Author name code: kurucz ADS astronomy entries on 2022-09-14 author:"Kurucz, Robert L." ------------------------------------------------------------------------ Title: Stellar limb darkening. A new MPS-ATLAS library for Kepler, TESS, CHEOPS, and PLATO passbands Authors: Kostogryz, N. M.; Witzke, V.; Shapiro, A. I.; Solanki, S. K.; Maxted, P. F. L.; Kurucz, R. L.; Gizon, L. Bibcode: 2022arXiv220606641K Altcode: The detection of the first exoplanet paved the way into the era of transit photometry space missions with a revolutionary photometric precision that aim at discovering new exoplanetary systems around different types of stars. With this high precision, it is possible to derive very accurately the radii of exoplanets which is crucial for constraining their type and composition. However, it requires an accurate description of host stars, especially their center-to-limb variation of intensities (so called limb darkening) as it affects the planet-to-star radius ratio determination. We aim at improving the accuracy of limb darkening calculations for stars with a wide range of fundamental parameters. We used the recently developed 1D MPS-ATLAS code to compute model atmosphere structures and to synthesize stellar limb darkening on a very fine grid of stellar parameters. For the computations we utilized the most accurate information on chemical element abundances and mixing length parameters including convective overshoot. The stellar limb darkening was fitted using the two most accurate limb darkening laws: the power-2 and 4-parameters non-linear laws. We present a new extensive library of stellar model atmospheric structures, the synthesized stellar limb darkening curves, and the coefficients of parameterized limb-darkening laws on a very fine grid of stellar parameters in the Kepler, TESS, CHEOPS, and PLATO passbands. The fine grid allows overcoming the sizable errors introduced by the need to interpolate. Our computations of solar limb darkening are in a good agreement with available solar measurements at different view angles and wavelengths. Our computations of stellar limb darkening agree well with available measurements of Kepler stars. A new grid of stellar model structures, limb darkening and their fitted coefficients in different broad filters is provided in CDS. Title: New Fe I Level Energies and Line Identifications from Stellar Spectra. III. Initial Results from UV, Optical, and Infrared Spectra Authors: Peterson, Ruth C.; Kurucz, Robert L. Bibcode: 2022ApJS..260...28P Altcode: 2021arXiv211214742P The spectrum of neutral iron is critical to astrophysics, yet furnace laboratory experiments cannot reach high-lying Fe I levels. Instead, Peterson & Kurucz and Peterson et al. adopted ultraviolet (UV) and optical spectra of warm stars to identify and assign energies for 124 Fe I levels with 1900 detectable Fe I lines, and to derive astrophysical gf values for over 1000 of these. An energy value was assumed for each unknown Fe I level, and confirmed if the wavelengths predicted in updated Kurucz Fe I calculations matched the wavelengths of four or more unidentified lines in the observed spectra. Nearly all these identifications were for LS levels, those characterized by spin-orbit coupling, whose lines fall primarily at UV and optical wavelengths. This work contributes nearly 100 new Fe I level identifications. Thirty-nine LS levels are identified largely by incorporating published positions of unidentified laboratory Fe I lines with wavelengths <2000 Å. Adding infrared (IR) spectra provided 60 Fe I jK levels, where a single outer electron orbits a compact core. Their weak IR lines are searchable, because their mutual energies obey tight relationships. For each new Fe I level, this work again makes publicly available its identification, its energy, and a list of its potentially detectable lines with theoretical gf values, totalling >16,000 lines. For over 2000 of these, this work provides astrophysical gf values adjusted semiempirically to fit the stellar spectra. The potential impact of this work on modeling UV and IR stellar spectra is noted. Title: MPS-ATLAS: A fast all-in-one code for synthesising stellar spectra Authors: Witzke, V.; Shapiro, A. I.; Cernetic, M.; Tagirov, R. V.; Kostogryz, N. M.; Anusha, L. S.; Unruh, Y. C.; Solanki, S. K.; Kurucz, R. L. Bibcode: 2021A&A...653A..65W Altcode: 2021arXiv210513611W Context. Stellar spectral synthesis is essential for various applications, ranging from determining stellar parameters to comprehensive stellar variability calculations. New observational resources as well as advanced stellar atmosphere modelling, taking three dimensional effects from radiative magnetohydrodynamics calculations into account, require a more efficient radiative transfer.
Aims: For accurate, fast and flexible calculations of opacity distribution functions (ODFs), stellar atmospheres, and stellar spectra, we developed an efficient code building on the well-established ATLAS9 code. The new code also paves the way for easy and fast access to different elemental compositions in stellar calculations.
Methods: For the generation of ODF tables, we further developed the well-established DFSYNTHE code by implementing additional functionality and a speed-up by employing a parallel computation scheme. In addition, the line lists used can be changed from Kurucz's recent lists. In particular, we implemented the VALD3 line list.
Results: A new code, the Merged Parallelised Simplified ATLAS, is presented. It combines the efficient generation of ODF, atmosphere modelling, and spectral synthesis in local thermodynamic equilibrium, therefore being an all-in-one code. This all-in-one code provides more numerical functionality and is substantially faster compared to other available codes. The fully portable MPS-ATLAS code is validated against previous ATLAS9 calculations, the PHOENIX code calculations, and high-quality observations. Title: HELIOS-K 2.0 Opacity Calculator and Open-source Opacity Database for Exoplanetary Atmospheres Authors: Grimm, Simon L.; Malik, Matej; Kitzmann, Daniel; Guzmán-Mesa, Andrea; Hoeijmakers, H. Jens; Fisher, Chloe; Mendonça, João M.; Yurchenko, Sergey N.; Tennyson, Jonathan; Alesina, Fabien; Buchschacher, Nicolas; Burnier, Julien; Segransan, Damien; Kurucz, Robert L.; Heng, Kevin Bibcode: 2021ApJS..253...30G Altcode: 2021arXiv210102005G Computing and using opacities is a key part of modeling and interpreting data of exoplanetary atmospheres. Since the underlying spectroscopic line lists are constantly expanding and currently include up to ∼1010-1011 transition lines, the opacity calculator codes need to become more powerful. Here we present major upgrades to the HELIOS-K GPU-accelerated opacity calculator and describe the necessary steps to process large line lists within a reasonable amount of time. Besides performance improvements, we include more capabilities and present a toolbox for handling different atomic and molecular data sets, from downloading and preprocessing the data to performing the opacity calculations in a user-friendly way. HELIOS-K supports line lists from ExoMol, HITRAN, HITEMP, NIST, Kurucz, and VALD3. By matching the resolution of 0.1 cm-1 and cutting length of 25 cm-1 used by the ExoCross code for timing performance (251 s excluding data read-in time), HELIOS-K can process the ExoMol BT2 water line list in 12.5 s. Using a resolution of 0.01 cm-1, it takes 45 s, equivalent to about 107 lines s-1. As a wavenumber resolution of 0.01 cm-1 suffices for most exoplanetary atmosphere spectroscopic calculations, we adopt this resolution in calculating opacity functions for several hundred atomic and molecular species and make them freely available on the open-access DACE database. For the opacity calculations of the database, we use a cutting length of 100 cm-1 for molecules and no cutting length for atoms. Our opacities are available for downloading from https://dace.unige.ch/opacityDatabase and may be visualized using https://dace.unige.ch/opacity. Title: Helium Enhancement in the Metal-rich Red Giants of ω Centauri Authors: Hema, B. P.; Pandey, Gajendra; Kurucz, R. L.; Allende Prieto, C. Bibcode: 2020ApJ...897...32H Altcode: 2020arXiv200506807H The helium-enriched (He-enriched) metal-rich red giants of ω Centauri, discovered by Hema & Pandey using the low-resolution spectra from the Vainu Bappu Telescope, and confirmed by the analyses of the high-resolution spectra obtained from the HRS-South African Large Telescope for LEID 34225 and LEID 39048, are reanalyzed here to determine their degree of He enhancement/hydrogen deficiency (H deficiency). The observed MgH band combined with model atmospheres with differing He/H ratios are used for the analyses. The He/H ratios of these two giants are determined by enforcing the fact that the derived Mg abundances from the Mg I lines and from the subordinate lines of the MgH band must be same for the adopted model atmosphere. The estimated He/H ratios for LEID 34225 and LEID 39048 are 0.15 ± 0.04 and 0.20 ± 0.04, respectively, whereas the normal He/H ratio is 0.10. Following the same criteria for the analyses of the other two comparison stars (LEID 61067 and LEID 32169), a normal He/H ratio of 0.10 is obtained. The He/H ratio of 0.15-0.20 corresponds to a mass fraction of helium (Z(He) = Y) of about 0.375-0.445. The range of helium enhancement and the derived metallicity of the program stars are in line with those determined for ω Cen's blue main-sequence stars. Hence, our study provides the missing link for the evolutionary track of the metal-rich helium-enhanced population of ω Centuari. This research work is the very first spectroscopic determination of the amount of He enhancement in the metal-rich red giants of ω Centauri using the Mg I and MgH lines. Title: Update of the HITRAN collision-induced absorption section Authors: Karman, Tijs; Gordon, Iouli E.; van der Avoird, Ad; Baranov, Yury I.; Boulet, Christian; Drouin, Brian J.; Groenenboom, Gerrit C.; Gustafsson, Magnus; Hartmann, Jean-Michel; Kurucz, Robert L.; Rothman, Laurence S.; Sun, Kang; Sung, Keeyoon; Thalman, Ryan; Tran, Ha; Wishnow, Edward H.; Wordsworth, Robin; Vigasin, Andrey A.; Volkamer, Rainer; van der Zande, Wim J. Bibcode: 2019Icar..328..160K Altcode: Correct parameterization of the Collision-induced Absorption (CIA) phenomena is essential for accurate modeling of planetary atmospheres. The HITRAN spectroscopic database provides these parameters in a dedicated section. Here, we significantly revise and extend the HITRAN CIA data with respect to the original effort described in Richard et al. [JQSRT 113, 1276 (2012)]. The extension concerns new collisional pairs as well as wider spectral and temperature ranges for the existing pairs. The database now contains CIA for N2sbnd N2, N2sbnd H2, N2sbnd CH4, N2sbnd H2O, N2sbnd O2, O2sbnd O2, O2sbnd CO2, CO2sbnd CO2, H2sbnd H2, H2sbnd He, H2sbnd CH4, H2sbnd H, Hsbnd He, CH4sbnd CH4, CH4sbnd CO2, CH4sbnd He, and CH4sbnd Ar collision pairs. The sources of data as well as their validation and selection are discussed. A wish list to eliminate remaining deficiencies or lack of data from the astrophysics perspective is also presented. Title: Including All the Lines: Data Releases for Spectra and Opacities through 2017 Authors: Kurucz, R. L. Bibcode: 2018ASPC..515...47K Altcode: I present a progress report on including all the lines in the line lists, including all the lines in the opacities, and including all the lines in the model atmosphere and spectrum synthesis calculations. The increased opacity will improve stellar atmosphere, pulsation, stellar interior, asteroseismology, nova, supernova, and other radiation-hydrodynamics calculations. At present I have produced atomic line data for computing opacities for 850 million lines for elements up to Zn and for the 4d elements from Sr through Pd. Of these, 2.31 million lines are between known energy levels, so they have good wavelengths for computing spectra. Work is continuing on Ga to Rb and on heavier elements. Data for each ion and merged line lists are available on my website <a href='kurucz.harvard.edu'>kurucz.harvard.edu</a>. Title: High Resolution Near-Infrared Spectroscopy of Cool Dwarf Stars Authors: Dupree, Andrea; Brickhouse, Nancy; Irwin, Jonathan; Kurucz, Robert; Newton, Elisabeth Bibcode: 2018csss.confE..87D Altcode: 2018arXiv181105572D We present results from a near infrared survey of the He I line (10830 Angstrom) in cool dwarf stars taken with the PHOENIX spectrograph at the 4-m Mayall telescope at Kitt Peak National Observatory. Spectral synthesis of this region reproduces some but not all atomic and molecular features. The equivalent width of the He line appears directly correlated with the soft X-ray stellar surface flux except among the coolest M dwarf stars, where the helium is surprisingly weak. Title: Stellar Atmospheric Modelling for the ACCESS Program Authors: Morris, Matthew; Kaiser, Mary Elizabeth; Bohlin, Ralph; Kurucz, Robert; ACCESS Team Bibcode: 2018AAS...23135527M Altcode: A goal of the ACCESS program (Absolute Color Calibration Experiment for Standard Stars) is to enable greater discrimination between theoretical astrophysical models and observations, where the comparison is limited by systematic errors associated with the relative flux calibration of the targets. To achieve these goals, ACCESS has been designed as a sub-orbital rocket borne payload and ground calibration program, to establish absolute flux calibration of stellar targets at <1 % precision, with a resolving power of 500 across the 0.35 to 1.7 micron bandpass.In order to obtain higher resolution spectroscopy in the optical and near-infrared range than either the ACCESS payload or CALSPEC observations provide, the ACCESS team has conducted a multi-instrument observing program at Apache Point Observatory. Using these calibrated high resolution spectra in addition to the HST/CALSPEC data, we have generated stellar atmosphere models for ACCESS flight candidates, as well as a selection of A and G stars from the CALSPEC database. Stellar atmosphere models were generated using Atlas 9 and Atlas 12 Kurucz stellar atmosphere software. The effective temperature, log(g), metallicity, and redenning were varied and the chi-squared statistic was minimized to obtain a best-fit model. A comparison of these models and the results from interpolation between grids of existing models will be presented. The impact of the flexibility of the Atlas 12 input parameters (e.g. solar metallicity fraction, abundances, microturbulent velocity) is being explored. Title: ACCESS, Absolute Color Calibration Experiment for Standard Stars: Integration, Test, and Ground Performance Authors: Kaiser, Mary Elizabeth; Morris, Matthew; Aldoroty, Lauren; Kurucz, Robert; McCandliss, Stephan; Rauscher, Bernard; Kimble, Randy; Kruk, Jeffrey; Wright, Edward L.; Feldman, Paul; Riess, Adam; Gardner, Jonathon; Bohlin, Ralph; Deustua, Susana; Dixon, Van; Sahnow, David J.; Perlmutter, Saul Bibcode: 2018AAS...23135534K Altcode: Establishing improved spectrophotometric standards is important for a broad range of missions and is relevant to many astrophysical problems. Systematic errors associated with astrophysical data used to probe fundamental astrophysical questions, such as SNeIa observations used to constrain dark energy theories, now exceed the statistical errors associated with merged databases of these measurements. ACCESS, “Absolute Color Calibration Experiment for Standard Stars”, is a series of rocket-borne sub-orbital missions and ground-based experiments designed to enable improvements in the precision of the astrophysical flux scale through the transfer of absolute laboratory detector standards from the National Institute of Standards and Technology (NIST) to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of 500 across the 0.35-1.7μm bandpass. To achieve this goal ACCESS (1) observes HST/ Calspec stars (2) above the atmosphere to eliminate telluric spectral contaminants (e.g. OH) (3) using a single optical path and (HgCdTe) detector (4) that is calibrated to NIST laboratory standards and (5) monitored on the ground and in-flight using a on-board calibration monitor. The observations are (6) cross-checked and extended through the generation of stellar atmosphere models for the targets. The ACCESS telescope and spectrograph have been designed, fabricated, and integrated. Subsystems have been tested. Performance results for subsystems, operations testing, and the integrated spectrograph will be presented. NASA sounding rocket grant NNX17AC83G supports this work. Title: ATLAS9: Model atmosphere program with opacity distribution functions Authors: Kurucz, Robert L. Bibcode: 2017ascl.soft10017K Altcode: ATLAS9 computes model atmospheres using a fixed set of pretabulated opacities, allowing one to work on huge numbers of stars and interpolate in large grids of models to determine parameters quickly. The code works with two different sets of opacity distribution functions (ODFs), one with "big" wavelength intervals covering the whole spectrum and the other with 1221 "little" wavelength intervals covering the whole spectrum. The ODFs use a 12-step representation; the radiation field is computed starting with the highest step and working down. If a lower step does not matter because the line opacity is small relative to the continuum at all depths, all the lower steps are lumped together and not computed to save time. Title: ACCESS: integration and pre-flight performance Authors: Kaiser, Mary Elizabeth; Morris, Matthew J.; Aldoroty, Lauren N.; Pelton, Russell; Kurucz, Robert; Peacock, Grant O.; Hansen, Jason; McCandliss, Stephan R.; Rauscher, Bernard J.; Kimble, Randy A.; Kruk, Jeffrey W.; Wright, Edward L.; Orndorff, Joseph D.; Feldman, Paul D.; Moos, H. Warren; Riess, Adam G.; Gardner, Jonathan P.; Bohlin, Ralph; Deustua, Susana E.; Dixon, W. V.; Sahnow, David J.; Perlmutter, Saul Bibcode: 2017SPIE10398E..15K Altcode: Establishing improved spectrophotometric standards is important for a broad range of missions and is relevant to many astrophysical problems. ACCESS, "Absolute Color Calibration Experiment for Standard Stars", is a series of rocket-borne sub-orbital missions and ground-based experiments designed to enable improvements in the precision of the astrophysical flux scale through the transfer of absolute laboratory detector standards from the National Institute of Standards and Technology (NIST) to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of 500 across the 0.35 - 1.7μm bandpass. This paper describes the sub-system testing, payload integration, avionics operations, and data transfer for the ACCESS instrument. Title: VizieR Online Data Catalog: New FeI level energies from stellar spectra. II. (Peterson+, 2017) Authors: Peterson, R. C.; Kurucz, R. L.; Ayres, T. R. Bibcode: 2017yCat..22290023P Altcode: All of the new space-based UV spectra were obtained at a two-pixel resolution of 110000 with the E230H echelle grating of the Space Telescope Imaging Spectrograph (STIS) on HST, under program GO-14161 (R. Peterson, PI). See section 2 for further explanations.

