mihalas

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Author name code: mihalas
ADS astronomy entries on 2022-09-14
author:"Mihalas, Dimitri"

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Title: Theory of Stellar Atmospheres
Authors: Hubeny, Ivan; Mihalas, Dimitri
2014tsa..book.....H Altcode:
No abstract at ADS

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Title: VizieR Online Data Catalog: Ca II H and K Measurements Made
at MWO (Duncan+ 1991)
Authors: Duncan, D. K.; Vaughan, A. H.; Wilson, O. C.; Preston,
G. W.; Frazer, J.; Lanning, H. H.; Misch, A.; Mueller, J.; Soyumer,
D.; Woodard, L.; Baliunas, S. L.; Noyes, R. W.; Hartmann, L. W.;
Porter, A.; Zwaan, K.; Middelkoop, F.; Rutter, R.; Mihalas, D.
2005yCat.3159....0D Altcode:
Summaries are presented of the photoelectric measurements of stellar
CaII H and K line intensity made at Mount Wilson Observatory during
the years 1966-1983. These results are derived from 65,263 individual
observations of 1296 stars. For each star, for each observing season,
the maximum, minimum, mean, and variation of the instrumental H and
K index "S" are given, as well as a measurement of the accuracy of
observation. A total of 3110 seasonal summaries are reported. These
observations were obtained with two instruments, HKP-1 and HKP-2. The
HKP-2 instrument is a four-channel chopping spectrometer which records
counts in 1.09{AA} FWHM triangular bandpasses centered in the H and
K lines as well as in two 20{AA} reference bandpasses centered on
3901.067 and 4001.067{AA}. The stellar activity is expressed by the
index S defined as S = {alpha} (Nh+Nk)/(Nr+Nv) where Nh and
Nk are the counts (corrected from background) in the H and K lines,
Nr and Nv those in the reference continuum bandpasses, and {alpha}
is a constant of proportionality used to correct for night-to-night
instrumental variations. Higher values of S generally correspond to
higher levels of chromospehric activities. Factors which effect the
ability to detect stellar activity variations and accurately measure
their amplitudes such as the accuracy of the H and K measurements and
scattered light contamination are discussed. Relations are given which
facilitate intercomparison of "S" values with residual intensities
from ordinary spectrophotometry, and for converting measurements to
absolute fluxes. (1 data file).

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Title: Quantitative Spectroscopy of Supernovae for Dark Energy Studies
Authors: Baron, E.; Branch, David; Jeffery, David; Nugent, Peter;
Thomas, Rollin; Bongard, Sebastien; Hauschildt, Peter H.; Kasen,
Daniel; Mihalas, Dimitri
2005astro.ph.10166B Altcode:
Detailed quantitative spectroscopy of Type Ia supernovae (SNe~Ia)
provides crucial information needed to minimize systematic effects in
both ongoing SNe Ia observational programs such as the Nearby Supernova
Factory, ESSENCE, and the SuperNova Legacy Survey (SNLS) and in proposed
JDEM missions such as SNAP, JEDI, and DESTINY. Quantitative spectroscopy
is mandatory to quantify and understand the observational strategy of
comparing “like versus like”. It allows us to explore evolutionary
effects, from variations in progenitor metallicity to variations in
progenitor age, to variations in dust with cosmological epoch. It
also allows us to interpret and quantify the effects of asphericity,
as well as different amounts of mixing in the thermonuclear explosion.

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Title: Cepheid Atmospheres
Authors: Mihalas, D.
2003ASPC..288..471M Altcode: 2003sam..conf..471M
No abstract at ADS

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Title: Stellar Atmosphere Modeling
Authors: Hubeny, Ivan; Mihalas, Dimitri; Werner, Klaus
2003ASPC..288.....H Altcode: 2003sam..conf.....H
No abstract at ADS

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Title: Laboratory and Astrophysical Radiation Hydrodynamics:
An Introduction
Authors: Mihalas, D.
2003ASPC..288..459M Altcode: 2003sam..conf..459M
The radiation received from stars provides the diagnostic tool to
infer temperatures, densities, hydrodynamic motions, and chemical
compositions in their atmospheres. For most stars it appears to be an
adequate first approximation to assume that there are no large-scale
hydrodynamic motions. However, in the most luminous stars the intense
radiation field deposits sufficient photon momentum in the outermost
layers to drive them off in a supersonic hydrodynamic flow. Likewise,
in exploding stars such as novae and supernovae, the dominant form of
energy and momentum content and transfer may reside not in the material
flow, but in the radiation field. Further, pulsating stars are driven by
an internal “radiation engine” in which the variation of the opacity
of the material with temperature and density acts as a thermodynamic
valve. In all these objects, and adequate analysis of the physics of
the atmosphere requires application of the discipline of Radiation
Hydrodynamics, where one considers the dynamics of a two-component
(at least!) radiating fluid. This talk will illustrate some aspects of
the radiation-material interaction that produce large-scale motions in
stellar atmospheres and envelopes, and make some connections between
stellar and laboratory radiation-driven phenomena.

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Title: Summary/Prognosis of the Workshop
Authors: Mihalas, D.
2003ASPC..288..677M Altcode: 2003sam..conf..677M
No abstract at ADS

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Title: Fifty Years of Research on Stellar Atmospheres
Authors: Mihalas, Dimitri
2001PASA...18..311M Altcode:
I would like to begin by saying what a pleasure it is for me
to be here. For my entire adult life I have wanted to come to
Australia. Actually, I have been invited to visit here twice before,
but each time I was thwarted by circumstances beyond my control. But
this time I was determined to (a) prove that the third time is indeed
the charm, and (b) pay homage to Walter Stibbs, who in my mind is the
epitome of a scholar and a gentleman. I have known Walter as colleague,
teacher, and friend, not to mention as an inspiration, both professional
and personal. So I am here today to try to give some sense of progress
in the study of stellar atmospheres, a field that Walter has graced
with his virtuosic touch. I will follow an unabashedly personal path,
describing the development as I experienced it. I will focus almost
entirely on early-type stars, where we may reasonably expect the
atmospheric layers to be homogeneous, and in radiative equilibrium. Only
at the end will I mention our nearest stellar neighbor, the Sun, which,
because we can study it in so much detail, offers counterexamples to
almost all of the the theory that works so well for early-type stars. I
offer apologies in advance to anyone this approach may offend.

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Title: VizieR Online Data Catalog: Radiative forces for stellar
envelopes (Seaton, 1997)
Authors: Seaton, M. J.; Yan, Y.; Mihalas, D.; Pradhan, A. K.
2000yCat.6089....0S Altcode:
(1) Primary data files, stages.zz These files give data for the
calculation of radiative accelerations, GRAD, for elements with nuclear
charge zz. Data are available for zz=06, 07, 08, 10, 11, 12, 13, 14,
16, 18, 20, 24, 25, 26 and 28. Calculations are made using data from
the Opacity Project (see papers SYMP and IXZ). The data are given
for each ionisation stage, j. They are tabulated on a mesh of (T, Ne,
CHI) where T is temperature, Ne electron density and CHI is abundance
multiplier. The files include data for ionisation fractions, for each
(T, Ne). The file contents are described in the paper ACC and as
comments in the code add.f (2) Code add.f This reads a file stages.zz
and creates a file acc.zz giving radiative accelerations averaged
over ionisation stages. The code prompts for names of input and output
files. The code, as provided, gives equal weights (as defined in the
paper ACC) to all stages. Th weights are set in SUBROUTINE WEIGHTS,
which could be changed to give any weights preferred by the user. The
dependence of diffusion coefficients on ionisation stage is given by a
function ZET, which is defined in SUBROUTINE ZETA. The expressions used
for ZET are as given in the paper. The user can change that subroutine
if other expressions are preferred. The output file contains values,
ZETBAR, of ZET, averaged over ionisation stages. (3) Files acc.zz
Radiative accelerations computed using add.f as provided. The user
will need to run the code add.f only if it is required to change
the subroutines WEIGHTS or ZETA. The contents of the files acc.zz
are described in the paper ACC and in comments contained in the code
add.f. (4) Code accfit.f This code gives gives radiative accelerations,
and some related data, for a stellar model. Methods used to interpolate
data to the values of (T, RHO) for the stellar model are based on
those used in the code opfit.for (see the paper OPF). The executable
file accfit.com runs accfit.f. It uses a list of files given in
accfit.files (see that file for further description). The mesh used
for the abundance-multiplier CHI on the output file will generally be
finer than that used in the input files acc.zz. The mesh to be used
is specified on a file chi.dat. For a test run, the stellar model
used is given in the file 10000_4.2 (Teff=10000 K, LOG10(g)=4.2) The
output file from that test run is acc100004.2. The contents
of the output file are described in the paper ACC and as comments in
the code accfit.f. (5) The code diff.f This code reads the output file
(e.g. acc1000004.2) created by accfit.f. For any specified
depth point in the model and value of CHI, it gives values of radiative
accelerations, the quantity ZETBAR required for calculation of diffusion
coefficients, and Rosseland-mean opacities. The code prompts for input
data. It creates a file recording all data calculated. The code diff.f
is intended for incorporation, as a set of subroutines, in codes for
diffusion calculations. (1 data file).

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Title: The MHD Equation of State with Post-Holtsmark Microfield
Distributions
Authors: Nayfonov, Alan; Däppen, Werner; Hummer, David G.; Mihalas,
Dimitri
1999ApJ...526..451N Altcode: 1999astro.ph..1360N
The Mihalas-Hummer-Däppen (MHD) equation of state is a part of the
Opacity Project (OP), where it mainly provides ionization equilibria
and level populations of a large number of astrophysically relevant
species. Its basic concept is the idea of perturbed atomic and ionic
states. At high densities, when many-body effects become dominant,
the concept of perturbed atoms loses its sense. For that reason,
the MHD equation of state was originally restricted to the plasma of
stellar envelopes, that is, to relatively moderate densities, which
should not exceed ρ&lt;10-2 g cm-3. However,
helioseismological analysis has demonstrated that this restriction is
much too conservative. The principal feature of the original Hummer
&amp; Mihalas paper is an expression for the destruction probability of
a bound state (ground state or excited) of a species (atomic or ionic),
linked to the mean electric microfield of the plasma. Hummer &amp;
Mihalas assumed, for convenience, a simplified form of the Holtsmark
microfield for randomly distributed ions. An improved MHD equation
of state (Q-MHD) is introduced. It is based on a more realistic
microfield distribution that includes plasma correlations. Comparison
with an alternative post-Holtsmark formalism (APEX) is made, and good
agreement is shown. There is a clear signature of the choice of the
microfield distribution in the adiabatic index γ1, which
makes it accessible to present-day helioseismological analysis. However,
since these thermodynamic effects of the microfield distribution are
quite small, it also follows that the approximations chosen in the
original MHD equation of state were reasonable. A particular feature
of the original MHD papers was an explicit list of the adopted free
energy and its first- and second-order analytical derivatives. The
corresponding Q-MHD quantities are given in the Appendix.

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Title: Shuster's Radiative Transfer Model of a Stellar Atmosphere
Authors: Mihalas, Dimitri
1999ApJ...525C..25M Altcode: 1999ApJC..525...25M
No abstract at ADS

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Title: Baade's Resolution of M32, NGC 205, and M31
Authors: Mihalas, Dimitri
1999ApJ...525C.359M Altcode: 1999ApJC..525..359M
No abstract at ADS

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Title: Book Review: Computational methods for astrophysical fluid
flow / Springer Verlag, 1998
Authors: Leveque, R. J.; Mihalas, D.; Dorfi, E. A.; Müller, E.
1999IrAJ...26...73L Altcode:
No abstract at ADS

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Title: Radiation Hydrodynamics
Authors: Mihalas, Dimitri
1998cmaf.conf..161M Altcode: 1998SAAS...27..161M
Basic Radiation Theory Specific Intensity Photon Number Density
Photon Distribution Function Mean Intensity Radiation Energy Density
Radiation Energy Flux Radiation Momentum Density Radiation Stress Tensor
(Radiation Pressure Tensor) Thermal Radiation Thermodynamics of Thermal
Radiation and a Perfect Gas The Transfer Equation Absorption, Emission,
and Scattering The Equation of Transfer Moments of the Transfer Equation
Lorentz Transformation of the Transfer Equation Lorentz Transformation
of the Photon 4-Momentum Lorentz Transformation of the Specific
Intensity, Opacity, and - Emissivity Lorentz Transformation of the
Radiation Stress Energy Tensor The Radiation 4-Force Density Vector
Covariant Form of the Transfer Equation Inertial-Frame Equations
of Radiation Hydrodynamics Inertial-Frame Radiation Equations
Inertial-Frame Equations of Radiation Hydrodynamics Comoving-Frame
Equation of Transfer Special Relativistic Derivation (D. Mihalas)
Consistency Between Comoving-Frame and Inertial-Frame Equations
Noninertial Frame Derivation (J. I. Castor) Analysis of O (v/c) Terms
Lagrangian Equations of Radiation Hydrodynamics Momentum Equation
Gas Energy Equation First Law of Thermodynamics for the Radiation
Field First Law of Thermodynamics for the Radiating Fluid Mechanical
Energy Equation Total Energy Equation Consistency of Different Forms
of the Radiating-Fluid Energy - and Momentum Equations Consistency
of Inertial-Frame and Comoving-Frame Radiation Energy - and Momentum
Equations Radiation Diffusion Radiation Diffusion Nonequilibrium
Diffusion The Problem of Flux Limiting Shock Propagation: Numerical
Methods Acoustic Waves Numerical Stability Systems of Equations
Implications of Shock Development Implications of Diffusive Energy
Transport Illustrative Example Numerical Radiation Hydrodynamics
Radiating Fluid Energy and Momentum Equations Computational
Strategy Energy Conservation Formal Solution Multigroup Equations An
Astrophysical Example Adaptive-Grid Radiation Hydrodynamics Front
Fitting Artificial Dissipation The Adaptive Grid The TITAN Code
References

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Title: The Quasi-stationary Structure of Radiating Shock Waves I. The
One-temperature Fluid
Authors: Sincell, M. W.; Gehmeyr, M.; Mihalas, D.
1997astro.ph.10097S Altcode:
We calculate the quasi-stationary structure of a radiating shock
wave propagating through a spherically symmetric shell of cold gas
by solving the time-dependent equations of radiation hydrodynamics
on an adaptive grid. We show that this code successfully resolves
the shock wave in both the subcritical and supercritical cases and,
for the first time, we have reproduced all the expected features --
including the optically thin temperature spike at a supercritical
shock front -- without invoking analytic jump conditions at the
discontinuity. We solve the full moment equations for the radiation
flux and energy density, but the shock wave structure can also be
reproduced if the radiation flux is assumed to be proportional to
the gradient of the energy density (the diffusion approximation), as
long as the radiation energy density is determined by the appropriate
radiative transfer moment equation. We find that Zel'dovich and Raizer's
analytic solution for the shock wave structure accurately describes a
subcritical shock but it underestimates the gas temperature, pressure,
and the radiation flux in the gas ahead of a supercritical shock. We
argue that this discrepancy is a consequence of neglecting terms which
are second order in the minimum shock compression ratio [$\eta_1 =
(\gamma-1)/(\gamma+1)$, where $\gamma$ is the adiabatic index] and the
inaccurate treatment of radiative transfer near the discontinuity. In
addition, we verify that the maximum temperature of the gas immediately
behind the shock is given by $T_{+} = 4 T_1/(\gamma+1)$, where $T_1$
is the gas temperature far behind the shock.

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Title: The Quasi-stationary Structure of Radiating Shock Waves
II. The Two-temperature Fluid
Authors: Sincell, M W; Gehmeyr, M; Mihalas, D
1997astro.ph.10095S Altcode:
We solve the equations of radiation hydrodynamics in the two-temperature
fluid approximation on an adaptive grid. The temperature structure
depends upon the electron-ion energy exchange length, $l_{ei}$, and the
electron conduction length, $l_{ec}$. Three types of radiating shock
structure are observed: subcritical, where preheating of the unshocked
gas is negligible; electron supercritical, where radiation preheating
raises the temperature of the unshocked electron fluid to be equal to
the final electron temperature; supercritical, where preheating and
electron-ion energy exchange raise the preshock $T_{e,i}$ to their
final post shock values. No supercritical shock develops when $l_{ei}$
is larger than the photospheric depth of the shocked gas because a
negligible amount of the ion energy is transferred to the electrons and
the shock is weakly radiating. Electron conduction smooths the $T_e$
profile on a length scale $l_{ec}$, reducing the radiation flux.

