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Author name code: milkey
ADS astronomy entries on 2022-09-14
author:"Milkey, Robert W."
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Title: Uniformity of the quiet solar disk: 3130 - 46700 Å
Authors: Livingston, W.; Galayda, E.; Milkey, R.
2011arXiv1110.1592L Altcode:
Taking advantage of the absence of solar activity in the recent 2008-9
epoch (no spots, few faculae), we have made equatorial and meridian disk
scans in continua from 3129 Å to 46700 Å. Averaging 20 scans at each
wavelength to suppress granulation, which takes a total of 35 minutes,
we achieve a system noise level of 0.01%. We believe this noise level
is a record low, not because of instrument improvements, but simply
because of observing procedures and the cooperation of the Sun and
sky. The observed solar fluctuations significantly exceed the noise
and range from 0.3% at 3130 Å, 0.05% at 34000 Å, to 0.06% at 46700
Å near disk center. These fluctuations (corresponding to about 3 K)
presumably arise from the incomplete averaging of granulation. Standard
solar models for limb darkening fit the data for true continuum
regions reasonably well. No significant differences are seen between
scan directions (EW, N-S). Perhaps our results can serve as a template
for exoplanet detection by the transit of quiet G2V-like stars.
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Title: Precision (±0.005%) Quiet Sun Limb Darkening Scans Show E-W
Vs N-S Chords Same.
Authors: Livingston, W. C.; Milkey, R.; Sheeley, N., Jr.
2008AAS...21115906L Altcode:
Using the 80-cm McMath-Pierce image, we compare equatorial and meridian
limb darkening and find they are identical. Observations consist of
20 scans over 30 minutes at 15648 Å (H- opacity minimum) and 34168
Å continua. Noise is sky and disk structure limited. System noise is
negligible at ± 0.005%; disk structure noise is ± 0.03% at 15648 Å
0.02% at 34168 Å. Our next step will be to compare these limb darkening
results with those predicted by solar models. Ref: Livingston &
Sheeley, 2008, ApJ 672 no.1, in press.
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Title: Digital data preservation for scholarly publications in
astronomy
Authors: Choudhury, Sayeed; di Lauro, Tim; Szalay, Alex; Vishniac,
Ethan; Hanisch, Robert; Steffen, Julie; Milkey, Robert; Ehling,
Teresa; Plante, Ray
2007IJDDC...2...20C Altcode:
Astronomy is similar to other scientific disciplines in that scholarly
publication relies on the presentation and interpretation of data. But
although astronomy now has archives for its primary research telescopes
and associated surveys, the highly processed data that is presented
in the peer-reviewed journals and is the basis for final analysis
and interpretation is generally not archived and has no permanent
repository. We have initiated a project whose goal is to implement
an end-to-end prototype system which, through a partnership of a
professional society, that society's scholarly publications/publishers,
research libraries, and an information technology substrate provided
by the Virtual Observatory, will capture high-level digital data as
part of the publication process and establish a distributed network of
curated, permanent data repositories. The data in this network will
be accessible through the research journals, astronomy data centers,
and Virtual Observatory data discovery portals.
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Title: Digital Data Preservation and Curation: A Collaboration Among
Libraries, Publishers, and the Virtual Observatory
Authors: Hanisch, R. J.; Steffen, J.; Choudhury, S.; Dilauro, T.;
Szalay, A.; Vishniac, E.; Ehling, T.; Milkey, R.; Plante, R.
2007ASPC..377...29H Altcode: 2007lisa.conf...29H
Astronomers are producing and analyzing data at ever more prodigious
rates. NASA's Great Observatories, ground-based national observatories,
and major survey projects have archive and data distribution systems
in place to manage their standard data products, and these are now
interlinked through the protocols and metadata standards agreed upon
in the Virtual Observatory. However, the digital data associated
with peer-reviewed publications is only rarely archived. Most often,
astronomers publish graphical representations of their data but not
the data themselves. Other astronomers cannot readily inspect the
data to either confirm the interpretation presented in a paper or
extend the analysis. Highly processed data sets reside on departmental
servers and the personal computers of astronomers, and may or may not be
available a few years hence. <P />We are investigating ways to preserve
and curate the digital data associated with peer-reviewed journals in
astronomy. The technology and standards of the VO provide one component
of the necessary technology. A variety of underlying systems can be used
to physically host a data repository, and indeed this repository need
not be centralized. The repository, however, must be managed and data
must be documented through high quality, curated metadata. Multiple
access portals must be available: the original journal, the host data
center, the Virtual Observatory, or any number of topically-oriented
data services utilizing VO-standard access mechanisms.
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Title: The Scholarly Journals of the American Astronomical Society
Authors: Milkey, Robert W.
2006ASSL..343..241M Altcode: 2006osa7.book..241M
The role of the AAS as a journal publisher is given a brief historical
review and the current operations of the journals are briefly
described. The AAS approaches oversight and governance of its journal
operations as an obligation to the astronomical research community
and the processes followed is described. These include the financial
arrangements for the non-profit operation of the journals. There are
substantial challenges in the present publishing environment and these
are touched on from the perspective of the AAS journal operations.
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Title: Electronic Journal Usage Patterns in Astronomy
Authors: Boyce, P. B.; Tenopir, C.; Milkey, R. W.