(2 data files). Title: New Fe I Level Energies and Line Identifications from Stellar Spectra. II. Initial Results from New Ultraviolet Spectra of Metal-poor Stars Authors: Peterson, Ruth C.; Kurucz, Robert L.; Ayres, Thomas R. Bibcode: 2017ApJS..229...23P Altcode: The Fe I spectrum is critical to many areas of astrophysics, yet many of the high-lying levels remain uncharacterized. To remedy this deficiency, Peterson & Kurucz identified Fe I lines in archival ultraviolet and optical spectra of metal-poor stars, whose warm temperatures favor moderate Fe I excitation. Sixty-five new levels were recovered, with 1500 detectable lines, including several bound levels in the ionization continuum of Fe I. Here, we extend the previous work by identifying 59 additional levels, with 1400 detectable lines, by incorporating new high-resolution UV spectra of warm metal-poor stars recently obtained by the Hubble Space Telescope Imaging Spectrograph. We provide gf values for these transitions, both computed as well as adjusted to fit the stellar spectra. We also expand our spectral calculations to the infrared, confirming three levels by matching high-quality spectra of the Sun and two cool stars in the H-band. The predicted gf values suggest that an additional 3700 Fe I lines should be detectable in existing solar infrared spectra. Extending the empirical line identification work to the infrared would help confirm additional Fe I levels, as would new high-resolution UV spectra of metal-poor turnoff stars below 1900 Å. Title: Chromospheric Models and the Oxygen Abundance in Giant Stars Authors: Dupree, A. K.; Avrett, E. H.; Kurucz, R. L. Bibcode: 2016ApJ...821L...7D Altcode: 2016arXiv160307381D Realistic stellar atmospheric models of two typical metal-poor giant stars in Omega Centauri, which include a chromosphere (CHR), influence the formation of optical lines of O I: the forbidden lines (λ6300, λ6363) and the infrared triplet (λλ7771-7775). One-dimensional semi-empirical non-local thermodynamic equilibrium (LTE) models are constructed based on observed Balmer lines. A full non-LTE formulation is applied for evaluating the line strengths of O I, including photoionization by the Lyman continuum and photoexcitation by Lyα and Lyβ. Chromospheric models (CHR) yield forbidden oxygen transitions that are stronger than those in radiative/convective equilibrium (RCE) models. The triplet oxygen lines from high levels also appear stronger than those produced in an RCE model. The inferred oxygen abundance from realistic CHR models for these two stars is decreased by factors of ∼3 as compared to values derived from RCE models. A lower oxygen abundance suggests that intermediate-mass AGB stars contribute to the observed abundance pattern in globular clusters. A change in the oxygen abundance of metal-poor field giants could affect models of deep mixing episodes on the red giant branch. Changes in the oxygen abundance can impact other abundance determinations that are critical to astrophysics, including chemical tagging techniques and galactic chemical evolution. Title: ACCESS Sub-system Performance Authors: Kaiser, Mary Elizabeth; Morris, Matthew J.; Aldoroty, Lauren Nicole; Godon, David; Pelton, Russell; McCandliss, Stephan R.; Kurucz, Robert L.; Kruk, Jeffrey W.; Rauscher, Bernard J.; Kimble, Randy A.; Wright, Edward L.; Benford, Dominic J.; Gardner, Jonathan P.; Feldman, Paul D.; Moos, H. Warren; Riess, Adam G.; Bohlin, Ralph; Deustua, Susana E.; Dixon, William Van Dyke; Sahnow, David J.; Lampton, Michael; Perlmutter, Saul Bibcode: 2016AAS...22714732K Altcode: ACCESS: Absolute Color Calibration Experiment for Standard Stars is a series of rocket-borne sub-orbital missions and ground-based experiments designed to leverage significant technological advances in detectors, instruments, and the precision of the fundamental laboratory standards used to calibrate these instruments to enable improvements in the precision of the astrophysical flux scale through the transfer of laboratory absolute detector standards from the National Institute of Standards and Technology (NIST) to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of 500 across the 0.35 to 1.7 micron bandpass.A cross wavelength calibration of the astrophysical flux scale to this level of precision over this broad a bandpass is relevant for the data used to probe fundamental astrophysical problems such as the SNeIa photometry based measurements used to constrain dark energy theories.We will describe the strategy for achieving this level of precision, the payload and calibration configuration, present sub-system test data, and the status and preliminary performance of the integration and test of the spectrograph and telescope. NASA APRA sounding rocket grant NNX14AH48G supports this work. Title: The Intersection of Atomic Physics and Astrophysics: Identifying UV Fe I Lines from Metal-Poor Turnoff Stars Authors: Peterson, Ruth C.; Ayres, Thomas R.; Kurucz, Robert L. Bibcode: 2015hst..prop14161P Altcode: Observational surveys are expanding, recording ever-fainter sources from the ultraviolet to the infrared. Needed to characterize them are observational ultraviolet templates at high spectral resolution and low metallicity for the oldest populations, and the laboratory astrophysics data essential to model objects such as stars and nebulae at all ages, metallicities, and redshifts.

We address this by proposing to complete the high-resolution UV spectral coverage of four key metal-poor turnoff stars. These are ideal as metal-poor templates of old stars and as the "laboratory source" for the identification of the thousands of lines of neutral iron that appear in stellar spectra, but are absent from or not identified in laboratory spectra. By matching existing stellar spectra to calculations of energy levels, line wavelengths, and gf-values, Peterson & Kurucz (2015) identified 66 Fe I levels with energies up to 8.4eV, yielding 2000 new lines from 1600 Angstroms to 5.4 microns, and empirical gf-values for 640 of these. The proposed work should yield ~500 new levels and ~10,000 new Fe I lines.

The new energy levels and line parameters also will be posted on the Kurucz website. The new spectra, and supporting theoretical calculations, will be integrated into the publicly available HST Advanced Spectral Library (ASTRAL) Treasury Project. This will leverage the utility of these archival spectral templates and atlases in such diverse areas as nucleosynthesis at early epochs, infrared analysis of dust-obscured giants, reconstructing the populations of nearby globular clusters and dwarf galaxies from their integrated light, and deriving age and metallicity for old, distant galaxies. Title: New Mn II energy levels from the STIS-HST spectrum of the HgMn star HD 175640 Authors: Castelli, F.; Kurucz, R. L.; Cowley, C. R. Bibcode: 2015A&A...580A..10C Altcode: 2015arXiv150407514C
Aims: The NIST database lists several Mn ii lines that were observed in the laboratory but not classified. They cannot be used in spectrum synthesis because their atomic line data are unknown. These lines are concentrated in the 2380-2700 Å interval. We aimed to assign energy levels and log gf values to these lines.
Methods: Semi-empirical line data for Mn ii computed by Kurucz were used to synthesize the ultraviolet spectrum of the slow-rotating, HgMn star HD 175640. The spectrum was compared with the high-resolution spectrum observed with the HST-STIS equipment. A UVES spectrum covering the 3050-10 000 Å region was also examined.
Results: We determined a total of 73 new energy levels, 58 from the STIS spectrum of HD 175640 and another 15 from the UVES spectrum. The new energy levels give rise to numerous new computed lines. We have identified more than 50% of the unclassified lines listed in the NIST database and have changed the assignment of another 24 lines. An abundance analysis of the star HD 175640, based on the comparison of observed and computed ultraviolet spectra in the 1250-3040 Å interval, is the by-product of this study on Mn ii.

Tables A.1 and A.2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/580/A10 Title: VizieR Online Data Catalog: New MnII energy levels (Castelli+, 2015) Authors: Castelli, F.; Kurucz, R. L.; Cowley, C. R. Bibcode: 2015yCat..35800010C Altcode: New MnII energy levels were determined from the analysis of an ultraviolet HST-STIS spectrum and a UVES optical spectrum. For each new level, the most significant lines from the level are listed in tablea1.dat. For each new line the wavelength, the computed loggf value, and the upper and lower energy levels are given.

tablea2.dat tabulates the MnII lines in the 2400-3040Å interval that are listed in the NIST database, observed in the spectrum, but not predicted by the MnII line list computed by Kurucz for this paper.

(2 data files). Title: VizieR Online Data Catalog: New FeI level energies from stellar spectra (Peterson+, 2015) Authors: Peterson, R. C.; Kurucz, R. L. Bibcode: 2015yCat..22160001P Altcode: The spectrum of the Fe I atom is critical to many areas of astrophysics and beyond. Measurements of the energies of its high-lying levels remain woefully incomplete, however, despite extensive laboratory and solar analysis. In this work, we use high-resolution archival absorption-line ultraviolet and optical spectra of stars whose warm temperatures favor moderate Fe I excitation. We derive the energy for a particular upper level in Kurucz's semiempirical calculations by adopting a trial value that yields the same wavelength for a given line predicted to be about as strong as that of a strong unidentified spectral line observed in the stellar spectra, then checking the new wavelengths of other strong predicted transitions that share the same upper level for coincidence with other strong observed unidentified lines. To date, this analysis has provided the upper energies of 66 Fe I levels. Many new energy levels are higher than those accessible to laboratory experiments; several exceed the Fe I ionization energy. These levels provide new identifications for over 2000 potentially detectable lines. Almost all of the new levels of odd parity include UV lines that were detected but unclassified in laboratory Fe I absorption spectra, providing an external check on the energy values. We motivate and present the procedure, provide the resulting new energy levels and their uncertainties, list all the potentially detectable UV and optical new Fe I line identifications and their gf values, point out new lines of astrophysical interest, and discuss the prospects for additional Fe I energy level determinations.