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Title: VizieR Online Data Catalog: Opacities from the Opacity Project
(Seaton+, 1995)
Authors: Seaton, M. J.; Yan, Y.; Mihalas, D.; Pradhan, A. K.
1997yCat.6080....0S Altcode:
1 CODES. ***** 1.1 Code rop.for ************ This code reads
opacity files written in standard OP format. Its main purpose is to
provide documentation on the contents of the files. This code,
like the other codes provided, prompts for the name of the file (or
files) to be read. The file names read in response to the prompt may
have up to 128 characters. 1.2 Code opfit.for ************** This code reads opacity files in standard OP format, and provides for
interpolation of opacities to any required values of temperature and
mass-density. The method used is described in OPF. The code prompts
for the name of a file giving all required control parameters. As
an example, the file opfit.dat is provided (users will need to
change directory names and file names). The use of opfit.for is
illustrated using opfit.dat. Most users will probably want to adapt
opfit.for for use as a subroutine in other codes. Timings for DEC
7000 ALPHA: 0.3 sec for data read and initialisations; then 0.0007 sec
for each temperature-density point. Users who like OPAL formats
should note that opfit.for has a facility to produce files of OP data
in OPAL-type formats. 1.3 Code ixz.for ************ This code
provides for interpolations to any required values of X and Z. See
IXZ. It prompts for the name of a file giving all required control
parameters. An example of such a file if provided, ixz.dat (the user
will need to change directory and file names). The output files
have names s92INT.'nnn'. The user specifies the first value of nnn,
and the number of files to be produced. 2. DATA FILES **********
2.1 Data files for solar metal-mix ******************************
Data for solar metal-mix s92 as defined in SYMP. These files are
from version 2 runs of December 1994 (see IXZ for details on Version
2). There are 213 files with names s92.'nnn', 'nnn'=201 to 413. Each
file occupies 83762 bytes. The file s92.version2 gives values of X
(hydrogen mass-faction) and Z (metals mass-fraction) for each value
of 'nnn'. The user can get s92.version2, select the values of 'nnn'
required, then get the required files s92.'nnn'. The user can see the
file in ftp, displayed on the screen, by typing "get s92.version2
-". The files s92.'nnn' can be used with opfit.for to obtain
opacities for any requires value of temperature and mass density. Files for other metal-mixtures will be added in due course. Send
requests to mjs@star.ucl.ac.uk. 2.2 Files for interpolation
in X and Z ********************************** The data files
have names s92xz.'mmm', where 'mmm'=001 to 096. They differ from
the standard OP files (such as s92.'nnn' --- section 2.1 above) in
that they contain information giving derivatives of opacities with
respect to X and Z. Each file s92xz.'mmm' occupies 148241 bytes. The interpolations to any required values of X and Z are made
using ixz.for. Timings: on DEC 7000 ALPHA, 2.16 sec for each
new-mixture file. For interpolations to some specified values of
X and Z, one requires just 4 files s92xz.'mmm'. Most users will not
require the complete set of files s92xz.'mmm'. The file s92xz.index
includes a table (starting on line 3) giving values, for each 'mmm'
file, of x,y,z (abundances by number-factions) and X,Y,Z (abundances
by mass-fractions). Users are advised to get the file s92.index, and
select values of 'mmm' for files required, then get those files. The files produced by ixz.for are in standard OP format and can
be used with opfit.for to obtain opacities for any required values
of temperature and mass density. 3 RECOMMENDED PROCEDURE FOR
USE OF OPACITY FILES **********************************************
(1) Get the file s92.version2. (2) If the values of X and
Z you require are available in the files s92.'nnn' then get those
files. (3) If not, get the file s92xz.index. (4) Select
from s92xz.index the values of 'mmm' which cover the range of X and
Z in which your are interested. Get those files and use ixz.for to
generate files for your exact required values of X and Z. (5) Note
that the exact abundance mixtures used are specified in each file (see
rop.for). Also each run of opfit.for produces a table of abundances. (6) If you want a metal-mix different from that of s92, contact
mjs@star.ucl.ac.uk. 4 FUTURE DEVELOPMENTS *******************
(1) Data for the calculation of radiative forces are provided as
the CDS catalog &lt;VI/89&gt; (added August 1997) (2) Facilities
will be added later which will enable the user to make calculations
giving files for any required mixtures. (9 data files).

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Title: Radiative Transfer in Astrophysics: Past, Present, and Future
Authors: Mihalas, D.
1996AAS...188.3201M Altcode: 1996BAAS...28..866M
The discipline of radiative transfer has provided the foundation for
the interpretation of essentially all astrophysical data. Some of the
major developments in the field in the 20th Century are reviewed, and
an attempt is made to identify directions for future research, and to
assess the likely importance of the discipine in the coming century.

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Title: First Results From TITAN
Authors: Gehmeyr, M.; Mihalas, D.
1994AAS...185.4006G Altcode: 1994BAAS...26Q1370G
1. We present the complete solutions to Noh's constant velocity shock
tube problem in planar, cylindrical, and spherical symmetry. 2. We
discuss the physical properties of radiating shocks for a completely
ionized hydrogen gas and highlight the transition from subcritical to
supercritical shocks. 3. We give first results from stellar variability
computations.

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Title: Adaptive grid radiation hydrodynamics with TITAN
Authors: Gehmeyr, M.; Mihalas, D.
1994PhyD...77..320G Altcode:
We have developed a code which solves the coupled sets of radiation
transfer and fluid dynamics equations (time dependent in one spatial
dimension) by employing a fully implicit adaptive grid procedure
to detect, resolve, and track the relevant physical structures. We
have formulated TITAN as a general purpose code, written it in a user
friendly manner, and documented it in detail. This code is available to
the (astrophysical) community for the application to a broad variety
of computational problems both as a research and a teching tool. We
demonstrate the code's power and versatility in a series of simple
problems. They range from pure hydrodynamics tests (shock tubes and
blast waves), via radiation transfer tests (radiative heating and
cooling), to radiation hydrodynamics tests (radiative shocks and blast
waves). These can be viewed as predecessors to a host of interesting
astrophysical problems such as nova and supernova explosions and
light curves, accretion onto compact objects, star formation, and
stellar variability.

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Title: Opacities for stellar envelopes
Authors: Seaton, M. J.; Yan, Y.; Mihalas, D.; Pradhan, A. K.
1994MNRAS.266..805S Altcode:
We define stellar envelopes to be those regions of stellar interiors
in which atoms exist and are not markedly perturbed by the plasma
environment. Availability of accurate and extensive atomic data is
a prime requirement for the calculation of envelope opacities. For
envelopes we adopt the criterion of mass density p &lt; 0.01 ρ≥g
cm-3. We present radiative Rosseland mean opacities
for envelopes obtained using atomic data calculated in an international
collaboration referred to as the Opacity Project, or OP. Equations of
state are calculated using an occupation-probability formalism. To
a good approximation, ionization equilibria and level populations
in envelopes depend only on the temperature T and electron density
Ne and are insensitive to chemical mixtures. Monochromatic
opacities for all abundant chemical elements are therefore calculated
on a grid of (T, Ne) values and are archived. Rosseland mean
opacities are then readily calculated for any chemical mixture. Tables
of Rosseland means, for any required mixtures and as functions of ρ
and T, are available on request in computer-readable form. The
present, op, results are compared with those from another recent
study, referred to as OPAL, by C. A. Iglesias and F. A. Rogers at
the Lawrence Livermore National Laboratory. The agreement between the
OP and OPAL calculations is generally good, although there are some
differences. Both calculations give results larger than those obtained
in earlier work, by factors of up to 3 or more.

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Title: Stellar Classification and the Theory of Stellar Atmospheres
Authors: Mihalas, D.
1994ASPC...60...41M Altcode: 1994mpyp.conf...41M
No abstract at ADS

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Title: Adaptive Grid Radiation Hydrodynamics with TITAN
Authors: Gehmeyr, M.; Mihalas, D.
1993AAS...183.4806G Altcode: 1993BAAS...25.1366G
TITAN solves the coupled sets of radiation transfer and fluid dynamics
equations (time dependent in one spatial dimension) by employing a
fully implicit adaptive grid procedure to detect, resolve, and track the
relevant physical structures. TITAN is formulated as a general purpose
code, written in a user friendly manner, and documented in detail. We
intend to make TITAN available to the astrophysical community for the
application to a broad variety of computational problems. We demonstrate
TITAN's power and versatility in a series of simple problems. They
range from pure hydrodynamics test (shock tubes and blast waves), via
radiation transfer test (radiative heating and cooling), to radiation
hydrodynamics tests (radiative shocks and blast waves). These can be
viewed as predecessors to a host of interesting astrophysical problems
such as nova and supernova explosions and light curves, accretion onto
compact objects, star formation, and stellar variability.

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Title: On Cepheids at Maximum and Minimum Light
Authors: Simon, Norman R.; Kanbur, Shashi M.; Mihalas, Dimitri
1993ApJ...414..310S Altcode:
It has been known for many decades that the spectral type of Cepheids
at light maximum is constant with period. We use hydrodynamic pulsation
models to explain this result in terms of the outward reach of the
hydrogen ionization front. On the other hand, we show that, at minimum
light, the Cepheid photospheric temperature is mainly a function of
amplitude. A number of observed Cepheids have published temperatures
that seem too hot at both maximum and minimum. We attribute this to
an overestimation of the reddening for these stars. A list is given.

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Title: ZEUS-2D: A Radiation Magnetohydrodynamics Code for
Astrophysical Flows in Two Space Dimensions. III. The Radiation
Hydrodynamic Algorithms and Tests
Authors: Stone, James M.; Mihalas, Dimitri; Norman, Michael L.
1992ApJS...80..819S Altcode:
The radiation hydrodynamical (RHD) algorithms in ZEUS-2D are
described. These algorithms use a tensor variable Eddington factor,
computed from a solution of the static transfer equation, to close the
system of radiation moment equations. This full transport algorithm,
which differs significantly from more commonly used methods based on
the diffusion approximation, is applicable in both optically thin and
thick media. Results computed by these algorithms on a new collection
of RHD test problems are presented. For the transfer equation, very
detailed tests are possible which compare the numerical solution for
the specific intensity at every point on a given tangent plane to the
known analytic solution. It is shown that, while the interpolation
inherent in the method of short characteristics makes the solution
diffusive, it is not overly so. For certain restricted geometries
and physical conditions, these methods reproduce the expected results
either identically or qualitatively.

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Title: The International Opacity Project
Authors: Seaton, M. J.; Mihalas, D.; Yan, Y.
1992AAS...180.2203S Altcode: 1992BAAS...24..759S
No abstract at ADS

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Title: The Opacity Project - Equation of State
Authors: Mihalas, D.
1992RMxAA..23..127M Altcode:
The equation of state used in the opacity calculations of the Opacity
Project is described briefly.

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Title: CA II H and K Measurements Made at Mount Wilson Observatory,
1966--1983
Authors: Duncan, Douglas K.; Vaughan, Arthur H.; Wilson, Olin C.;
Preston, George W.; Frazer, James; Lanning, Howard; Misch, Anthony;
Mueller, Jean; Soyumer, David; Woodard, L.; Baliunas, Sallie L.;
Noyes, Robert W.; Hartmann, Lee W.; Porter, Alain; Zwaan, Cornelis;
Middelkoop, Frans; Rutten, Rene G. M.; Mihalas, Dimitri
1991ApJS...76..383D Altcode:
Summaries are presented of the photoelectric measurements of stellar
Ca II H and K line intensity made at Mount Wilson Observatory during
the years 1966-1983. These results are derived from 65,263 individual
observations of 1296 stars. For each star, for each observing season,
the maximum, minimum, mean, and variation of the instrumental H and
K index 'S' are given, as well as a measurement of the accuracy of
observation. A total of 3110 seasonal summaries are reported. Factors
which affect the ability to detect stellar activity variations and
accurately measure their amplitudes, such as the accuracy of the H and K
measurements and scattered light contamination, are discussed. Relations
are given which facilitate intercomparison of 'S' values with residual
intensities derived from ordinary spectrophotometry, and for converting
measurements to absolute fluxes.

---------------------------------------------------------
Title: The Quest for Physical Realism in Stellar Atmospheric Modeling
Authors: Mihalas, D.
1991ASIC..341..127M Altcode: 1991sabc.conf..127M
No abstract at ADS

---------------------------------------------------------
Title: The UK/US Opacity Project
Authors: Mihalas, D.
1990BAAS...22R.847M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Equation of State for Stellar Envelopes. IV. Thermodynamic
Quantities and Selected Ionization Fractions for Six Elemental Mixes
Authors: Mihalas, Dimitri; Hummer, D. G.; Mihalas, Barbara Weibel;
Daeppen, Werner
1990ApJ...350..300M Altcode:
The free-energy minimization technique in the form developed in the
preceding papers in this series is employed to evaluate thermodynamic
quantities and ionization fractions on a fine temperature and density
grid for six astrophysical mixtures of 15 elements. The mixtures
range from that appropriate to super-metal-rich stars, through solar
abundance, to that for extreme Population II objects. In this paper,
the results for solar abundances are summarized in a form that is
illustrative and which facilitates comparison with the results from
other equation of state calculations.

---------------------------------------------------------
Title: Magnetohydrodynamic Simulations of Mass Outflows from Star
Forming Regions
Authors: Stone, J. M.; Norman, M. L.; Mihalas, D.
1990IAUS..140..351S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Recent Progress and Future Prospects in the Study of Stellar
Atmospheres
Authors: Mihalas, Dimitri
1990arpf.symp...51M Altcode: 1990arpf.conf...51M
A review of the study of stellar atmospheres is presented, with
particular emphasis on the development of the basic theory. Attention is
also given to improvements in instrumentation, magnetic field studies,
geometrical problems, and spatial resolution.

---------------------------------------------------------
Title: Current Status of the Opacity Project
Authors: Mihalas, D.
1990ASPC...11...99M Altcode: 1990cbsp.proc...99M
No abstract at ADS

---------------------------------------------------------
Title: Numerical Simulation of Mass Outflows from Star Forming Regions
Authors: Stone, James M.; Norman, Michael L.; Mihalas, Dimitri
1989ASSL..156..207S Altcode: 1989admf.proc..207S
Observational studies of star forming regions in the Galaxy have
demonstrated the ubiquity of mass outflows from objects in the late
stages of star formation. The most dramatic examples of these flows
are molecular bipolar outflows and optical jets. This paper summarizes
the results from observational studies of these two classes of objects,
and outlines the major theoretical problems in understanding how such
flows are generated. Then, a project currently underway to address these
problems in detail is described. This project centers on increasingly
sophisticated numerical simulations of mass outflows from star-forming
regions using a multiphysics hydrocode being developed at the NCSA.

---------------------------------------------------------
Title: Progress Toward an Improved Equation of State and Opacity
for Stellar Envelopes
Authors: Mihalas, Dimitri
1989upsf.conf...59M Altcode: 1989IAUCo.111...59M
This paper describes an international project for computing new
stellar envelope opacities and equation of state data, together with
the progress achieved in the 5 years since its initiation. Attention
is given to the computations of the wave functions and energy levels,
and the calculations for the equation of state and the opacity code. The
methods used in these computations are described.

---------------------------------------------------------
Title: Book Review: Numerical radiative transfer. / Cambridge U
Press, 1988
Authors: Mihalas, D.
1988Obs...108..243M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The HAO/Lowell/AFGL Solar-Stellar Spectrophotometer
Authors: Fisher, R. R.; Ramsey, L. W.; Gilliland, R. L.; Radick, R.;
Lockwood, G. W.; Mihalas, D.
1988BAAS...20..994F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Detection of Supergiant Variability with the HAO/Lowell/AFGL
Solar Stellar Spectrophotometry Project(S3)
Authors: Ramsey, L. W.; Mihalas, D.; Radick, R.; Gilliland, R. L.;
Lockwood, G. W.; Fisher, R.; Gallagher, J.
1988BAAS...20.1012R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Stellar Observing Program of the HAO/Lowell/AFGL
Solar-Stellar Spectrophotometry Project (S3)
Authors: Gilliland, R. L.; Mihalas, D.; Ramsey, L. W.; Radick, R.;
Lockwood, G. W.
1988BAAS...20..994G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Equation of State for Stellar Envelopes. III. Thermodynamic
Quantities
Authors: Daeppen, Werner; Mihalas, Dimitri; Hummer, D. G.; Mihalas,
Barbara Weibel
1988ApJ...332..261D Altcode:
The authors derive general formulae for the computation of the
thermodynamic properties of a partially ionized (and/or dissociated)
multicomponent gas in terms of second derivatives of the free energy
with respect to temperature, volume, and occupation numbers. For the
free energy used in previous work the authors give explicit analytical
expressions for all derivatives required to construct the thermodynamic
quantities. Representative results for several different thermodynamic
properties of a hydrogen-helium plasma with N(He)/N(H) = 0.10 are
presented as color plots.

---------------------------------------------------------
Title: Towards Self-Consistent Numerical Models of Protostellar
Outflows
Authors: Stone, J. M.; Norman, M. L.; Mihalas, D.
1988BAAS...20Q1093S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Detection of supergiant variability with the HAO/Lowell/AFGL
solar-stellar spectrophotometry project (S3).
Authors: Mihalas, D.; Ramsey, L. W.; Radick, R.; Gilliland, R. L.;
Lockwood, G. W.; Fisher, R.; Gallagher, J.
1988BAAS...20.1012M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Solar Observing Program of the HAO/Lowell/AFGL
Solar-Stellar Spectrophotometry Project (S3)
Authors: Mihalas, D.; Radick, R.; Lockwood, G. W.; Gilliland, R. L.;
Ramsey, L. W.; Fisher, R.; Livingston, W.; White, O. R.
1988BAAS...20Q1008M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Equation of State for Stellar Envelopes. I. an Occupation
Probability Formalism for the Truncation of Internal Partition
Functions
Authors: Hummer, D. G.; Mihalas, Dimitri
1988ApJ...331..794H Altcode:
The authors have formulated a new equation of state for material in
stellar envelopes, subject to the limits T ⪉ 107K and
ρ ⪉ 10-2g cm-3. Under these conditions,
the method of free energy minimization can be used to allow for
nonideal effects; this method ensures thermodynamic consistency
among the material properties. A chemical picture is used in which
atomic and molecular particles retain their identities. An occupation
probability formalism is used to represent the effects of the plasma
in establishing a finite partition function, and attention is paid
to representing these effects in a way that is consistent from the
point of view of statistical mechanics. The use of the static screened
Coulomb potential to calculate level shifts and to estimate the cutoff
of the internal partition function is shown by elementary arguments
to be invalid. For most of the parameter space relevant to stellar
envelopes, perturbations arising from the plasma ions are shown to be
dominant in establishing the internal partition functions.