2001AAS...199.1004B Altcode: 2001BAAS...33.1320B
Starting in 1995 the major journals in astronomy have become available
on the Web. In addition, the searchable database of astronomical
literature within the Astrophysics Data System (ADS) has become more
nearly complete. The back issues of the major astronomical journals are
also available on the ADS site. The literature is now well linked to the
information in the astronomical data centers. In a related development,
the electronic preprint servers are apparently playing a larger role
in the dissemination of astronomical information. In order to assess
the impact of the ready availability of information over the Internet
we have surveyed the astronomical community to develop information
about the use of electronic information resources. We will present the
preliminary results of our survey on the use of the electronic journals,
the Astrophysics Data System, and the astro-ph preprint server. We have
teamed with Carol Tenopir and Don King who have made similar studies
of the impact of the electronic availability of information on other
fields. This study was supprted by a grant from NASA to the AAS.
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Title: US Astronomy
Authors: Marvel, K.; Milkey, R.
2000eaa..bookE2938M Altcode:
As the 19th century ended, astronomy underwent a period of rapid
growth in the United States, a growth that was fueled by both the
expansion of the university system and private philanthropy and which
also paralleled the growth in astrophysical research. For the first
half of the 20th century, the US government took little interest in
the funding of astronomical research, concentrating on those a...
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Title: Electronic Publishing and The American Astronomical Society
Authors: Milkey, R. W.
1999AAS...19510001M Altcode: 1999BAAS...31.1519M
Electronic Publishing has created, and will continue to create, new
opportunities and challenges for representing scientific work in new
media and formats. The AAS will position itself to take advantage of
these, both for newly created works and for improved representation
of works already published. It is the view of the AAS that we hold the
works that we publish in trust for our community and are obligated to
protect the integrity of these works and to assure that they continue
to be available to the research community. Assignment of copyright to
the AAS by the author plays a central role in the preservation of the
integrity and accessability of the literature published by the American
Astronomical Society. In return for such assignment the AAS allows the
author to freely use the work for his/her own purpose and to control
the grant of permission to third parties to use such materials. The AAS
retains the right to republish the work in whatever format or medium,
and to retain the rights after the author's death. Specific advantages
to this approach include: Assurance of the continued availability of the
materials to the research and educational communities; A guarantee of
the intellectual integrity of the materials in the archive; Stimulation
of the development of new means of presentation or of access to the
archival literature; and Provision of a uniformity of treatment for
copyright issues and to relieve the individual authors of much of the
administrative work.
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Title: Obituary: Margaret Russell Edmondson, 1914-1999
Authors: Landolt, Arlo; Milkey, Robert W.
1999BAAS...31.1596L Altcode:
No abstract at ADS
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Title: The Effectiveness of the AAS REU Program
Authors: Hemenway, M. K.; Boyce, P. B.; Milkey, R. W.
1996AAS...188.2002H Altcode: 1996BAAS...28R.851H
In an attempt to address the particular needs of astronomy faculty and
undergraduate students, in 1991 the Education Office of the American
Astronomical Society approached the National Science Foundation with
a unique proposal for funding through the Research Experiences for
Undergraduates program. The goals of the AAS program were to "slow
the hemorrhage of students out of science...", extend the REU program
to non-NSF-funded scientists, to reach under-represented women and
minority students particularly in small educational institutions,
and to encourage research scientists there to mentor students. As
this grant has now expired, the AAS has surveyed the 44 mentors
and their students to assess the program's effect on the mentor and
the mentor's career; the educational institution; and the student's
education and career choices. More than half the mentors responded
by the abstract deadline. The program clearly had an effect upon the
individuals involved. The greatest effect (in 85% of the cases) was
to develop more interest in the mentor's research project both among
the students and among the mentor's faculty colleagues. The mentors
rated the grant to be a medium or strong factor in their student's
decision to pursue graduate study, which 90% of them did. All but
one of the AAS-REU students attended an AAS meeting and 3/4 of those
gave a paper on their project research. Over 90% of the mentors felt
that the research experience strongly promoted a greater interest in
science, a greater understanding of science and a desire to continue
in science. According to the mentors, this was a very positive and
beneficial program for the students as well as for themselves.
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Title: Hydrogen and Helium Excitation by Extreme Ultraviolet Radiation
for the Production of White-Light Flares
Authors: Poland, A. I.; Milkey, R. W.; Thompson, W. T.
1988SoPh..115..277P Altcode:
White-light flares are defined as those flares that produce significant
enhancement of emission in the visible light continuum. The source
of energy for this emission has not yet been identified with several
possibilities being suggested: heating of the lower chromosphere by some
mechanical or magnetic means, or by soft X-ray or extreme ultraviolet
radiation from coronal loops being absorbed in the lower chromosphere
and re-emitted in the visible.
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Title: The rotational velocities of white dwarfs. II.
Authors: Pilachowski, Catherine A.; Milkey, Robert W.
1987PASP...99..836P Altcode:
The authors have extended their recent work on the rotational
velocities of white dwarfs by analysis of the sharp core of the Hα
line to a larger sample of stars with the goal of eventually obtaining
the distribution of rotational velocities and thereby improving the
understanding of the question of retention of angular momentum in the
later stages of evolution of these stars. There are no stars in the
sample which show v sin i > 60 km s<SUP>-1</SUP>.
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Title: Spectroscopic orbital elements for a double-lined binary in
NGC 752.
Authors: Pilachowski, C. A.; Willmarth, D. W.; Halbedel, E. M.;
Mathieu, R. D.; Hobbs, L. M.; Milkey, R. W.; Saha, A.
1986PASP...98.1321P Altcode:
Orbital elements for a double-lined spectroscopic binary in the
intermediate-age galactic cluster NGC 752 are reported. The binary is
located just above the cluster main-sequence turnoff, and is a confirmed
proper-motion and radial-velocity member. The equal amplitudes of the
primary and the secondary velocity curves indicate that the stars have
equal masses.
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Title: Hydrogen and Helium Excitation by EUV Radiation for the
Production of White-Light Falres
Authors: Thompson, W. T.; Poland, A. I.; Milkey, R. W.
1986BAAS...18..899T Altcode:
No abstract at ADS
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Title: H-alpha line profiles in DA white dwarfs.
Authors: Milkey, R. W.; Pilachowski, C. A.
1985PASP...97..634M Altcode:
Rotational velocities have been determined for several white dwarfs
from the sharp NLTE core of the Hα profile. A new synthetic profile has
been computed for T<SUB>eff</SUB> = 16,000K, log g = 8.0 white dwarfs;
this profile fits closely the observed spectra of white dwarfs of this
temperature. The authors confirm that Wolf 485A rotates with a velocity
v sin i = 42±9 km s<SUP>-1</SUP>. Rotational velocities in 40 Eri B,
SA 29-130, and L970-30 are less than 20 km s<SUP>-1</SUP>.
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Title: The rotational velocities of white dwarfs.
Authors: Pilachowski, C. A.; Milkey, R. W.
1984PASP...96..821P Altcode:
High-resolution profiles of the sharp core of H-alpha have been
observed in 7 DA white dwarfs. Theoretical NLTE H-alpha profiles
have been calculated using blanketed, LTE model atmospheres. Profiles
synthesized using an effective temperature of 20,000 K model closely
match the observed profiles for stars in the range 19,000 K to 23,000 K,
but profiles synthesized from lower-temperature model atmospheres are
too weak to match the H-alpha cores in stars cooler than 17,000 K. The
theoretical profiles have been rotationally broadened to compare with
the observed profiles to derive rotational velocities for the hotter
stars in our sample. For the cooler stars, the rotationally broadened
profile of 40 Eri B has been used to provide limits on rotational
velocities.
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Title: H α Profiles in DA White Dwarfs
Authors: Milkey, R. W.; Pilachowski, C. A.
1984BAAS...16..492M Altcode:
No abstract at ADS
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Title: Structure and spectrum of quiencent prominences. IV. The
ultraviolet ionization continua of hydroden and helium.
Authors: Heasley, J. N.; Milkey, R. W.
1983ApJ...268..398H Altcode:
The formation of the ground-state ionization continua of hydrogen
and neutral helium in quiescent prominences has been investigated
by using isothermal and isobaric slab models. The hydrogen and helium
ionization equilibria are dominated by the extreme ultraviolet radiation
field incident on the prominence. The Lyman continuum brightness is
dependent only on the incident radiation and the optical thickness of
the prominence. The ratio of the intensity in the He I to the Lyman
continuum is principally a function of the hardness of the incident
radiation and the helium abundance and is only secondarily a function
of the optical thickness of the slab and the gas pressure. The color
temperatures of the continua, when corrected for optical depth effects,
are good indicators of the electron temperature in the prominence. The
slab models used in this study, which were developed to reproduce the
visible spectrum hydrogen and helium lines, are in reasonable agreement
with existing ultraviolet observations.
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Title: Partial redistribution in the solar photospheric Ba II
spectrum.
Authors: Rutten, R. J.; Milkey, R. W.
1979ApJ...231..277R Altcode:
Recent studies of the effects of partial frequency redistribution
(PRD) on the formation of strong chromospheric resonance lines are
extended to weaker lines formed in the photosphere. Methods that have
been derived to compute the PRD formation of the Ca II spectrum are
applied to the solar Ba II spectrum. It is found that PRD is important
in the formation of the 4554-A resonance line, and the results confirm
that its effects on the line source function explain the emission
wings of this line observed near the limb. Source function structure
and line profiles for Ba II 4554 A and Ba II 5854 A are discussed;
they may serve as an example for estimating effects of PRD in other
photospheric lines in stellar atmospheres.
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Title: Discussion
Authors: Acton, L. W.; Engvold, O.; Milkey, R. W.; Orrall, F. Q.;
Zirin, H.
1979phsp.coll..354A Altcode: 1979IAUCo..44..354A
No abstract at ADS
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Title: Solar optical telescope (SOT).
Authors: Dunn, R. B.; Fisher, R.; Harvey, J.; Lemaire, P.; Milkey,
R.; Smithson, R.; Beckers, J.; Mehltretter, J. P.; Zirin, H.
1979MmArc.106..135D Altcode:
No abstract at ADS
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Title: Frequency Redistribution Effects in the Formation of Lyman
a in Prominences and Their Influence on the Ratio of Hα to Lα.
Authors: Milkey, R. W.; Heasley, J. N.; Schmahl, E. J.; Engvold, O.
1979phsp.coll...53M Altcode: 1979IAUCo..44...53M
No abstract at ADS
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Title: Science opportunities with the SOT.
Authors: Dunn, R. B.; Fisher, R.; Harvey, J.; Lemaire, P.; Milkey,
R.; Smithson, R.; Beckers, J.; Mehltretter, J. P.; Zirin, H.
1979MmArc.106..245D Altcode:
No abstract at ADS
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Title: Models of Thermodynamic Properties of Prominences.
Authors: Milkey, R. W.
1979phsp.coll..349M Altcode: 1979phsp.conf..349M; 1979IAUCo..44..349M
The thermodynamic properties of solar prominences are considered
insofar as they relate to the energetics and mass transport of the
latter. The present emphasis is on obtaining accurate indicators of
electron temperature, electron energy and thickness from the line
and recombination emission spectra of prominences. Some proposals for
future work in this field are presented.
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Title: Structure and spectrum of quiescent
prominences. III. Application of theoretical models in helium
abundance determinations.
Authors: Heasley, J. N.; Milkey, R. W.
1978ApJ...221..677H Altcode:
The solar helium abundance has been investigated by using spectra
of quiescent prominences. The physical parameters (T, P, y, xi, M)
describing an isothermal and isobaric model of the prominence can be
determined from observations of hydrogen, helium, and ionized calcium
lines. Given these parameters, it may be shown that low values of
the helium abundance, such as those inferred from solar wind data,
are inconsistent with the prominence data. The helium-to-hydrogen
ratio is indicated to be 0.10 + or - 0.025 by number.
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Title: The fundamental bands of CO in Arcturus: evidence for an
inhomogeneous chromosphere.
Authors: Heasley, J. N.; Ridgway, S. T.; Carbon, D. F.; Milkey, R. W.;
Hall, D. N. B.
1978ApJ...219..970H Altcode:
We compare new high-spectral-resolution observations of the fundamental
vibration-rotation bands of CO in the Arcturus spectrum with synthetic
spectra for a representative set of existing model atmospheres of
this star. The Ayres and Linsky model of the lower chromosphere-upper
photosphere does not reproduce the observed spectrum in any respect. We
conclude that there is not a homogeneous chromosphere typical of that
model on Arcturus. It does not appear possible to reproduce both the Ca
II K line wings and the CO fundamental lines with a single-component
model. Several alternative sets of synthetic spectra are able to
reproduce the observed CO spectrum. We are not able at this time to
decide which of these most accurately represents the true atmospheric
structure of Arcturus because departures from LTE may be important in
the CO line formation. If such departures occur, the layers in which the
CO lines form will be hotter than those inferred from an LTE analysis.
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Title: The Ca II emission lines in quiescent prominences.
Authors: Heasley, J. N.; Milkey, R. W.; Engvold, O.
1977SoPh...51..315H Altcode:
Observations of the Ca II H, K, and infrared triplet lines are compared
with theoretical predictions from the slab models of Heasley and Milkey
(1976). While the theoretical models describe the hydrogen and helium
emission spectra of quiescent prominences satisfactorily the predicted
Ca II lines are systematically too bright. The most likely reason
for the discrepancy is the inapplicability of the symmetric slab
prominence model for lines which become even moderately optically
thick in prominences.
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Title: An Evaluation of a Model Chromosphere for Arcturus Using the
5-Micron Bands of Carbon Monoxide.
Authors: Heasley, J. N.; Ridgway, S. T.; Carbon, D. F.; Milkey, R. W.;
Hall, D. N. B.
1977BAAS....9..324H Altcode:
No abstract at ADS
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Title: Solar luminosity variation. I. C I 5380 as a temperature
indicator and a search for global oscillations.
Authors: Livingston, W.; Milkey, R.; Slaughter, C.
1977ApJ...211..281L Altcode:
The high-excitation, weak Fraunhofer line C 1 5380.3 A is shown to
originate within the same photospheric layers as the Sun's continuous
radiation. By monitoring the central depth of the C I line relative to
the local continuum, in unfocused sunlight, we may follow temperature,
and hence luminosity changes of the whole Sun as a function of time. The
technique is practically insensitive to telluric absorption effects and
instrumental spectral response. A power spectrum analysis of 100 hours
of observations reveals no dominant oscillation of period P rising above
the 3 a uncertainty limit of 0.4 K for m < p < 60 . For power at
2h40m the limit is 1.0 K; for 5h20m, 2.0 K. The day-to-day fluctuation
for a 3 month period is 0.85 K rms (which corresponds to 0.06% in the
solar constant, or 0.0006 mag in luminosity). Subject headings: Sun:
atmospheric motions - Sun: general
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Title: Structure and spectrum of quiescent prominences. II. Hydrogen
and helium spectra.
Authors: Heasley, J. N.; Milkey, R. W.
1976ApJ...210..827H Altcode:
Theoretical emission-line intensities for hydrogen and helium in models
of quiescent prominences have been computed and are compared with
the absolute intensities measured by Landman and Illing (1976). The
models required to match the observations have electron temperatures in
the range from 7500 to 9500 K and gas pressures equal to or slightly
greater than the coronal value. The calculations indicate a probable
lower limit of 0.05 to the helium-to-hydrogen number ratio for the
prominence studied.
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Title: Sodium Line Formation in Arcturus. II. The Use of Empirical
and Opacity Sampling Models and the Nature of Partial Redistribution
Effects
Authors: Kelch, Walter L.; Milkey, Robert W.
1976ApJ...208..428K Altcode:
In a previous paper, we presented calculations of departure
coefficients, D line profiles, and subordinate line strengths for
sodium lines in Arcturus using a model atmosphere calculated with
straight mean opacities. This paper presents results of similar
calculations using an empirical model of Arcturus inferred from the
Ca ii H and K lines and a model atmosphere calculated by the opacity
sampling method. We also compare partial redistribution calculations
of the D2 line profile to the complete redistribution profile. We find
that the partial redistribution D2 profile has deeper core and inner
wing regions and slightly shallower outer wings. We also find that
the partial redistribution calculation may affect the strengths of
certain subordinate transitions. Subject headings: line formation -
radiative transfer - stars: atmospheres - stars: individual
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Title: Departures from LTE in the fundamental bands of CO in cool
stars.
Authors: Carbon, D. F.; Milkey, R. W.; Heasley, J. N.
1976ApJ...207..253C Altcode:
A method is presented for solving the coupled statistical equilibrium
and radiative transfer equations for the vibrational-rotational
transitions in the ground electronic state of CO. The technique is
subject to the assumption that the rotational levels within each
vibrational level are in LTE. We applied this method to three cool
stellar models within its range of applicability and find that the LTE
and non-LTE spectra are substantially different for the cooler models.
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Title: The fundamental bands of CO as chromospheric indicators in
late-type giant stars.
Authors: Heasley, J. N.; Milkey, R. W.
1976ApJ...205L..43H Altcode:
Synthetic spectra are presented for the vibrational-rotational
fundamental transitions in the ground electronic state of CO for the
upper-photosphere-lower-chromosphere atmospheric model of Arcturus
derived by Ayres (1975). It is found that the CO spectrum is formed
in LTE and the strongest molecular lines exhibit emission cores
reflecting the chromospheric temperature rise. The CO fundamental bands
offer an excellent observational probe for the presence of stellar
chromospheres and a consistency check for chromospheric models derived
from traditional chromospheric indicators.
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Title: Sodium Line Formation in Arcturus: The Use of Selected Models
and Results of Partial Redistribution Calculations
Authors: Kelch, W.; Milkey, R.
1976BAAS....8..308K Altcode:
No abstract at ADS
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Title: Resonance-line transfer with partial
redistribution. VII. Angle-dependent redistribution.
Authors: Milkey, R. W.; Shine, R. A.; Mihalas, D.
1975ApJ...202..250M Altcode:
A method is presented for treating radiative transfer in resonance
lines, allowing for the full angle and frequency dependence of
redistribution in the scattering process, as seen in the laboratory
frame. The case of an equivalent-two-level-atom source function
is considered; the problem to be treated is then linear in the
radiation field. We apply this method to the Ca II lines in the
solar atmosphere, using a redistribution function which takes into
account a mixture of coherence in the atom's frame, with Doppler
redistribution in the laboratory frame (for atoms which have not
suffered an elastic collision), and of complete redistribution in the
laboratory frame (for atoms that are collisionally perturbed during the
emission process). Both the angle-averaged approximation and the full
angle-dependent solution were obtained, and were compared to assess,
differentially, the effects of angular redistribution upon the computed
line profile and its center-to-limb behavior. For the Ca II line in a
homogeneous solar chromosphere the angle-dependent effects are found to
be negligible, indicating that one may use angle-averaged redistribution
functions when studying partial redistribution effects in line profiles.
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Title: Resonance line transfer with partial redistribution. VI. The
Ca II K-line in solar-type stars.
Authors: Shine, R. A.; Milkey, R. W.; Mihalas, D.
1975ApJ...201..222S Altcode:
Using model atmospheres for solar-type stars based on scaled
temperature distributions, we discuss the effects of partial frequency
redistribution on the Ca ii K-line profiles. We show that the partial
redistribution calculations lead to a significantly lower intensity
at K1 than given by calculations based on the assumption of complete
redistribution. This implies that fits to observed fluxes with
complete redistribution calculations could tend to underestimate
systematically the value of the temperature at the chromospheric
temperature minimum. Subject headings: chromospheres, stellar - line
formation - radiative transfer
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Title: Resonance line transfer with partial redistribution. IV. A
generalized formulation for lines with common upper states.
Authors: Milkey, R. W.; Shine, R. A.; Mihalas, D.
1975ApJ...199..718M Altcode:
A generalized formulation is given for treating partial redistribution
effects in transfer problems in resonance lines with common upper
states. The formulation allows explicitly for the possibility that
several spectral lines may arise in transitions from a given upper
level to several sharp lower levels, including, for example, the
ground state and metastable states. Line profiles for the Ca II H and
K lines have been calculated, accounting for the partial frequency
coherence of scattered photons. These profiles are compared with
calculations made with identical atomic and atmospheric models but
assuming complete redistribution. Very significant differences between
the profiles obtained using these two different physical descriptions
of the scattering process are found, and it is now apparent that the
assumption of complete redistribution is a serious oversimplification
of the actual physical situation. The results question the validity of
equating brightness temperatures observed at K<SUB>1</SUB> in stellar
spectra with minimum temperatures in stellar chromospheres; it appears
likely that such a procedure will systematically underestimate the
value of T-min.
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Title: The Line Response Function of Stellar Atmospheres and the
Effective Depth of Line Formation
Authors: Beckers, J. M.; Milkey, R. W.
1975SoPh...43..289B Altcode:
The response function defines the response of line profiles to a
depth variation of such atmospheric parameters as velocity, magnetic
field and turbulence. The properties of this function are derived and
compared with the so-called contribution function.
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Title: Resonance Line Transfer with Partial Redistribution. V. The
Solar CA II Lines
Authors: Shine, R. A.; Milkey, R. W.; Mihalas, Dimitri
1975ApJ...199..724S Altcode:
Line profiles for the Ca II H and K lines have been calculated,
accounting for the partial frequency coherence of scattered
photons. These profiles are compared with calculations made with
identical atomic and atmospheric models but assuming complete
redistribution. Very significant differences between the profiles
obtained using these two different physical descriptions of the
scattering process are found, and it is now apparent that the
assumption of complete redistribution is a serious oversimplification
of the actual physical situation. The partial sredistribution (PRD)
results are in substantially better agreement with observation
than the complete redistribution (CRD) profiles in describing (a)
the center-to-limb behavior of the intensity at K1 and K2, (b) the
center-to-limb behavior of the wavelength positions of K1 and K2,
and (c) the relative behavior of the H and K profiles, as a function
of wavelength, at disk center. Further, we find that we may match
the observed absolute intensity at K1 with a minimum chromospheric
electron temperature of about 4450 K, and that the HSRA temperature
minimum is too low when partial redistribution effects are taken into
account. This result raises questions about the validity of equating
brightness temperatures observed at K1 in stellar spectra with minimum
temperatures in stellar chromospheres; it appears likely that such a
procedure will systematically underestimate the value of Tmin. Subject
headings: chromosphere, solar - line formation - radiative transfer
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Title: Heights of Formation of Non-Magnetic Solar Lines Suitable
for Velocity Studies
Authors: Altrock, R. C.; November, L. J.; Simon, G. W.; Milkey, R. W.;
Worden, S. P.
1975SoPh...43...33A Altcode:
Heights of formation of lines that do not exhibit Zeeman splitting
are calculated using an LTE, partial non-LTE, and full non-LTE
approach. Non-magnetic (g=0) lines are valuable for velocity
investigations in quiet-Sun magnetic field regions, and a knowledge
of their formation heights is useful for obtaining three dimensional
velocity profiles in these regions.
---------------------------------------------------------
Title: Comments concerning the photoionization model for excitation
of resonance lines of He I and He II in the solar chromosphere.
Authors: Milkey, R. W.
1975ApJ...199L.131M Altcode:
Recently there has been much discussion of the production of the
solar resonance lines of He I and He II by extreme-ultraviolet photons
impinging on the upper chromosphere and photoionizing He I and He II,
with the subsequent recombinations producing the emission lines. In this
paper the consequences of this model for the emergent line profiles
are examined and are shown to lead to an apparent contradiction with
the observed profiles.
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Title: Resonance line transfer with partial redistribution. III. Mg
II resonance lines in solar-type stars.
Authors: Milkey, R. W.; Ayres, T. R.; Shine, R. A.
1975ApJ...197..143M Altcode:
We discuss the gravity dependence of the Mg II resonance lines
calculated with inclusion of effects of partial redistribution in
frequency. Using chromospheric models scaled from a solar model, we
demonstrate the increased decoupling of the radiation temperature of
the k1 feature from the minimum electron temperature in lower-gravity
models. The limb darkening of the k-line in the main-sequence model
is also discussed.
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Title: Calculations of Profiles for the CaII H and K Lines Including
Partial Redistribution Effects
Authors: Shine, R. A.; Milkey, R. W.; Mihalas, D.
1975BAAS....7Q.360S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Resonance line transfer with partial redistribution: II. The
solar Mg II lines.
Authors: Milkey, R. W.; Mihalas, D.
1974ApJ...192..769M Altcode:
Line profiles for the Mg II h and k lines have been calculated,
accounting for the partial frequency redistribution of photons. These
profiles are compared with the complete redistribution calculations
under identical assumptions for the atomic and atmospheric models,
and the inadequacy of the latter approximation is demonstrated. In
particular, the temperature as deduced from the intensities at h1 and
k1 under the assumption of complete redistribution appears to be a
lower limit for the chromospheric temperature minimum. The partial
redistribution profiles are in substantially better agreement with
observation than complete redistribution results in describing the
wavelength position of h1 and k1, and the relative behavior of the h
and k profiles.
---------------------------------------------------------
Title: The Effect of Partial Frequency Redistribution on the Formation
of the Wings of Lyman-α
Authors: Milkey, R. W.; Mihalas, Dimitri
1974BAAS....6U.291M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Formation of the Luminosity-Sensitive 0 I Multiplet at 7774 A
Authors: Johnson, H. R.; Milkey, R. W.; Ramsey, L. W.
1974ApJ...187..147J Altcode:
We have calculated line profiles and equivalent widths for the 7774 A
multiplet of 0 i for model atmospheres in the range = K for surface
gravities in the range log g = 4. .0. A kinetic equilibrium (KE)
treatment of line formation can partially account for the observed
luminosity sensitivity of these lines and considerably modifies the
derived microturbulent broadening parameter. Line profiles obtained
from KE line-formation theory are much deeper than LTE profiles, and
we present new observations of Canopus (F0 Ib) to verify the essential
correctness of our treatment. Subject headings: atmospheres, stellar -
line formation - spectra, infrared
---------------------------------------------------------
Title: Partial Redistribution Effects in the Solar Magnesium II
Resonance Lines.
Authors: Milkey, R. W.; Mihalas, D. M.
1974BAAS....6R.221M Altcode:
No abstract at ADS
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Title: Helium Excitation in the Solar Chromosphere: he i in a
Homogeneous Chromosphere
Authors: Milkey, R. W.; Heasley, J. N.; Beebe, H. A.
1973ApJ...186.1043M Altcode:
We report kinetic equilibrium calculations for an He i atom with
13 bound levels in a homogeneous model chromosphere. We evaluate
the effectiveness of coronal radiation in producing ionization of
chromospheric helium and the methods of populating the excited levels
from which the visible and infrared transitions arise. The homogeneous
model gives a reasonable representation of quiet-Sun, disk-center
conditions, but fails to reproduce the eclipse data. Subject headings:
atomic processes - chromospheres, solar - spectra, solar
---------------------------------------------------------
Title: Calculation of the Solar Chromospheric Lα Profile Allowing
for Partial Redistribution Effects
Authors: Milkey, R. W.; Mihalas, Dimitri
1973SoPh...32..361M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Resonance-Line Transfer with Partial Redistribution: a
Preliminary Study of Lyman a in the Solar Chromosphere
Authors: Milkey, R. W.; Mihalas, Dimitri
1973ApJ...185..709M Altcode:
This paper presents a method for solving resonance-line transfer
problems including a detailed treatment of the effects of partial
redistribution. Calculations were madefor a schematic representation
of La in the solar chromosphere. We find that the usual assumption bf
complete redistribution leads to spurious estimates of number densities,
the Lyman continuum, and the La profile, and thus we support the
conclusions of Vernazza and of Vernazza, Avrett, and Loeser. Although
we have made too many simplifications in the current computations
to be able to compare with the observed La profile in detail, the
differential behavior of our results for several cases supports the
suggestion made in the papers cited above that the scattering in the
La wing is well described as dominantly coherent. The methods developed
here are easily extended to more realistic models and can be applied to
many other lines of interest. Subject headings: chromosphere, solar -
line formation - radiative transfer
---------------------------------------------------------
Title: Low-temperature free-free emission: infrared excesses in
Be stars.
Authors: Milkey, R. W.; Dyck, H. M.
1973ApJ...181..833M Altcode:
We discuss the possibility that the infrared emission observed for
certain Ae and Be stars may be produced by low temperature free-free
processes in the circumstellar region. The problems associated with H -
are discussed and it is shown that, for an optically thin sphere, if H -
free-free processes dominate in the infrared, then one ought to see a
strong free-bound continuum in the visible superposed on the stellar
continuum. The same arguments can be applied to the electronproton
process. Thus we are left with the fact that a free-free-like opacity
fits the observed infrared fluxes but without a corresponding physical
picture of the specific mechanism. Subject headings: Be stars -
circumstellar shells - infrared sources - opacities
---------------------------------------------------------
Title: The Excitation of Chromospheric Helium
Authors: Milkey, R. W.; Heasley, J. N.; Beebe, H. A.
1973BAAS....5U.277M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Infrared Excesses in Early-Type Stars: Free-Free Emission
Authors: Dyck, H. M.; Milkey, R. W.
1972PASP...84..597D Altcode:
INFRARED EXCESSES IN EARLY-TYPE STARS: FREE-FREE EMISSION* H. M. DYCK
AND R. W. MILKEY Kitt Peak National Observatoryt It has been previously
shown that some hot stars exhibit infrared excesses which may be
explained by high-temperature (T 10,000 K) free-free emission. We
demonstrate that the infrared color excesses of many other hot stars
may be explained as low-temperature (T $ 3000 K) free-free emission. We
present a model for the circumstellar region in which metal atoms are
radiatively ionized by the stellar flux and infrared emission occurs
from H-minus free-free transitions. Key words: infrared excesses -
early-type stars - free-free emission
---------------------------------------------------------
Title: Solar Rotation: The Photospheric Height Gradient
Authors: Livingston, W.; Milkey, R.
1972SoPh...25..267L Altcode:
For selected pairs of Fraunhofer lines the height of formation has been
calculated corresponding to that portion of the profile intercepted by
the magnetograph exit slits. A photospheric height discrimination of
150-300 km is realized. In 1971 simultaneous measurements of equatorial
angular velocity from spectroscopic displacements of these line pairs
indicate no height gradient in excess of 1%.
---------------------------------------------------------
Title: A Study of D_{3} Emission in a Solar Flare by Use of
Narrow-Band Filtergrams
Authors: Milkey, Robert W.; Harvey, Karen L.
1972PASP...84..400M Altcode:
We report observations of helium D3 emission in the solar flare
of 11 February 1970 made at the Lockheed Solar Observatory. The
morphological relationship between the D3 and Ha emission is explored,
and a photometric reduction technique is applied to the filtergrams
to determine peak intensity of the D3 emission relative to the local
quiet sun continuum. Key words: flare - filtergram - helium D3
---------------------------------------------------------
Title: The Effect of Resonance-Line Transfer on Hydrogen Ionization
Authors: Beebe, H. A.; Milkey, R. W.
1972ApJ...172L.111B Altcode:
Non-LTE calculations have been carried out on a model of a hydrogen
atom in the solar chromosphere. In evaluating the assumption of
detailed balance in Lyman- , we have found that radiative transfer
with a Voigt profile alters the hydrogen ionization equilibrium above
a Lyman-continuum optical depth of about 10 .
---------------------------------------------------------
Title: A computational program for the solution of non-LTE transfer
problems by the complete linearization method
Authors: Auer, L. H.; Heasley, J. N.; Milkey, R. W.
1972CoKit.555.....A Altcode: 1972QB4.K55n555....
No abstract at ADS
---------------------------------------------------------
Title: The Time Behavior of Temperature and Emission Measure in
X-Ray Flares
Authors: Milkey, Robert W.; Blocker, Norman K.; Chambers, William H.;
Fehlau, Paul E.; Fuller, Jack C.; Kunz, Walter E.
1971SoPh...20..400M Altcode:
X-ray observations from Vela-5 spacecraft of five flares occurring in
November and December 1969 were leduced to temperatures and emission
measures as a function of time. This reduction was done assuming
a thermal spectrum including free-free and free-bound emission. A
phenomenological model is proposed to explain the nature of the time
behavior of the temperature and emission measure.
---------------------------------------------------------
Title: Comments on the Decay Phase of Impulsive Solar X-Ray Bursts.
Authors: Milkey, R. W.
1971BAAS....3..460M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Comments on X-ray bursts - Halpha profile relationships.
Authors: Milkey, R. W.; Blocker, N. K.; Chambers, W. H.; Fehlau,
P. E.; Fuller, J. C.; Kunz, W. E.
1971BAAS....3R.263M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Origin of Flare Produced Hard X-Rays
Authors: Milkey, R. W.
1971SoPh...16..465M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectral hardening during X-ray bursts.
Authors: Kunz, W. E.; Blocker, N. K.; Chambers, W. H.; Fehlau, P. E.;
Fuller, J. C.; Milkey, R. W.
1971BAAS....3S.262K Altcode:
No abstract at ADS
---------------------------------------------------------
Title: On the Frequency Dependence of Acoustic Emission by Isotropic
Turbulence
Authors: Milkey, Robert W.
1970SoPh...14...77M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Notice: Publication of Vela Solar X-Ray Observations
Authors: Milkey, R. W.
1970BAAS....2..360M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar X-Ray Monitoring by the Vela V and VI Satellites
Authors: Blocker, N. K.; Chambers, W. H.; Fehlau, P. E.; Fuller,
J. C.; Kunz, W. E.; Milkey, R. W.
1970BAAS....2T.295B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Chromospheric Heating above Supergranular Boundaries
Authors: Milkey, Robert W.
1970SoPh...14...62M Altcode:
A geometrical optics technique developed in order to study
energy transport by weak fast-mode hydromagnetic shock waves in a
non-homogeneous, anisotropic medium has been applied to the problem
of the heating of the chromosphere in the regions of intensified
magnetic field which occur above the boundaries of supergranular
cells. The results of the calculation indicate that there should
be a temperature enhancement in the regions of the chromospheric
network. This temperature enhancement is advanced as a possible
mechanism for the origin of the observed calcium emission network.
---------------------------------------------------------
Title: Chromospheric heating above supergranular boundaries / by
Robert W. Milkey
Authors: Milkey, Robert William
1970PGLO..106...63M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Heating of the Chromospheric Network by Hydromagnetic Waves.
Authors: Milkey, Robert William
1970PhDT.........1M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Transport of Mechanical Energy in the Chromosphere
Authors: Milkey, Robert W.
1969BAAS....1R.287M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Profiles of Mg II and Ca II Lines in Nonhomogeneous
Chromospheres.
Authors: Beebe, Herbert A.; Johnson, Hollis R.; Milkey, Robert W.
1968AJS....73R.166B Altcode:
Intensity profiles of Ca II and Mg II resonance line cores are
calculated for several nonhomogeneous solar atmospheric models at
various points across the disk. A self-consistent solution of the
radiative transfer and steady-state equations assuming complete
redistribution for scattering in the line is separately obtained for
each of the two atmospheric components under the usual plane-parallel
approximation. Each ion is represented by a model atom consisting
of two bound levels and a continuum. Horizontal nonhomogeneity is
approximated by a uniform cell enclosed by a rectangular boundary in
order to simulate the chromospheric supergranular network. Both cell
and boundary models follow the Bilderberg continuum atmosphere out
to the temperature minimum. The cell atmosphere is characterized by
an isothermal or mildly rising temperature structure from that point
outward, whereas the boundary temperature rises much more steeply. Two
boundary models (models I and II) based on magnetohydrodynamic studies
of the network from a concurrent investigation by one of the authors
(R.W.M.), have been investigated in detail. Other chromospheric models
are under study. The profiles, which are averages over projected areas
of the inhomogeneities, can be made to match the observed reversals
in both the Ca and Mg line cores, the limb darkening of the entire
Ca K core, and the minimum temperature of 46000K with an optically
thick chromosphere. Restrictions placed on the models by observations
are discussed.
---------------------------------------------------------
Title: Hydromagnetic Waves in the Chromosphere.
Authors: Milkey, Robert W.
1968AJS....73R..72M Altcode:
Two-dimensional ray paths have been calculated for fast mode
hydromagnetic waves in the solar photo- sphere and lower chronosphere. A
horizontally varying magnetic field such as that proposed by Parker
(Astrophys. J. 138, 552,1963) is introduced into the problem in order
to gain some insight into the nature of chromospheric heating above
the boundary of a supergranular cell. It is shown that if density
and pressure are uniform horizontally the rays are refracted away
from the region of field concentration; a variation in pressure and
density may cause rays to be refracted toward the concentration of
field and density.
---------------------------------------------------------
Title: On the Uniqueness of Solutions in Radiative Transfer
Authors: Milkey, Robert W.
1967ApJ...148..935M Altcode:
No abstract at ADS