(3 data files). Title: Identifying New Fe I Levels from Stellar Spectra Authors: Peterson, Ruth; Kurucz, Robert L. Bibcode: 2015AAS...22544906P Altcode: The spectrum of the Fe I atom is critical to many areas of astrophysics and beyond. Measurements of the energies of its high-lying levels remain woefully incomplete, however, despite extensive laboratory and solar analysis. Here we discuss work by Peterson & Kurucz (2014, ApJS, in press) to identify such levels using high-resolution archival absorption-line ultraviolet and optical spectra of stars, whose warm temperatures favor moderate Fe I excitation. To date this analysis has provided the upper energies of 66 Fe I levels. Many are of higher excitation than is accessible to laboratory experiments; several exceed the Fe I ionization energy. These levels provide new identifications for over two thousand potentially detectable lines. We describe and illustrate our method, which is based on matching the strengths and positions of unidentified spectral features to the lines sharing a particular upper level in Kurucz's semi-empirical calculations. We also highlight the improvements these new identifications bring to the determination of the abundances of trace elements in individual stars, and to the ability of calculations of cool stellar spectra to match low-resolution observations of stars and old stellar systems. Title: New Fe I Level Energies and Line Identifications from Stellar Spectra Authors: Peterson, Ruth C.; Kurucz, Robert L. Bibcode: 2015ApJS..216....1P Altcode: 2014arXiv1406.0933P The spectrum of the Fe I atom is critical to many areas of astrophysics and beyond. Measurements of the energies of its high-lying levels remain woefully incomplete, however, despite extensive laboratory and solar analysis. In this work, we use high-resolution archival absorption-line ultraviolet and optical spectra of stars whose warm temperatures favor moderate Fe I excitation. We derive the energy for a particular upper level in Kurucz's semiempirical calculations by adopting a trial value that yields the same wavelength for a given line predicted to be about as strong as that of a strong unidentified spectral line observed in the stellar spectra, then checking the new wavelengths of other strong predicted transitions that share the same upper level for coincidence with other strong observed unidentified lines. To date, this analysis has provided the upper energies of 66 Fe I levels. Many new energy levels are higher than those accessible to laboratory experiments; several exceed the Fe I ionization energy. These levels provide new identifications for over 2000 potentially detectable lines. Almost all of the new levels of odd parity include UV lines that were detected but unclassified in laboratory Fe I absorption spectra, providing an external check on the energy values. We motivate and present the procedure, provide the resulting new energy levels and their uncertainties, list all the potentially detectable UV and optical new Fe I line identifications and their gf values, point out new lines of astrophysical interest, and discuss the prospects for additional Fe I energy level determinations. Title: ACCESS: status and pre-flight performance Authors: Kaiser, Mary Elizabeth; Morris, Matthew J.; Peacock, Grant O.; McCandliss, Stephan R.; Rauscher, Bernard J.; Kimble, Randy A.; Kruk, Jeffrey W.; Pelton, Russell; Wright, Edward L.; Mott, D. Brent; Wen, Yiting; Feldman, Paul D.; Moos, H. Warren; Riess, Adam G.; Gardner, Jonathan P.; Benford, Dominic J.; Woodgate, Bruce E.; Bohlin, Ralph; Deustua, Susana E.; Dixon, W. V.; Sahnow, David J.; Kurucz, Robert; Lampton, Michael; Perlmutter, Saul Bibcode: 2014SPIE.9143E..4YK Altcode: Establishing improved spectrophotometric standards is important for a broad range of missions and is relevant to many astrophysical problems. ACCESS, Absolute Color Calibration Experiment for Standard Stars", is a series of rocket-borne sub-orbital missions and ground-based experiments designed to enable improvements in the precision of the astrophysical flux scale through the transfer of absolute laboratory detector standards from the National Institute of Standards and Technology (NIST) to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of 500 across the 0.35 - 1.7μm bandpass. This paper describes the payload status, sub-system testing, and data transfer for the ACCESS instrument. Title: RR Lyrae studies with Kepler: showcasing RR Lyr Authors: Kolenberg, Katrien; Kurucz, Robert L.; Stellingwerf, Robert; Nemec, James M.; Moskalik, Paweł; Fossati, Luca; Barnes, Thomas G. Bibcode: 2014IAUS..301..257K Altcode: Four years into the Kepler mission, an updated review on the results for RR Lyrae stars is in order. More than 50 RR Lyrae stars in the Kepler field are observed with Kepler and each one of them can provide us with new insight into this class of pulsating stars. Ground-based spectroscopy of the Kepler targets allows us to narrow down their physical parameters. Previously, we already reported a 50% occurrence rate of modulation in the RRab stars, a large variety of modulation behavior, period doubling in several Blazhko stars, the detection of higher- overtone radial modes, probable non-radial modes and new types of multiple-mode RR Lyrae pulsators, among both the RRab and the RRc stars. In addition, the quasi-continuous photometry obtained over several years with Kepler allows one to observe changes in Blazhko behavior and additional longer cycles. These observations have sparked new theoretical modelling efforts. In this short paper we showcase RR Lyr itself. The star has been observed with Kepler in short cadence, and some remarkable features of its pulsation behavior are unveiled in this long-studied prototype, through the Kepler photometry and additional spectroscopic data. Title: Model Atmosphere Codes: ATLAS12 and ATLAS9 Authors: Kurucz, Robert L. Bibcode: 2014dapb.book...39K Altcode: No abstract at ADS Title: High-cadence high-resolution spectroscopy of the prototype RR Lyrae Authors: Kolenberg, Katrien; Bergstrom, Z.; Kurucz, R. L.; Fossati, L.; Barnes, T. G.; Bergstrom, Zoey; Kurucz, Robert L.; Barnes, Thomas G.; Fossati, Luca Bibcode: 2014AAS...22315626K Altcode: RR Lyrae stars play an important role in astrophysics as standard candles and tracers of galactic history, but several aspects of their pulsation remain mysterious. RR Lyr, the prototype of the class, has been studied for over a century. Recently, it was observed in high (1-minute) cadence by the Kepler spacecraft, revealing several new features of its pulsation. We present a set of high-cadence, high-resolution spectra that were obtained simultaneously with the short-cadence photometry in the star and that allow us to study the star's photospheric dynamics in detail. Title: ACCESS: Thermal Mechanical Design, Performance, and Status Authors: Kaiser, Mary Elizabeth; Morris, M. J.; McCandliss, S. R.; Rauscher, B. J.; Kimble, R. A.; Kruk, J. W.; Wright, E. L.; Bohlin, R.; Kurucz, R. L.; Riess, A. G.; Pelton, R.; Deustua, S. E.; Dixon, W. V.; Sahnow, D. J.; Benford, D. J.; Gardner, J. P.; Feldman, P. D.; Moos, H. W.; Lampton, M.; Perlmutter, S.; Woodgate, B. E. Bibcode: 2014AAS...22314918K Altcode: Systematic errors associated with astrophysical data used to probe fundamental astrophysical questions, such as SNeIa observations used to constrain dark energy theories, are now rivaling and exceeding the statistical errors associated with these measurements. ACCESS: Absolute Color Calibration Experiment for Standard Stars is a series of rocket-borne sub-orbital missions and ground-based experiments designed to enable improvements in the precision of the astrophysical flux scale through the transfer of absolute laboratory detector standards from the National Institute of Standards and Technology (NIST) to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of 500 across the 0.35 - 1.7μm bandpass. Achieving this level of accuracy requires characterization and stability of the instrument and detector including a thermal background that contributes less than 1% to the flux per resolution element in the NIR. We will present the instrument and calibration status with a focus on the thermal mechanical design and associated performance data. The detector control and performance will be presented in a companion poster (Morris, et al). NASA APRA sounding rocket grant NNX08AI65G supports this work. Title: How to Build a Model of the Atmosphere and Spectrum Authors: Kurucz, Robert L. Bibcode: 2014dapb.book...25K Altcode: No abstract at ADS Title: Problems with Atomic and Molecular Data: Including All the Lines Authors: Kurucz, Robert L. Bibcode: 2014dapb.book...63K Altcode: No abstract at ADS Title: ACCESS: Detector Control and Performance Authors: Morris, Matthew J.; Kaiser, M.; McCandliss, S. R.; Rauscher, B. J.; Kimble, R. A.; Kruk, J. W.; Wright, E. L.; Bohlin, R.; Kurucz, R. L.; Riess, A. G.; Pelton, R.; Deustua, S. E.; Dixon, W. V.; Sahnow, D. J.; Mott, D. B.; Wen, Y.; Benford, D. J.; Gardner, J. P.; Feldman, P. D.; Moos, H. W.; Lampton, M.; Perlmutter, S.; Woodgate, B. E. Bibcode: 2014AAS...22314917M Altcode: ACCESS, Absolute Color Calibration Experiment for Standard Stars, is a series of rocket-borne sub-orbital missions and ground-based experiments that will enable improvements in the precision of the astrophysical flux scale through the transfer of absolute laboratory detector standards from the National Institute of Standards and Technology (NIST) to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of 500 across the 0.35 to 1.7 micron bandpass (companion poster, Kaiser et al.). The flight detector and detector spare have been selected and integrated with their electronics and flight mount. The controller electronics have been flight qualified. Vibration testing to launch loads and thermal vacuum testing of the detector, mount, and housing have been successfully performed. Further improvements to the flight controller housing have been made. A cryogenic ground test system has been built. Dark current and read noise tests have been performed, yielding results consistent with the initial characterization tests of the detector performed by Goddard Space Flight Center’s Detector Characterization Lab (DCL). Detector control software has been developed and implemented for ground testing. Performance and integration of the detector and controller with the flight software will be presented. NASA APRA sounding rocket grant NNX08AI65G supports this work. Title: ATLAS12: Opacity sampling model atmosphere program Authors: Kurucz, Robert L. Bibcode: 2013ascl.soft03024K Altcode: ATLAS12 is an opacity sampling model atmosphere program to allow computation of models with individual abundances using line data. ATLAS12 is able to compute the same models as ATLAS9 which uses pretabulated opacities, plus models with arbitrary abundances. ATLAS12 sampled fluxes are quite accurate for predicting the total flux except in the intermediate or narrow bandpass intervals because the sample size is too small. Title: ACCESS: Design, Strategy, and Test Performance Authors: Kaiser, Mary Elizabeth; Morris, M. J.; McCandliss, S. R.; Rauscher, B. J.; Kimble, R. A.; Kruk, J. W.; Wright, E. L.; Pelton, R. S.; Feldman, P. D.; Moos, H. W.; Riess, A. G.; Benford, D. J.; Foltz, R.; Gardner, J. P.; Mott, D. B.; Wen, Y.; Woodgate, B. E.; Bohlin, R.; Deustua, S. E.; Dixon, W. V.; Sahnow, D. J.; Kurucz, R. L.; Lampton, M.; Perlmutter, S. Bibcode: 2013AAS...22135008K Altcode: Improvements in the astrophysical flux scale are needed to answer fundamental scientific questions ranging from cosmology to stellar physics. In particular, the precise calibration of the flux scale across the visible-NIR bandpass is fundamental to the precise determination of dark energy parameters based on SNeIa photometry. ACCESS, Absolute Color Calibration Experiment for Standard Stars, is a series of rocket-borne sub-orbital missions and ground-based experiments that will enable improvements in the precision of the astrophysical flux scale through the transfer of absolute laboratory detector standards from the National Institute of Standards and Technology (NIST) to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of 500 across the 0.35 to 1.7 micron bandpass. The telescope is a Dall-Kirkham Cassegrain with a 15.5-inch primary. The spectrograph is a Rowland circle design, with the grating operating as a low order (m=1-4) echelle, a Fery prism provides cross dispersion, and a HST/WFC3 heritage HAWAII-1R HgCdTe detector is used across the full spectral bandpass. The telescope mirrors have received their flight coatings. The flight detector and detector spare have been integrated with their electronics and flight mount. The controller electronics have been flight qualified. Vibration testing to launch loads and thermal vacuum testing of the detector, mount, and housing have been performed. Detector characterization testing is in progress (Morris et al.). Fabrication, integration, and automation of the ground-based calibration subsystems are also in progress. The ACCESS design, calibration strategy, and ground-based integration and test results will be presented. Launch is expected this year. NASA sounding rocket grant NNX08AI65G and DOE DE-FG02-07ER41506 support this work. Title: ACCESS: Detector Performance Authors: Morris, Matthew J.; Kaiser, M.; Rauscher, B. J.; Kimble, R. A.; Kruk, J. W.; Mott, D. B.; Wen, Y.; Foltz, R.; McCandliss, S. R.; Pelton, R. S.; Wright, E. L.; Feldman, P. D.; Moos, H. W.; Riess, A. G.; Benford, D. J.; Gardner, J. P.; Woodgate, B. E.; Bohlin, R.; Deustua, S. E.; Dixon, W. V.; Sahnow, D. J.; Kurucz, R. L.; Lampton, M.; Perlmutter, S. Bibcode: 2013AAS...22135007M Altcode: ACCESS, Absolute Color Calibration Experiment for Standard Stars, is a series of rocket-borne sub-orbital missions and ground-based experiments that will enable improvements in the precision of the astrophysical flux scale through the transfer of absolute laboratory detector standards from the National Institute of Standards and Technology (NIST) to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of 500 across the 0.35 to 1.7 micron bandpass (overview Kaiser et al.). The flight detector and detector spare have been integrated with their electronics and flight mount. The controller electronics have been flight qualified. Vibration testing to launch loads and thermal vacuum testing of the detector, mount, and housing have been performed. The flight detector controller boards have been installed into a ruggedized flight housing. They have been successfully vacuum tested for periods significantly longer than the flight length, and components have been heat-sunk and reinforced as necessary. Thermal stability tests have been performed, and results will be presented. Goddard Space Flight Center’s Detector Characterization Lab (DCL) executed initial characterization tests for the flight detector in 2007. These were repeated in 2012, to ensure and establish baseline performance. Current lab characterization tests at Johns Hopkins are ongoing, and results will be presented. NASA sounding rocket grant NNX08AI65G supports this work. Title: ACCESS: design and sub-system performance Authors: Kaiser, Mary Elizabeth; Morris, Matthew J.; McCandliss, Stephan R.; Rauscher, Bernard J.; Kimble, Randy A.; Kruk, Jeffrey W.; Pelton, Russell; Mott, D. B.; Wen, Yiting; Foltz, Roger; Quijada, Manuel A.; Gum, Jeffery S.; Gardner, Jonathan P.; Kahle, Duncan M.; Benford, Dominic J.; Woodgate, Bruce E.; Wright, Edward L.; Feldman, Paul D.; Hart, Murdock; Moos, H. Warren; Riess, Adam G.; Bohlin, Ralph; Deustua, Susana E.; Dixon, W. V.; Sahnow, David J.; Kurucz, Robert; Lampton, Michael; Perlmutter, Saul Bibcode: 2012SPIE.8442E..46K Altcode: Establishing improved spectrophotometric standards is important for a broad range of missions and is relevant to many astrophysical problems. ACCESS, “Absolute Color Calibration Experiment for Standard Stars”, is a series of rocket-borne sub-orbital missions and ground-based experiments designed to enable improvements in the precision of the astrophysical flux scale through the transfer of absolute laboratory detector standards from the National Institute of Standards and Technology (NIST) to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of 500 across the 0.35-1.7µm bandpass. Title: DASCH Discovery of a Possible Nova-like Outburst in a Peculiar Symbiotic Binary Authors: Tang, Sumin; Grindlay, Jonathan E.; Moe, Maxwell; Orosz, Jerome A.; Kurucz, Robert L.; Quinn, Samuel N.; Servillat, Mathieu Bibcode: 2012ApJ...751...99T Altcode: 2011arXiv1110.0019T We present photometric and spectroscopic observations of a peculiar variable (designated DASCH J075731.1+201735 or J0757) discovered from our DASCH project using the digitized Harvard College Observatory archival photographic plates. It brightened by about 1.5 mag in B within a year starting in 1942, and then slowly faded back to its pre-outburst brightness from 1943 to 1950s. The mean brightness level was stable before and after the outburst, and ellipsoidal variations with a period of P = 119.18 ± 0.07 days are seen, suggesting that the star is tidally distorted. Radial-velocity measurements indicate that the orbit is nearly circular (e = 0.02 ± 0.01) with a spectroscopic period that is the same as the photometric period. The binary consists of a 1.1 ± 0.3 M ⊙ M0III star, and a 0.6 ± 0.2 M ⊙ companion, very likely a white dwarf (WD). Unlike other symbiotic binaries, there is no sign of emission lines or a stellar wind in the spectra. With an outburst timescale of ~10 years and estimated B-band peak luminosity MB ~ 0.7, J0757 is different from any other known classic or symbiotic novae. The most probable explanation of the outburst is hydrogen shell burning on the WD, although an accretion-powered flare cannot be ruled out. Title: Division IX / Commission 25 / Working Group Infrared Astronomy Authors: Milone, Eugene F.; Young, Andrew T.; Bell, Roger A.; Bessell, Michael; Boyl, Richard P.; Carter, Brian; Clark, T. Alan; Cohen, Martin; Fry, David J. I.; Garrison, Robert; Glass, Ian S.; Graham, John; Granada, Anahi; Hillenbrand, Lynn; Kurucz, Robert L.; McLean, Ian; Mountain, Matthew; Riecke, George; Riffel, Rogerio; Samec, Ronald G.; Schiller, Stephen J.; Simons, Douglas; Skrutskie, Michael; Stagg, C. Russell; Sterken, Christiaan L.; Thompson, Roger I.; Tokunaga, Alan; Volk, Kevin; Wing, Robert Bibcode: 2012IAUTA..28..297M Altcode: The formal commissioning of the IRWG occurred at the 1991 Buenos Aires General Assembly, following a Joint Commission meeting at the IAU GA in Baltimore in 1988 that identified the problems with ground-based infrared photometry. The meeting justification, papers, and conclusions, can be found in Milone (1989). In summary, the challenges involved how to explain the failure to achieve the milli-magnitude precision expected of infrared photometry and an apparent 3% limit on system transformability. The proposed solution was to redefine the broadband Johnson system, the passbands of which had proven so unsatisfactory that over time effectively different systems proliferated, although bearing the same ``JHKLMNQ'' designations; the new system needed to be better positioned and centered in the spectral windows of the Earth's atmosphere, and the variable water vapour content of the atmosphere needed to be measured in real time to better correct for atmospheric extinction. Title: Iron abundance in the prototype PG 1159 star, GW Vir pulsator PG 1159 - 035, and related objects Authors: Werner, K.; Rauch, T.; Kruk, J. W.; Kurucz, R. L. Bibcode: 2011A&A...531A.146W Altcode: 2011arXiv1105.5276W We performed an iron abundance determination of the hot, hydrogen deficient post-AGB star PG 1159 - 035, which is the prototype of the PG 1159 spectral class and the GW Vir pulsators, and of two related objects (PG 1520 + 525, PG 1144 + 005), based on the first detection of Fe viii lines in stellar photospheres. In another PG 1159 star, PG 1424 + 535, we detect Fe vii lines. In all four stars, each within Teff = 110 000-150 000 K, we find a solar iron abundance. This result agrees with our recent abundance analysis of the hottest PG 1159 stars (Teff = 150 000-200 000 K) that exhibit Fe x lines. On the whole, we find that the PG 1159 stars are not significantly iron deficient, in contrast to previous notions.

Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer. FUSE was operated for NASA by the Johns Hopkins University under NASA contract NAS5-32985. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26666. Title: Including all the lines Authors: Kurucz, Robert L. Bibcode: 2011CaJPh..89..417K Altcode: No abstract at ADS Title: ACCESS: Mission Overview, Fabrication Status, and Preliminary Performance Authors: Kaiser, Mary Elizabeth; McCandliss, S. R.; Sahnow, D. J.; Dixon, W. V.; Feldman, P. D.; Gaither, B. W.; Moos, H. W.; Pelton, R. S.; Riess, A. G.; Rauscher, B. J.; Kimble, R. A.; Kruk, J. W.; Benford, D. J.; Gardner, J. P.; Hill, R. J.; Kahle, D. M.; Mott, D. B.; Waczynski, A.; Wen, Y.; Woodgate, B. E.; Bohlin, R. C.; Deustua, S. E.; Kurucz, R.; Lampton, M.; Perlmutter, S.; Wright, E. L. Bibcode: 2011AAS...21725412K Altcode: 2011BAAS...4325412K Improvements in the precision of the astrophysical flux scale are needed to answer fundamental scientific questions ranging from cosmology to stellar physics. ACCESS - Absolute Color Calibration Experiment for Standard Stars (Kaiser et al., 2009) is a sub-orbital program with a rocket-borne payload that will enable the transfer of absolute laboratory detector standards from NIST to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of R = 500 across the 0.35-1.7 micron bandpass. The ACCESS flight detector has been selected and initial tests have been performed. The detector flight electronics are being fabricated. The optical system fabrication is in progress. The ground calibration system fabrication and component testing has begun. The cornerstone of the ground calibration system is the artificial star system that will be used to transfer the NIST photodiode detector standards to the telescope payload and hence the stars. First flight is anticipated for late 2011 from White Sands Missile Range. We will present the instrument overview, status of the instrument fabrication, and the calibration and observation strategy. Support for this work was provided by NASA through grant NNX08AI65G and DOE through grant DE-FG02-07ER41506. Title: New Fe ii energy levels from stellar spectra Authors: Castelli, F.; Kurucz, R. L. Bibcode: 2010A&A...520A..57C Altcode: 2010arXiv1006.5606C
Aims: The spectra of B-type and early A-type stars show numerous unidentified lines in the whole optical range, especially in the 5100-5400 Å interval. Because Fe ii transitions to high energy levels should be observed in this region, we used semiempirical predicted wavelengths and gf-values of Fe ii to identify unknown lines.
Methods: Semiempirical line data for Fe ii computed by Kurucz are used to synthesize the spectrum of the slow-rotating, Fe-overabundant CP star HR 6000.
Results: We determined a total of 109 new 4f levels for Fe ii with energies ranging from 122 324 cm-1 to 128 110 cm-1. They belong to the Fe ii subconfigurations 3d6(3P)4f (10 levels), 3d6(3H)4f (36 levels), 3d6(3F)4f (37 levels), and 3d6(3G)4f (26 levels). We also found 14 even levels from 4d (3 levels), 5d (7 levels), and 6d (4 levels) configurations. The new levels have allowed us to identify more than 50% of the previously unidentified lines of HR 6000 in the wavelength region 3800-8000 Å. Tables listing the new energy levels are given in the paper; tables listing the spectral lines with log gf ≥ -1.5 that are transitions to the 4f energy levels are given in the Online Material. These new levels produce 18 000 lines throughout the spectrum from the ultraviolet to the infrared.

Tables 6-9 are also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/520/A57 Title: VizieR Online Data Catalog: New FeII energy levels from stellar spectra (Castelli+, 2010) Authors: Castelli, F.; Kurucz, R. L. Bibcode: 2010yCat..35200057C Altcode: 2010yCat..35209057C FeII lines in the 3800-8000Å region, produced by transitions to the FeII subconfigurations (3P)4f, (3H)4f, (3F)4f, and (3G)4f are given in Tables 6, 7, 8, and 9, respectively. Only lines with loggf>=-1.5 are listed. Most of these lines can be observed in the UVES spectrum of HR 6000 and have allowed us to identify more than 50% of the previously unidentified lines (Castelli & Hubrig, 2007A&A...475.1041C).