---------------------------------------------------------
Title: The Equation of State for Stellar Envelopes. II. Algorithm
and Selected Results
Authors: Mihalas, Dimitri; Dappen, Werner; Hummer, D. G.
1988ApJ...331..815M Altcode:
A free-energy-minimization method for computing the dissociation and
ionization equilibrium of a multicomponent gas is discussed. The adopted
free energy includes terms representing the translational free energy
of atoms, ions, and molecules; the internal free energy of particles
with excited states; the free energy of a partially degenerate
electron gas; and the configurational free energy from shielded
Coulomb interactions among charged particles. Internal partition
functions are truncated using an occupation probability formalism
that accounts for perturbations of bound states by both neutral and
charged perturbers. The entire theory is analytical and differentiable
to all orders, so it is possible to write explicit analytical formulas
for all derivatives required in a Newton-Raphson iteration; these are
presented to facilitate future work. Some representative results for
both Saha and free-energy-minimization equilibria are presented for
a hydrogen-helium plasma with N(He)/N(H) = 0.10. These illustrate
nicely the phenomena of pressure dissociation and ionization, and
also demonstrate vividly the importance of choosing a reliable cutoff
procedure for internal partition functions.

---------------------------------------------------------
Title: Atomic processes and radiation transport in stars
Authors: Mihalas, Dimitri
1988AIPC..168...42M Altcode:
To illustrate the tremendous range in physical conditions encountered
in analyses of radiation from various astrophysical sources, we
discuss representative physical conditions in several zones of a
typical star. Even though these zones do not cover the full range
of physical conditions encountered in the most exotic astronomical
objects, they nevertheless give a good idea of the kinds of data
required in astrophysical work. Moreover they provide a sequence
of states progressively farther from equilibrium. We discuss
the physical mechanisms important in determining the internal state
(i.e., excitation and ionization degrees) of the material in each
of the regimes chosen, and comment on whether one should expect
equilibrium or non-equilibrium distribution functions. In parallel,
we delineate the major issues affecting the transport of radiation
through typical astrophysical media; material properties, equilibrium
versus non-equilibrium, velocity fields, and dynamics. We attempt to
emphasize the close interplay between the nature of the radiation field
and the state of the material. We also try to mention where progress
is being slowed by lack of data for atomic processes, and indicate
what kinds of data are still needed.

---------------------------------------------------------
Title: Book-Review - Radiation Hydrodynamics in Stars and Compact
Objects - I.A.U COLL.89
Authors: Mihalas, D.; Winkler, K. H. A.; King, A.
1987Obs...107..219M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book Review - Physics of the Sun
Authors: Sturrock, P. A.; Holzer, T. E.; Mihalas, D. M.; Ulrich,
R. K.; Carson, T. R.
1987Obs...107..173S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Statistical Mechanics of Partially Ionized Stellar Plasmas:
The Planck-Larkin Partition Function, Polarization Shifts, and
Simulations of Optical Spectra
Authors: Dappen, Werner; Anderson, Lawrence; Mihalas, Dimitri
1987ApJ...319..195D Altcode:
We discuss a recent controversy about the Planck-Larkin partition
function, and present optical simulations of high-quality spectra
from laboratory hydrogen plasmas (Wiese, Kelleher, and Paquette) using
several partition function formalisms. We point out that the controversy
has arisen from a misunderstanding about the use of the Planck-Larkin
partition function. A Planck-Larkin cancellation may still have its
place in equations of state that are based on quantum-statistical
many-body theory (i.e., the "physical picture"). However, experimental
evidence shows that it is inconsistent to use the Planck-Larkin
partition function as the internal partition function in simple
models of reacting gases (i.e., the "chemical picture"). Moreover,
the more sophisticated equations of state of the physical picture
will have to be subjected to the same comparison with experimental
data. We also address the question of plasma polarization shifts of
bound-state energies. We discuss the static-screened Coulomb potential
(SSCP) as an atomic potential: from theoretical considerations and
observational constraints we conclude that it should not be used. The
only useful result of the SSCP potential its prediction of the number
of excited be obtained by alternative means, e.g., by an occupation
probability formalism.

---------------------------------------------------------
Title: Book-Review - Radiation Hydrodynamics in Stars and Compact
Objects
Authors: Mihalas, D.; Winkler, K. H. A.
1987S&T....73Q.395M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - Physics of the Sun - VOL.1 - the Solar
Interior - VOL.2 - the Solar Atmosphere - VOL.3 - Astrophysics and
Solar-Terrestrial Relations
Authors: Sturrock, P. A.; Holzer, T. E.; Mihalas, D. M.; Ulrich, R. K.
1987ApL....25..267S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - Physics of the Sun - V.I - the Solar Interior
- V.II - the Solar Atmosphere - V.III - Astrophysics and Solar /
Terrestrial Relations
Authors: Sturrock, P. A.; Holzer, T. E.; Mihalas, D. M.; Ulrich,
R. K.; Parker, E. N.
1986Natur.323..210S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The computation of radiation transport using Feautrier
variables. II. Spectrum line formation in moving media.
Authors: Mihalas, D.; Kunasz, P. B.
1986JCoPh..64....1M Altcode:
The Feautrier symmetric/antisymmetric radiation field averages are
presently applied to the solution of line transport problems in moving
media. These methods, which have proven to be useful in a variety of
astrophysical applications, are suggested to be applicable to other
areas of computational physics. Attention is given to algorithms
for both observer-frame and comoving-frame approaches, noting their
respective advantages and shortcomings.

---------------------------------------------------------
Title: Book-Review - the Life and Death of Stars
Authors: Cooke, D. A.; Mihalas, D.
1986S&T....71..362C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - the Transfer of Spectral Line Radiation
Authors: Cannon, C. J.; Mihalas, D.
1986Obs...106...23C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - Foundations of Radiation Hydrodynamics
Authors: Mihalas, D.; Mihalas, B. W.; Machado, M. E.
1986SoPh..103..409M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Introduction and Overview
Authors: Mihalas, D.
1986LNP...255....1M Altcode: 1986IAUCo..89....1M; 1986rhsc.conf....1M
No abstract at ADS

---------------------------------------------------------
Title: Physics of the Sun. Vol. I: The solar interior. Vol. II:
The solar atmosphere. Vol. III: Astrophysics and solar-terrestrial
relations.
Authors: Sturrock, P. A.; Holzer, T. E.; Mihalas, D. M.; Ulrich, R. K.
1986psvi.book.....S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Physics of the sun. Volume 3: Astrophysics and
solar-terrestrial relations
Authors: Sturrock, P. A.; Holzer, T. E.; Mihalas, D. M.; Ulrich, R. K.
1986psun....3.....S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Physics of the sun. Volume 2: The solar atmosphere
Authors: Sturrock, P. A.; Holzer, T. E.; Mihalas, D. M.; Ulrich, R. K.
1986psun....2.....S Altcode:
Aspects related to the solar interior are discussed, taking into account
thermonuclear reactions in the solar interior, atomic and radiative
processes in the solar interior, hydrodynamic and hydromagnetic
phenomena in the deep solar interior, rotation and magnetic fields,
solar waves and oscillations, and observations and theories of solar
convection, global circulation, and magnetic fields. In a discussion
of the solar atmosphere, attention is given to the radiation output,
the chromospheric fine structure, physical processes in the solar
corona, magnetic energy storage and conversion in the solar atmosphere,
the acceleration and propagation of solar flare energetic particles,
solar radio emission, and structure, dynamics, and heating of the solar
atmosphere. Other subjects explored are concerned with astrophysics and
solar-terrestrial relations. The formation of the sun and its planets
is considered along with the solar neutrino problem, solar and stellar
magnetic activity, the effects of solar electromagnetic radiation on
the terrestrial environment, and the effect of the solar wind.

---------------------------------------------------------
Title: Radiation Hydrodynamics in Stars and Compact Objects
Authors: Mihalas, Dimitri; Winkler, Karl-Heinz A.
1986LNP...255.....M Altcode: 1986IAUCo..89.....M; 1986rhsc.conf.....M
No abstract at ADS

---------------------------------------------------------
Title: The Equations of Radiation Hydrodynamics
Authors: Mihalas, D.
1986ASIC..188...45M Altcode: 1986arh..conf...45M
The purpose of this paper is to give an overview of the role of
radiation in the transport of energy and momentum in a combined
matter-radiation fluid. The transport equation for a moving radiating
fluid is presented in both a fully Eulerian and a fully Lagrangean
formulation, along with conservation equations describing the
dynamics of the fluid. Special attention is paid to the problem of
deriving equations that are mutually consistent in each frame, and
between frames, to O(v/c). A detailed analysis is made to show that
in situations of broad interest, terms that are formally of O(v/c)
actually dominate the solution.

---------------------------------------------------------
Title: Physics of the sun
Authors: Sturrock, P. A.; Holzer, T. E.; Mihalas, D. M.; Ulrich, R. K.
1986psun....1.....S Altcode: 1986QB521.P48......
Aspects related to the solar interior are discussed, taking into account
thermonuclear reactions in the solar interior, atomic and radiative
processes in the solar interior, hydrodynamic and hydromagnetic
phenomena in the deep solar interior, rotation and magnetic fields,
solar waves and oscillations, and observations and theories of solar
convection, global circulation, and magnetic fields. In a discussion
of the solar atmosphere, attention is given to the radiation output,
the chromospheric fine structure, physical processes in the solar
corona, magnetic energy storage and conversion in the solar atmosphere,
the acceleration and propagation of solar flare energetic particles,
solar radio emission, and structure, dynamics, and heating of the solar
atmosphere. Other subjects explored are concerned with astrophysics and
solar-terrestrial relations. The formation of the sun and its planets
is considered along with the solar neutrino problem, solar and stellar
magnetic activity, the effects of solar electromagnetic radiation on
the terrestrial environment, and the effect of the solar wind.

---------------------------------------------------------
Title: Book-Review - Foundations of Radiation Hydrodynamics
Authors: Mihalas, D.; Mihalas, B. W.; King, A.
1985Obs...105..238M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - Foundations of Radiation Hydrodynamics
Authors: Mihalas, D.; Mihalas, B.
1985S&T....70..231M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - Methods in Radiative Transfer
Authors: Kalkofen, W.; Mihalas, D.
1985Obs...105...52K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The computation of radiation transport using Feautrier
variables. I - Static media
Authors: Mihalas, D.
1985JCoPh..57....1M Altcode:
A review is presented of methods for solving the radiation transport
equation in terms of the symmetric and antisymmetric averages first
introduced by Feautrier (1964). These methods have enjoyed good
success and have achieved considerable popularity in astrophysics. Both
formulation and algorithms are discussed briefly, and basic references
are provided in order to provide easy access to workers in other fields
where these methods may prove applicable.

---------------------------------------------------------
Title: Implicit adaptive-grid radiation hydrodynamics.
Authors: Winkler, K. -H. A.; Norman, M. L.; Mihalas, D.
1985mts..conf..145W Altcode:
Contents: I. Introduction. II. Physical equations. III. Adaptive-mesh
equations. IV. Numerical equations. V. The adaptive mesh. VI. Numerical
techniques: Tensor artificial viscosity. Artificial mass and heat
diffusion. On the use of Δξ, Δm, and (δm/δt). Advection. Solution
procedure and control. VII. Ordinary gas dynamics: shock
tubes. VIII. Radiation hydrodynamics: a supercritical shock. IX. A
"Hilbert program" for nonlinear radiation hydrodynamics.

---------------------------------------------------------
Title: Book-Review - Stellar Atmospheric Structural Patterns
Authors: Thomas, R. N.; Mihalas, D.
1984Obs...104..275T Altcode:
No abstract at ADS

---------------------------------------------------------
Title: On the Propagation of Acoustic Waves in a Radiative Fluid
Authors: Mihalas, D.; Mihalas, B. W.
1984ApJ...283..469M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The H− equilibrium using coupled rate
equations for H−, H, H+, H2,
and H2+
Authors: Lites, B. W.; Mihalas, D.
1984SoPh...93...23L Altcode:
We formulate rate equations for the reaction network
coupling H, H−, H+, H2, and
H2+. We attempt to systematize the notation,
and to write the equations in a form suitable for modern computational
methods of handling the coupled rate equations and radiative transfer
equations, for both dynamical and static atmospheres. We have accounted
for more processes than are generally considered in most current work;
some of these may have an impact on the equilibrium of H−
(hence its opacity) and on charge conservation (hence the proton
density) in the atmospheres of solar-type stars.

---------------------------------------------------------
Title: Adaptive-mesh radiation hydrodynamics - II. The radiation
and fluid equations in relativistic flows.
Authors: Mihalas, D.; Winkler, K. -H. A.; Norman, M. L.
1984JQSRT..31..479M Altcode:
The authors derive the radiation and fluid equations for relativistic
flows in conservative form in a completely adaptive coordinate system.

---------------------------------------------------------
Title: Adaptive-mesh radiation hydrodynamics - I. The radiation
transport equation in a completely adaptive coordinate system.
Authors: Winkler, K. -H. A.; Norman, M. L.; Mihalas, D.
1984JQSRT..31..473W Altcode:
The authors formulate the radiation transport equation in a completely
adaptive coordinate system, which they define as a system in which
the mesh in spacetime, angles and frequency adapts automatically to
the dynamical evolution of the radiation field and fluid flow.

---------------------------------------------------------
Title: Foundations of radiation hydrodynamics
Authors: Mihalas, D.; Mihalas, B. W.
1984oup..book.....M Altcode:
This book is the result of an attempt, over the past few years, to
gather the basic tools required to do research on radiating flows
in astrophysics. The microphysics of gases is discussed, taking into
account the equation of state of a perfect gas, the first and second
law of thermodynamics, the thermal properties of a perfect gas, the
distribution function and Boltzmann's equation, the collision integral,
the Maxwellian velocity distribution, Boltzmann's H-theorem, the time
of relaxation, and aspects of classical statistical mechanics. Other
subjects explored are related to the dynamics of ideal fluids, the
dynamics of viscous and heat-conducting fluids, relativistic fluid flow,
waves, shocks, winds, radiation and radiative transfer, the equations
of radiation hydrodynamics, and radiating flows. Attention is given
to small-amplitude disturbances, nonlinear flows, the interaction of
radiation and matter, the solution of the transfer equation, acoustic
waves, acoustic-gravity waves, basic concepts of special relativity,
and equations of motion and energy.

---------------------------------------------------------
Title: On the Relevance of the MK System and Process to the Theory
of Stellar Atmospheres
Authors: Mihalas, D.
1984mpsc.conf....4M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - the A-Type Stars - Problems and Perspectives
Authors: Wolff, S. C.; Mihalas, D.
1984S&T....67..332W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - 100,000,000,000 Suns
Authors: Kippenhahn, R.; Mihalas, D.
1984S&T....68..134K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Foundations of radiation hydrodynamics
Authors: Mihalas, Dimitri; Weibel Mihalas, Barbara
1984frh..book.....M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Stellar rotation in lower main-sequence stars measured from
time variations in H and K emission-line fluxes. II. Detailed analysis
of the 1980 observing season data.
Authors: Baliunas, S. L.; Hartmann, L.; Noyes, R. W.; Vaughan, H.;
Preston, G. W.; Frazer, J.; Lanning, H.; Middelkoop, F.; Mihalas, D.
1983ApJ...275..752B Altcode:
For a sample of 47 lower main-sequence stars, including the Sun,
and eight evolved stars, the relative strength of the Ca II H and
K emission cores has been measured daily over a nearly continuous
interval during 1980 July through October at Mount Wilson. From these
time series measurements of chromospheric emission, rotation rates
have been inferred with quantitative estimates of both the reality and
precision of the rotation periods. We find rotation rates easily for
the main-sequence stars with strong emission or those later than about
spectral type K0. With this technique, rotation rates can be measured
precisely for the first time for equatorial velocities as slow as 1 km
s-1 and independently of the aspect of the rotation axis. In
a limited range of spectral type, a small sample of stars indicates that
chromospheric emission decreases smoothly as a function of rotation
period. No conclusion can be drawn on the question of the reality
of a discontinuity in chromospheric emission as a function of time
(the "Vaughan-Preston" gap for stars in the solar neighborhood). In our sample of giant stars, the G2 III star HD 218658 shows a
persistent fluctuation of 4.6 days, a period that is inconsistent with
stellar rotation. The G0 III star HD 6903 is a previously unreported
FK Comae-type star. For a few main-sequence stars, measurements
continued beyond 1980 October suggest the presence of active longitudes
(if not individual active regions) persisting through the observing
season 1981.

