R. E.; van der Hucht, K. A.
1978ApJS...38...29S Altcode:
Results are reported for a study of the near-UV spectrum of Arcturus
as recorded with a balloon-borne echelle spectrograph-vidicon detector
system in the spectral region from 2700 to 3300 A at 0.1-A resolution. A
condensed version of the Arcturus spectrum is provided along with
profile descriptions and identifications for 383 absorption features
detected in the near-UV. Elements definitely present include Na, Mg, Al,
Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Zr, and La. Elements
with spectral features indicating possible presence include Be, O, S,
K, Ga, Ge, Nb, Sn, Gd, and Bi. Line blocking is shown to be extensive
in the spectral region studied, and eight possible continuum 'windows'
are found in the near-UV. Emission lines of chromospheric origin due
to Mg II, Fe I, Fe II, and possibly Cr II are also identified in the
region from 2736 to 3303 A. It is noted that the Fe I emission lines
at 2823 and 2844 A are optically pumped.

---------------------------------------------------------
Title: The Ca II V/R ratio and mass loss.
Authors: Stencel, R. E.
1978ApJ...223L..37S Altcode:
High-dispersion coude spectrograms of 181 MK standards of types early
F through late M, including luminosity classes Ia, Ib, II, and III,
are analyzed. It is shown that the brightness ratio of the V and R
self-reversed emission peaks (denoted V/R) in the center of the Ca II
K line is correlated with spectral type as well as with certain other
spectral-type and luminosity-sensitive parameters, including indicators
of mass loss and the H-K wing emission lines. The observations indicate
that V/R varies smoothly from less than unity in late K and M giants
to greater than unity for G giants. This trend appears to be true for
bright giants as well but not necessarily for supergiants and seems
to hold for the average V/R for a given star, although short-term
variations in V/R occur. It is suggested that the V/R values, which
can be interpreted in terms of atmospheric motions, may indirectly
relate to effects of evolutionary changes in stellar structure and
that V/R among late-type stars could be useful as an indicator of both
chromospheric activity and the state of stellar evolution.

---------------------------------------------------------
Title: Spatial structure in lines in the 3398 3526 å region at the
extreme limb: Observation, identification and interpretation
Authors: Canfield, R. C.; Pasachoff, J. M.; Stencel, R. E.; Beckers,
J. M.
1978SoPh...58..263C Altcode:
We have obtained spectrograms of high spatial and spectral resolution
of the extreme solar limb, using the vacuum tower telescope of
Sacramento Peak Observatory. We have identified emission lines in
the range 3398-3526 Å, and classified them according to intensity,
spatial structure (intensity variation), and profile. Some lines show
spatial intensity variation; others do not. We show that this effect
is related to the abundance of the element responsible for the line
and the mean lower-level excitation potential of interlocked lines. We
explain the effect in terms of radiative interlocking with other lines,
as well as the characteristic size of the volume contributing to the
mean intensity.

---------------------------------------------------------
Title: Mid-UV Emission Lines in Late-Type Giants and Supergiants.
Authors: Stencel, R. E.; van der Hucht, K. A.; Kondo, Y.
1978BAAS...10R.453S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Extensions of the Wilson-Bappu Effect among Very Luminous Stars
Authors: Stencel, R. E.
1978IAUS...80...59S Altcode:
It has been stated that the technique used by Wilson and Bappu (1957)
in their study of the observational correlation of MV
and the logarithm of the full width at half maximum of the Ca II
K-line central emission for G, K, and M stars has a plus or minus
0.5 mag accuracy. A tabulation by Wilson (1976) suggests, however,
that the error may be only plus or minus 0.3 mag. This accuracy makes
the approach valuable for late-type supergiants since other methods
suffer from comparable errors. A description is in this connection
presented of a new class of emission lines in late-type giant and
supergiant spectra that exhibit MV correlated widths,
yet are detectable among the brightest stars.

---------------------------------------------------------
Title: Astronomical spectroscopy.
Authors: Stencel, R.; Blair, W.; Conat-Stencel, S.
1978Ast.....6f...6S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Can Partial Redistribution Explain the Ca II H-K Wing
Emission Lines?
Authors: Stencel, R. E.
1977BAAS....9Q.634S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Contents of the Near UV Spectra of Arcturus and Procyon.
Authors: van der Huct, K.; Stencel, R. E.; Faraggiana, R.; Kondo, Y.
1977BAAS....9..570V Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Emission lines in the wings of Ca II H and K. II. Stellar
observations - dependence of line width on luminosity and related
topics.
Authors: Stencel, R. E.
1977ApJ...215..176S Altcode:
Weak emission lines in the extensive wings of the Ca II H and K
resonance lines are studied using high-dispersion spectrograms of 48
bright MK standard stars of all luminosity classes and spectral types
F, G, K, and M. It is found that weak absorption lines in spectra of
dwarf stars become weak emission lines as luminosity increases for a
given spectral type and that this variation resembles the center-to-limb
variation of similar lines in the solar spectrum. Evidence is obtained
indicating that the transition from absorption to emission begins in
early F supergiants, continues through G-type bright giants, and ends
with the K and M giants. It is shown that the line-depth or contrast
variation of H-K wing emission with luminosity in a given spectral
type mimics the center-to-limb variation of line-depth or contrast of
solar H-K wing emission and that there is a correlation between line
width and luminosity for H-K wing emission that is analogous to the
Wilson-Bappu effect in H-K core emission. The apparent sensitivity of
this correlation to the depth of line formation is used to investigate
the depth dependence of total nonthermal broadening velocity and
differential motions in several stars of different spectral types and
luminosity classes.

---------------------------------------------------------
Title: H and K Wing Emission Lines in Late-Type Stars.
Authors: Stencel, R. E.
1977PhDT.........1S Altcode:
The observation, empirical properties and interpretation, of spectral
emission lines from metals and rare-earth elements which occur in the
extensive wings of the resonance lines of singly-ionized calcium among
cool stars were studied. The observations are discussed in terms of a
study of nearly 1000 high-dispersion spectrograms of over 225 stars of
spectral types F2 to M6 and all luminosity classes. It is concluded that
the H-K wing emission lines do occur frequently among cool luminous
stars, and the strength of their appearance is dependent on stellar
luminosity aand possibly on atmospheric effects that asymmetrize the
central emission profiles of the Ca II H and K lines.

---------------------------------------------------------
Title: Observation Effects of Stellar Evolution on Cool Stellar
Atmospheres.
Authors: Stencel, R. E.
1977BAAS....9..345S Altcode:
No abstract at ADS

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Title: H and K wing emission lines in late-type stars
Authors: Stencel, Robert Edward
1977PhDT.......304S Altcode:
No abstract at ADS

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Title: Between stars and space.
Authors: Stencel, R. E.
1977Ast.....5i..34S Altcode:
No abstract at ADS

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Title: Emission lines in the wings of Ca II H and K. I. Initial
solar observations and implications.
Authors: Canfield, R. C.; Stencel, R. E.
1976ApJ...209..618C Altcode:
We apply solar observations to the problem of proper identification of
the atomic species and the mechanism of formation of emission lines
in the wings of the Ca ii H and K lines. Emission lines of both rare
earths and metals appear to be present in the Sun. Their behavior
in the solar spectrum implies that emission lines of metals will be
useful in studies of chromospheres of other stars in which they are
observed. Subject headings: line identifications - Sun: chromosphere -
Sun: spectra

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Title: Fine Structure Variations in High-Spatial-Resolution Solar
Spectra.
Authors: Pasachoff, J. M.; Canfield, R. C.; Stencel, R. E.; Beckers,
J. M.
1976BAAS....8..501P Altcode:
No abstract at ADS

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Title: Astronomy and Cosmology at Angkor Wat
Authors: Stencel, Robert; Gifford, Fred; Moron, Eleanor
1976Sci...193..281S Altcode:
No abstract at ADS

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Title: Stellar Emission Lines in the Wings of Calcium H and K
Authors: Stencel, R. E.; Canfield, R. C.
1976BAAS....8..307S Altcode:
No abstract at ADS

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Title: Emission Lines In The Wings of H and K Ca II
Authors: Stencel, R. E.
1975BAAS....7..359S Altcode:
No abstract at ADS

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Title: The composition of Beta Coronae Borealis.
Authors: Stencel, R. E.; Cowley, C. R.
1975PDAO...14..305S Altcode:
No abstract at ADS

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Title: Limb emission lines near solar H and K: λλ 3900 to 4000 å
Authors: Stencel, Robert E.
1973SoPh...33...59S Altcode:
No abstract at ADS

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Title: A binary model for the symbiotic star AG Pegasi.
Authors: Cowley, A.; Stencel, R.
1973ApJ...184..687C Altcode:
Measurements of the radial velocity of the underlying M giant absorption
spectrum in AG Peg reveal a small-amplitude variation with P = 830.14
days. The emission lines of this symbiotic star are found to vary in
antiphase with the absorptions and probably arise mainly around the
hot secondary star. Variations in the number of emission lines and
the strength of the M star may be due to partial occultations of each
component by the other. Gas streaming distorts the emission velocity,
so it is difficult to determine the exact mass ratio. It is shown
that if the M giant is not more massive than 6 , then the mass of the
emission object falls between 1 and 1.5 . Subject headings: binaries -
combination spectra - emission4ine stars - stars, individual

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Title: Evidence for the Binary Nature of the Symbiotic Star AG Pegasi.
Authors: Cowley, A. P.; Stencel, R. E.
1973BAAS....5..328C Altcode:
No abstract at ADS

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Title: The 1971 Eclipse of 32 Cygni: UBV and Spectrophotometric
Observations
Authors: Griffiths, Donald W.; Stencel, Robert E.
1972PASP...84..427G Altcode:
Standard UBV and 20 A spectrophotometry at four blue wavelengths
obtained during the November 1971 eclipse of 32 Cyg is reported. Key
words: photometry - eclipsing binary

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Title: An amateur's map of Mars in 1971.
Authors: Stencel, R. E.
1971S&T....42..181S Altcode:
No abstract at ADS