(4 data files). Title: ACCESS: design and preliminary performance Authors: Kaiser, Mary Elizabeth; Kruk, Jeffrey W.; McCandliss, Stephan R.; Rauscher, Bernard J.; Kimble, Randy A.; Pelton, Russell S.; Sahnow, David J.; Dixon, W. V.; Feldman, Paul D.; Gaither, Bryan W.; Lazear, Justin S.; Moos, H. Warren; Riess, Adam G.; Benford, Dominic J.; Gardner, Jonathan P.; Hill, Robert J.; Kahle, Duncan M.; Mott, D. Brent; Waczynski, Augustyn; Wen, Yiting; Woodgate, Bruce E.; Bohlin, Ralph C.; Deustua, Susana E.; Kurucz, Robert; Lampton, Michael; Perlmutter, Saul; Wright, Edward L. Bibcode: 2010SPIE.7731E..3IK Altcode: 2010SPIE.7731E.112K ACCESS, Absolute Color Calibration Experiment for Standard Stars, is a series of rocket-borne sub-orbital missions and ground-based experiments designed to enable improvements in the precision of the astrophysical flux scale through the transfer of absolute laboratory detector standards from the National Institute of Standards and Technology (NIST) to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of 500 across the 0.35.1.7μm bandpass. Establishing improved spectrophotometric standards is important for a broad range of missions and is relevant to many astrophysical problems. Systematic errors associated with problems such as dark energy now compete with the statistical errors and thus limit our ability to answer fundamental questions in astrophysics. The ACCESS design, calibration strategy, and an updated preliminary performance estimate are discussed. Title: ACCESS: Mission Overview, Design and Status Authors: Kaiser, Mary Elizabeth; McCandliss, Stephan R.; Pelton, Russell; Sahnow, David; Dixon, W. V.; Feldman, Paul D.; Gaither, Bryan W.; Lazear, Justin S.; Moos, H. Warren; Riess, Adam; Rauscher, Bernard J.; Kruk, Jeffrey W.; Kimble, Randy A.; Benford, Dominic J.; Foltz, Roger; Gardner, Jonathan P.; Hill, Robert J.; Kahle, Duncan M.; Malumuth, Eliot; Mott, D. Brent; Waczynski, Augustyn; Wen, Yiting; Woodgate, Bruce E.; Bohlin, Ralph C.; Deustua, Susana; Kurucz, Robert; Lampton, Michael; Perlmutter, Saul; Wright, Edward L. Bibcode: 2010hstc.workE..10K Altcode: ACCESS, Absolute Color Calibration Experiment for Standard Stars, is a series of rocket-borne sub-orbital missions and ground-based experiments designed to enable improvements in the precision of the astrophysical flux scale through the transfer of absolute laboratory detector standards from the National Institute of Standards and Technology (NIST) to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of 500 across the 0.35-1.7 μm bandpass. Establishing improved spectrophotometric standards is important for a broad range of missions and is relevant to many astrophysical problems. Systematic errors associated with problems such as dark energy now compete with the statistical errors and thus limit our ability to answer fundamental questions in astrophysics. The ACCESS payload and ground calibration components currently span a range of readiness levels extending from the design phase, through procurement, fabrication, and component test phases. The strategy for achieving a <1% spectrophotometric calibration accuracy, a description and status of the instrument and the ground calibration system, and the NIST traceability components are discussed. Title: New Fe II energy levels from stellar spectra Authors: Castelli, Fiorella; Kurucz, Robert L. Bibcode: 2010arXiv1007.1552C Altcode: The spectra of B-type and early A-type stars show mumerous unidentified lines in the whole optical range, especially in the 5100-5400 A interval. Because Fe II transitions to high energy levels should be observed in this region, we used semiempirical predicted wavelengths and gf-values of Fe II to identify unknown lines. Semiempirical line data for Fe II computed by Kurucz are used to synthesize the spectrum of the slow-rotating, Fe-overabundant CP star HR 6000. We determined a total of 109 new 4f levels for Fe II with energies ranging from 122324 cm^-1 to 128110 cm^-1. They belong to the Fe II subconfigurations 3d^6(^3P)4f (10 levels), 3d^6(^3H)4f (36 levels), 3d^6(^3F)4f (37 levels), and 3d^6(^3G)4f (26 levels). We also found 14 even levels from 4d (3 levels), 5d (7 levels), and 6d (4 levels) configurations. The new levels have allowed us to identify more than 50% of the previously unidentified lines of HR 6000 in the wavelength region 3800-8000 A. Tables listing the new energy levels are given in the paper; tables listing the spectral lines with log gf >/= -1.5 that are transitions to the 4f energy levels are given in the Online Material. These new levels produce 18000 lines throughout the spectrum from the ultraviolet to the infrared. Title: An improved high-resolution solar reference spectrum for earth's atmosphere measurements in the ultraviolet, visible, and near infrared Authors: Chance, K.; Kurucz, R. L. Bibcode: 2010JQSRT.111.1289C Altcode: No abstract at ADS Title: Division IX / Commission 25 / Working Group: Infrared Astronomy Authors: Milone, Eugene F.; Young, Andrew T.; Bell, Roger A.; Bessell, Michael; Boyl, Richard P.; Cohen, Martin; Fry, David J. I.; Garrison, Robert; Garrison, Robert; Glass, Ian S.; Graham, John; Granada, Anahi; Hillenbrand, Lynn; Kurucz, Robert L.; McLean, Ian; Mountain, Matthew; Riecke, George; Riffel, Rogerio; Samec, Ronald G.; Schiller, Stephen J.; Simons, Douglas; Skrutskie, Michael; Stagg, C. Russell; Sterken, Christiaan L.; Thompson, Roger I.; Tokunaga, Alan; Volk, Kevin; Wing, Robert Bibcode: 2010IAUTB..27..229M Altcode: The formal origin of the IRWG occured at the Buenos Aires General Assembly, following a Joint Commission meeting at the IAU GA in Baltimore in 1988 that identified the problems with ground-based infrared photometry. The situation is summarized in Milone (1989). In short, the challenges involved how to explain the failure to achieve the milli-magnitude precision expected of infrared photometry and an apparent 3% limit on system transformability. The proposed solution was to redefine the broadband Johnson system, the passbands of which had proven so unsatisfactory that over time effectively different systems proliferated, although bearing the same JHKLMNQ designations; the new system needed to be better positioned and centered in the atmospheric windows of the Earth's atmosphere, and the variable water vapour content of the atmosphere needed to be measured in real time to better correct for atmospheric extinction. Title: Biological damage due to photospheric, chromospheric and flare radiation in the environments of main-sequence stars Authors: Cuntz, Manfred; Guinan, Edward F.; Kurucz, Robert L. Bibcode: 2010IAUS..264..419C Altcode: 2009arXiv0911.1982C We explore the biological damage initiated in the environments of F, G, K, and M-type main-sequence stars due to photospheric, chromospheric and flare radiation. The amount of chromospheric radiation is, in a statistical sense, directly coupled to the stellar age as well as the presence of significant stellar magnetic fields and dynamo activity. With respect to photospheric radiation, we also consider detailed synthetic models, taking into account millions or hundred of millions of lines for atoms and molecules. Chromospheric UV radiation is increased in young stars in regard to all stellar spectral types. Flare activity is most pronounced in K and M-type stars, which also has the potential of stripping the planetary atmospheres of close-in planets, including planets located in the stellar habitable zone. For our studies, we take DNA as a proxy for carbon-based macromolecules, guided by the paradigm that carbon might constitute the biochemical centerpiece of extraterrestrial life forms. Planetary atmospheric attenuation is considered in an approximate manner. Title: ACCESS: Enabling an Improved Flux Scale for Astrophysics Authors: Kaiser, Mary Elizabeth; Kruk, J. W.; McCandliss, S. R.; Sahnow, D. J.; Rauscher, B. J.; Kimble, R. A.; Wright, E. L.; Dixon, W. V.; Feldman, P. D.; Moos, H. W.; Reiss, A. G.; Pelton, R. S.; Gaither, B. W.; Benford, D. J.; Gardner, J. P.; Hill, R. J.; Woodgate, B. E.; Bohlin, R. C.; Deustua, S. E.; Kurucz, R.; Lampton, M.; Perlmutter, S. Bibcode: 2010AAS...21544119K Altcode: 2010BAAS...42..404K Improvements in the precision of the astrophysical flux scale are needed to answer fundamental scientific questions ranging from cosmology to stellar physics. In particular, the precise calibration of the flux scale across the bandpass extending from 0.35 - 1.7 microns is fundamental to the precise determination of dark energy parameters based on SNeIa photometry. ACCESS - Absolute Color Calibration Experiment for Standard Stars (Kaiser et al., 2009) is a rocket-borne payload that will enable the transfer of absolute laboratory detector standards from NIST to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of R = 500 across the 0.35-1.7 micron bandpass.

Among the strategies being employed to minimize calibration uncertainties are: (1) judicious selection of standard stars (previous calibration heritage, minimal spectral features, robust stellar atmosphere models), (2) execution of observations above the Earth's atmosphere (eliminates atmospheric contamination of the stellar spectrum), (3) a single optical path and detector (to minimize visible to NIR cross-calibration uncertainties), (4)

establishment of an a priori error budget, (5) on-board monitoring of instrument performance, and (6) fitting stellar atmosphere models to the data to search for discrepancies and enable extrapolation to wavelengths outside the ACCESS bandpass. The instrument design, calibration and observing strategy will be presented.

Support for this work was provided by NASA through grant NNX08AI65G and DOE through grant DE-FG02-07ER41506. Title: A New View of Vega's Composition, Mass, and Age Authors: Yoon, Jinmi; Peterson, Deane M.; Kurucz, Robert L.; Zagarello, Robert J. Bibcode: 2010ApJ...708...71Y Altcode: We present estimates of Vega's composition, mass, and age based on a simultaneous fit of high-resolution metal line profiles, the wings of the Balmer lines, the absolute visible/near-IR fluxes, and high angular resolution triple phase data from the Navy Prototype Optical Interferometer to gravity-darkened Roche models. This substantially expands our earlier analysis. We determine that Vega has a much lower mass, 2.135 ± 0.074 M sun, than generally assumed. This strongly supports the contention that Vega is metal-poor throughout (Z ~ 0.008), suggesting it was formed that way. Assuming a uniform composition equal to that derived for the surface, and the luminosity and radius obtained here, we derive a best estimate of Vega's age, 455 ± 13 Myr, and mass, 2.157 ± 0.017 M sun, by fitting to standard isochrones. We continue to argue that Vega is much too old to be coeval with other members of the Castor moving group and is thus unlikely to be a member. The updated chemical abundances continue to support the conclusion that Vega is a λ Boo star. Title: ACCESS: Enabling an Improved Flux Scale for Astrophysics Authors: Kaiser, Mary Elizabeth; Kruk, Jeffrey W.; McCandliss, Stephan R.; Sahnow, David J.; Barkhouser, Robert H.; Van Dixon, W.; Feldman, Paul D.; Moos, H. Warren; Orndorff, Joseph; Pelton, Russell; Riess, Adam G.; Rauscher, Bernard J.; Kimble, Randy A.; Benford, Dominic J.; Gardner, Jonathan P.; Hill, Robert J.; Woodgate, Bruce E.; Bohlin, Ralph C.; Deustua, Susana E.; Kurucz, Robert; Lampton, Michael; Perlmutter, Saul; Wright, Edward L. Bibcode: 2010arXiv1001.3925K Altcode: Improvements in the precision of the astrophysical flux scale are needed to answer fundamental scientific questions ranging from cosmology to stellar physics. The unexpected discovery that the expansion of the universe is accelerating was based upon the measurement of astrophysical standard candles that appeared fainter than expected. To characterize the underlying physical mechanism of the "Dark Energy" responsible for this phenomenon requires an improvement in the visible-NIR flux calibration of astrophysical sources to 1% precision. These improvements will also enable large surveys of white dwarf stars, e.g. GAIA, to advance stellar astrophysics by testing and providing constraints for the mass-radius relationship of these stars. ACCESS (Absolute Color Calibration Experiment for Standard Stars) is a rocket-borne payload that will enable the transfer of absolute laboratory detector standards from NIST to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of R = 500 across the 0.35-1.7 micron bandpass. Among the strategies being employed to minimize calibration uncertainties are: (1) judicious selection of standard stars (previous calibration heritage, minimal spectral features, robust stellar atmosphere models), (2) execution of observations above the Earth's atmosphere (eliminates atmospheric contamination of the stellar spectrum), (3) a single optical path and detector (to minimize visible to NIR cross-calibration uncertainties), (4) establishment of an a priori error budget, (5) on-board monitoring of instrument performance, and (6) fitting stellar atmosphere models to the data to search for discrepancies and confirm performance. Title: New identified (^3H)4d-(^3H)4f transitions of Fe II from UVES spectra of HR 6000 and 46 Aquilae Authors: Castelli, F.; Kurucz, R.; Hubrig, S. Bibcode: 2009A&A...508..401C Altcode: 2009arXiv0909.1936C Aims. The analysis of the high-resolution UVES spectra of the CP stars HR 6000 and 46 Aql has revealed the presence of an impressive number of unidentified lines, in particular in the 5000-5400 Å region. Because numerous 4d-4f transitions of FeII lie in this spectral range, and because both stars are iron overabundant, we investigate whether the unidentified lines are FeII.
Methods: ATLAS12 model atmospheres with parameters T_eff = 13 450 K, log g = 4.3 and T_eff = 12 560 K, log g = 3.8 were computed for the individual abundances of the stars HR 6000 and 46 Aql, respectively, to use them as spectroscopic sources to identify FeII lines and determine FeII gf-values. After identifying several unknown lines in the stellar spectra as (3H)4d-(3H)4f transitions of FeII, we derived astrophysical log gf-values for them. The energies of the upper levels were assigned on the basis of both laboratory iron spectra and predicted energy levels.
Results: We determined 21 new levels of FeII with energies between 122 910.9 cm-1 and 123 441.1 cm-1. They allowed us to add 1700 new lines to the FeII linelist in the wavelength range 810-15 011 Å. Many of these lines are sufficiently strong to contribute to the spectra of Population I late B-type stars, even when their iron abundance is subsolar. In the 5000-6000 Å region discussed in this paper, the astrophysical and computed log gf-values show good general agreement and greatly improve the synthetic spectrum of both HR 6000 and 46 Aql. However, many features remain unidentified indicating that further work to classify FeII high energy levels has still to be done

This study is the result of a collaboration with Sveneric Johansson, who unfortunately died before this paper started to be written.

Tables 4-6, and Appendices A and B are only available in electronic form at http://www.aanda.org Title: Astrobiology in the Environments of Main-Sequence Stars: Effects of Photospheric Radiation Authors: Cuntz, M.; Gurdemir, L.; Guinan, E. F.; Kurucz, R. L. Bibcode: 2009ASPC..420..253C Altcode: 2007arXiv0712.3260C We explore if carbon-based macromolecules (such as DNA) in the environments of stars other than the Sun are able to survive the effects of photospheric stellar radiation, such as UV-C. Therefore, we focus on main-sequence stars of spectral types F, G, K, and M. Emphasis is placed on investigating the radiative environment in the stellar habitable zones. Stellar habitable zones are relevant to astrobiology because they constitute circumstellar regions in which a planet of suitable size can maintain surface temperatures for water to exist in fluid form, thus increasing the likelihood of Earth-type life. Title: Including All the Lines Authors: Kurucz, Robert L. Bibcode: 2009AIPC.1171...43K Altcode: 2009arXiv0912.5371K I present a progress report on including all the lines in the linelists, including all the lines in the opacities, including all the lines in the model atmosphere and spectrum synthesis calculations, producing high-resolution, high-signal-to-noise atlases that show (not quite) all the lines, so that finally we can determine the properties of stars from a few of the lines. Title: New extended atomic data in cool star model atmospheres. Using Kurucz's new iron data in MAFAGS-OS models Authors: Grupp, F.; Kurucz, R. L.; Tan, K. Bibcode: 2009A&A...503..177G Altcode: 2009arXiv0906.5449G Context: Cool star model atmospheres are a common tool for the investigation of stellar masses, ages and elemental abundance composition. Theoretical atmospheric models strongly depend on the atomic data used when calculating them.
Aims: We present the changes in flux and temperature stratification when changing from iron data computed by R.L. Kurucz in the mid 90s to the Kurucz 2009 iron computations.
Methods: MAFAGS-OS opacity sampling atmospheres were recomputed with Kurucz 2009 iron atomic data as implemented in the VALD database by Ryabchikova. Temperature stratification and emergent flux distribution of the new version, called MAFAGS-OS9, is compared to the former version and to solar flux measurements.
Results: Using the Kurucz line lists converted into the VALD format and new bound-free opacities for Mg i and Al i leads to changes in the solar temperature stratification by not more than 28 K. At the same time, the calculated solar flux distribution shows significantly better agreement between observations and theoretical solar models. These changes in the temperature stratification of the corresponding models are small, but nevertheless of a magnitude that affects stellar parameter determinations and abundance analysis. Title: ACCESS - Absolute Color Calibration Experiment for Standard Stars Authors: Kaiser, Mary Elizabeth; Kruk, J. W.; McCandliss, S. R.; Sahnow, D. J.; Dixon, W. V.; Feldman, P. D.; Moos, H.; Riess, A. G.; Rauscher, B. J.; Kimble, R. A.; Benford, D. J.; Gardner, J. P.; Woodgate, B. E.; Bohlin, R. C.; Duestua, S. E.; Kurucz, R.; Lampton, M.; Perlmutter, S.; Wright, E. L. Bibcode: 2009AAS...21347515K Altcode: 2009BAAS...41..437K ACCESS is a rocket-borne payload with a ground-based calibration and performance monitoring program. It is designed to transfer the NIST absolute laboratory standards to the stars with a precision and calibration accuracy of 1% at a spectral resolving power greater than 500 across the 0.35-1.7 micron bandpass. This represents a significant improvement in the absolute and relative astrophysical flux calibration systems, especially at NIR wavelengths.

Several strategies will be employed to minimize calibration uncertainties. The standard star sample is comprised of stars with previous calibration heritage, minimal spectral features, and robust stellar atmosphere models. Observations will be conducted above the Earth's atmosphere to eliminate atmospheric

contamination of the stellar spectrum. To avoid calibration uncertainties between the visible and the NIR spectra, a single optical path and detector will be used. An a priori error budget will be established. Instrument performance will be tracked through the use of an on-board calibration monitor. Each standard star will be observed twice to establish repeatability. We will present the instrument design, observing and calibration strategies and error budget for ACCESS. Results of laboratory tests relevant to the design of the on-board calibration monitor will also be presented.

Establishing improved spectrophotometric standards is important for a broad range of missions and is relevant to many astrophysical problems. In particular, the precise calibration of the flux scale across the bandpass extending from 0.35 - 1.7 microns is fundamental to the precise determination of dark energy parameters based on SNeIa photometry.

Support for this work was provided by NASA through grant NNX08AI65G and DOE through grant DE-FG02-07ER41506. Title: Division IX / Commission 25 / Working Group Infrared Astronomy Authors: Milone, Eugene F.; Young, Andrew T.; Bauwens, Eva; Bell, Roger A.; Bessell, Michael S.; Cohen, Martin; Garrison, Robert; Glass, Ian S.; Graham, John A.; Henden, Arne A.; Hensberge, Herman; Hillenbrand, Lynne A.; Howell, Steve B.; Kidger, Mark R.; Kurucz, Robert L.; Landolt, Arlo U.; McLean, Ian S.; Mountain, Matthew; Rieke, George H.; Schiller, Stephen J.; Simons, Douglas A.; Skrutskie, Michael F.; Stagg, C. Russell; Sterken, Christiaan L.; Thompson, Roger I.; Tokunaga, Alan T.; Volk, Kevin Bibcode: 2009IAUTA..27..313M Altcode: As we have noted before, the WG-IR was created following a Joint Commission Meeting at the IAU General Assembly in Baltimore in 1988, a meeting that provided both diagnosis and prescription for the perceived ailments of infrared photometry at the time. The results were summarized in Milone (1989). The challenges involve how to explain the failure to systematically achieve the milli-magnitude precision expected of infrared photometry and an apparent 3% limit on system transformability. The proposed solution was to re-define the broadband Johnson system, the passbands of which had proven so unsatisfactory that over time effectively different systems proliferated although bearing the same JHKLMNQ designations; the new system needed to be better positioned and centered in the atmospheric windows of the Earth's atmosphere, and the variable water vapour content of the atmosphere needed to be measured in real time to better correct for atmospheric extinction. Title: Most Population III Supernovae are Duds Authors: Kurucz, Robert L. Bibcode: 2008arXiv0808.3282K Altcode: One Population III dud supernova produces enough oxygen to enable ten million solar masses of primordial gas to bind into M dwarfs. This is possible because radiation from other Population III stars implodes the mixture of oxygen ejecta and primordial gas into a globular cluster. Model atmosphere calculations for oxygen dwarfs show that water blocks most of the infrared flux. The flux is redistributed into the visible to produce an unfamiliar, distinctive energy distribution. One million dud supernovae in a large protogalaxy are sufficient to produce the "dark matter" halo. Title: On-board calibration monitor for tracking instrument sensitivity Authors: Kruk, J. W.; Kaiser, M. E.; McCandliss, S. R.; Orndorff, J.; Barkhouser, R. H.; Sahnow, D. J.; Benford, D. J.; Bohlin, R. C.; Deustua, S. E.; Dixon, W. V.; Feldman, P. D.; Gardner, J. P.; Kimble, R. A.; Kurucz, R.; Lampton, M.; Moos, H. W.; Perlmutter, S.; Rauscher, B. J.; Riess, A. G.; Woodgate, B. E.; Wright, E. L. Bibcode: 2008SPIE.7014E..5JK Altcode: 2008SPIE.7014E.184K The On-board Calibration Monitor (OCM) is being developed as an integral component of the ACCESS instrument and as a pathfinder for other missions. It provides stable full-aperture illumination of the telescope for tracking the instrument sensitivity as a function of time. The light source is composed of an ensemble of LED pairs with central wavelengths that span the spectral range of the instrument and illuminate a diffuser that is observed by the full optical path. Feedback stabilization of the light source intensity is achieved by photodiode monitoring of each LED. This stable source will provide real time knowledge of the ACCESS sensitivity throughout the 5-year duration of the program. The present status of the design and laboratory evaluation of the OCM system will be presented. Title: ACCESS: absolute color calibration experiment for standard stars Authors: Kaiser, Mary Elizabeth; Kruk, Jeffrey W.; McCandliss, Stephan R.; Sahnow, David J.; Rauscher, Bernard J.; Benford, Dominic J.; Bohlin, Ralph C.; Deustua, S. E.; Dixon, W. V.; Feldman, P. D.; Gardner, J. P.; Kimble, R. A.; Kurucz, R.; Lampton, M.; Moos, H. W.; Perlmutter, S.; Riess, A. G.; Woodgate, B. E.; Wright, E. L. Bibcode: 2008SPIE.7014E..5YK Altcode: 2008SPIE.7014E.197K ACCESS is a recently approved rocket-borne payload with a ground-based calibration and performance monitoring program that is designed to transfer the National Institute of Standards and Technology (NIST) absolute laboratory standards to the stars with a precision and calibration accuracy of 1% across the 0.35-1.7μm bandpass. This represents a significant improvement in the absolute and relative astrophysical flux calibration system, particularly at near-infrared (NIR) wavelengths. Establishing improved spectrophotometric standards is important for a broad range of missions and is relevant to many astrophysical problems. In particular, the precise calibration of the flux scale across the bandpass extending from 0.35-1.7 μm is fundamental to the precise determination of dark energy measurements based on SNeIa photometry. Title: Astrobiological effects of F, G, K and M main-sequence stars Authors: Cuntz, M.; Gurdemir, L.; Guinan, E. F.; Kurucz, R. L. Bibcode: 2008IAUS..249..203C Altcode: 2007arXiv0712.3257C; 2007IAUS..249..203C We focus on the astrobiological effects of photospheric radiation produced by main-sequence stars of spectral types F, G, K, and M. The photospheric radiation is represented by using realistic spectra, taking into account millions or hundred of millions of lines for atoms and molecules. DNA is taken as a proxy for carbon-based macromolecules, assumed to be the chemical centerpiece of extraterrestrial life forms. Emphasis is placed on the investigation of the radiative environment in conservative as well as generalized habitable zones. Title: ACCESS - Absolute Color Calibration Experiment for Standard Stars Authors: Kaiser, Mary Elizabeth; Kruk, J. W.; McCandliss, S. R.; Sahnow, D. J.; Dixon, W. V.; Feldman, P. D.; Moos, H. W.; Riess, A. G.; Rauscher, B. J.; Benford, D. J.; Gardner, J. P.; Kimble, R. A.; Woodgate, B. E.; Bohlin, R. C.; Kurucz, R.; Deustua, S. E.; Lampton, M.; Perlmutter, S.; Wright, E. L. Bibcode: 2007AAS...211.1123K Altcode: 2007BAAS...39..748K ACCESS is a recently approved series of rocket-borne sub-orbital missions and ground-based experiments that will establish a network of standard stars with absolute fluxes that are directly traceable to ground based laboratory standards maintained by NIST. The goal of this program is to establish a high-precision spectrophotometric calibration system in the visible and near-infrared. An absolute spectrophotometric calibration accuracy of <1% will be achieved in the 0.35-1.7 micron bandpass at a spectral resolution of greater than 500, which represents a significant improvement in the absolute calibration in the NIR bandpass. Standard star observations extending to 10th magnitude will establish the first links in a chain of stellar calibrators. Measurement of absolute fluxes of a small number of standard stars enables the existing networks of standards to be placed on an improved absolute scale and makes them available to all telescopes.

ACCESS will reduce uncertainties in the current standard star calibration system by: (1) judicious selection of standard stars, (2) observing above the Earth's atmosphere, (3) using a single optical path and detector, (4) establishing an a priori error budget, (5) performing NIST traceable sub-system and end-to-end payload calibrations, and (6) monitoring and tracking payload performance.

Having improved spectrophotometric standards is important for a broad range of missions and is relevant to many astrophysical problems. It is fundamental to the precise determination of dark energy measurements using SNeIa photometry. In addition, our understanding of stellar physics will be extended through stellar atmosphere modeling of our target stars. Title: Division IX / Commission 25 / Working Group Infrared Astronomy Authors: Milone, Eugene F.; Young, Andrew T.; Bell, Roger A.; Bessell, Michael S.; Cohen, Martin; Garrison, Robert F.; Glass, Ian S.; Graham, John A.; Hillenbrand, Lynne A.; Kurucz, Robert L.; Mountain, Matthew; Rieke, George H.; Schiller, Stephen J.; Simons, Douglas A.; Skrutskie, Michael F.; Stagg, C. Russell; Sterken, Christiaan L.; Thompson, Roger I.; Tokunaga, Alan T.; Volk, Kevin; Volk Bibcode: 2007IAUTB..26..195M Altcode: The WG-IR was created following a Joint Commission Meeting at the IAU General Assembly in Baltimore in 1988, a meeting that provided both diagnosis and prescription for the perceived ailments of infrared photometry at the time. The results were summarized in Milone (1989). The challenges involve how to explain the failure to systematically achieve the milli-magnitude precision expected of infrared photometry and an apparent 3% limit on system transformability. The proposed solution was to redefine the broadband Johnson system, the passbands of which had proven so unsatisfactory that over time effectively different systems proliferated although bearing the same JHKLMNQ designations; the new system needed to be better positioned and centered in the atmospheric windows of the Earth's atmosphere, and the variable water vapour content of the atmosphere needed to be measured in real time to better correct for atmospheric extinction. Title: ACCESS - Absolute Color Calibration Experiment for Standard Stars Authors: Kaiser, Mary Elizabeth; Kruk, J. W.; McCandliss, S. R.; Sahnow, D. J.; Dixon, W.; Feldman, P. D.; Moos, H.; Riess, A.; Rauscher, B. J.; Kimble, R. A.; Gardner, J. P.; Woodgate, B. E.; Bohlin, R. C.; Deustua, S. E.; Kurucz, R.; Perlmutter, S.; Wright, E. L. Bibcode: 2007AAS...20925403K Altcode: 2007BAAS...39..274K ACCESS is a proposed series of rocket-borne sub-orbital missions whose purpose is to establish a network of standard stars with absolute fluxes that are directly traceable to ground based laboratory calibration standards maintained by NIST. Our goal is to obtain an absolute spectrophotometric calibration accuracy of <1% in the 0.35-1.7 micron bandpass at a spectral resolution of greater than 500. This represents a significant improvement in the absolute calibration in the NIR bandpass. This fundamental astrophysics experiment will establish the first links in a chain of stellar calibrators including standard stars (10th magnitude) observable by major telescopes, thus enabling the ultimate calibration to extend to faint magnitudes. This calibration program is important for a broad range of missions and relevant to many astrophysical problems. It is fundamental to photometrically based dark energy missions which use supernova type Ia and will provide the first steps in the calibration path required to support the determination of brightness as a function of distance for SNIae. In addition, it will enable improved stellar atmosphere models, furthering our understanding of stellar physics. Title: Cryptoplanet update Authors: Kurucz, Robert L. Bibcode: 2007arXiv0704.2860K Altcode: We have had several talks recently reviewing 11 years of exoplanet discoveries through radial velocity variations, or from transits, or from microlensing. More than 200 exoplanets have been found, including some around pulsars that we do not discuss here. My physical definition for a planet is a roughly spherical, self-gravitating body more massive than 10**26 g formed from the leftover material in a protostellar disk after the protostar forms. Radiation from the protostar pushes the inner wall of the disk outward. The material agglomerates and forms planets in radial sequence. The outer planets are formed slowly by classical dynamical mechanisms acting in the snow zone. Planets have dense cores because of agglomeration. Not one of the exoplanets discovered thus far is a planet. They are cryptoplanets formed from matter ejected by protostars. When protostars have excessive infall at high latitudes, they partially balance angular momentum through outflow at the equator as they spin up. The ejected matter is trapped in the magnetic torus formed between the star and the disk, like a tokamak. The tokamak eventully reconnects and magnetic compression forms self-gravitating remnants trapped and compressed by a closed spherical magnetic field, spheromaks. Cooled spheromaks are cryptoplanets. They orbit near the star. They can merge with each other or fall into the star or be ejected. They can grow by accreting gas. They have a low density core and abundances characteristic of the protostar. Their masses, radii, densities, and orbits are random, and are inconsistent with the parameters for planets. They tend to have lower density than planets. Title: The precession of Mercury and the deflection of starlight by special relativity alone Authors: Kurucz, Robert L. Bibcode: 2006astro.ph..8434K Altcode: I show that the precession of the orbit of Mercury and the deflection of starlight by the Sun are effects of special relativity alone when the gravitational field of a particle is treated in the same way as the electric field of a charged particle . General relativity is not needed to explain them. Title: Computed Hβ indices from ATLAS9 model atmospheres Authors: Castelli, F.; Kurucz, R. L. Bibcode: 2006A&A...454..333C Altcode: Aims.Grids of Hβ indices based on updated (new-ODF) ATLAS9 model atmospheres were computed for solar and scaled solar metallicities [+0.5], [+0.2], [0.0], [ -0.5] , [ -1.0] , [ -1.5] , [ -2.0] , [ -2.5] and for α enhanced compositions [+0.5a], [0.0a], [ -0.5a] , [ -1.0a] , [ -1.5a] , [ -2.0a] , [ -2.5a] , and [ -4.0a] .
Methods: .Indices for T_eff > 5000 K were computed with the same methods as described by Lester et al. (1986, LGK86) except for a different normalization of the computed natural system to the standard system. LGK86 used special ODFs to compute the fluxes. For T_eff ≤ 5000 K we computed the fluxes using the synthetic spectrum method. In order to assess the accuracy of the computed indices comparisons were made with the indices computed by Smalley & Dworetsky (1995, A&A, 293, 446, MD95) and with the empirical relations T_eff-Hβ given by Alonso et al. (1996, A&A, 313, 873) for several metallicities. Furthermore, for cool stars, temperatures inferred from the computed indices were compared with those of the fundamental stars listed by MD95. The same kind of comparison was made between gravities for B-type stars.
Results: .The temperatures from the computed indices are in good agreement, within the error limits, with the literature values for 4750 K ≤ T_eff ≤ 8000 K, while the gravities agree for T_eff > 9000 K. The computed Hβ indices for the Sun and for Procyon are very close to the observed values. The comparison between the observed and computed Hβ indices as function of the observed Hβ has shown a very small trend which almost completely disappears when only stars hotter than 10 000 K are considered. The trend due to the cool stars is probably related with the low accuracy of the fundamental T_eff which are affected by large errors for most of the stars.
Title: Identification of the broad solar emission features near 117 nm Authors: Avrett, E. H.; Kurucz, R. L.; Loeser, R. Bibcode: 2006A&A...452..651A Altcode: 2006astro.ph..3361A Wilhelm et al. have recently called attention to the unidentified broad emission features near 117 nm in the solar spectrum. They discuss the observed properties of these features in detail but do not identify the source of this emission. We show that the broad autoionizing transitions of neutral sulfur are responsible for these emission features. Autoionizing lines of ion{S}{i} occur throughout the spectrum between Lyman alpha and the Lyman limit. Sulfur is a normal contributor to stellar spectra. We use non-LTE chromospheric model calculations with line data from the Kurucz 2004 ion{S}{i} line list to simulate the solar spectrum in the range 116 to 118 nm. We compare the results with SUMER disk-center observations from Curdt et al. and limb observations from Wilhelm et al. Our calculations generally agree with the SUMER observations of the broad autoionizing ion{S}{i} emission features, the narrow ion{S}{i} emission lines, and the continuum in this wavelength region, and agree with basic characteristics of the center-to-limb observations. In addition to modeling the average spectrum, we show that a change of ±200 K in the temperature distribution causes the intensity to change by a factor of 4. This exceeds the observed intensity variations 1) with time in quiet regions at these wavelengths, and 2) with position from cell centers to bright network. These results do not seem compatible with current dynamical models that have temporal variations of 1000 K or more in the low chromosphere. Title: Radiatively-Driven Cosmology in the Cellular Automaton Universe Authors: Kurucz, Robert L. Bibcode: 2006astro.ph..5469K Altcode: This is an updated version of my paper "An outline of radiatively-driven cosmology" (Kurucz 2000). Here the Big Bang universe is replaced by a finite cellular automaton universe with no expansion (Kurucz 2006). The Big Bang is replaced by many little bangs spread throughout the universe that interact to produce the initial perturbations that form Population III stars, globular clusters, and galaxies, but no large-scale structure. These perturbations evolve into the universe as we now observe it. Evolution during the first billion years is controlled by radiation. Globular clusters are formed by radiatively-driven implosions, galaxies are formed by radiatively-triggered gravitational collapse of systems of globular clusters, and voids and the microwave background are formed by radiatively-driven expansion. After this period most of the strong radiation sources are exhausted and the universe relaxes into gravitational old age as we know it. To relieve the boredom we present the results of gedanken experiments (Kurucz 1992) in a traditional, linear, chronological sequence in the hope of stimulating research on the many topics considered. Title: Elementary Physics in the Cellular Automaton Universe Authors: Kurucz, Robert L. Bibcode: 2006astro.ph..5467K Altcode: General relativity is a mathematical model that uses sophisticated geometry to describe simple physics. It agrees with experiment in the few tests that can be made, but the whole edifice is not physics. Instead of using observations to test that model, I derive a simple empirical model of elementary physics and cosmology from the observations. The observations imply that the universe is a finite cellular automaton; that there is no curved space; that fundamental particles are massless; that "massy" particles, including electrons, are composed of fundamental particles; that gravitational mass is inertial mass; that black holes are made from neutrons compressed into bosons; that the universe was produced from cold compressed particles, not radiation; and that the universe is not expanding. Title: High Resolution Irradiance Spectrum from 300 to 1000 nm Authors: Kurucz, Robert L. Bibcode: 2006astro.ph..5029K Altcode: The FTS scans that made up the Kitt Peak Solar Flux Atlas by Kurucz, Furenlid, Brault, and Testerman (1984) have been re-reduced. An approximate telluric atmospheric model was determined for each FTS scan. Large-scale features produced by O3 and O2 dimer were computed and divided out. The solar continuum level was found by fitting a smooth curve to high points in each scan. The scans were normalized to the fitted continuum to produce a residual flux spectrum for each FTS scan. The telluric line spectrum was computed using HITRAN and other line data for H2O, O2, and CO2. The line parameters were adjusted for an approximate match to the observed spectra. The scans were divided by the computed telluric spectra to produce residual irradiance spectra. Artifacts from wavelength mismatches, deep lines, etc, were removed by hand and replaced by linear interpolation. Overlapping scans were fitted together to make a continuous spectrum from 300 to 1000 nm. All the above steps were iterative. The monochromatic error varies from 0.1 to 1.0 percent. The residual spectrum was calibrated two different ways: First by normalizing it to the continuum of theoretical solar model ASUN (Kurucz 1992), and second, by degrading the spectrum to the resolution of the observed irradiance (Thuillier et al. 2004) to determine a normalization function that was then applied to the high resolution spectrum. Title: VizieR Online Data Catalog: Computed Hbeta indices from ATLAS9 model (Castelli+, 2006) Authors: Castelli, F.; Kurucz, R. L. Bibcode: 2006yCat..34540333C Altcode: Grids of H{beta} indices based on updated (new-ODF) ATLAS9 model atmospheres were computed for solar and scaled solar metallicities [+0.5], [+0.2], [0.0], [-0.5], [-1.0], [-1.5], [-2.0], [-2.5] and for alpha enhanced compositions [+0.5a], [0.0a], [-0.5a], [-1.0a], [-1.5a], [-2.0a], [-2.5a], and [-4.0a]. Indices for Teff>5000K were computed with the same methods as described by Lester, Gray & Kurucz (1986ApJS...61..509L) (LGK86) except for a different normalization of the computed natural system to the standard system. LGK86 used special ODFs to compute the fluxes. For Teff less or equal to 5000K we computed the fluxes using the synthetic spectrum method. In order to assess the accuracy of the computed indices comparisons were made with the indices computed by Smalley & Dworetsky (1995A&A...293..446S) (MD95) and with the empirical relations Teff-H{beta} given by Alonso et al. (1996A&A...313..873A) for several metallicities. Furthermore, for cool stars, temperatures inferred from the computed indices were compared with those of the fundamental stars listed by MD95. The same kind of comparison was made between gravities for B-type stars. The temperatures from the computed indices are in good agreement, within the error limits, with the literature values for Teff between 4750K and 8000K, while the gravities agree for Teff>9000K. The computed H{beta} indices for the Sun and for Procyon are very close to the observed values. The comparison between the observed and computed H{beta} indices as function of the observed H{beta} has shown a very small trend which almost completely disappears when only stars hotter than 10000K are considered. The trend due to the cool stars is probably related with the low accuracy of the fundamental Teff which are affected by large errors for most of the stars.

(1 data file). Title: Including all the Lines Authors: Kurucz, R. L. Bibcode: 2006EAS....18..129K Altcode: We present a progress report on including all the lines in the linelists, including all the lines in the opacities, including all the lines in the model atmosphere and spectrum synthesis calculations, producing high-resolution, high-signal-to-noise atlases that show (not quite) all the lines, so that finally we can determine the properties of stars from a few of the lines. Title: Status of the physics of substellar objects Authors: Jones, H. R. A.; Viti, S.; Tennyson, J.; Barber, B.; Harris, G.; Pickering, J. C.; Blackwell-Whitehead, R.; Champion, J. -P.; Allard, F.; Hauschildt, P. H.; Jorgensen, U. G.; Ehrenfreund, P.; Stachowska, E.; Ludwig, H. -G.; Martin, E.; Pavlenko, Ya.; Lyubchik, Yu.; Kurucz, R. L. Bibcode: 2005AN....326..920J Altcode: A full understanding of the properties of substellar objects is one of the major challenges facing astrophysics. Since their discovery in 1995, we have discovered hundreds of brown dwarfs and extrasolar planets. While these discoveries have enabled important comparisons with theory, observational progress has been much more rapid than the theoretical understanding of cool atmospheres. The reliable determination of mass, abundances, gravities and temperatures is not yet possible. The key problem is that substellar objects emit their observable radiation in the infrared region of the spectrum where our knowledge of atomic, molecular and line broadening data is poor. Here we report on the status of PoSSO (Physics of SubStellar Objects). In order to understand brown dwarfs and extrasolar planets increasing more like those in our solar system, we are studying a wide range of processes. Here we give an update on the project and sketch an outline of atoms, molecules and processes requiring study. Title: ACCESS - Absolute Color Calibration Experiment for Standard Stars Authors: Kaiser, M. E.; Dixon, W. V.; Feldman, P. D.; Kruk, J. W.; McCandliss, S. R.; Moos, H. W.; Sahnow, D. J.; Rauscher, B. J.; Gardner, J. P.; Kimble, R. A.; Schwartz, P. C.; Woodgate, B. E.; Bohlin, R. C.; Deustua, S. E.; Kurucz, R.; Perlmutter, S. Bibcode: 2005AAS...20717312K Altcode: 2005BAAS...37.1440K ACCESS is a proposed series of rocket-borne sub-orbital missions whose purpose is to establish a network of standard stars with absolute fluxes that are directly traceable to ground based laboratory standards maintained by NIST. Our goal is to obtain an absolute spectrophotometric calibration accuracy of <1% in the 0.35-1.7 micron bandpass at a spectral resolution of greater than 500. This represents a significant improvement in the absolute calibration in the NIR bandpass. This fundamental astrophysics experiment will establish the first links in a chain of stellar calibrators including standard stars (10th magnitude) observable by major telescopes, thus enabling the ultimate calibration to extend to faint magnitudes.

This calibration program is important for a broad range of missions and relevant to many astrophysical problems. In particular, it is fundamental to photometrically based dark energy missions which use supernova type Ia. Title: How Similar are Starspots to Sunspots? Authors: Rajaguru, S. P.; Kurucz, R. L.; Hasan, S. S. Bibcode: 2005BASI...33..362R Altcode: No abstract at ADS Title: The Solar Oxygen Abundance, and the Rare Isotopes of C and O, Derived from Infrared Spectra of Carbon Monoxide Authors: Ayres, T. R.; Plymate, C.; Keller, C.; Kurucz, R. L. Bibcode: 2005AGUSMSP41B..09A Altcode: A detailed abundance analysis is presented for solar oxygen based on the ΔV=1 fundamental (4.6~μm) and ΔV=2 (2.3~μm) first-overtone rovibrational bands of carbon monoxide observed above the Earth's atmosphere at very high spectral resolution and high signal-to-noise by the Shuttle-borne ATMOS Fourier transform spectrometer (FTS). Additional observations to define the reference photospheric thermal structure were taken of the CO fundamental bands in an atmospheric window at 2145~cm-1 (4.6~μm) using the 1~m FTS of the McMath-Pierce telescope at Kitt Peak and a fast tip/tilt image stabilization system. The latter allowed measurements at the extreme limb where the highly slanted rays probe into the outer layers of the photosphere. High spatial resolution "movies" of weak CO lines at disk center taken under excellent seeing conditions with the Infrared Imaging Spectrometer (IRIS), also on the McMath-Pierce telescope, further constrained thermal and velocity fluctuations in the layers in which the abundance-sensitive CO lines form. This work is meant to complement a series of recent studies which have revised the previously recommended solar oxygen abundance downward by nearly a factor of two; although in fact our conclusions do not support such a revision. The oxygen abundance recovered in the present work is 700±70~ppm (parts per million relative to hydrogen) compared with the proposed downward revision to 460±60~ppm, and the recommended value of 650±100~ppm of a decade ago. In our analysis, a fixed C/O ratio of 0.5, derived in independent work, was assumed; so the associated carbon abundance is 350~ppm. New accurate values for the solar abundance ratios of the rare isotopes of C and O also are reported: 12C/13C= 70, 16O/17O= 400, and 16O/18O= 2000. All three ratios are lower than terrestrial or meteoritic values (indicating higher isotopic abundances). We find no evidence in the ATMOS3 spectra for measurable 14C16O lines. Title: New atlases for solar flux, irradiance, central intensity, and limb intensity Authors: Kurucz, Robert L. Bibcode: 2005MSAIS...8..189K Altcode: I have produced a revised FTS Kitt Peak Solar Flux Atlas for 300 to 1000 nm (Kurucz 2005) and a new high resolution Kitt Peak Irradiance Atlas from 300 to 1000 nm with the telluric lines removed. I am now working on central intensity and limb intensity atlases for the same region. If I can get funding I will extend these atlases to 5.5 mu m. I will also produce atlases with the observed and computed spectra and line identifications. Title: Physical, numerical, and computational limits for Kurucz codes Authors: Kurucz, Robert L. Bibcode: 2005MSAIS...8...73K Altcode: We outline physical, numerical, and computational limits on Kurucz's codes, for model atmospheres, ATLAS12 and ATLAS9, spectrum synthesis, SYNTHE, and abundance analysis, WIDTH9. Title: ATLAS12, SYNTHE, ATLAS9, WIDTH9, et cetera Authors: Kurucz, Robert L. Bibcode: 2005MSAIS...8...14K Altcode: The problem we address is including the opacity of millions or hundreds of millions of lines in model stellar atmosphere calculations, then generating detailed, realistic spectra from those model atmospheres, then modelling the observation process, and finally comparing the calculated spectra to observed spectra to determine the properties of stars so that we can understand their evolution and the evolution of galaxies. We describe the current status of Kurucz's programs and atomic and molecular line data. Title: Rapid computation of line opacity in SYNTHE and DFSYNTHE Authors: Kurucz, Robert L. Bibcode: 2005MSAIS...8...76K Altcode: Methods are suggested for speeding up the computation of opacity. Title: PoSSO Physics of SubStellar Objects Authors: Jones, Hugh; Viti, Serena; Tennyson, Jonathan; Barber, Bob; Pickering, Juliet; Blackwell-Whitehead, Richard; Champion, Jean-Paul; Allard, France; Hauschildt, Peter; Jørgensen, Uffe; Ehrenfreund, Pascale; Stachowska, Ewa; Ludwig, Hans-Günter; Pavlenko, Yakiv; Lyubchik, Yuri; Kurucz, Robert Bibcode: 2005hris.conf..477J Altcode: A full understanding of the properties of substellar objects is one of the major challenges facing astrophysics. Since their discovery in 1995, we have discovered hundreds of brown dwarfs and extrasolar planets. While these discoveries have enabled important comparisons with theory, observational progress has been much more rapid than the theoretical understanding of cool atmospheres. The determination of mass, abundances, gravities and temperatures is not yet possible. The key problem is that substellar objects emit their observable radiation in the infrared region of the spectrum where our knowledge of atomic, molecular and line broadening data is poor. In order to understand these objects, and extra-solar planets increasing more like those our Solar System, we urge the wider physical chemistry community to engage in this exciting new field. Here we sketch an outline of the atoms, molecules and processes requiring study. Title: Including all the lines Authors: Kurucz, Robert L. Bibcode: 2005MSAIS...8...86K Altcode: Of the line data on my website, 99 % have predicted wavelengths and can be used only to compute opacities. One percent have good wavelengths between known levels and can be used for detailed spectrum calculations for comparision to observed spectra. The line data with good wavelengths account for only one-half of the observed lines. The gf values and damping constants for most lines must be adjusted to match observed spectra. We know that the higher configurations are missing from the line lists. We know that heavier elements are missing from the line lists. We know that isotopic and hyperfine splittings are missing from the line lists. We know that many molecules are missing from the line lists. Leaving out all these lines systematically underestimates the opacity, produces energy distributions with systematic errors, and leads to abundance determinations with large systematic errors. We need much better laboratory analyses including hyperfine and isotopic splitting. We need better calculations that fill in the higher configurations and the heavier elements. We need better measurements and calculations for all the significant diatomic and polyatomic molecules including all the isotopomers. I am doing as much as I can to fill in the missing data and to make it available on my web site. Title: The binary progenitor of Tycho Brahe's 1572 supernova Authors: Ruiz-Lapuente, Pilar; Comeron, Fernando; Méndez, Javier; Canal, Ramon; Smartt, Stephen J.; Filippenko, Alexei V.; Kurucz, Robert L.; Chornock, Ryan; Foley, Ryan J.; Stanishev, Vallery; Ibata, Rodrigo Bibcode: 2004Natur.431.1069R Altcode: 2004astro.ph.10673R The brightness of type Ia supernovae, and their homogeneity as a class, makes them powerful tools in cosmology, yet little is known about the progenitor systems of these explosions. They are thought to arise when a white dwarf accretes matter from a companion star, is compressed and undergoes a thermonuclear explosion. Unless the companion star is another white dwarf (in which case it should be destroyed by the mass-transfer process itself), it should survive and show distinguishing properties. Tycho's supernova is one of only two type Ia supernovae observed in our Galaxy, and so provides an opportunity to address observationally the identification of the surviving companion. Here we report a survey of the central region of its remnant, around the position of the explosion, which excludes red giants as the mass donor of the exploding white dwarf. We found a type G0-G2 star, similar to our Sun in surface temperature and luminosity (but lower surface gravity), moving at more than three times the mean velocity of the stars at that distance, which appears to be the surviving companion of the supernova. Title: A Calibration of FWHM vs. υ for UV Lines Authors: Ramírez, I.; Koenigsberger, G.; Kurucz, R. L. Bibcode: 2004IAUS..215...19R Altcode: No abstract at ADS Title: Is missing Fe I opacity in stellar atmospheres a significant problem? Authors: Castelli, F.; Kurucz, R. L. Bibcode: 2004A&A...419..725C Altcode: We present an empirical model-atmosphere investigation of missing Fe I opacity. Houdashelt et al. (\cite{houd00}) estimated that if Dragon & Mutschlecner (\cite{dm80}) Fe I cross sections used in the MARCS model atmospheres (Gustafsson et al. \cite{gus75}) were replaced by the Bautista (\cite{bau97}) cross sections the solar continuous flux would be reduced by 15% in the near ultraviolet. That would imply systematic errors in models for F, G, and K stars. As a consequence, since ATLAS9 (Kurucz \cite{k93a}) uses an approximation to the same Dragon & Mutschlecner (\cite{dm80}) opacities, there should also be similar systematic errors in ATLAS9 models that required this investigation. Bound-free Fe I cross sections computed by Bautista (\cite{bau97}) in the framework of the IRON Project were used to generate the continuous Fe I absorption coefficient. It was incorporated in the Kurucz (\cite{k93a}) ATLAS9 code, in place of that currently used, which is based on approximate cross sections by Kurucz. By combining Opacity Distribution Functions (ODFs) computed without the contribution of Fe I autoionization lines with the new Fe I absorption coefficient which is crowded with autoionization resonances, we obtained solar metallicity model atmospheres and energy distributions for several combinations of T_eff and log g. The comparison of these models with the standard ATLAS9 models has shown that there are no differences in the T-τRoss relations, while there are some changes in the energy distributions for Teff,≤ 7000 K, but limited to small wavelength regions around 2150 Å, where Kurucz has less opacity, and 3350 Å, where Bautista has less opacity. The differences are of the order of 25% and less than 10%, respectively. That around 2150 Å disappears for Teff,≤ 5500 K owing to the fall of the emergent flux at these wavelengths in cool stars. This behaviour is independent of the gravity. The explanation is that our line list actually has more autoionizing opacity than Bautista's but it is treated as bound-bound line opacity rather than as bound-free opacity. Title: ATLAS and SYNTHE under Linux Authors: Sbordone, L.; Bonifacio, P.; Castelli, F.; Kurucz, R. L. Bibcode: 2004MSAIS...5...93S Altcode: 2004astro.ph..6268S We have successfully ported under GNU Linux ATLAS 9, the widely used stellar atmosphere modeling code, as well as both the SYNTHE suite of programs, its ``companion'' for spectral synthesis, and WIDTH, used to derive chemical abundances from equivalent widths of spectral lines. The porting has been realized by using the Intel Fortran Compiler. Our aim was to port the codes with the minimum possible amount of modifications: full compatibility with the VMS version has been maintained, along with all the codes functionalities. Dramatic improvement in calculation speed with respect to the VMS version has been achieved. The full suite of codes is intended to be freely available to everyone. Title: Spatially Resolved STIS Spectroscopy of Betelgeuse's Outer Atmosphere Authors: Lobel, A.; Aufdenberg, J.; Dupree, A. K.; Kurucz, R. L.; Stefanik, R. P.; Torres, G. Bibcode: 2004IAUS..219..641L Altcode: 2003IAUS..219E.158L; 2003astro.ph.12076L We present spatially resolved spectra observed with HST-STIS of the upper chromosphere and dust envelope of Alpha Orionis (M2 Iab). In the fall of 2002 a set of five high-resolution near-UV spectra was obtained by scanning at intensity peak-up position and four off-limb target positions up to one arcsecond, using a small aperture, to investigate the thermal conditions and flow dynamics in the outer atmosphere of this important nearby cool supergiant star. Based on Mg II h & k, Fe II 2716 A, C II 2327 A, and Al II ] 2669 A emission lines we provide the first evidence for the presence of warm chromospheric plasma at least 1 arcsecond away from the star at ~40 R* (1 R*~700 Rsun). The STIS spectra reveal that Betelgeuse's upper chromosphere extends far beyond the circumstellar H alpha envelope of ~5 R*, determined from previous ground-based imaging. The flux in the broad and self-absorbed resonance lines of Mg II decreases by a factor of ~700 compared to the flux at chromospheric disk center. We observe strong asymmetry changes in the Mg II h and Si I resonance line profiles when scanning off-limb, signaling the outward acceleration of gas outflow in the upper chromosphere. From the radial intensity distributions of Fe I and Fe II emission lines we determine the radial non-LTE iron ionization balance. We compute that the local kinetic gas temperatures of the warm chromospheric gas component in the outer atmosphere exceed 2600 K, when assuming local gas densities of the cool gas component we determine from radiative transfer models that fit the 9.7 um silicate dust emission feature. The spatially resolved STIS spectra directly demonstrate that warm chromospheric plasma co-exisists with cool gas in Betelgeuse's circumstellar dust envelope. Title: New Grids of ATLAS9 Model Atmospheres Authors: Castelli, F.; Kurucz, R. L. Bibcode: 2003IAUS..210P.A20C Altcode: 2004astro.ph..5087C New opacity distribution functions (ODFs) for several metallicities have been computed. The main improvements upon previous ODFs computed by Kurucz (1990) are: (1) the replacement of the solar abundances from Anders & Grevesse (1989) with those from Grevesse & Sauval (1998); (2) the replacement of the TiO lines provided by Kurucz (1993) with the TiO lines from Schwenke (1998), as distributed by Kurucz (1999a); (3) the addition of the H2O lines from Partridge & Schwenke (1997), as distributed by Kurucz (1999b); (4) the addition of the H I-H I and H I-H+ quasi-molecular absorptions near 1600Å and 1400Å computed according to Allard et al. (1998). Other minor improvements are related with some changes in a few atomic and molecular data. New grids of ATLAS9 model atmospheres for Teff from 3500 K to 50000 K and log g from 0.0 dex to 5.0 dex have been computed for several metallicities with the new ODFs. Preliminary comparisons of results from the old and new models have shown differences in the energy distributions of stars cooler than 4500 K, in the ultraviolet energy distribution of metal-poor A-type stars, in the U-B and u-b color indices for Teff ≤ 6750 K and in all the color indices for Teff ≤ 4000 K. Title: Search for the Companions of Galactic SNe Ia Authors: Ruiz-Lapuente, Pilar; Comeron, Fernando; Smartt, Stephen; Kurucz, Robert; Mendez, Javier; Canal, Ramon; Filippenko, Alex; Chornock, Ryan Bibcode: 2003fthp.conf..140R Altcode: 2003astro.ph..4109R The central regions of the remnants of Galactic SNe Ia have been examined for the presence of companion stars of the exploded supernovae. We present the results of this survey for the historical SN 1572 and SN 1006. The spectra of the stars are modeled to obtain Teff, log g and the metallicity. Radial velocities are obtained with an accuracy of 5-10 km s-1. Implications for the nature of the companion star in SNeIa follow. Title: A Few Things We Do Not Know About Stars and Model Atmospheres Authors: Kurucz, R. L. Bibcode: 2003IAUS..210...45K Altcode: No abstract at ADS Title: The Photospheric Absorption Lines in the Ultraviolet Spectrum of the Multiple System HD 5980 Authors: Koenigsberger, Gloria; Kurucz, Robert L.; Georgiev, Leonid Bibcode: 2002ApJ...581..598K Altcode: We search for radial velocity variations in the ultraviolet spectra of the erupting Wolf-Rayet/luminous blue variable system HD 5980, located in the Small Magellanic Cloud. We obtain an average radial velocity of 22+/-22 km s-1 for five observations in 1999 at different orbital phases, -39+/-24 km s-1 for one observation in 2001, and 20+/-45 km s-1 for one observation in 2002. These velocities are with respect to the SMC O3 star MPG 355, which is used as one of the templates. Hence, radial velocity variations on the 19.265 day (star A+star B) orbital timescale attributable to the erupting star (star A) of the system are not detected, thus confirming that the visible absorption lines in the spectrum have their origin in a third stellar component (star C). We propose that star A has very broad (vsini~250 km s-1) absorption lines, which would escape detection in the complicated emission-line spectrum of the system. Such broad lines, combined with the 128 km s-1 orbital motion, would lead to a lower amplitude fictitious radial velocity curve when the stationary set of absorption lines is measured. We conclude that line profile variations at orbital phase 0.0 from one epoch of observations to another are associated with these broad underlying absorption lines, arising in the unstable photosphere of star A. The analysis is performed with the aid of synthetic UV spectra that are calculated from LTE line-blanketed atmosphere models, and the HST Space Telescope Imaging Spectrograph spectra of four O-type stars in the cluster NGC 346, to which HD 5980 is believed to belong. We estimate Teff and obtain values of vsini and the mean radial velocity for MPG 324 [O4 V((f))], MPG 368 [O4-5 V((f))], MPG 355 [O3 V(f*)], and MPG 113 (OC 6Vz). Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. Title: The Progenitor of Supernova 1993J Revisited Authors: Van Dyk, Schuyler D.; Garnavich, Peter M.; Filippenko, Alexei V.; Höflich, Peter; Kirshner, Robert P.; Kurucz, Robert L.; Challis, Peter Bibcode: 2002PASP..114.1322V Altcode: 2002astro.ph..8382V From Hubble Space Telescope images with 0.05" resolution, we identify four stars brighter than V=25 mag within 2.5" of SN 1993J in M81, which contaminated previous ground-based brightness estimates for the supernova progenitor. Correcting for the contamination, we find that the energy distribution of the progenitor is consistent with that of an early K-type supergiant star with MV~-7.0+/-0.4 mag and an initial mass of 13-22 Msolar. The brightnesses of the nearby stars are sufficient to account for the excess blue light seen from the ground in preexplosion observations. Therefore, the SN 1993J progenitor did not necessarily have a blue companion, although by 2001, fainter blue stars are seen in close proximity to the supernova. These observations do not strongly limit the mass of a hypothetical companion. A blue dwarf star with a mass up to 30 Msolar could have been orbiting the progenitor without being detected in the ground-based images. Explosion models and observations show that SN 1993J progenitor had a helium-rich envelope. To test whether the helium abundance could influence the energy distribution of the progenitor, we calculated model supergiant atmospheres with a range of plausible helium abundances. The models show that the presupernova colors are not strongly affected by the helium abundance longward of 4000 Å, and abundances ranging between solar and 90% helium (by number) are all consistent with the observations. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained in part from the data archive of the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. Title: Atomic and molecular data needs for astrophysics Authors: Kurucz, Robert L. Bibcode: 2002AIPC..636..134K Altcode: We need a list of all the energy levels of all atoms and molecules that matter (qualifiers below). Except for the simplest species, it is impossible to generate accurate energy levels or wavelengths theoretically. They must be measured in the laboratory. From the list of energy levels can be generated all the lines. Given the low accuracy required, 1 - 10%, all the other data we need can eventually be computed or measured. With the energy levels and line positions known, one can measure gf values, lifetimes, damping, or one can determine a theoretical or semiempirical Hamiltonian whose eigenvalues and eigenvectors produce a good match to the observed data, and that can then be used to generate additional radiative and collisional data for atoms or molecules. For atoms and ions, we need all levels, including hyperfine and isotopic splittings, for n <= 9 below the lowest ionization limit and as much as practicable above. Lifetimes and damping constants depend on sums over the levels. Inside stars there are thermal and density cutoffs that limit the number of levels, but in circumstellar, interstellar, and intergalactic space, photoionization and recombination can populate high levels, even for high ions. We need all stages of ionization for elements at least up through Zn. In the sun there are unidentified asymmetric triangular features that are unresolved multiplets of light elements with n .le. 20. Simple spectra should be analyzed up to n = 20. Levels that connect to the ground or to low levels should be measured to high n, say n = 80. The high levels are necessary to match line series merging into continua. All the magnetic dipole, electric quadrupole, and maybe higher-pole, forbidden lines are required as well. Most of the universe is low density plasma or gas. If the Hamiltonian is well determined, forbidden lines should be reliably computable. For molecules, we need all levels below the first dissociation limit and as much as is practicable above, especially levels of all states that connect to the ground state. Stars populate levels to high V and to high J. In the sun there are many broad bumpy features that are molecular bands that are not in the line lists. For the cooler stars we need all the diatomics among all the abundant elements, and, essentially, the hydrides and oxides for all elements (especially ScO, TiO, VO, YO, ZrO, LaO). For M stars triatomics also become important. Much more laboratory and computational work is needed for H2O. In the brown dwarfs and "planets" methane is important and it needs more laboratory and computational work. We can produce more science by investing in laboratory spectroscopy rather than by building giant telescopes that collect masses of data that cannot be correctly interpreted. Title: Convective Intensification of Magnetic Flux Tubes in Stellar Photospheres Authors: Rajaguru, S. P.; Kurucz, R. L.; Hasan, S. S. Bibcode: 2002ApJ...565L.101R Altcode: 2002astro.ph..1026R The convective collapse of thin magnetic flux tubes in the photospheres of Sun-like stars is investigated using realistic models of the superadiabatic upper convection zone layers of these stars. The strengths of convectively stable flux tubes are computed as a function of surface gravity and effective temperature. We find that while stars with Teff>=5500 K and logg>=4.0 show flux tubes highly evacuated of gas, and hence strong field strengths due to convective collapse, cooler stars exhibit flux tubes with lower field strengths. Observations reveal the existence of field strengths close to thermal equipartition limits even in cooler stars, implying highly evacuated tubes, for which we suggest possible reasons. Title: A Few Things We Do Not Know About the Sun and F-G Stars Authors: Kurucz, R. L. Bibcode: 2002BaltA..11..101K Altcode: 2002OAst...11..101K We do not: know how to make realistic model atmospheres, understand convection, consider variation in microturbulent velocity, understand spectroscopy, have good spectra of the Sun or any star, have energy distributions for the Sun or any star, know how to determine abundances, know the abundances of the Sun or any star, have good atomic and molecular data, identify one half of the lines in solar spectrum. Title: A few things we do not know about stars and model atmospheres Authors: Kurucz, Robert L. Bibcode: 2002ASSL..274....3K Altcode: 2001astro.ph..5400K We list a few things that we do not understand about stars and that most people ignore. These are all hard problems. We can learn more cosmology by working on them to reduce the systematic errors they introduce than by trying to derive cosmological results that are highly uncertain. Title: Research on Spectroscopy, Opacity, and Atmospheres Authors: Kurucz, Robert L. Bibcode: 2001STIN...0212434K Altcode: With this funding I produced a web site kurucz.harvard.edu that can also be accessed by FTP. it has a 73GB disk that holds all of my atomic and diatomic molecular data, my tables of distribution function opacities, my grids of model atmospheres, colors, fluxes, etc., my programs that are ready for distribution, and most of my recent papers. Atlases and computed spectra will be added as they are completed. New atomic and molecular calculations will be added as they are completed. Title: Ultraviolet spectra for lambda Boo (HD 125162) computed with H2 opacities and Lyman-alpha H-H and H-H+ opacities Authors: Castelli, F.; Kurucz, R. L. Bibcode: 2001A&A...372..260C Altcode: New opacity distribution functions (ODF) have been computed for use with the ATLAS9 model atmosphere code of Kurucz. One of the improvements upon the Kurucz (\cite{kur90}) ODFs is the addition to the line blanketing of the Lyman-alpha H-H and H-H+ quasi-molecular absorptions near 1600 Å and 1400 Å. New-ODF fluxes are expected to reproduce the ultraviolet observations of lambda Boo stars and metal-poor A-type stars in a more realistic way than previous computations did. In this paper we compare low- and high-resolution IUE observations of lambda Boo (HD 125162, HR 5351) with fluxes and synthetic spectra based on ATLAS9 models and new-ODFs, which were computed for [M/H]=-2.0 for all the elements, except CNO. For C, N, and O, abundances log (Nelem/Ntot) equal to -3.85, -3.99, and -3.11, respectively, were adopted. We selected lambda Boo in order to compare results from the new-ODFs with those from Allard et al. (\cite{allar98a}, \cite{allar98b}), who tested their semi-classical computations of the H-H and H-H+ quasi-molecular absorptions on this star. The analysis of the IUE high-resolution spectrum has shown that lines of H2 are a very important source of line opacity for lambda Boo shortward 1600 Å. When both atomic and molecular lines are considered, the slope of the observed energy distribution is well reproduced in the whole region 1300-3000 Å by the new-ODF model, but the H-H quasi-molecular absorption at 1600 Å is computed about 10% too strong. The fit of the low-resolution IUE image SWP17872 to a small grid of new-ODF models gives parameters Teff= 8650 K, log g=4.0, while the fit of the high-resolution image SWP42081, rebinned at the low resolution wavelength step size, gives parameters Teff=8500 K, log g=4.0. These last parameters are in close agreement with Teff=8550 K, log g=4.1 obtained by fitting the visible energy distribution. The different IUE images are discussed. Title: The "Extra-Solar Giant Planets" are Brown Dwarfs Authors: Kurucz, Robert L. Bibcode: 2001astro.ph..5160K Altcode: After an M, K, G, or F star forms, it magnetically compresses the infall dregs to produce a close in brown dwarf. Title: The formation of life Authors: Kurucz, Robert L. Bibcode: 2000astro.ph.11209K Altcode: The formation of life is an automatic stage in the consolidation of rocky or "terrestrial" planets. The organic (=carbonaceous) matter, light elements, gases, and water must "float" toward the surface and the heavier metals must sink toward the center. Random processes in the molecular soup that fills microfractures in unmelted crust eventually produce self-replicating microtubules. In an appendix I suggest that some primordial crust remains because there is not enough consolidation energy to melt the whole planet. Energy is lost when iron planetesimals first partially melt and then coalesce to form the molten iron planetary core. Stony planetesimals accrete onto the surface of an already consolidated core. Title: Solar Spectroscopy: Visible Emission Authors: Kurucz, R. Bibcode: 2000eaa..bookE2232K Altcode: 2001EAA.....3.2744K There are several perspectives from which to consider the solar spectrum. One is obviously as a tool for studying the Sun itself. The temperature and pressure variation with depth, the composition, the magnetic fields, the changing structure and velocity fields on the surface can be derived from high-resolution, high signal-to-noise spectra that also have high spatial and temporal resolution.... Title: A correction to the pp reaction Authors: Kurucz, Robert L. Bibcode: 2000astro.ph..3029K Altcode: These descriptive comments are made to encourage detailed three-body, relativistic, quantum collision calculations for the pp reaction. In stars, coulomb barrier tunneling, as in the pp reaction, is not a two-body process. Tunneling is mediated by an energetic electron that interacts with the colliding particles. The presence of such an electron lowers the potential barrier and increases the probability of tunneling by orders of magnitude. The solar luminosity can be maintained with a central temperature near 10 million K where the neutrino production rates correspond to the observed rates. Current stellar interior and evolutionary models need substantial revision. Title: A few things we do not know about the sun and F stars and G stars Authors: Kurucz, Robert L. Bibcode: 2000astro.ph..3069K Altcode: WE do not know how to make realistic model atmospheres; understand convection; consider the variation in microturbulent velocity; understand spectroscopy; have good spectra of the sun or any other star; have energy distributions for the sun or any other star; know how to determine abundances; know the abundances of the sun or any other star; have good atomic and molecular data; One half the lines in the solar spectrum are not identified. We should get our own house in order before worrying about the neighbors. Title: An outline of radiatively-driven cosmology Authors: Kurucz, Robert L. Bibcode: 2000astro.ph..3381K Altcode: A Big Bang universe consisting, before recombination, of H, D, 3He, 4He, 6Li, and 7Li ions, electrons, photons, and massless neutrinos, at closure density, with a galaxy-size perturbation spectrum but no large-scale structure, will evolve into the universe as we now observe it. Evolution during the first billion years is controlled by radiation. Globular clusters are formed by radiatively-driven implosions, galaxies are formed by radiatively triggered gravitational collapse of systems of globular clusters, and voids are formed by radiatively-driven expansion. After this period the strong radiation sources are exhausted and the universe has expanded to the point where further evolution is determined by gravity and universal expansion. Title: Working Group on Infrared Astronomy: (Groupe de Travail Pour L'Astronomie Infrarouge) Authors: Milone, Eugene F.; Bell, Roger A.; Bessell, Michael; Garrison, Robert; Cohen, Martin; Glass, Ian S.; Kurucz, Robert L.; Mountain, Matthew; Riecke, George; Schiller, Stephen J.; Simon, Douglas; Skrutskie, Michael; Stagg, Christopher S.; Sterken, Chris; Thompson, Roger I.; Tokunaga, Alan; Young, Andrew T. Bibcode: 2000IAUTA..24..336M Altcode: No abstract at ADS Title: Acoustic wave energy fluxes for late-type stars. II. Nonsolar metallicities Authors: Ulmschneider, P.; Theurer, J.; Musielak, Z. E.; Kurucz, R. Bibcode: 1999A&A...347..243U Altcode: Using the Lighthill-Stein theory with modifications described by Musielak et al. (1994), the acoustic wave energy fluxes were computed for late-type stars with the solar metal abundance (population I stars) by Ulmschneider et al. (1996). We now extend these computations to stars with considerably lower metal content (population II stars with 1/10 to 1/1000 of solar metallicity) and find that the acoustic fluxes calculated for stars of different spectral types and different luminosities are affected differently by the metallicity. It is found that the Hertzsprung-Russel diagram can be subdivided into three domains (labeled I, II and III) representing a different dependence of the generated acoustic fluxes on the stellar metal abundance. For the high T_eff stars of domain I there is no dependence of the generated acoustic fluxes on metallicity. In domain III are stars with low T_eff. Here the generated acoustic fluxes are lowered roughly by an order of magnitude for every decrease of the metal content by an order of magnitude. Finally, domain II represents the transition between the other two domains and the generated acoustic fluxes strongly depend on T_eff. The boundaries between the domains I and II, and II and III can be defined by simple relationships between stellar effective temperatures and gravities. Title: Calculation of Solar Irradiances. I. Synthesis of the Solar Spectrum Authors: Fontenla, Juan; White, Oran R.; Fox, Peter A.; Avrett, Eugene H.; Kurucz, Robert L. Bibcode: 1999ApJ...518..480F Altcode: Variations in the total radiative output of the Sun as well as the detailed spectral irradiance are of interest to terrestrial and solar-stellar atmosphere studies. Recent observations provide measurements of spectral irradiance variations at wavelengths in the range 1100-8650 Å with improved accuracy, and correlative studies give procedures for estimating the spectral irradiance changes from solar activity records using indicators such as those derived from Ca II K and Mg II indices. Here we describe our approach to physical modeling of irradiance variations using seven semiempirical models to represent sunspots, plage, network, and quiet atmosphere. This paper gives methods and details, and some preliminary results of our synthesis of the variations of the entire irradiance spectrum. Our calculation uses object-oriented programming techniques that are very efficient and flexible. We compute at high spectral resolution the intensity as a function of wavelength and position on the disk for each of the structure types corresponding to our models. These calculations include three different approximations for the line source function: one suited for the very strong resonance lines where partial redistribution (PRD) is important, another for the most important nonresonance lines, and another approximation for the many narrow lines that are provided in Kurucz's listings. The image analysis and calculations of the irradiance variation as a function of time will be described in a later paper. This work provides an understanding of the sources of variability arising from solar-activity surface structures. We compute the Lyα irradiance to within 3% of the observed values. The difference between our computations and the Neckel & Labs data is 3% or less in the near-IR wavelengths at 8650 Å, and less than 1% in the red at 6080 Å. Near 4100 Å we overestimate the irradiance by 9%-19% because of opacity sources missing in our calculations. We also compute a solar cycle variability of 49% in the Lyα irradiance, which is very close to observed values. At wavelengths between 4100 Å and 1.6 μm, we obtain spectral irradiance variations ranging from -0.06% to 0.46% in the visible--the higher values correspond to the presence of strong lines. The variability in the IR between 1.3 and 2.2 μm is ~-0.15%. Title: Effect of the variation of electronic dipole moment on theoretical spectra: application to the λ Bootis stars Authors: Allard, N. F.; Drira, I.; Faraggiana, R.; Gerbaldi, M.; Kielkopf, J. F.; Kurucz, R. Bibcode: 1999AIPC..467..264A Altcode: 1999sls..conf..264A No abstract at ADS Title: 1999 TiO linelist from Schwenke (1998). Authors: Kurucz, Robert Bibcode: 1999KurCD..24.....K Altcode: No abstract at ADS Title: H2O linelist from Partridge and Schwenke (1997), part 1 of 2. Authors: Kurucz, Robert Bibcode: 1999KurCD..25.....K Altcode: No abstract at ADS Title: New Lyman alpha-opacities and consequences on stellar spectra Authors: Allard, N. F.; Drira, I.; Faraggiana, R.; Gerbaldi, M.; Kielkopf, J. F.; Kurucz, R. Bibcode: 1999ASPC..169..457A Altcode: 1999ewwd.conf..457A No abstract at ADS Title: H2O linelist from Partridge and Schwenke (1997), part 2 of 2. Authors: Kurucz, Robert Bibcode: 1999KurCD..26.....K Altcode: No abstract at ADS Title: Fe II emission lines in the UV spectrum of Sirius-A and VEGA Authors: van Noort, M.; Lanz, T.; Lamers, H. J. G. L. M.; Kurucz, R. L.; Ferlet, R.; Hebrard, G.; Vidal-Madjar, A. Bibcode: 1998A&A...334..633V Altcode: 1998astro.ph..3127V We present high-quality HST/GHRS spectra in the Hydrogen Lalpha spectral region of Vega and Sirius-A. Thanks to the signal-to-noise ratio achieved in these observations and to the similarity of the two spectra, we found clear evidence of emission features in the low flux region, lambda lambda 1190-1222 Angstroms. These emission lines can be attributed unambiguously to Fe Ii and Cr Ii transitions. In this spectral range, silicon lines are observed in absorption. We built a series of non-LTE model atmospheres with different, prescribed temperature stratification in the upper atmosphere and treating Fe Ii with various degrees of sophistication in non-LTE. Emission lines are produced by the combined effect of the Schuster mechanism and radiative interlocking, and can be explained without the presence of a chromosphere. Silicon absorption lines and the Lalpha profile set constraints on the presence of a chromosphere, excluding a strong temperature rise in layers deeper than tau_R ~ 10(-4) . Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555. Title: Analysis of IUE Spectra of Λ Bootis Stars in the Framework of New Quasi-Molecular Opacities Authors: Allard, N.; Kurucz, R.; Gerbaldi, M.; Faraggiana, R. Bibcode: 1998ESASP.413..105A Altcode: 1998uabi.conf..105A No abstract at ADS Title: LTE Models Authors: Kurucz, R. L. Bibcode: 1998HiA....11..646K Altcode: The author can compute arbitary-abundance models and spectra at high resolution using millions of atomic and diatomic molecular lines. Examples are given for Sakurai's object and for a λ Boo star. The author is continuing to improve the input line data. Title: Acoustic and MHD Wave Energy Fluxes for Late-Type Stars Authors: Musielak, Z. E.; Cuntz, M.; Ulmschneider, P.; Theurer, J.; Kurucz, R. Bibcode: 1997AAS...191.1206M Altcode: 1997BAAS...29.1228M The vast amount of observational data collected at wavelengths ranging from X-rays to radio waves have indicated the ubiquity of stellar chromospheres among late-type stars. In addition, there is growing observational evidence for inhomogeneous and locally strong magnetic fields in stellar atmospheres. It is reasonable to assume that stellar magnetic inhomogeneities may be similar to the `flux tube' structures observed in the solar atmosphere outside sunspots. If so, two distinct components of stellar chromospheres must be recognized, namely, non-magnetic component, where acoustic waves are responsible for the heating, and magnetic component, where MHD tube waves supply energy for the heating. To construct theoretical models of stellar chromospheres (see paper by Cuntz et al. presented at this meeting), it is necessary to know the amount of non-radiative energy generated in stellar convective zones and carried by acoustic and MHD tube waves through stellar photospheres. In this paper, we discuss the correct status of computing acoustic and MHD wave energy fluxes for the Sun and late-type dwarfs. Our calculations are based on grey LTE mixing-length convection zone models and both linear and non-linear theories of wave generation are used. New acoustic and MHD wave energy fluxes are presented for stars of population I and II in the range of effective temperatures T_eff 2000 - 10000 K and gravities log g = 1 - 8. The turbulent flow field is represented by an extended Kolmogorov spatial and modified Gaussian temporal energy spectrum. The mixing-length parameter is varied in the range alpha = 1 - 2. We find that the obtained acoustic wave energy strongly depend on stellar chemical composition and that MHD fluxes show wide variations for a given spectral type, variations which can be attributed to changes in the stellar flux tube filling factor. We discuss the range of the filling factor for which the calculated MHD fluxes may account for the observed levels of chromospheric activity. Title: (Erratum) Notes on the convection in the ATLAS9 model atmospheres. Authors: Castelli, F.; Gratton, R. G.; Kurucz, R. L. Bibcode: 1997A&A...324..432C Altcode: Erratum to Astron. Astrophys. 318, 841 (1997) Title: Fundamental parameters of Cepheids. IV. Radii and luminosities. Authors: Bersier, D.; Burki, G.; Kurucz, R. L. Bibcode: 1997A&A...320..228B Altcode: A temperature scale for Cepheids is presented, based on Geneva photometry. It uses new atmosphere models computed at various values of microturbulent velocity. The scale so-obtained is compared to other ones and the importance of microturbulence effects is shown. This calibration is applied to 20 Cepheids for which the variation of microturbulence is known. The detailed variations of temperature and gravity are derived. The behavior of the photometric gravity is in very good agreement with the effective gravity (sum of GM/R^2^ and of the derivative of the radial velocity). Thus static atmosphere models can be used to describe the temperature and gravity variations in Cepheids under the following conditions: i) the microturbulence has to be taken into account, ii) the effective gravity must be considered instead of the static gravity, iii) in some cases, a small phase interval around minimum radius does not give reliable results. The temperature and bolometric corrections are then used to derive radii and distances via the Baade-Wesselink technique. The resulting Period-Radius and Period-Luminosity relations are discussed. Our results compare very well with similar analysis based on infra-red (JHK) photometry. Title: A calibration of Geneva photometry for B to G stars in terms of Teff, log G and [M/H] Authors: Kunzli, M.; North, P.; Kurucz, R. L.; Nicolet, B. Bibcode: 1997A&AS..122...51K Altcode: We have used recent Kurucz models and numerous standard stars to improve the calibration of the Geneva photometric system proposed a few years ago. A new photometric diagram for the classification of intermediate stars (8500 <= Teff <= 11000 K) is proposed and fills a gap that the previous calibration had left open. Evidence is given for a clear inadequacy of the new Kurucz models in the region of the parameter space where convection begins to take over radiation in the star's atmosphere. This problem makes the determination of the surface gravity difficult, but leaves that of the other parameters apparently unaffected. The determination of metallicity is considerably improved, thanks to the homogeneous spectroscopic data published recently by \cite[Edvardsson et al. (1993)]{ref23}. Instead of showing the traditional diagrams, we chose to publish the diagrams of the physical parameters with the inverted grids inside, i.e. the lines of constant photometric parameters. Title: Notes on the convection in the ATLAS9 model atmospheres. Authors: Castelli, F.; Gratton, R. G.; Kurucz, R. L. Bibcode: 1997A&A...318..841C Altcode: The mixing-length theory for the convection, as it is used in the ATLAS9 code (Kurucz, 1993a), is summarized and discussed. We investigated the effect of the modification called ``approximate overshooting'' on the model structure of the Sun and of stars with T_eff_ included between 4000K and 8500K, logg included between 2.5 and 4.5, and metallicities [M/H]=0.0 and [M/H]=-3.0. We found that the Kurucz solar model (SUNK94) with the ``overshooting'' option switched on reproduces more observations than that without ``overshooting''. In the Hgamma_ and Hbeta_ regions no solar model is able to reproduce the level of the true continuum deduced from high-resolution observations absolutely calibrated. At 486 nm the computed continuum is about 6.6% higher than that inferred from the observed spectrum. We found that the largest effect of the ``approximate overshooting'' on the model structure occurs for models with T_eff_>6250K and it decreases with decreasing gravity. The differences in (b-y), (B-V), and (V-K) indices computed from models with the ``overshooting'' option switched on and off, correspond to T_eff_ differences which may amount up to 180K, 100K, 60K respectively. The differences in T_eff_ from Balmer profiles may amount up to 340K and they occur also for T_eff_<6250K down to about 5000K. The c_1_ index yields gravity differences {DELTA}logg as a function of logg which, for each T_eff_, grow to a maximum value. The maximum {DELTA}logg decreases with increasing temperatures and ranges, for solar metallicity, from 0.7 dex at logg=0.5 and T_eff_=5500K to 0.2dex at logg=4.5 and T_eff_=8000K. This behaviour does not change for [M/H]=-3.0. Comparisons with the observations indicate that model parameters derived with different methods are more consistent when the ``overshooting'' option is switched off (NOVER models), except for the Sun. In particular for Procyon, T_eff_ and logg from NOVER models are closer to the parameters derived from model independent methods than are T_eff_ and logg derived from the Kurucz (1995) grids. However, no model is able to explain the whole observed spectrum of either the Sun or Procyon with a unique T_eff_, regardless of whether the ``overshooting'' option is switched on or off. Independently of the convection option, the largest differences in T_eff_ derived with different methods are of the order of 200K for Procyon and 150K for the Sun. Title: Progress on Model Atmospheres and Line Data (Invited Paper) Authors: Kurucz, R. L. Bibcode: 1997ESASP.419..193K Altcode: 1997fiso.work..193K I can compute arbitrary-abundance models and spectra at high resolution using millions of atomic and diatomic molecular lines. I am improving the input line data. Title: Model Atmospheres for Individual Stars with Arbitrary Abundances Authors: Kurucz, Robert L. Bibcode: 1997fbs..conf...33K Altcode: 1997LDP....22...33K No abstract at ADS Title: Progress on model atmospheres and line data. Authors: Kurucz, R. L. Bibcode: 1997IAUS..189..217K Altcode: 1998IAUS..189..217K The author discusses errors in theory and in interpreting observations that are produced by the failure to consider resolution in space, time, and energy. He discusses convection in stellar model atmospheres and in stars. One dimensional convective models can never work well, but the errors in predicted diagnostics for temperature, gravity, and abundances can be calibrated. The author discusses the variation of microturbulent velocity with depth, effective temperature, and gravity. These variations must be dealt with in computing models and grids and in any type of photometric calibration. The author describes the state of the art in computing a model atmosphere and complete spectrum for stars with arbitrary abundances. He has made no significant progress on atomic or molecular line data for the last two years, but he will soon begin large scale production. He will continue to distribute the results on CD-ROMs, and he will make them available on the World Wide Web. Title: Progress on Model Atmospheres and Line Data. Authors: Kurucz, R. Bibcode: 1997fsp..proc..217K Altcode: No abstract at ADS Title: VizieR Online Data Catalog: B to G stars calibration in Geneva photometry (Kunzli+, 1997) Authors: Kunzli, M.; North, P.; Kurucz, R. L.; Nicolet, B. Bibcode: 1996yCat..41220051K Altcode: We have used recent Kurucz models and many standard stars to revise previous calibrations of the Geneva photometric parameters in terms of Teff, logg, and [M/H]. In addition, new parameters pT and pG were defined, which are the Geneva equivalents of Stromgren's a and r parameters and allow to estimate Teff and logg for stars with intermediate temperature (spectral type A0-A3). A fortran code (calib.f) has been written, which applies our calibration to stars measured in the Geneva system. A conspicuous change in slope appears in the grid d vs B2-V1. It seems to be linked with the onset of convection in the superficial layers of the star's envelope. (1 data file). Title: VizieR Online Data Catalog: Semiempirical gf Values (Kurucz + 1975) Authors: Kurucz, R. L.; Peytremann, E. Bibcode: 1996yCat.6010....0K Altcode: This table of gf values for 265,587 atomic lines is selected from the line data used to calculate line-blanketed model atmospheres (Kurucz et al. 1974). The data are especially useful for line identification and spectral synthesis in solar and stellar spectra. Except for 10,100 lines taken from the literature, the gf values have been calculated semiempirically by using scaled Thomas-Fermi-Dirac radial wavefunctions and eigenvectors found through least-squares fits to observed energy levels. Included in the calculation were the first five or six stages of ionization for sequences up through nickel. Published gf values have been included for elements heavier than nickel. The tabulation is restricted to lines with wavelengths less than 10um.

(1 data file). Title: Research on Spectroscopy, Opacity, and Atmospheres Authors: Kurucz, Robert L.; Bell, Barbara Bibcode: 1996sao..reptR....K Altcode: This line list is a replacement for the Kurucz-Peytremann line list. We have combined all the atomic files from CDROM 18 into 534910 line files GFALL.DAT and GFELEM.DAT. These are the data we actually use to compute spectra. They are not up to date. References are given in GFALL.REF or GFELEN.REF. There are no references after 1988. For light elements there are no references after 1979. We have the literature into the 1990's but have not had manpower or funding to update everything. Our current plan is to make a new semiempirical calculation for each species and at that time to include all the data from the literature. One new development is the inclusion of hyperfine splitting for the iron group elements using hyperfine data from the literature through 1993. The data are very incomplete. We have not yet included data for isotopic splitting. We supply a program for splitting the line list for a species. It reads the hyperfine and isotopic splitting parameters for levels and computes the oplittings whenever those levels appear. Lines with no splitting data are copied untouched. Because Sc, Mn, and Co are monoisotopic, only the hyperfine splittings are needed. Since 51V is much more abundant than S0V, the isotope shifts are small for 51V, and we approximate V with 51V. GFALLKYP.DAT has 754946 lines including hyperfine Sc(I), V(I), Mn(I), and Co(I). A bibliography for last year (1994-1995) is also attached. Title: On-line atomic & molecular data for astronomy. Authors: Smith, P. L.; Esmond, J. R.; Heise, C.; Kurucz, R. L. Bibcode: 1996uxsa.conf..513S Altcode: 1996uxsa.coll..513S Very few of the atomic and molecular data used in analyses of astronomical spectra are currently available in World Wide Web (WWW) databases that are searchable with hypertext browsers. The authors have begun to rectify this situation by making the extensive atomic data files of R. L. Kurucz and R. L. Kelly available with simple search procedures. They have also made a number of other useful atomic and molecular data files available on the WWW and have established links to other on-line atomic and molecular databases. All can be accessed from the database homepage with URL: http://cfa-www.harvard.edu/amp/amdata.html. Title: Status of the ATLAS 12 Opacity Sampling Program and of New Programs for Rosseland and for Distribution Function Opacity Authors: Kurucz, R. L. Bibcode: 1996ASPC..108..160K Altcode: 1996mass.conf..160K No abstract at ADS Title: Model Stellar Atmospheres and Real Stellar Atmospheres Authors: Kurucz, R. L. Bibcode: 1996ASPC..108....2K Altcode: 1996mass.conf....2K No abstract at ADS Title: The UV Spectrum of Lambda Boo Authors: Gerbaldi, M.; Gulati, R. K.; Faraggiana, R.; Kurucz, R. L. Bibcode: 1996ASPC..108..270G Altcode: 1996mass.conf..270G No abstract at ADS Title: A new opacity-sampling model atmosphere program for arbitrary abundances Authors: Kurucz, R. L. Bibcode: 1996IAUS..176..523K Altcode: No abstract at ADS Title: Research on Spectroscopy, Opacity, and Atmospheres Authors: Kurucz, Robert L. Bibcode: 1996sao..reptS....K Altcode: The main accomplishment was the merging of all the atomic line data into one wavelength-sorted list that is simple to use. We have combined all the atomic files from a CDROM into 534,910 line files GFALL.DAT and GFELEN.DAT. These are the data we use to compute spectra. They are not up to date. References are given in GFALL.REF or GFELEK.REF. There are no references after 1988, and for light elements there are no references after 1979. One new development is the inclusion of hyperfine splitting for the iron group elements using hyperfine data from the literature through 1993. The data are very incomplete. We have supplied a program for splitting the line list for a species. It reads the hyperfine and isotopic splitting parameters for levels and computes the splittings whenever those levels appear. Lines with no splitting data are copied untouched. Because Sc, Mn, and Co are monoisotopic, only the hyperfine splittings are needed. Since 51V is much more abundant than 50V, the isotope shifts are small for 51V, and we approximate V with 51V. GFALLHYP.DAT has 754,946 lines including hyperfine Sc I, V I, Mn I, and Co I. Title: The Primordial Lithium Abundance Authors: Kurucz, Robert L. Bibcode: 1995ApJ...452..102K Altcode: The D lines of Li I in extreme Population II stars hotter than 5500 K are highly temperature sensitive because lithium is nearly all ionized. A one-dimensional model atmosphere represents a space and time average over the actual three-dimensional, moving, hot and cold convective structure. Neutral Li does not have the average behavior represented by the one-dimensional model. Lithium is overionized by a factor of 10 so that the Li abundance computed from a one-dimensional model is too small by this same factor. Consequently, log (NLi/Ntotal) + 12 > 3.0.

This higher Li abundance resolves the only discrepancy in the radiatively driven cosmological model of the universe previously discussed by Kurucz. Because the baryon density is high enough to produce a flat, or nearly flat, universe, the number of stars can increase by a factor of 10, and the amount of radiation given off by those stars in the first billion years can increase by a factor of 10 over what is possible with a low baryon density. This model can explain the formation of Population III stars, globular clusters, galaxies, quasars, voids, galaxy clusters, streaming, and large-scale structure. It can explain isolated galactic evolution and morphology including bulges, disks, and abundances. Title: Synthetic DDO colours. Authors: Morossi, C.; Franchini, M.; Malagnini, M. L.; Kurucz, R. L. Bibcode: 1995A&A...295..471M Altcode: Calibrated synthetic DDO colours computed from Kurucz (1993) atmosphere models and fluxes are presented. The transformation equations to make synthetic colours consistent with the observational system are derived by using a set of calibration stars for which atmosphere parameters are known from high resolution spectroscopy. The synthetic C(45-48) versus C(42-45) diagram is compared with observational sequences of Population I giants and dwarfs and a good agreement is obtained. The metallicity effect in the synthetic diagram is discussed. The obtained results lead to the conclusion that synthetic calibrated DDO colours are valuable tools for analysing Population I and II late-type stars and for computing integrated colours of globular clusters and galaxies. Title: VizieR Online Data Catalog: Theoretical Stellar Flux Spectra for F- to K-type Stars (Buser+ 1992) Authors: Buser, R.; Kurucz, R. L. Bibcode: 1995yCat.6078....0B Altcode: In conjunction with Kurucz' (1979a,b) models for O to G stars, the present models for F- to K- stars provide an extensive, quasi-homogeneous grid of low-resolution theoretical flux spectra for a significant range in stellar parameters covering mostly of the observed HR diagram. The file bklate.dat contains 242 theoretical model atmosphere flux distributions for late-type stars. These flux distributions were calculated by Buser & Kurucz in 1983-5 using published and unpublished models by Gustafsson and his associates. Please refer to the publication (A&A 264, 447) for a full description of the calculations and a discussion of synthetic UBVRI photometry computed from these models. The models cover the following ranges in the parameter space: ----------------------------------------------------------- number fraction of hydrogen xH =0.9 all models turbulent velocity [km/s] vturb =2.00 234 models vturb =5.00 8 models ----------------------------------------------------------- 3750 <= Teff <= 6000 (K) 0.75 <= log.g <= 5.25 (cm/s/s) -3.00 <= [Fe/H] <= 0.50 (dex) ----------------------------------------------------------- