Author name code: stencel ADS astronomy entries on 2022-09-14 author:"Stencel, Robert E." ------------------------------------------------------------------------ Title: Spectropolarimetry of the disk of epsilon Aurigae during the 2010 total eclipse Authors: Melnick, D.; Stencel, R. E. Bibcode: 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. 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 Bibcode: 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. 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. Bibcode: 2019RNAAS...3..121L Altcode: 2019RNAAS...3h.121L No abstract at ADS 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 Bibcode: 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. 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 Bibcode: 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. 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. Bibcode: 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. 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. Bibcode: 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. Title: Astronomy In Denver: Polarization of Stellar Wind Bow Shocks Authors: Lin, Austin A.; Shrestha, Manisha; Wolfe, Tristan; Stencel, Robert E.; Hoffman, Jennifer L. Bibcode: 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. Title: MESA models for the evolutionary status of the epsilon Aurigae disk-eclipsed binary system Authors: Stencel, Robert E.; Gibson, Justus Bibcode: 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. Title: Astronomy in Denver: Centenary of the 1918 total solar eclipse across Denver Authors: Stencel, Robert E. Bibcode: 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 . Title: Astronomy in Denver: Probing Interstellar Circular Polarization with Polvis, a Full Stokes Single Shot Polarimeter Authors: Wolfe, Tristan; Stencel, Robert E. Bibcode: 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. Title: MESA models of the evolutionary state of the interacting binary epsilon Aurigae Authors: Gibson, Justus L.; Stencel, Robert E. Bibcode: 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. 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. Bibcode: 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. Title: Developing a Single-shot Polarimeter for Astronomy with Stessed-engineered Optics Authors: Wolfe, Tristan; Stencel, Robert E. Bibcode: 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. Title: Re-development of the Mount Evans Womble Observatory Authors: Stencel, Robert E. Bibcode: 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 . Title: Interferometric studies of disk-eclipsed binary star systems Authors: Stencel, Robert E. Bibcode: 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. Title: Commissioning Results of a New Polarimeter: Denver University Small Telescope Polarimeter (DUSTPol) Authors: Wolfe, T. M.; Stencel, R.; Cole, G. Bibcode: 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. Title: Probing disk inhomogeneities using spectropolarimetry in the extreme binary epsilon Aurigae Authors: Geise, Kathleen; Stencel, Robert Bibcode: 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. 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. Bibcode: 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. 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. Bibcode: 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. Title: Spitzer observations of epsilon Aurigae's disk temperature Authors: Pearson, Richard L.; Stencel, Robert E.; Hoard, Donald W.; Howell, Steve B. Bibcode: 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. Title: ε Aurigae: A Two Century Long Dilemma Persists Authors: Stencel, Robert E. Bibcode: 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. Title: Constraints from Asymmetric Heating: Investigating the Epsilon Aurigae Disk Authors: Pearson, Richard L., III; Stencel, Robert E. Bibcode: 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 >=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. Title: A Look Inside the Disk in the ɛ Aurigae Binary System Authors: Stencel, R. E. Bibcode: 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. Bibcode: 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. Bibcode: 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 (>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. 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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 ε Aurigae System: a Brief Review With Proposed Numerical Solutions Authors: Pearson, R. L.; Stencel, R. E. Bibcode: 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. Bibcode: 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 http://www.aanda.orgFITS 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 http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/544/A91 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. Bibcode: 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). 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Title: UV-Blue (CCD) and Historic (Photographic) Spectra of epsilon Aurigae - Summary Authors: Griffin, R. E.; Stencel, R. E. Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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 http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/530/A146 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 & photometry obtained with SpeX/IRTF, Spitzer/IRAC, mid-infrared data with BASS on IRTF & AEOS, MIRSI on IRTF and MIRAC4 on MMT, along with MIRSI on IRTF and MIRAC4 on MMT & Denver's TNTCAM2 at WIRO, and an Optec SSP-4 J&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. Bibcode: 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&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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 >= 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 >= 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 Bibcode: 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 >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. Bibcode: 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. Bibcode: 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 >~ 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. Bibcode: 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 Bibcode: 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 Bibcode: 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 & 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 2009JAVSO..37..212S Altcode: No abstract at ADS Title: The Biggest, Baddest, Coolest Stars Authors: Luttermoser, D. G.; Smith, B. J.; Stencel, R. E. Bibcode: 2009ASPC..412.....L Altcode: No abstract at ADS Title: The Wilson-Bappu Effect - 50 Years Later Authors: Stencel, R. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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 (< 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 (> 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 (<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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 2006dasg.book.....S Altcode: No abstract at ADS Title: Challenges and Opportunities in Operating a High-Altitude Site Authors: Stencel, Robert E. Bibcode: 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. Bibcode: 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 & 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 Bibcode: 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. Bibcode: 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 Bibcode: 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 & 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 & MIPS SED data to clarify the nature and evolutionary status of this large protoplanetary-like disk & 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 & velocities of gas from the secondary are known from absorption lines detected in the last eclipse. The mass of the system & 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 & 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 & properties via the full range of SST spectroscopy coverage [IRS & MIPS SED]; Seeking evidence for mass-loss history in extended material around the system [MIPS]; Establishing baselines of these & 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 Bibcode: 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. Bibcode: 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 (>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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 (>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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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&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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 2001AAS...199.9219S Altcode: 2001BAAS...33R1443S De Laverny et al. (1998 A& 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. Bibcode: 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 & 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. Bibcode: 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&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. Bibcode: 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&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. Bibcode: 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. Bibcode: 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 &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. Bibcode: 2000IAUS..177..527C Altcode: No abstract at ADS Title: Prospects for Mid-infrared Imaging and Polarimetry with Denver's TNTCAM2 Authors: Stencel, Robert E. Bibcode: 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 &#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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 1999ApJ...520..215F Altcode: We obtained 3.6-20 μm photometry of 38 bright [IRAS Fν(12 μm)>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 >~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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 & 26:1321; 1998 BAAS 29:1272 & 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 & 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 & Backman 1994, Ap&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. Bibcode: 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. Bibcode: 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. Bibcode: 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 & 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 & Paresce 1993, Protostars and Planets III, ed. Levy & 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 & 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 & 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1995IAUS..176P.162C Altcode: No abstract at ADS Title: Nineteenth Episode Monitoring of Long Period Eclipsing Systems Authors: Stencel, Robert E. Bibcode: 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. Bibcode: 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 & Acoustic Soundings, Mt.Evans Observatory Authors: Stencel, R. E.; Dahm, M. A.; Jalakas, M.; Klebe, D.; Emerson, G.; Butenhoff, C.; Gehrz, R. D. Bibcode: 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) < 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1993IAUS..155..405B Altcode: No abstract at ADS Title: Molecular catastrophes and circumstellar SiO masers Authors: Stencel, Robert E. Bibcode: 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. Bibcode: 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. Bibcode: 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 <2 pr mm and <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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1991mcch.conf..206C Altcode: No abstract at ADS Title: Ultraviolet Monitoring of VV Cephei Authors: Stencel, Robert E. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1990ASPC....9..411J Altcode: 1990csss....6..411J No abstract at ADS Title: Mapping the UV Circumstellar Nebulae of Cool Stars Authors: Stencel, Robert E. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1989BAAS...21..790S 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. Bibcode: 1989BAAS...21..795M Altcode: No abstract at ADS Title: Oxygen-rich mass loss from carbon-rich stars-some implications Authors: Stencel, Robert E.; Pesce, Joseph E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1988iue..prop.3240S Altcode: No abstract at ADS Title: S Per Authors: Stencel, Robert E. Bibcode: 1988iue..prop.3256S Altcode: No abstract at ADS Title: Summary of Final Discussion Authors: Stencel, R. E. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1987iue..prop.2899S Altcode: No abstract at ADS Title: UV Observations of the Southern Star HR 3126 Authors: Stencel, Robert Bibcode: 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. Bibcode: 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. Bibcode: 1987LNP...291.....L Altcode: 1987csss....5.....L No abstract at ADS Title: Symbiotic Stars Authors: Nussbaumer, Harry; Stencel, Robert E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1986IrAJ...17..353S Altcode: No abstract at ADS Title: Chromospheric Dust Formation, Stellar Masers and Mass Loss Authors: Stencel, R. E. Bibcode: 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. Bibcode: 1986LNP...254..430A Altcode: 1986csss....4..430A No abstract at ADS Title: Photometry of the recent eclipse of Epsilon Aurigae. Authors: Stencel, R. E. Bibcode: 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. Bibcode: 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. Bibcode: 1986NASCP2403A...8H Altcode: No abstract at ADS Title: Chromospheric dust formation, stellar masers and mass loss. Authors: Stencel, R. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1985IBVS.2748....1S Altcode: No abstract at ADS Title: Chromospheric Dust Formation and Mass Loss Authors: Stencel, R. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1985eepa.rept.....S Altcode: 1985QB823.A17...... No abstract at ADS Title: Eg And Authors: Stencel, Robert E. Bibcode: 1985iue..prop.2282S Altcode: No abstract at ADS Title: On the rarity of FK COM stars. Authors: Hagen, W.; Stencel, R. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 & possibly periodic variations in the UV spectrum of 56 Pegasi. Authors: Stencel, R. E.; Neff, J. E.; McClure, R. D. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1984BAAS...16..984W Altcode: No abstract at ADS Title: Epsilon Aurigae 1982-1984 Eclipse Campaign Report Authors: Hopkins, J. L.; Stencel, R. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1983BAAS...15..652H Altcode: No abstract at ADS Title: Epsilon-Aurigae Report and Analysis Program Authors: Stencel, R. E. Bibcode: 1983mca..symp..238S Altcode: No abstract at ADS Title: Flare-like activity of red giant stars Authors: Stencel, R. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1982BAAS...14..979S Altcode: No abstract at ADS Title: A Far Ultraviolet Spectroscopy Explorer (FUSE) Authors: Weiler, E. J.; Stencel, R. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1981BAAS...13..547S Altcode: No abstract at ADS Title: Are Discrepant Asymmetry Red Giants Necessarily Hybrid Stars? Authors: Mullan, D. J.; Stencel, R. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1981BAAS...13..885B Altcode: No abstract at ADS 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. Bibcode: 1981BAAS...13..548H 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1981syst.work...25S Altcode: No abstract at ADS Title: Chromospheric Densities & Geometrical Extensions of Late-Type Giant & Supergiants Authors: Stencel, Robert E. Bibcode: 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. Bibcode: 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. Bibcode: 1981syst.work....5S Altcode: No abstract at ADS Title: MGII Profiles of Symbiotic Stars Authors: Stencel, R.; Michalitsianos, A. G.; Kafatos, M. Bibcode: 1981syst.work...30S Altcode: No abstract at ADS Title: An Emission Measure Analysis of the High Dispersion SWP Spectra Authors: Stencel, Robert E. Bibcode: 1981iue..prop..833S Altcode: No abstract at ADS Title: High resolution flux profiles of the Mg II h & k lines in evolved F8 to M5 stars. Authors: Stencel, R. E.; Mullan, D. J.; Basri, G. S.; Linsky, J. L. Bibcode: 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. Bibcode: 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. Bibcode: 1981iue..prop..865S Altcode: No abstract at ADS Title: SWP High Resolution Spectra & Emission Measure Analysis of Yellow Bright Giants with Coronae Authors: Stencel, Robert E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1980BAAS...12..869B Altcode: No abstract at ADS Title: Solar and Stellar Resonance Line Emission Cores and Inferred Magnetic Topology Authors: Stencel, R. E. Bibcode: 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. Bibcode: 1980BAAS...12..806S Altcode: No abstract at ADS Title: Addendum - Detection of Mass Loss in Stellar Chromospheres Authors: Stencel, R. E.; Mullan, D. J. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 & K and their spatial intensity variations Authors: Rutten, R. J.; Stencel, R. E. Bibcode: 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 & K near the solar limb. Emission lines in the wings of H & 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 & 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. Bibcode: 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. Bibcode: 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. Bibcode: 1980SAOSR.389..183S Altcode: 1980csss....1..183S No abstract at ADS Title: Depth-dependence of turbulence in stellar atmospheres Authors: Stencel, R. E. Bibcode: 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. Bibcode: 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. Bibcode: 1980IAUS...88..237K Altcode: No abstract at ADS Title: Study of Chromospheres and Circumstellar Envelopes in G, K, M Supergiants Authors: Stencel, Robert E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1979BAAS...11..423K Altcode: No abstract at ADS Title: Handbook of Unusual Natural Phenomena %a William R. Corliss Authors: Stencel, Robert E. Bibcode: 1979Arch....2c..23S Altcode: No abstract at ADS Title: Natural Solar Architecture: A Passive Primer %a David Wright Authors: Stencel, Robert E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1978BAAS...10R.453S Altcode: No abstract at ADS Title: Extensions of the Wilson-Bappu Effect among Very Luminous Stars Authors: Stencel, R. E. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1977BAAS....9..345S Altcode: No abstract at ADS Title: H and K wing emission lines in late-type stars Authors: Stencel, Robert Edward Bibcode: 1977PhDT.......304S Altcode: No abstract at ADS Title: Between stars and space. Authors: Stencel, R. E. Bibcode: 1977Ast.....5i..34S Altcode: No abstract at ADS 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. Bibcode: 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 Title: Fine Structure Variations in High-Spatial-Resolution Solar Spectra. Authors: Pasachoff, J. M.; Canfield, R. C.; Stencel, R. E.; Beckers, J. M. Bibcode: 1976BAAS....8..501P Altcode: No abstract at ADS Title: Astronomy and Cosmology at Angkor Wat Authors: Stencel, Robert; Gifford, Fred; Moron, Eleanor Bibcode: 1976Sci...193..281S Altcode: No abstract at ADS Title: Stellar Emission Lines in the Wings of Calcium H and K Authors: Stencel, R. E.; Canfield, R. C. Bibcode: 1976BAAS....8..307S Altcode: No abstract at ADS Title: Emission Lines In The Wings of H and K Ca II Authors: Stencel, R. E. Bibcode: 1975BAAS....7..359S Altcode: No abstract at ADS Title: The composition of Beta Coronae Borealis. Authors: Stencel, R. E.; Cowley, C. R. Bibcode: 1975PDAO...14..305S Altcode: No abstract at ADS Title: Limb emission lines near solar H and K: λλ 3900 to 4000 å Authors: Stencel, Robert E. Bibcode: 1973SoPh...33...59S Altcode: No abstract at ADS Title: A binary model for the symbiotic star AG Pegasi. Authors: Cowley, A.; Stencel, R. Bibcode: 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 Title: Evidence for the Binary Nature of the Symbiotic Star AG Pegasi. Authors: Cowley, A. P.; Stencel, R. E. Bibcode: 1973BAAS....5..328C Altcode: No abstract at ADS Title: The 1971 Eclipse of 32 Cygni: UBV and Spectrophotometric Observations Authors: Griffiths, Donald W.; Stencel, Robert E. Bibcode: 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 Title: An amateur's map of Mars in 1971. Authors: Stencel, R. E. Bibcode: 1971S&T....42..181S Altcode: No abstract at ADS