---------------------------------------------------------
Title: On the propagation of acoustic waves in a radiating fluid
Authors: Mihalas, D.; Mihalas, B. W.
1983ApJ...273..355M Altcode:
The linearized Lagrangian radiation equations of Castor (1972) are
used in order to obtain a virtually complete and physically satisfying
view of acoustic wave dynamics in a radiating fluid. It is assumed
that the radiation field is quasi-static, all dynamical radiation
terms are ignored, and the Eddington approximation is applied. It is
noted that it would be useful to proceed with the complementary study
of the time evolution of initial disturbances.

---------------------------------------------------------
Title: The photometric variability of solar-type stars. III. Results
from 1981-82, including parallel observations of thirty-six Hyades
stars.
Authors: Radick, R. R.; Mihalas, D.; Lockwood, G. W.; Thompson,
D. T.; Warnock, A., III; Hartmann, L. W.; Worden, S. P.; Henry, G. W.;
Sherlin, J. M.
1983PASP...95..621R Altcode:
A photometric survey of main-sequence stars in the Pleiades, Hyades,
and Malmquist Field, to investigate variability among solar-type
stars, had been continued at Cloudcroft Observatory for a second
season. Possibly six of 40 Pleiades stars, two (possibly six) of 49
Hyades stars and possibly four of 42 stars in the Malmquist Field
are found to be variable. Parallel observations of Hyades stars were
obtained also at Lowell Observatory. These measurements, which achieved
better precision, reveal significiant variations in eleven (possibly 16)
of 36 Hyades stars, all of spectral type F7 V-K2 V. Agreement between
the two surveys is acceptable. The two seasons of the Cloudcroft survey
show that changes in the mean annual brightness of the Hyades stars
accompany changes in the amplitude of their short-term variability,
in the sense that a star tends to become fainter as its variability
increases and vice versa. Color effects are absent.

---------------------------------------------------------
Title: Book-Review - Galactic Astronomy - Structure and Kinematics
Authors: Mihalas, D.; Binney, J.; Antonov, V. A.
1983Afz....19..505M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Comments on the dynamical effects of radiative viscosity
Authors: Mihalas, D.
1983ApJ...266..242M Altcode:
Diffusion limit radiation stress intensity tensor term size and
radiating fluid dynamical equation term size estimates are presented,
with emphasis on radiative viscosity effects. A complete parallelism is
demonstrated between radiation and material terms, and Castor's (1972)
comoving frame radiation energy and momentum equations, augmented
by Buchler's (1979, 1982) acceleration terms, are shown to provide a
completely consistent treatment of all effects associated with both
radiation viscosity and the equivalent inertia of radiation enthalpy
and radiant energy flux. Questions arising in connection with radiative
viscous dissipation are discussed, and it is noted that in certain
physically reasonable situations, the radiative viscous dissipation
function may be only O(v-squared/c-squared) relative to the dominant
radiative term in the radiating fluid gas-energy equation.

---------------------------------------------------------
Title: The photometric variability of solar-type stars. I. Preliminary
results for the Pleiades, Hyades and the Malmquist field.
Authors: Radick, R. R.; Hartmann, L.; Mihalas, D.; Worden, S. P.;
Africano, J. L.; Klimke, A.; Tyson, E. T.
1982PASP...94..934R Altcode:
The young main sequence stars in the Pleiades and Hyades clusters, and
old disk stars in the Malmquist Field near the north galactic pole,
have been observed by precision photometry in order to determine
the prevalance of variability among solar type stars. Significant
variations have been found in at least five, and possibly ten, of 44
Hyades stars, and possibly one of the 41 stars in the Malmquist Field,
all of which are of spectral type F8 V-K2 V.

---------------------------------------------------------
Title: Time-dependent radiative transfer with automatic flux limiting
Authors: Mihalas, D.; Weaver, R.
1982JQSRT..28..213M Altcode:
A simple method for solving the time-dependent transfer problem is
discussed. This scheme is automatically flux-limited and affords
physical insight into how flux limitation occurs. A second-order,
time-dependent radiation energy equation that is similar in form to
the diffusion limit radiation energy equation is then developed. This
time-dependent energy equation approaches physically reasonable
equations in optically thick and thin regions. Computational aspects
of solving this energy equation are discussed.

---------------------------------------------------------
Title: The acceleration and propagation of solar flare energetic
particles
Authors: Forman, M. A.; Ramaty, R.; Zweibel, E. G.; Holzer, T. E.;
Mihalas, D.; Sturrock, P. A.; Ulrich, R. K.
1982STIN...8329162F Altcode:
Observations and theories of particle acceleration in solar flares
are reviewed. The most direct signatures of particle acceleration
in flares are gamma rays, X-rays and radio emissions produced by the
energetic particles in the solar atmosphere and energetic particles
detected in interplanetary space and in the Earth's atmosphere. The
implication of these observations are discussed. Stochastic and shock
acceleration as well as acceleration in direct electric fields are
considered. Interplanetary particle propagation is discussed and
an overview of the highlights of both current and promising future
research is presented.

---------------------------------------------------------
Title: On iterative solutions of the LTE model atmosphere problem.
Authors: Mihalas, D.; Weaver, R. P.; Sanderson, J. G.
1982JQSRT..28...53M Altcode:
We discuss iterative methods for solving the coupled radiative-transfer
and energy-balance equations in the LTE model atmospheres problem
including isotropic coherent scattering. We show that iterative
solution (e.g. by SOR techniques) of the grand matrix encountered
in such problems is vastly more efficient than a direct solution,
and is easily vectorized. The final computational effort is linear
in the number of depths and frequencies considered, and thus this
approach opens the door for the computation of both static and dynamic
line-blanketed models using large numbers of depth-points and huge
numbers of frequencies. The iterative methods discussed here can be
applied to line-formation problems with complete redistribution and to
certain classes of problems with partial redistribution (e.g. Compton
scattering problems in the Fokker-Planck approximation).

---------------------------------------------------------
Title: Book-Review - Galactic Astronomy - Part One - Structure
and Kinematics
Authors: Mihalas, D.; Binney, J.; Robson, I.
1982JBAA...92..204M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: On the solution of the time-dependent inertial-frame equation
of radiative transfer in moving media to O(v/c).
Authors: Mihalas, D.; Klein, R. I.
1982JCoPh..46...97M Altcode:
It is demonstrated that practical schemes can be developed for treating
the hybrid time-dependent transfer equation including O(v/c) terms both
stably and efficiently, and their coupling into radiation-hydrodynamical
calculations is sketched. The mixed-frame equation of transfer and
the frequency-dependent and frequency-integrated moment equations are
developed. The relative sizes of the terms in the transfer equation
and the requirement for keeping all v/c terms in order to obtain
exact consistency with the energy equation for the radiating fluid
are addressed. The computational approach is discussed in Feautrier
variables, including a second-order formulation. Several schemes for
the solution method are presented along with test calculations for
an unattenuated square wave, attenuated radiation front, irradiated
grey atmosphere, and velocity effects in a moving atmosphere. How
the transfer equation to O(v/c) can be coupled to the hydrodynamic
equations in both an Eulerian and Lagrangian formulation is indicated.

---------------------------------------------------------
Title: Book-Review - Galactic Astronomy - ED.2
Authors: Mihalas, D.; Binney, J.; Barrow, J. D.
1982Natur.295..440M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - Galactic Astronomy - Structure and Kinematics
Authors: Mihalas, D.; Binney, J.; Jones, D.
1982Obs...102..245M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - Galactic Astronomy - Structure and Kinematics
Authors: Mihalas, D.; Binney, J.; Schmidt-Kaler, T.
1982SSRv...32..468M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - the Sun as a Star
Authors: Jordan, S.; Mihalas, D.
1982S&T....63..262J Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Stellar atmospheres.
Authors: Mihalas, D. M.
1982stat.book.....M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - Galactic Astronomy - Structure and Kinematics
Authors: Mihalas, D.; Binney, J.
1981Sci...214..829M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Comment on Radiative Transfer in Spherically Symmetric
Flows by Castor, J.I.
Authors: Mihalas, D.
1981ApJ...250..373M Altcode:
Castor's comoving-frame equation of transfer is re-derived retaining
a term omitted from one of the coefficients in his metric. This term
is important when the flow changes significantly on time scales Δt
∼ Δr/c, so that the fluid acceleration is comparable with cv/r
or c(dv/dr). When the term is retained, terms that depend on the
acceleration now appear in the coefficients of Castor's transfer
equation, in agreement with independent derivations by Buchler and
Mihalas.

---------------------------------------------------------
Title: Stellar rotation in lower main-sequence stars measured from
time variations in H and K emission-line fluxes. I. Initial results.
Authors: Vaughan, A. H.; Baliunas, S. L.; Middelkoop, F.; Hartmann,
L. W.; Mihalas, D.; Noyes, R. W.; Preston, G. W.
1981ApJ...250..276V Altcode:
Fluxes at 1 Å bands at the centers of the H and K lines in 46 lower
main sequence field stars, and in eight selected subgiants and giant
stars, have been measured at nightly intervals in the course of a
nearly continuous 14-week observing run. In 19 stars we have found
clear evidence of rotational modulation, from which values of the
rotational periods can be assigned by inspection. In nine others,
periods have been found by an autocorrelation analysis of the flux
records. The periods obtained imply rotation velocities that are in
good accord with spectroscopically determined values of V sin i in
the literature for 13 of the stars we have observed. Much of
the short term scatter in H-K flux observed by Wilson appears to be
caused by rotational modulation, although variations on other time
scales are also present. As many as 80% of the chromospherically
active (i.e., young) stars display prominent rotational modulation,
and in some cases the phase of the modulation remained unchanged for
the entire observing period, suggesting that markedly asymmetric and
long-lived distributions of active regions are common in such stars. At a given (B - V) &lt; 1.0, the strength of H-K emission is shown
to vary as a function of rate of rotation, suggesting that rotation,
rather than initial conditions or age per se, is the chief parameter
influencing chromospheric output. From data on stellar activity
cycles available at present, it is suggested that periodic cycles
resembling the Sun's are almost exclusively found in stars with
rotation periods in excess of about 20 days; and, except for this
threshold effect, the cycle periods are uncorrelated with rotation rate.

---------------------------------------------------------
Title: A preliminary interpretation of stellar chromospheric CA II
emission variations within the framework of stellar dynamo theory.
Authors: Durney, B. R.; Mihalas, D.; Robinson, R. D.
1981PASP...93..537D Altcode:
Recent stellar chromospheric Ca II emission data are analyzed
and interpreted within the framework of simple concepts of dynamo
theory. From an examination of the rotation rates and B-V indexes of
26 stars as presented by Vaughn at el. (1981) and the background flux
values derived by Wilson (1978) for 18 reference stars, an empirical
relation is derived between dynamo number, calculated from the B-V
index and rotation rate, and stellar chromospheric emission flux. The
Ca-emission cycle morphology of the sample stars is then examined,
and differences between the four morphological classes identified
are explained in terms of the correlation of large dynamo numbers
with the presence of several interfering magnetic modes of different
spatial scales, which do not exhibit a marked cyclic behavior, and
small numbers with the excitation of only a single mode. The gap
noted by Vaughn and Preston (1980) in the relation between the log
of the emission flux with (B-V) is then interpreted as representing
a transition from a multiple-mode dynamo to a single-mode dynamo as
the dynamo number decreases.

---------------------------------------------------------
Title: On the stimulated emission terms in partial redistribution
calculations
Authors: Baschek, B.; Oxenius, J.; Mihalas, D.
1981A&A....97...43B Altcode:
It is shown that the formulation given by Mihalas (1978) of the
stimulated emission term in partial redistribution calculations is
incorrect. It is noted that in the solar and stellar computations
presented thus far in the literature this error is of no importance
because the stimulated emission terms were negligible. However,
for computations for lines in which h-nu/kT is not large compared
with unity, the error could have serious consequences and the correct
formulation should therefore be used. To this end, corrected, albeit
approximate, equations are given for the various cases of interest.

---------------------------------------------------------
Title: The Photometric Variability of Main Sequence Stars
Authors: Radick, R. R.; Hartmann, L. W.; Mihalas, D. M.; Worden, S. P.
1981BAAS...13R.832R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Solar Stellar Connection: what Observations are Needed?
Authors: Mihalas, D.
1981siwn.conf..193M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Difference-equation methods for the solution of radiative
transfer problems in media with discontinuities
Authors: Mihalas, D.
1981JQSRT..25..145M Altcode:
Difference-equation methods are developed for solving the equation
of transfer in media with discontinuities in their physical
properties. These should prove useful in calculating the radiation
field in dynamical atmospheres having shocks. Two examples with
thermal or scattering source functions, for which exact solutions
can be obtained, are used to evaluate the accuracy of the techniques,
which prove quite satisfactory.

---------------------------------------------------------
Title: The activity cycles of stars.
Authors: Wilson, O. C.; Vaughan, A. H.; Mihalas, D.
1981SciAm.244b..82W Altcode: 1981SciAm.244...82W
No abstract at ADS

---------------------------------------------------------
Title: The activity cycles of stars
Authors: Wilson, O. C.; Vaughan, A. H.; Mihalas, D.
1981SciAm.244b.104W Altcode: 1981SciAm.244..104W
The activity cycle of the sun is reviewed with attention to the
contributions of Galileo, Schwabe, Wolf, Maunder, Carrington, Hale,
Babcock and Parker. The use of the H-K photometer in the observation of
the chromospheric variability of 91 sun-like stars at the Mount Wilson
Observatory is discussed. It is estimated that more than half of the
main-sequence stars less massive than 1.5 solar masses may show cyclic
behavior. The chromospheric variations for 12 sunlike stars are given.

---------------------------------------------------------
Title: Book-Review - the Brightest Stars
Authors: de Jager, C.; Mihalas, D.
1981S&T....61..432D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Book-Review - Galactic Astronomy - Structure and Kinematics
Authors: Mihalas, D.
1981S&T....62..592M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Galactic astronomy. Structure and kinematics
Authors: Mihalas, D.; Binney, J.
1981gask.book.....M Altcode:
An overview of the Milky Way Galaxy is provided and aspects of
astronomical background are considered, taking into account positions
and coordinate systems, proper motions, parallax, radial velocities,
stellar spectra, magnitudes and colors, absolute energy distributions,
and astronomical catalogs and atlases. The physical properties of
stars and the interstellar medium are examined, giving attention
to stellar distances, stellar masses, stellar radii, an analysis of
stellar spectra, spiral arm and disk stars, spheroidal-component stars,
stellar structure and evolution, pulsating variable stars, and questions
of interstellar absorption. The space distribution of stars and the
chemical elements in the Milky Way Galaxy are discussed along with
the large-scale structure and stellar content of galaxies, the solar
motion, the stellar residual-velocity distribution, and the rotation of
galaxies. A description is presented of the large-scale distribution
of gas in galaxies, taking into consideration the distribution of
neutral hydrogen in the Milky Way Galaxy and in other galaxies,
molecular clouds in the Milky Way Galaxy, and the galactic center.

---------------------------------------------------------
Title: A Radiative Transfer Model of Filamentary Prominences
Authors: Bornmann, P. L.; Mihalas, D.
1980BAAS...12Q.909B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Solution of the comoving-frame equation of transfer
in spherically symmetric flows. VII - Angle-dependent partial
redistribution
Authors: Mihalas, D.
1980ApJ...238.1034M Altcode:
A method is presented for treating line scattering with general
redistribution in angle and frequency in spherical expanding
flows. The scheme employs a solution of the moment equations for the
source function coupled with a ray-by-ray formal solution for angular
shape factors. In both steps the differencing is straightforward and
numerically stable.

---------------------------------------------------------
Title: Radiative transfer in spherical flows with nonmonotonic
velocity fields - The observer's frame reconsidered
Authors: Mihalas, D.
1980ApJ...238.1042M Altcode:
It is shown that for spherically symmetric flows with nonmonotonic
velocity fields, the solution of the two-level-atom transfer equation in
the observer's frame remains a viable method, even at high flow speeds,
on computers with vector-processing capabilities. This result is of
importance because for such cases comoving-frame methods are, at best,
extremely difficult (no successful calculation having been published
to date), and Sobolev-theory methods become both cumbersome to use
and inaccurate in many situations of interest. The basic algorithm is
described and is illustrated by computations for spherically symmetric
decelerating expansions.

---------------------------------------------------------
Title: Solution of the comoving-frame equation of transfer in
spherically symmetric flows. VI - Relativistic flows
Authors: Mihalas, D.
1980ApJ...237..574M Altcode:
Within the framework of special relativity, radiative transport
equations describing exactly, i.e., to all orders in (v/c), the
interaction of radiation and matter in spherically symmetric flows are
derived. The full angle- and frequency-dependent transfer equation,
frequency-dependent moment equations, and frequency-integrated moment
equations are obtained. The frequency-integrated moment equations
are shown to be precisely equivalent to the equations obtained from
the four-divergence of the radiation stress-energy tensor, and all
three sets of equations recover the results obtained earlier by
Castor in the limit (v/c) much less than 1. A method of solution of
the steady-flow transfer equation is discussed, and two illustrative
examples are presented.

---------------------------------------------------------
Title: Physics of the Chromosphere - Corona / Wind Complex and Mass
Loss in Stellar Atmospheres
Authors: Mihalas, D. H.
1980HiA.....5..521M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Some speculations concerning the significance of Beals's type
III P Cygni line profiles.
Authors: Mihalas, D.; Conti, P. S.
1980ApJ...235..515M Altcode:
It is suggested that Beals's Type III P Cygni profiles, in which
additional emission appears blueward of the blueshifted absorption
feature, may be produced in stars in which the inner parts of
the expanding envelope (stellar wind) are forced into corotation
with the star out to a few stellar radii by a weak global magnetic
field. Numerical estimates are made for the O4ef star Xi Pup which
suggest that the Alfvenic radius (limit of corotation) is about 2.1
stellar radii, and that the required magnetic field at that point is
about 70 Gauss. The braking time scale implied by angular momentum
loss to the wind is short compared with the main-sequence (hydrogen
core-burning) lifetime of the star and the present high mass loss rate.

---------------------------------------------------------
Title: Curves of growth and line profiles in expanding and rotating
atmospheres
Authors: Mihalas, D.
1979MNRAS.189..671M Altcode:
A study of diagnosing velocity fields in expanding and rotating stellar
atmospheres is presented. Line profiles are calculated by solving for
the source function in the comoving fluid frame, and computing emergent
intensities using a formal solution in the observer's frame. Results are
presented for equivalent widths, line depth, line shift, line width, and
asymmetry parameters, and it is shown that the standard curve of growth
cannot yield unique physically meaningful results. Line-shape parameters
appear to provide sufficient information to estimate the broad features
of the flow, and it is shown that a fundamental assumption upon which
all present Fourier methods are based is invalid. Possible approaches
for overcoming the problem are suggested.

---------------------------------------------------------
Title: Book-Review - Stellar Atmospheres
Authors: Mihalas, D.; Ivanov, V. V.
1979SvA....23..386M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Theory of Stellar Atmospheres
Authors: Mihalas, D.
1979IAUTA..17b.193M Altcode: 1979IAUT...17..193M
No abstract at ADS

---------------------------------------------------------
Title: Two-dimensional radiative transfer. I. Planar geometry.
Authors: Mihalas, D.; Auer, L. H.; Mihalas, B. R.
1978ApJ...220.1001M Altcode:
Differential-equation methods for solving the transfer equation in
two-dimensional planar geometries are developed. One method, which uses
a Hermitian integration formula on ray segments through grid points,
proves to be extremely well suited to velocity-dependent problems. An
efficient elimination scheme is developed for which the computing time
scales linearly with the number of angles and frequencies; problems
with large velocity amplitudes can thus be treated accurately. A very
accurate and efficient method for performing a formal solution is
also presented. A discussion is given of several examples of periodic
media and free-standing slabs, both in static cases and with velocity
fields. For the free-standing slabs, two-dimensional transport effects
are significant near boundaries, but no important effects were found
in any of the periodic cases studied.

---------------------------------------------------------
Title: Solution of the comoving-frame equation of transfer in
spherically symmetric flows. V. Multilevel atoms.
Authors: Mihalas, D.; Kunasz, P. B.
1978ApJ...219..635M Altcode:
The coupled radiative transfer and statistical equilibrium equations
for multilevel ionic structures in the atmospheres of early-type
stars are solved. Both lines and continua are treated consistently;
the treatment is applicable throughout a transonic wind, and allows
for the presence of background continuum sources and sinks in the
transfer. An equivalent-two-level-atoms approach provides the solution
for the equations. Calculations for simplified He (+)-like model atoms
in parameterized isothermal wind models indicate that subordinate
line profiles are sensitive to the assumed mass-loss rate, and to the
assumed structure of the velocity law in the atmospheres.

---------------------------------------------------------
Title: Stellar atmospheres
Authors: Mihalas, Dimitri
1978stat.book.....M Altcode: 1978QB809.M5.......
The radiation field is considered along with the equation of transfer,
the grey atmosphere, absorption cross-sections, the equations of
statistical equilibrium, and the solution of the transfer equation. A
description of model atmospheres is presented, taking into account the
classical model-atmospheres problem, Local Thermodynamic Equilibrium
(LTE) radiative-equilibrium models, convection and models for late-type
stars, the results of LTE model-atmosphere calculations for early-type
stars, non-LTE radiative-equilibrium models for early-type stars,
extended atmospheres, and semiempirical solar models. Attention is given
to the line absorption profile, classical treatments of line transfer,
non-LTE line transfer in the case of the two-level atom and the
multilevel atom, line formation with partial frequency redistribution,
radiative transfer in moving atmospheres, the equations of hydrodynamics
for an ideal compressible fluid, coronal winds, radiation hydrodynamics,
and radiatively driven winds.

---------------------------------------------------------
Title: Boundary conditions with mass loss: the radiatively-driven
wind model.
Authors: Mihalas, D.
1977saif.conf..175M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Erratum and Addendum: "Solution of the comoving-frame equation
of transfer in spherically symmetric flows. IV. Frequency-dependent
source functions for scattering by atoms and electrons [Astrophys. J.,
Vol. 210, p. 419 - 433 (1976)].
Authors: Mihalas, D.; Kunasz, P. B.; Hummer, D. G.
1977ApJ...214..337M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Solution of the comoving-frame equation of transfer in
spherically symmetric flows. IV. Frequency-dependent source functions
for scattering by atoms and electrons.
Authors: Mihalas, D.; Kunasz, P. B.; Hummer, D. G.
1976ApJ...210..419M Altcode:
A numerical method is presented of solving the radiative transfer
equation in the comoving frame of a spherically symmetric expanding
atmosphere in which both the line and the electron-scattering source
function can depend on frequency (i.e., when there is partial frequency
redistribution in the scattering process). This method is used to assess
the adequacy of various assumptions regarding frequency redistribution
in the comoving frame and to discuss the effects of electron scattering
more accurately than previously possible. The methods developed here
can be used in realistic model atmospheres to account for the (major)
effects of electron scattering upon emergent flux profiles.

---------------------------------------------------------
Title: Solution of the Comoving-Frame Equation of Transfer in
Spherically Symmetric Flows. III. Effect of Aberration and Advection
Terms
Authors: Mihalas, Dimitri; Kunasz, P. B.; Hummer, D. G.
1976ApJ...206..515M Altcode:
We investigate the importance of the advection and aberration terms,
which are of order V/c, in the comoving-frame transfer equation in
spherical geometry. Characteristic trajectories are found which reduce
the spatial derivatives to a perfect differential, and a generalization
of the numerical procedure developed in the earlier papers of this
series that permits the integration of the transfer equation on these
characteristics is presented. For cases in which V/c 1, a perturbation
solution is developed which reduces the problem to that solved in the
first paper in this series. For velocities of the form V(r) r (n = 0,
1, 2), it is shown that the magnitude of the effects arising from the
advection and aberration terms is about 5 V/c relative to the solution
with these terms omitted. In stellar winds V/c &lt;% 0.01; hence we
conclude that aberration and advection terms may safely be ignored,
and that consideration of the Doppler-shift term alone is adequate in
the computation of spectra from such expanding atmospheres. Subject
headings: radiative transfer - stars: atmospheres

---------------------------------------------------------
Title: Structure and spectrum of quiescent prominences: energy
balance and hydrogen spectrum.
Authors: Heasley, J. N.; Mihalas, D.
1976ApJ...205..273H Altcode:
In this paper we present theoretical models of quiescent prominences
which satisfy the constraints of radiative, magnetohydrostatic,
and statistical equilibrium. We obtain reasonable models only if we
assume that the exciting ultraviolet radiation field can penetrate
diffusely into the slab, or that there is a source of nonradiative
energy input. The computed temperatures in our models are in good
agreement with observational estimates. The models reproduce most
observed features of these objects quite well, and should provide
a good starting point to study further the formation of prominence
spectra and the effects of nonradiative energy inputs.

---------------------------------------------------------
Title: Resonance-line transfer with partial
redistribution. VIII. Solution in the comoving frame for moving
atmospheres.
Authors: Mihalas, D.; Shine, R. A.; Kunasz, P. B.; Hummer, D. G.
1976ApJ...205..492M Altcode:
The effects of partial frequency redistribution in the scattering
process for lines formed in moving atmospheres are analyzed using a
general method that allows the transfer equation to be solved in the
comoving frame of the gas. The same chromospheric and atomic model
studied by Cannon and Vardavas (1974) is employed in the calculations,
but a depth scale with logarithmically spaced points is adopted. It is
found that in both static and moving atmospheres, the profiles obtained
with complete and partial frequency redistribution are virtually
identical. The large differences in profiles obtained by Cannon and
Vardavas when they used complete and partial redistribution are shown
to be spurious (and physically unreal) effects resulting from angle
averaging in the observer's frame instead of the comoving frame.

---------------------------------------------------------
Title: Solution of the comoving-frame equation of transfer in
spherically symmetric flows. II. Picket-fence models.
Authors: Mihalas, D.; Kunasz, P. B.; Hummer, D. G.
1976ApJ...203..647M Altcode:
To examine the effect of the radial flow of atmospheric material on
the temperature distribution in a stellar atmosphere, a picket-fence
model with Gaussian lines is formulated and solved numerically
in the comoving frame of the gas, which is assumed to move with a
prescribed velocity law. Extensive results have been obtained for
both static and dynamical models, with planar and moderately extended
spherical geometries. For static models, the effect of lines on the
temperature distribution is virtually independent of extension. When
a large-scale velocity field is imposed, significant surface heating
and additional back-warming are found; the magnitude of these effects
increases with the extension of the atmosphere. If a significant flow
velocity persists to sufficient depth, the enhanced escape probability
can lead to a cooling in the deeper layers, which competes with the
back-warming. The results obtained here suggest that the deposition of
energy arising from the intrusion of line opacity into the continuum,
caused by velocity gradients, could influence the dynamics of the flow.-

---------------------------------------------------------
Title: Radiative transfer in expanding atmospheres
Authors: Mihalas, D.
1976pmas.conf..347M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Theory of stellar atmospheres (Théorie des atmosphères
stellaires).
Authors: Cayrel, R.; Mihalas, D.
1976IAUTA..16b.189C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Solution of the comoving-frame equation of transfer
in spherically symmetric flows. I. Computational method for
equivalent-two-level-atom source functions.
Authors: Mihalas, D.; Kunasz, P. B.; Hummer, D. G.
1975ApJ...202..465M Altcode:
A method for solving the line-formation problem using the full
comoving-frame formulation of the radiative-transfer equation is
presented for the case of spherically symmetric atmospheres expanding
with arbitrarily large velocities. A stable differencing scheme and a
frequency-by-frequency elimination procedure are developed to solve the
partial differential equations that describe the radiation field in the
comoving frame. It is noted that this method allows computation of the
radiation field from a given model atmosphere which must specify the
depth dependence of all the relevant physical variables. Numerical
results obtained for several models involving line formation by
two-level atoms, electron scattering, and continuous absorption are
discussed which simulate situations in the stellar winds of hot stars
and similar objects. The force exerted by radiation on the gas is
examined in a number of situations, and flux profiles are described
for very high-velocity flows with very weak or nonexistent continuum
and electron-scattering opacities. It is concluded that the mechanism
proposed by Noerdlinger and Rybicki (1974) for the destruction of
radially driven envelopes in planar geometries becomes inoperative
even in the case of slightly extended spherical configurations.

---------------------------------------------------------
Title: An Archetype Hydrogen Atmosphere Problem
Authors: Athay, R. G.; Mihalas, D.; Shine, R. A.
1975SoPh...45...15A Altcode:
Populations for the first three bound states and the continuum of
hydrogen are determined for an isothermal, hydrostatic atmosphere at 20
000 K. The atmosphere is treated as being optically thin in the Balmer
and Paschen continua and illuminated by continuum radiation at these
wavelengths with prescribed radiation temperatures. The atmosphere is
optically thick in the 2-1, 3-1, 3-2 and c-1 transitions. Three stages
of approximation are treated: radiative detailed balance in the 2-1,
3-1 and 3-2 transitions,

---------------------------------------------------------
Title: Theory of extended stellar atmospheres. II. A grid of static
spherical models for O stars and planetary nebula nuclei.
Authors: Kunasz, P. B.; Hummer, D. G.; Mihalas, D.
1975ApJ...202...92K Altcode:
Spherical static non-LTE model atmospheres are presented for stars
from 30 to 60 solar masses at various points on their evolutionary
tracks, and for some nuclei of planetary nebulae at two points of
a modified Harman-Seaton sequence. The method of Mihalas and Hummer
was employed, which uses a parametrized radiation force multiplier
to simulate the force of radiation arising from the entire line
spectrum. However, in the present work the density structure
computed in the LTE models was held fixed in the calculation of
the corresponding non-LTE models; in addition, the opacity of an
average light ion was taken into account. The effects of sphericity,
as distinct from those arising from a density structure modified by
a large radiation force, were investigated by computing a few planar
models using the same parametrized radiation force multiplier as for
the spherical models. Extensive tables are given of monochromatic
magnitudes, continuum jumps and gradients, Stroemgren-system colors,
monochromatic extensions, and the profiles and equivalent widths of
the hydrogen lines for all models.

---------------------------------------------------------
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.

---------------------------------------------------------
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

---------------------------------------------------------
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 K1 in stellar
spectra with minimum temperatures in stellar chromospheres; it appears
likely that such a procedure will systematically underestimate the
value of T-min.

---------------------------------------------------------
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

---------------------------------------------------------
Title: INVITED - Solar and Stellar Spectroscopy.
Authors: Mihalas, D.
1975BAAS....7..448M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Solution of the Co-Moving Frame Equation of Transfer in
Spherically Symmetric Flows. II. Picket-Fence Models.
Authors: Mihalas, D.; Kunasz, P. B.; Hummer, D. G.
1975BAAS....7..449M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: He I lambda 4922 profiles in B stars: calculations with an
improved line broadening theory.
Authors: Mihalas, D.; Barnard, A. J.; Cooper, J.; Smith, E. W.
1975ApJ...197..139M Altcode:
Theoretical profiles for the He I A4922 line in B star spectra have
been computed using the improved broadening theory of Barnard, Cooper,
and Smith, and the level populations calculated by Auer and Mihalas
from a simultaneous self-consistent solution of the coupled transfer
and statistical equilibrium equations. The revised broadening theory
yields excellent agreement with laboratory measurements of the width
and intensity of the forbidden (2p ) transition. The results of this
paper show that stellar profiles computed with the new theory are
in excellent agreement with observed profiles, and the discrepancies
between observation and theory that existed previously have now been
removed. Subject headings: early-type stars - line profiles

---------------------------------------------------------
Title: Solution of the Co-moving Frame Equation of Transfer in
Spherically Symmetric Flows.
Authors: Mihalas, D.; Kunasz, P. B.; Hummer, D. G.
1975BAAS....7R.256M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Solution of the co-moving frame equation of transfer in
spherically symmetric flows.
Authors: Mihalas, D.; Kunasz, P. B.; Hummer, D. G.
1975BAAS....7..256M Altcode:
No abstract at ADS

---------------------------------------------------------
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: Effects of Departures from LTE and Atmospheric Extension on
Colors and Theoretical Continuum Parameters
Authors: Mihalas, Dimitri
1975mpth.conf..241M Altcode: 1975mpth.proc..241M
No abstract at ADS

---------------------------------------------------------
Title: Erratum Resonance-Line Transfer with Partial Redistribution:
a Preliminary Study of Lyman a in the Solar Chromospherer
Authors: Milkey, W.; Mihalas, Dimitri
1975ApJ...195..831M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A non-LTE model stellar atmosphere computer program
Authors: Mihalas, D.; Heasley, J. N.; Auer, L. H.
1975STIN...7630128M Altcode:
A computer program was developed for calculating model atmospheres of
early-type stars subject to the constraints of radiative, hydrostatic,
and statistical equilibrium, by means of a complete-linearization
technique. This program is available through the NCAR High Altitude
Observatory's Radiative Transfer Library.

---------------------------------------------------------
Title: Observations of the C III lambda 8500
(3s1S-3p1P) line in O and Of stars.
Authors: Mihalas, D.; Frost, S. A.; Lockwood, G. W.
1975PASP...87..153M Altcode:
Measurements from coude infrared image-tube spectra of the equivalent
widths of the C iii A8500 (3s1S-3p1P0), Heii x10124 (n = 4- n = 5),
and hydrogen P8 lines have been made for several 0 and Of stars,
and are presented here. An attempt to measure the C ni xx9701-15
complex (3p3P0-3d3D) was thwarted by interference from telluric H20
absorption. The C iii x8500 line strengths provide useful constraints
on possible theoretical models, and suggest, on the basis of the
calculations of Nussbaumer (1971), that the C iii x5696 (3p2P0-3d'D)
and x8500 lines are formed in relatively extended atmospheres,
with a dilution factor 0.1. Key words: Of stars - stellar spectra -
stellar atmospheres

---------------------------------------------------------
Title: Progress towards an interpretation of stellar spectra.
Authors: Mihalas, D.
1974AJ.....79.1111M Altcode:
Review of the changes which occurred over the last 10 to 15 years in
the approach to the interpretation of stellar spectra, and discussion
of the structure and physical assumptions of the underlying theory. The
status of current research is examined, with special attention to the
effects of departures from the assumption of LTE in stellar spectra,
and to extended and expanding atmospheres. Promising areas of future
research are pointed out.

---------------------------------------------------------
Title: Theory of extended stellar atmospheres. I. Computational
method and first results for static spherical models.
Authors: Mihalas, D.; Hummer, D. G.
1974ApJS...28..343M Altcode:
A method is presented that makes possible, for the first time, the
calculation of extended spherical non-LTE model stellar atmospheres in
hydrostatic and radiative equilibrium. This method is a generalization
of the complete-linearization technique of Auer and Mihalas. Models
have been obtained for a star with 60 solar masses, 1,000,000 solar
luminosities, and 24 solar radii, whose atmosphere is characterized by
an effective temperature of 39,500 K and a surface gravity log g = 3.45,
i.e., with a spectral type near O6. These models are differentiated by
the magnitude and radial dependence of a radiation force multiplier that
is inserted into the equation of hydrostatic equilibrium to simulate
the effect of radiation force on opacity sources which have not been
included explicitly in the calculation. Models have been obtained very
close to the limit at which the radiation force and gravity balance;
as this condition is approached, the atmospheres become more and
more extended.

---------------------------------------------------------
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: Theoretical Helium i Emission-Line Intensities for Quiescent
Prominences
Authors: Heasley, J. N.; Mihalas, Dimitri; Poland, A. I.
1974ApJ...192..181H Altcode:
Self-consistent solutions of the combined statistical equilibrium
and transfer equations have been carried out for a rather
complete multilevel, multi-ion model helium atom in model quiescent
prominences. The excitation and ionization of both He I and He ii were
considered simultaneously, and detailed calculations of the radiative
transfer in the resonance lines and ground-state continua of both
these ions were made, allowing for the effects of overlapping hydrogen
transitions. A large number of excited states have been included in the
computation, so that a fairly comprehensive set of predicted subordinate
line intensities are now available for comparison with observation. A
preliminary comparison of the predicted values with published singleti
triplet ratio observations shows good agreement for all the pairs of
lines considered. Subject headings: atomic processes - line formation -
prominences, solar

---------------------------------------------------------
Title: He I lambda 4471 profiles in B stars: calculation with an
improved line-broadening theory.
Authors: Mihalas, D.; Barnard, A. J.; Cooper, J.; Smith, E. W.
1974ApJ...190..315M Altcode:
Theoretical profiles for the He I A4471 line in B-star spectra
have been computed using an improved broadening theory of Barnard,
Cooper, and Smith, together with level populations determined by a
self-consistent solution by Auer and Mihalas of the coupled transfer
and statistical-equilibrium equations. The broadening theory has been
constructed to provide a more accurate description of the intensity
and width of the forbidden (2p 3P0-4f 3F ) transition as measured
in laboratory experiments. The results presented in this paper show
that this revision of the broadening theory leads to computed stellar
profiles which are in much better agreement with observed profiles
than any previously obtained. Subject headings: early-type stars -
line profiles

---------------------------------------------------------
Title: Some Observational Implications of Extended Static O-Star
Model Atmospheres
Authors: Mihalas, Dimitri; Hummer, David G.
1974ApJ...189L..39M Altcode:
Some results and observational implications are presented for the
first extended spherical non-LTE model atmospheres in hydrostatic and
radiative equilibrium. These models all correspond to a star with =
60 , L = 1.25 X 106 Lo and R = 24 , with an effective temperature
Te 39,500 K and surface gravity log g 3.45 (spectral type near
06). They are differentiated by the magnitude and radial dependence
of a radiation-force multiplier , inserted into the equation of
hydrostatic equilibrium, to simulate the effect of radiation force
on opacity sources (e.g., lines) that have not been included in the
calculations. It has been possible to obtain models very close to the
limit at which the radiation force balances the gravity. Hydrogen and
helium (`7= 0.1) constitute the gas; siz hydrogen lines are treated
explicitly. These models show La in emission, the lower Balmer lines
in absorption, the Balmer jump in absorption, and both infrared and
ultraviolet excesses relative to the visual. Continuum jumps and
gradients, -system colors, and equlvalent widths of Ha, Hp, and H
are tabulated and discussed briefly. Subject headings: atmospheres,
stellar - radiative transfer

---------------------------------------------------------
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: Theoretical helium I emission line intensities for quiescent
prominences.
Authors: Heasley, J. N.; Mihalas, D.; Poland, A. I.
1974BAAS....6..219H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Theoretical Helium I Emission Line Intensities for Quiescent
Prominences.
Authors: Heasley, J. N.; Mihalas, D.; Poland, A. I.
1974BAAS....6..220H Altcode:
No abstract at ADS

---------------------------------------------------------
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

---------------------------------------------------------
Title: The N III Emission Lines in the Of Stars
Authors: Mihalas, Dimitri
1973PASP...85..593M Altcode:
Recent work has lead to an improved understanding of the physical
mechanisms which produce the NIH emission lines in Of stars. The present
status of the problem is briefly reviewed in this paper. Key words:
Of stars - stellar spectra - emission lines

---------------------------------------------------------
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: On the helium-spectrum variations of 56 Arietis and a Centauri.
Authors: Mihalas, D.
1973ApJ...184..851M Altcode:
It is shown that the observed helium-line variations in 56 Ari
and a Cen can be explained by a surface distribution involving two
symmetrically placed helium-rich caps at the poles of an axis inclined
at a large angle to the axis of rotation. It is proposed that this
axis be identified with the symmetry axis of a magnetic field with
both toroidal and poloidal components, similar to that analyzed by
Mestel and Takhar, and it is argued that the surface distribution may
be a natural consequence of such a field. Subject headings: magnetic
stars - spectrum variables - stars, individual

---------------------------------------------------------
Title: Analyses of light-ion spectra in stellar atmospheres. V. Neon
I in B stars.
Authors: Auer, L. H.; Mihalas, D.
1973ApJ...184..151A Altcode:
A detailed calculation, allowing fully for departures from LTE, for
stars in the range B2 to B5 shows that the neon abundance deduced from
LTE analyses is systematically in error by about a factor of five. The
results obtained from the simultaneous self-consistent solution of the
transfer and statistical equilibrium equations, for a realistic model
neon atom, are in excellent agreement with observed Ne I equivalent
widths at an abundance of log N(Ne) = 8.0, on the usual scale with log
N(H) = 12.0. Thus the long-standing discrepancy between the stellar neon
abundance and that found from solar, nebular, and cosmic-ray estimates
is removed. Implications for nucleosynthesis and interior opacities are
noted. Subject headings: abundances, stellar - atmospheres, stellar -
early-type stars

---------------------------------------------------------
Title: Interpreting Early-Type Stellar Spectra
Authors: Mihalas, Dimitri
1973S&T....46...79M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Analyses of Light Ion Spectra in Stellar Atmospheres.IV. H
II in the B Stars
Authors: Auer, L. H.; Mihalas, Dimitri
1973ApJS...25..433A Altcode:
Results of an extensive set of computations of the He I spectrum in B
stars, allowing for departures from LTE, using rather complete model
atoms, non-LTE model atmospheres, and somewhat improved broadening
theory, are presented and discussed. Among the major conclusions we
derive are the following: (1) While departures from LTE alter equivalent
widths but little in the blue- violet spectral region, their effects
are quite large for lines in the visual-red region (e.g., A6678). (2)
Very good agreement is obtained in the comparison of our calculated
profiles with observed He iline profiles both in the wings and in the
cores (except for some triplets at spectral types B0 and B1). (3) Some
of the largest effects of departures from LTE occur at the highest and
lowest effective temperatures, where the lines are relatively weak. (4)
The usually quoted blue-violet singlet/triplet ratio is unaffected
by departures from LTE to within the errors of observation. Other
line ratios (e.g., A6678/A5876), however, are strongly affected. (5)
The systematic wavelength-effect noted by Norris is explained. Good
agreement is obtained with most of the conclusions of Johnson and Poland
and Poland, though some significant differences arising from non-LTE
effects in the model atmospheres are noted. The present results allow
analysis for a much wider range of stellar spectral types and luminosity
classes with a much higher level of physical consistency than hitherto
possible. Subject headings: atmospheres, stellar - early-type stars -
line formation

---------------------------------------------------------
Title: Analyses of light-ion spectra in stellar atmospheres.
Authors: Mihalas, D.; Hummer, D. G.
1973ApJ...179..827M Altcode:
An analysis of the N iii emission lines in 0 stars has been
carried out on the basis of a detailed solution of the coupled
statistical-equilibrium and transfer equations for a multiline,
multilevel, multi-ion ensemble. Our calculations, using static,
plane-parallel models reproduce successfully the observed emission
at AA4634, 4640, 4641 (3p 2P -3d 2D) and absorption at AA4097,
4103 (3s 2S-3p 2P ). The multiplet is found to come into emission
at the observed temperature for both main-sequence and low-gravity
objects. The equivalent widths of the emission lines agree very well
with those measured for the class of Of stars thought to have compact
atmospheres, i.e., those classified as O((f)) by Walborn. In these stars
the basic physical mechanism responsible for this phenomenon is the
overpopulation of 3d by means of dielectronic recombinations from the
low-lying 2s2p(1P )3d autoionizing states with cascades 3d 3p. The 3p
state is drained by the "two-electron jumps" coupling 3p to the 2s2p2
(25, 2p, 2D) states, thus preventing emission in the 3s-3p lines. The
possible importance of the Swings mechanism to the fully developed
Of stars (in Walborn's sense) is pointed out, and the irrelevance of
the Bowen mechanism to all Of stars is firmly demonstrated. The fact
that the N iii emission lines can be produced in static nonextended
atmospheres in radiative equilibrium has the far-reaching significance
that the presence of emission lines in a spectrum is not in itself
sufficient evidence for the existence of a stellar chromosphere
(i.e., an extended, nonradiatively heated region). Subject headings:
atmospheres, stellar - emission-line stars line formation Of-type stars

---------------------------------------------------------
Title: Analyses of light-ion spectra in stellar atmospheres. II. The
calcium II K-line in B stars.
Authors: Mihalas, D.
1973ApJ...179..209M Altcode:
A calculation of the Ca ii K-line strength in the middle B stars has
been performed by means of a self-consistent solution of the equations
of transfer and steady-state statistical equilibrium. The multilevel
model ion, with many explicitly computed bound-bound transitions, is
treated as part of a multi-ion system (Ca ii, Ca iii, Ca iv). Results
are given for two abundances and microturbulent velocities, and
are used to assess systematic errors in LTE diagnostics of these
parameters. Near the main sequence for the middle B stars the results
show that departures from LTE have a negligibly important effect on
the K-line equivalent width, but at higher temperature and lower
gravities these departures become ever more important, and in the
extreme cases can result in errors in the abundance deduced from LTE
of a factor of five, or spurious micro turbulent velocities of up to 3
km 5 - . These effects are less spectacular than those found earlier
by the author for Mg ii, but insofar as the K-line is at all typical
of a line of comparable strength in these stars, the results may have
fartherreaching implications of errors in the usual LTE diagnostics. A
discussion of the K-line strengths in L Her and y Peg indicates that
they are compatible with a Ca abundance in these stars equal to the
solar abundance. Subject headings: abundances, stellar - atmospheres,
stellar - early-type stars - line formation

---------------------------------------------------------
Title: The Effects of Departures from LTE in Stellar Spectra
Authors: Mihalas, Dimitri; Athay, R. Grant
1973ARA&A..11..187M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Analyses of Light-Ion Spectra in Stellar
Atmospheres. I. Magnesium II in B and O Stars
Authors: Mihalas, Dimitri
1972ApJ...177..115M Altcode:
A calculation of the spectrum of Mg ii in B and 0 stars, using a rather
complete model atom allowing for many explicitly calculated transitions
in steady-state statistical equilibrium, has been performed. These
computations give a good fit to tbe observed equivalent widths of the
A4481 line on the entire range from B5 through 06, assuming a solar
abundance for magnesium. In contrast, for the earliest spectral
types, the LTE predictions fit the data poorly, and are shown to
yield abundances systematically in error by an order of magi'itude
or more. These results open again serious questions concerning the
validity of LTE abundances for at least the 0 and early B stars,
and suggest strongly that further analyses are needed to delineate
the ions and spectral types for which the LTE assumption fails.

---------------------------------------------------------
Title: Non-Lte Effects on Continuum and Hydrogen-Line Parameters in
B and O Stars
Authors: Mihalas, Dimitri
1972ApJ...176..139M Altcode:
Using a homogeneous set of non-LTE models (which allow for bound-bound
transitions) on the range 15 000 &lt; &lt; 55,000 K at several
gravities, the effects of departures from LTE upon the continuum and
Balmer lines are evaluated. Several observational discriminants of
non-LTE effects are discussed; in certain specific examples considered,
the available data are well fitted by the non-LTE calculations.

---------------------------------------------------------
Title: Observations of the he II λ10124 Line in O and of Stars
Authors: Mihalas, Dimitri; Lockwood, G. W.
1972ApJ...175..757M Altcode:
Observed equivalent widths of He ii X10124 in absorption-line 0 stars
are found to be in agreement with non-LTE computations assuming no
overlap of II and He ii lines, and in disagreement with the predictions
of LTE and of non-LTE calculations assuming exact coincidence of
even-even He ii lines and the corresponding hydrogen lines. it is
therefore inferred that pumping of He ii transitions by H lines does
not actually occur in the 0 stars. The discovery of the l0124 line
in emission in Pup (0Sf) argues further in this direction; and with
the often-cited selectivity of the He ii emission mechanism now much
weakened, it is suggested that the causes of the emission must involve
chromospheric phenomena. Analysis of source-sink terms in equivalent-
two-level-atom source functions suggests trends that are compatible
with the observed behavior of various lines.

---------------------------------------------------------
Title: ON THE N III λλ4640, 4097 LINES IN Of STARS
Authors: Mihalas, Dimitri; Hummer, D. G.; Conti, Peter S.
1972ApJ...175L..99M Altcode:
Detailed calculations based on non-LTE plane-parallel model atmospheres
show that the N iii emission lines at XX4634, 4640, 4641 observed
in Of stars are produced primarliy by dielectronic recombination to
3d 3D followed by the 3d-3p transition in a compact atmosphere. The
3P state in turn is drained by two-electron transitions to the 2p2
levels. We find that X4640 is in emission for Teff &lt; 37,0000
K for main-sequence objects (55,0000 K for giants), while X4097
remains strongly in absorption, in accordance with observations. The
calculated equivalent widths are in substantial agreement with the
observed values for those Of stars with He II X4686 in absorption,
i.e., for those objects designated by Walborn as O((f)).

---------------------------------------------------------
Title: INVITED PAPER Recent Progress in the Interpretation of Band
O Star Spectra.
Authors: Mihalas, D.
1972BAAS....4..333M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Non-Lte Model Atmospheres. VII. The Hydrogen and Helium
Spectra of the O Stars
Authors: Auer, L. H.; Mihalas, Dimitri
1972ApJS...24..193A Altcode:
An extensive series of non-LTE calculations of the H, He I, and
He II spectra of 0 stars has been carried out by using relatively
complete atomic models, allowing for several levels and lines
simultaneously. Results are presented for continuum fluxes and for
equivalent widths and profiles of the lines. Detailed comparisons
are made with the spectra of eleven 0 and B0 stars. It is found that
major departures from LTE play a dominant role in the formation of
the H and He spectra of these stars. With the non-LTE models we are
able to obtain for the first time a consistent explanation of the
observations of both lines and continua. The present results show that
an assumed helium/hydrogen ratio of 0.10 reproduces the observations;
thus present estimates of abundances in 0 stars helium are consistent
with those derived by other methods.

---------------------------------------------------------
Title: Non-LTE model atmospheres for B and O stars.
Authors: Mihalas, D.
1972nmab.book.....M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Comment on the Interpretation of the Broad Component of N
III λλ4634-4640 Emission in of Stars
Authors: Mihalas, Dimitri
1971ApJ...170..541M Altcode:
The stabilizing transition from the N iii autoionizing term 2s2p(1P0)3d
2F to the bound double- excitation term 2s2p(1P0)3p 2D gives rise to
a very broadened doublet at the wavelengths 4623 and 4630 A. A study
of the rate at which the process occurs suggests that this stabilizing
transition may appreciably contribute to the broad emission ("band")
component near 4634-4640 as observed by Wilson and Underhill. It further
appears that dielectronic recombination to the 2s23d level from 2s2p
(LP0)3d via the 2s2p H 2s2 stabilizing transition occurs at a rate
sufficiently large to outweigh direct radiative recombinations and
at a substantial fraction of the decay rate of 2s23d H 2s23p; this
process may therefore play an important role in producing the "line"
component of the N iii x4634-4640 emission.

---------------------------------------------------------
Title: Theoretical analysis of stellar spectra.
Authors: Mihalas, D.
1971tsa..conf....1M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: On the excitation mechanism of M emission in the Of stars
Authors: Brucato, Robert J.; Mihalas, Dimitri
1971MNRAS.154..491B Altcode:
A simplified statistical equilibrium calculation has been carried
out to examine the mechanism of the N iii AA 4634-41 emission in Of
stars. It is shown that the Swings mechanism, based on pumping in the
ultra-violet AA 374 and 452 transitions is probably correct, while
the Bowen mechanism, applicable in nebulae, is almost certainly not
operative in the Of stars. The possible importance of dielectronic
recombinations to the 3d state is pointed out.

---------------------------------------------------------
Title: Theoretical Analysis of Stellar Spectra
Authors: Mihalas, D.
1971tdas.conf....1M Altcode: 1971SAAS....1....1M
Basic Concepts and Assumptions The goals of stellar atmospheres
analysis The specification of the state of the atmosphere Basic
definitions Conservation relations Formulation and Solution of
Transfer Problems Formal solution Solution by integral-equation
methods Iteration Direct methods Solution by differential-equation
methods The eigenvalue approach The Riccatti transformation
(Rybicki's method) Difference equation methods (Feautrier's method)
Difference equation methods : Rybicki's Variant The Equations of
Statistical Equilibrium The microscopic implications of LTE The rate
equations Limiting cases Opacity and emissivity Continuum - Formation
Problems Solution by iteration Simultaneous solution of the transfer
and statistical equilibrium - problem The constraint of radiative
equilibrium Line-Formation : the Two - Level Atom Without continuum
- thermalization lengths With continuum - collision domination and
photoionization domination Line-Formation : the Multi-Level Problem
Equivalent two-level-atom approach Multiplets, conversion lengths,
source function equality The complete linearization method A Survey
of Non-LTE Effects in Early-type Stars Survey of results in the
continuum for A,B, and O-stars The hydrogen lines in the B-stars The
hydrogen-helium spectrum of the O-stars

---------------------------------------------------------
Title: Theorie des atmospheres stellaires
Authors: Mihalas, D.; Pagel, B.; Souffrin, P.
1971tdas.conf.....M Altcode: 1971QB809.M52......; 1971tsat.book.....M; 1971SAAS....1.....M
No abstract at ADS

---------------------------------------------------------
Title: Non-Lte Model Atmospheres.VI. Limb Darkening and Rotation
Broadening of H&amp;alpha
Authors: Mihalas, Dimitri; Auer, L. H.
1970ApJ...161.1129M Altcode:
The center-to-limb variation and rotation broadening of Ha are discussed
for LTE and non-LTE atmospheres. The center-to-limb variation is quite
different in these two cases; these differences should be measurable by
observations of certain eclipsing-binary systems, and such observations
could provide a sensitive test of the theory. It is also shown that
(a) significant differences exist between rotationbroadened profiles
in the LTE and non-LTE cases and (b) Ha may serve as a useful indicator
of rotation velocity.

---------------------------------------------------------
Title: Erratum: Constant-Flux Convective Model Atmospheres
Authors: Mihalas, Dimitri
1970ApJ...161..375M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Comment on 'Far Ultraviolet Photometry of Orion Stars'
by G. R. Carruthers
Authors: Mihalas, Dimitri
1970Ap&SS...8...50M Altcode:
It is shown that the ultraviolet flux-deficiency, recently discovered
by Carruthers, in early-type supergiants compared to dwarfs of the same
spectral type can be explained in terms of the effects of differences
in surface-gravity and effective temperature between stars of these
two luminosity classes. It thus appears that this deficiency does not
represent a serious discrepancy between theory and observation.

---------------------------------------------------------
Title: Non-Lte Model Atmospheres. V. Multi-Line Hydrogen-Helium
Models for O and Early B Stars
Authors: Mihalas, Dimitri; Auer, L. H.
1970ApJ...160.1161M Altcode:
Results of calculations of non-LTE model atmospheres including the
effects of La, L , L , Ha, Hp, and Pa are presented for models on
the range 250000 K &lt; &lt; 50000 K, with log g = 4 and N(He)/ N(H)
= 0.10. The non-LTE results suggest a severe breakdown of LTE at T0ff
&gt; 350000 K. Substantial changes occur in the far-ultraviolet fluxes;
these may be of importance in the interpretation of the excitation
of emission nebulae. In the visible, the Balmer jump is significantly
increased by non-LTE effects for models with T0ff &gt; 350000 K, which
implies large changes in effective temperatures for 0 stars inferred
from observations of the Balmer jump. Striking changes occur in the
hydrogen-line profiles. Vhen non-LTE effects are included, Ha and Hp
are computed to be almost 3 times as strong at 400000 K as in LTE. Pa is
found to have an emission core in the highest-temperature models. This
result is analogous to the situation at lower temperatures where Ba is
computed to go into emission. In both cases the emission core is due
to coupling to a rise in surface temperature in the non-LTE models;
observations are desirable to test the reality of this predicted effect.

---------------------------------------------------------
Title: Non-Lte Model Atmospheres.IV. Results for Multi-Line
Computations
Authors: Auer, L. H.; Mihalas, Dimitri
1970ApJ...160..233A Altcode:
Results are presented for model atmospheres in hydrostatic, radiative,
and steady-state statistical equilibrium, including bound-bound
transitions. These calculations allow for the effects of Ha, HP, H ,
Pa, PP, and Ba. Stark profiles of Edmonds, Schinter, and Wells are used
to compute detailed line profiles. With the full non-LTE calculation we
have been able to predict correctly the entire line profile, including
the line core. The wings of Ha are found to weaken while those of H
remain unaffected by departures from LTE. Non-LTE effects strengthen
the Paschen lines so that comparison of Paschen lines with Balmer lines
should provide a sensitive observational indicator of departures from
LTE. Ba has an emission core, because of a rise in surface temperature,
and may be a useful diagnostic tool in the analysis of real stellar
atmospheres. The surface-temperature rise found in earlier work
persists, the boundary temperature differing little from that obtained
by allowing for Ha, HP, and Pa only. The energy distribution in the
continuum is little affected by departures from LTE, except at very
low gravities and in the unobservable Lyman continuum.

---------------------------------------------------------
Title: Model atmospheres for the central stars of planetary nebulae.
Authors: Hummer, D. G.; Mihalas, D.
1970MNRAS.147..339H Altcode:
Approximately 70 model atmospheres for the central stars of
planetary nebulae have been computed under the assumptions of
hydrostatic, radiative and local thermodynamic equilibrium and of
stratification. These models have effective temperatures and surface
gravities in the range and log . The atmospheres have been taken to
consist of hydrogen, helium, oxygen, nitrogen, carbon and neon, and the
opacity included contributions from both ground and excited states of
each ion. The transfer equation is solved using Feautrier's method and
the temperature corrections are calculated by means of the Krook-Avrett
procedure. Particular attention is given to the effects of gravity
and chemical composition on the surface fluxes. The photon fluxes in
the H I, He I and He ii continua and the stellar flux at H have been
tabulated for use in the determination of Zanstra temperatures.

---------------------------------------------------------
Title: On the use of variable Eddington factors in non-LTE stellar
atmospheres computations
Authors: Auer, L. H.; Mihalas, Dimitri
1970MNRAS.149...65A Altcode:
It is shown that by use of variable Eddington factors, the accuracy
of differenceequation solutions of transfer problems may be greatly
improved with only small additional computational effort. It is found
that a direct iterative calculation of the Eddington factors leads to
a strongly convergent procedure. The resulting set of equations is
of wide applicability to problems involving non-coherent radiative
transfer. The method is illustrated by application to the classical
grey problem, and to a non-LTE stellar atmospheres computation.

---------------------------------------------------------
Title: Stellar atmospheres
Authors: Mihalas, Dimitri
1970stat.book.....M Altcode: 1970QB809.M5.......
No abstract at ADS

---------------------------------------------------------
Title: Non-Lte Model Atmospheres. III. a Complete-Linearization Method
Authors: Auer, Lawrence H.; Mihalas, Dimitri
1969ApJ...158..641A Altcode:
In this paper we present a method of solving transfer prob'ems subject
to constraints of radiative, hydrostatic, and statistical equilibrium,
by using a complete-linearization technique. This approach de-
parts rather markedly from the traditional methods, and yields a
computational scheme that is stable and strongly convergent. The form
of the equations assures that the coupling among all physical variables
is fully accounted for self-consistently to first order at each stage
of the calculation; convergence is global and quadratic. The constraint
equations are included in a particularly transparent way, which allows
easy generalization and elaboration. Sample models of pure-hydrogen
atmospheres are presented; among these, one includes Ha, H~3, and Pa
self-consistently with the continua. Models that were obtained only
with great effort by using earlier techniques have been recomputed
with no hint of difficulty by using the method described in this paper

---------------------------------------------------------
Title: The Effects of Line Shifts on the Temperature Distribution
in Stellar Atmospheres
Authors: Mihalas, Dimitri
1969ApJ...157.1363M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Brackett-Alpha Emission in Non-Lte Model Stellar Atmospheres
Authors: Auer, L. H.; Mihalas, Dimitri
1969ApJ...156L.151A Altcode:
Recent computations of non-LTE model stellar atmospheres predict the
appearance of Brackett- a (Ba) in emission. This line at 4.05 ~&amp;
lies in a window of the absorption spectrum of the terrestrial
atmosphere and should be observed as a test of this theoretical
prediction

---------------------------------------------------------
Title: A Possible Mechanism for Energization of Stellar Winds in
Early-Type Stars
Authors: Mihalas, Dimitri
1969ApJ...156L.155M Altcode:
Expanding envelopes observed in early-type supergiants (and other
related stars) are suggested to be stellar winds energized by the
mechanical-energy flux produced in a Rayleigh-Taylor instability zone
in the photospheres of these stars

---------------------------------------------------------
Title: Non-Lte Model Atmospheres. II. Effects of Balmer α
Authors: Auer, L. H.; Mihalas, Dimitri
1969ApJ...156..681A Altcode:
Four models of pure-hydrogen stellar atmospheres in radiative
equilibrium with Teff = 15000 and log g = 4 are presented. Results are
given for both the LTE and non-LTE cases, with and without the inclusion
of Ha. The calculations show that (a) Ha causes a temperature rise,
not a drop, at the surface, (b) the direct effect of cooling in the
line is less important than the indirect effects of changing level
popu- lations, and (c) the Balmer and Paschen jumps are unaltered by
non-LTE effect

---------------------------------------------------------
Title: Non-Lte Model Atmospheres. I. Radiative Equilibrium Models
with - Alpha
Authors: Auer, L. H.; Mihalas, Dimitri
1969ApJ...156..157A Altcode:
We present models of stellar atmospheres of pure hydrogen in
hydrostatic, radiative, and statistical equilibrium, including
for the first time Lyman-a as well as continua. Only by the direct
inclusion of Ly-a may we properly evaluate the effect of this strong
line on the structure of the atmosphere. A new temperature-correction
scheme was used. It is of the constraint type, is capable of handling
very large opacity variations, and guarantees vanishingly small flux
derivatives. The model atom assumed the upper fourteen levels in LTE,
but permitted non-LTE deviations in the lower two levels. This model
was suffi- cient to show that: (a) non-LTE effects from the continua
cause a temperature rise at the surface; (b) this rise is partially
offset by the inclusion of Ly-a, which causes a temperature drop,
the non-LTE drop being very much smaller than the LTE; (c) Ly-a is
so optically thick that it does not affect the formation of even the
Lyman continuum; and (d) there is essentially no back-warming due to
Ly-a in either the LTE case or the non-LTE case

---------------------------------------------------------
Title: Review of Publications- Galactic Astronomy
Authors: Mihalas, Dimitri
1969JRASC..63...48M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Non-LTE Model Atmospheres
Authors: Auer, L. H.; Mihalas, D.
1969tons.conf..229A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Line Formation with Non-Coherent Scattering by
Electrons. II. Calculations with Model Atmospheres
Authors: Auer, Lawrence H.; Mihalas, Dimitri
1968ApJ...153..923A Altcode:
The effect of non-coherent scattering by electrons and atoms on
line formation in early-type stars has been studied using model
atmospheres. Variability of the physical parameters has been fully in-
cluded. The effect of the non-coherency of the scattering by electrons
is noticeable for a line like He ii X4200 but not for a much stronger
one like He ii X4686. The solution in the core is dominated by the
degree to which scattering (by atoms) occurs, while the wings are
unaffected. The observed profile of He ii X4686 in 10 Lac can be
fitted if the core of the line is deepened by scattering and broadened
by rotation

---------------------------------------------------------
Title: Statistical Equilibrium Model Atmospheres for Early-Type
Stars.IV. Remarks on Observational Tests
Authors: Mihalas, Dimitri
1968ApJ...153..317M Altcode:
A comparison is made between LTE and non-LTE models and observation
following the approach of Strom and Kalkofen. It is found that near the
main sequence the two sets of models are nearly indis- tinguishable
but that large effects exist at lower gravities. The importance of
very accurate values for the absolute-energy calibration of stars
is emphasized

---------------------------------------------------------
Title: Line Formation with Non-Coherent Scattering by
Electrons. I. Parameterized Models
Authors: Auer, L. H.; Mihalas, Dimitri
1968ApJ...153..245A Altcode:
We examine in this paper the effects of the non-coherence of the
radiation scattered by electrons upon the formation of spectral lines
A flexible numerical approach, making use of the difference-equation
meth- od of solving the transfer equation, is developed and applied to
simplified models in which the lines are taken to be either in LTE or
non-LTE, and allowance is made for electron scattering and continuous
absorption. Radiation scattered by the atom is assumed to be completely
redistributed, although the method is general enough to account for
arbitrary redistribution functions. The present calculation dif- fers
from earlier work in that the electrons are assumed to be located in
the same layers as the line and continuum opacity sources Compared to
the case of coherent electron scattering, measurable changes in the
line profile occur if the electron-scattering coefficient outweighs
continuum absorption. Emission lines are decreased slightly in intensity
and develop extensive emission wings. Absorption lines are widened
and deepened, and emission humps are obliterated

---------------------------------------------------------
Title: Solution of Transfer Equations Subject to the Constraint of
Radiative Equilibrium
Authors: Auer, L. H.; Mihalas, Dimitri
1968ApJ...151..311A Altcode:
A method is proposed for solving transfer equations subject to
the constraint of radiative equilibrium. The approach uses the
differential-equation form of the transfer equation and thus allows
easy generaliza- tion. A description is given of the equations and
boundary conditions, and results for gray and non-gray cases are
discussed. We obtain rapid convergence at all depths It appears
that this method should be effective in non-LTE cases, though in
practice it may be limited by the size of matrix that can be inverted
economically. I. INTRODUCTIO

---------------------------------------------------------
Title: Galactic astronomy
Authors: Mihalas, Dimitri; Routly, Paul Mcrae
1968gaas.book.....M Altcode: 1968QB857.7.M53....
No abstract at ADS

---------------------------------------------------------
Title: Statistical Equilibrium Model Atmospheres for Early-Type
Stars. III. Hydrogen and Helium Continua
Authors: Mihalas, Dimitri; Stone, Michael E.
1968ApJ...151..293M Altcode:
Results are presented for model atmospheres allowing for departures
from LTE in hydrogen, helium, and ionized helium on the temperature
range 100000 K «= Teff «= 360000 K. The essential simplifying
assumption we make is that all radiative bound-bound transitions
are in detailed balance. While this assumption is valid in certain
physical circumstances, it is not everywhere correct, and the results
de- rived here should be regarded as oniy exploratory As was the case
in earlier results, the departures we find are quite small and have
only small effects upon the emergent energy distribution, so that LTE
appears to be a fairly adequate approximation in the calculation of
the continuous energy distribution. No information concerning line
formation can be inferred from the present results

---------------------------------------------------------
Title: Erratum: Statistical-Equilibrium Model Atmospheres for
Early-Type Stars. I. Hydrogen Continua
Authors: Mihalas, Dimitri
1967ApJ...150.1168M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Statistical-Equilibrium Model Atmospheres for Early-Type
Stars. II. Formation of the Lyman Continuum
Authors: Mihalas, Dimitri
1967ApJ...150..909M Altcode:
Results are presented for model atmospheres which allow for deviations
from LTE in the first ten bound states of hydrogen. Particular attention
is given to the problem of solving the transfer equation in the Lyman
continuum, using the approach of introducing the appropriate statistical
equilibrium equation explicitly into the expression for the source
function. The solution is carried out using Feautrier's method which
treats the transfer equation directly in its differential equation
form. Full variation with depth and frequency of all relevant parameters
is allowed. The present solutions are not yet fully physically realistic
since transfer in the bound-bound transitions is not included. From
the present work, however, it appears that use of Feautrier's method
will allow the treatment of the complete problem.

---------------------------------------------------------
Title: Line Formation with Non-Coherent Electron Scattering in O
and B Stars
Authors: Hummer, D. G.; Mihalas, D.
1967ApJ...150L..57H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Statistical-Equilibrium Model Atmospheres for Early-Type
Stars. I. Hydrogen Continua
Authors: Mihalas, Dimitri
1967ApJ...149..169M Altcode:
Model atmospheres have been constructed for selected effective
temperatures and gravities appropriate to early-type stars, allowing in
an approximate way for deviations from LTE in the first ten bound states
of hydrogen The essential approximation involved is the assumption
of radiative detailed balance in the lines, which seems valid in the
region of continuum formation. The resulting models are thought to
be adequate for interpretation of the observed energy distribution of
stars but cannot be used for discussions of line profiles We find that
the deviations from LTE are quite small and that the predicted fluxes
agree closely with those of LTE models.

---------------------------------------------------------
Title: The Calculation of Model Stellar Atmospheres
Authors: Mihalas, Dimitri
1967MComP...7....1M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Fine Analysis of the Manganese Star 53 Tauri
Authors: Auer, L. H.; Mihalas, D.; Aller, L. H.; Ross, J. E.
1967mrs..conf..433A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Manganese Star 53 Tauri. II. Fine Analysis
Authors: Auer, L. H.; Mihalas, D.; Aller, L. H.; Ross, J. E.
1966ApJ...145..153A Altcode:
An abundance analysis of the manganese star 53 Tauri is carried
out making use of a model atmosphere with 0 = 0.413, log g = 3.5,
N(He)/N(H) = 0.15. The model reproduces the observed hydrogenline
profiles with good accuracy. The abundance analysis shows that all
of the metals ligbter than titanium have normal abundance. Helium
is found to be underabundant by a factor of 5, so that N(He)/ N(H) =
0.03, and the effective gravity accordingly becomes log g = 3.62. From
titanium onward, the elements show large overabundance factors, except
for iron and chromium, both of which are normal. Manganese is found
to be 120 times overabundant; this value is based on both Mn I and
Mn ii lines (the two ions giving good agreement), making use of new
laboratoryJ-values for Mn ii.

---------------------------------------------------------
Title: Balmer-Line Model Atmospheres for A-Type Stars
Authors: Mihalas, Dimitri
1966ApJS...13....1M Altcode:
Results are reported for computations of a grid of model atmospheres
for A stars which take into detailed account the effects of blanketing
by hydrogen lines. The models are in radiative equilibrium and allow
explicitly for Ha through H20. Tables of emergent fluxes are presented
which allow detailed comparisons with observations. Colors computed
for these models agree very well with those obtained observationally
for main-sequence stars after the effects of metal-line blanketing are
removed. An effective-temperature scale is derived for main-sequence
stars of classes B8 to F2, which is in satisfactory agreement with
fundamental interferometer measures and Popper's scale. A detailed
comparison is made with the absolute-energy distribution of Vega. From
the observed H profile and energy distribution in the visible we
obtain log g = 4 and 0, = 0.525 (T, = 9600 K). It is found that the
Balmer jump for the model is larger than the value now accepted in
Code's and Oke's energy distributions, but is in very good agreement
with Bahner's measurement. It is suggested that Bahner's result be
seriously considered in future work. Finally we find fairly good
agreement between the observed number of Balmer lines visible as a
function of spectral class and the computed number, although this
result holds only statistically.

---------------------------------------------------------
Title: Studies of the Peculiar a Stars. III. Model-Atmosphere
Line-Strength Calculations with Application to the A_{p} Stars
Authors: Mihalas, Dimitri; Henshaw, James L.
1966ApJ...144...25M Altcode:
Calculations are carried out to obtain accurate curves of growth for
selected lines of C ii, Mg ir, 0 1, Si ii, and Si iii using model
atmospheres. The results are given for a wide range of effective
temperatures and gravities for the models and of assumed abundances for
the lines; these results should be applicable to abundance analyses for
stars on the range of about B3 to F2. As an example of application we
rediscuss the observations of Ap stars published by Sargent and Searle,
and find good agreement with their results which were based on less
elaborate techniques. We derive new information from X 4200 of Si ii
and from the C ii lines. We find that the infrared lines of Mg and
0 are observed too strong according to our calculations, and suggest
that turbulent motions may be present in the outer atmospheric layers
where these lines are formed.

---------------------------------------------------------
Title: A Model for a BI V Star with Line Blanketing.
Authors: Mihalas, Dimitri M.; Morton, Donald C.
1965ApJ...142..253M Altcode:
A model in radiative equilibrium has been computed for log g = 40,
T = 21914 K (0 = 0.23), taking into account the blanketing by the
strongest lines in the ultraviolet where the majority of the flux
emerges (911 6 &lt; X &lt; 1600 A) it was found that the visible
spectrum closely resembles that of an un- blanketed model with log g
= 4 0, T = 24001 K (0 = 0 21) Both models were classified at B1 V on
the basis of the Balmer discontinuity. Thus at this spectral type the
effective temperature assigned on the basis of the unblanketed model
was too high by nearly 2100 K. The bolometric correction was estimated
to be -200 mag for the blanketed model as compared with -240 mag for the
unbianketed one of the same spectral type Details of the model are given
in tabular form and the emergent flux distribution is shown graphically.

---------------------------------------------------------
Title: Model Atmospheres and Line Profiles for Early-Type Stars.
Authors: Mihalas, Dimitri
1965ApJS...11..184M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Constant-Flux Convective Model Atmospheres.
Authors: Mihalas, Dimitri
1965ApJ...141..564M Altcode:
Modtl atmospheres have been constructed using the mixing4ength theory
to describe the convective transport of energy. The condition of flux
constancy is enforced allowing for the simultaneous energy transport
by convection and non-gray radiative processes, using a modification of
the temperature-correction procedure proposed by Avrett and Krook. The
modified equations allow for the convection terms explicitly and, in
a more general sense, show that the Avrett-Krook procedure provides a
powerful formalism for enfordng the condition of flux constancy in the
presence of non-radiative terms. A grid of models has been constructed
on the range 0.5 &lt; 0 &lt; 0.7 and 2 &lt; log g &lt; 444 assuming
(1/H) = land (t/H) = 2. It is found that the presence of convection
produces substantial changes in the structure of the atmosphere at
depth, while the overlying radiative layer is virtually unchanged. The
emergent flux distribution in the continuum and line profiles are
examined with the view of obtaining a criterion for distinguishing
convective models from radiative, and the two assumed mixing lengths
from one another It is found that only the emergent flux in the rocket
or satellite ultraviolet provides such a measure in the sense that
the ultraviolet fluxes are appreciably smaller for the convective
models. The profiles of HT computed for the convective models differ
from those for the radiative models by less than 1 or 2 per cent in
all but a few cases, and thus do not provide a clear criterion for
establishing convection On the other hand, it is found that in the
convective models lines from certain neutral metals may be strengthened
relative to the ionic lines, compared to the radiative models. A more
detailed solution of the statistical equilibrium equations should be
carried out to confirm this conclusion.

---------------------------------------------------------
Title: An Archetype Non-Gray Stellar Atmosphere.
Authors: Gingerich, Owen; Mihalas, Dimitri; Matsushima, Satoshi;
Strom, Stephen
1965ApJ...141..316G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Model Atmospheres and Line Profiles for Early-Type Stars.
Authors: Mihalas, Dimitri
1965ApJS....9..321M Altcode:
Model atmospheres have been constructed over a wide range of temperature
and gravities. The condition of radiative equilibrium is enforced
using a modification of the temperature-correction scheme devised by
Avrett and Krook, thus extending the work of Gingerich to the realm
of higher temperatures; flux constancy is attained to within 10.5
per cent to a depth of TSTD = 10 or more, the standard wave- length
being either X 400() or X 5050. The source function is determined from
the Milne-Eddington equation allowing for coherent scattering in the
continuum. The properties of the atmospheres are described and given in
detailed tabular form, and data of rather general use is presented. For
each model we have computed H and H profiles and equivalent widths,
and for the hotter models, profiles and equivalent widths of XX 4686,
4200, 4542, 5412 of He ii, and XX 5876, 4713, 38, and 4121 of He
1. When necessary, allowance has been made in the computation of the
hydrogen-line profiles for the overlapping Pickering-series lines of
He ii. Complete profiles are given for the hydrogen lines because of
their great practical utility, but only equivalent widths are tabulated
for the helium lines.

---------------------------------------------------------
Title: A Spectroscopic Estimate of the Atmospheric Properties of O
and B Stars.
Authors: Mihalas, Dimitri
1964ApJ...140..885M Altcode:
Equivalent widths of lines in the spectra of six 0 stars were measured
using the coude' scanner of the 100-inch telescope. These data and those
in the literature for r Sco are fitted to theoretical line-strength
calculations in an attempt to derive the effective temperatures,
gravities, and helium abundances of these stars. It is found that the
effective temperatures and gravities are well determined, while the
helium abundance can be estimated only with fair accuracy; it appears
that the best estimate for N(He) /N(H) is about 0 15 or 0.2. Comparisons
are made between the computed and observed profiles for X 4686 in Sco
and 10 Lac; a good fit with the 10 Lac observations can be obtained
only with a turbulent velocity of the order of 20 km/sec.

---------------------------------------------------------
Title: The Abundance of Magnesium in the Atmospheres of O and B Stars.
Authors: Henry, Richard C.; Mihalas, Dimitri
1964ApJ...140..873H Altcode:
Equivalent widths have been computed for the ionized magnesium
line X 4481 using flux-constant models and accurate numerical
techniques. Several abundance steps have been taken for each model;
the models have temperatures appropriate to stars in the range of
O9 V to A2 V. Fits are made to the mean observed line strength as a
function of spectral type as obtained from data in the literature. A
nearly constant mean value of N(Mg)/N(H) = 2.2 X t0- is derived over
the range of spectral types of B1 to A2; a larger value is obtained
for B0 and O9 stars, but this is thought to be spurious. This analysis
reaffirms the discrepancy between solar and B-star Mg abundance.

---------------------------------------------------------
Title: Photoelectric Equivalent Widths in ρ Leo and π4
ORI.
Authors: Mihalas, D.
1964ApJ...139..764M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Model Atmosphere Studies of Early Type Stars.
Authors: Mihalas, Dimitri
1964AJ.....69S.144M Altcode:
A sequence of model atmospheres has been constructed on the range
0.1&lt;0 &lt; 0.7 using an IBM 7090. The source function is given by the
Milne-Eddington equation, which allows for coherent scattering. Flux
constancy is enforced to +0.5% or better by use of the Krook-Avrett
procedure (Avrett, F. H., and Krook, M., A strophys. J. 137, 874,1963),
which has been modified simply to allow for scattering terms; this
procedure is stable and quickly convergent. The opacity consists of
absorption by H, H-, He I, He ii, and H2+, Thompson scattering by free
electrons and Rayleigh scattering by neutral H. We took account of
the temperature and pressure dependence of the partition functions in
the ionization equilibrium of H and He. Neither the effects of lines
nor departures from LTE are accounted for. For 0.45&lt;Oe&lt;0.7,
models were made with 1~&lt;log g&lt;4.44 while for 0.1&lt;Oe&lt;0.4
they were made with log g=3.5, 4.0, and 4.5, all assuming N(He)/N(H) =
0.15. At the higher temperatures sequences were made with changes in
the assumed helium abundance. H~ and H~ profiles were computed using
Griem's Stark broadening theory, and for the hotter models we computed
the profiles of HeiX5876, X4438, X4121 and Hell X5412, X4686, X4542,
and X4200. The computed line strengths have been fitted to observations
of six 0-type stars, made with the photoelectric spectrum scanner
at the coudk of the 100-in. telescope, and estimates made of these
stars' effective temperatures, gravities, and helium abundances. This
work was done during tenure of an NSF Predoctoral Fellowship and
the Van Maanen Fellowship administered by the California Institute
of Technology. The results were partly revised and extended during
tenure of the Higgins Fellowship at Princeton University, making use
of computer facilities supported in part by NSF Grant NSF-GP5 79. of
Washington, Pasadena, California.-A sequence of model atmospheres
has been constructed on the range 0.1&lt;0 &lt; 0.7 using an IBM
7090. The source function is given by the Milne-Eddington equation,
which allows for coherent scattering. Flux constancy is enforced to
+0.5% or better by use of the Krook-Avrett procedure (Avrett, F. H.,
and Krook, M., A strophys. J. 137, 874,1963), which has been modified
simply to allow for scattering terms; this procedure is stable
and quickly convergent. The opacity consists of absorption by H,
H-, He I, He ii, and H2+, Thompson scattering by free electrons and
Rayleigh scattering by neutral H. We took account of the temperature
and pressure dependence of the partition functions in the ionization
equilibrium of H and He. Neither the effects of lines nor departures
from LTE are accounted for. For 0.45&lt;Oe&lt;0.7, models were made
with 1~&lt;log g&lt;4.44 while for 0.1&lt;Oe&lt;0.4 they were made
with log g=3.5, 4.0, and 4.5, all assuming N(He)/N(H) = 0.15. At the
higher temperatures sequences were made with changes in the assumed
helium abundance. H~ and H~ profiles were computed using Griem's
Stark broadening theory, and for the hotter models we computed the
profiles of HeiX5876, X4438, X4121 and Hell X5412, X4686, X4542, and
X4200. The computed line strengths have been fitted to observations
of six 0-type stars, made with the photoelectric spectrum scanner at
the coudk of the 100-in. telescope, and estimates made of these stars'
effective temperatures, gravities, and helium abundances. This work was
done during tenure of an NSF Predoctoral Fellowship and the Van Maanen
Fellowship administered by the California Institute of Technology. The
results were partly revised and extended during tenure of the Higgins
Fellowship at Princeton University, making use of computer facilities
supported in part by NSF Grant NSF-GP5 79.

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Title: Model atmosphere studies of early type stars
Authors: Mihalas, Dimitri
1964PhDT........92M Altcode: 1964PhDT.........4M
Model atmospheres have been constructed over a wide range of
temperature and gravities. The condition of radiative equilibrium
is enforced using a variation of the temperature correction scheme
devised by M. Krook, thus extending the work of Gingerich to the realm
of higher temperatures; flux constancy is attained to within [plus or
minus]1% to a depth of [tau][subscript STD] = 10 or more, the standard
wavelength being either [lamda]4000 or [lamda]5050. The source function
is determined from the Milne-Eddington equation allowing for coherent
scattering in the continuum. The properties of the atmospheres are
described and given in detailed tabular form, and data of rather general
use is presented.For each model we have computed H[beta] and H[alpha]
profiles and equivalent widths, and for the hotter models, profiles and
equivalent widths of [lamda]4686, [lamda]4200, [lamda]4542 [lamda]5412
of He II and [lamda]5876, [lamda]4713, [lamda]4438, and [lamda]4121 of
He I. Interpolating formulae are devised to describe the temperature and
gravity variations of the line strengths.A fit is carried out between
theory and observations made with the 100" coude scanner of six O-type
stars, yielding the effective temperature, gravity, and an estimate of
the helium abundance for these stars. It is found that the computed
hydrogen and ionized helium lines appear consistent with observation
whereas the computed neutral helium lines seem to be incorrect for these
spectral types. The results indicate that a typical O9 star has
the following properties: [theta][subscript e] = 0.146, log g = 4.2,
N(He)/N(H) ~ 0.15 or 0.2, and from an assumed mass-luminosity law we
find: R/R[...] = 10, [...] = 60, and L/L [...] = 1.4 x 10 [superscript
5]. The helium abundance derived here is in substantial agreement
with that found by the Kiel group but in disagreement with nebular
studies. The masses and radii are probably quite doubtful because of
the possible incorrectness of the assumed mass-luminosity law.

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Title: Decay times of Type I supernovae light curves.
Authors: Mihalas, D.
1963PASP...75..256M Altcode:
No abstract at ADS

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Title: Light Curve of Humason's Supernova in Virgo.
Authors: Mihalas, Dimitri M.
1962AJ.....67S.118M Altcode:
The supernova discussed in this paper was discovered by M. L. Humason
in a faint anonymous galaxy in Virgo (a=13h08rn51S, a=+3C4025~~,
1950) during the 1959 Palomar Supernova Search under the direction
of F. Zwicky. This object is number 64 on Zwicky's list. A large
number of photographic observations were subsequently made by several
observers with the 48- inch Schmidt telescope, and by Arp, Miller,
and Zwicky with the 200" telescope; Arp obtained U,B,V magnitudes of
the supernova on 5 nights and the galaxy itself on one night. Spectra
were obtained by Greenstein and Zwicky, and will be discussed by them
elsewhere. The observations extend over about 275 days. The light curve
shows a sharp initial decline of 0.07 TABLE I. Half4ife Supernova (days)
a 5N64 4.80 0.81 SN NGC 1003 5.53 0.90 SN IC 4182 5.12 0.89 mag./day in
B for roughly 40 days followed by a more gradual linear decline of 0.018
mag./day, which is very similar to the behavior of the type I supernovae
in NGC 1003 and IC 4182 discussed by Baade and Zwicky. B-V reddens
linearly at 0.04 mag./day followed by a period of roughly constant B -
V. The time interval between the (estimated) maximum and the change
in slope is about 40 days, again in good agreement with other type I
supernovae. It has long been known that the tail of a type I light curve
could be explained by an exponential intensity decay with a half-life of
55 days or a decay time of 79.3 days. From the data presently at hand it
seems that in addition the initial decline can also be fitted by such
a decay formula. If we assume that I=I0[aexp(-t/T1)+,&amp;exp(-t/T2)],
where a+fl= 1, and T2&gt; T1, we can calculate T1 assuming the T2 given
above. This operation has been carried out for SN 64, SN NGC 1003, and
SN IC 4182, the latter two taken frnm the data published by Baade and
Zwicky. The results are given in Table I; a good fit was obtained in
each case. Note that the table gives the half-life, not T~. Thus the
average half-life is 5.15*0.25 days and the ratio of the intensities
of the two components is always nearly 9:1. The observed maximum was
at B= 14.1; correction for absorption in the Virgo galaxy yields B0 =
13.9. With a distance modulus of 33 mag., obtained from an estimate
of the absolute magnitude of the galaxy, (MB)e~-19.1. This work was
performed during tenure of an NSF pre-doctoral fellowship.

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Title: Light Curve of Humason's Supernova in Virgo
Authors: Mihalas, Dimitri M.
1962PASP...74..116M Altcode:
No abstract at ADS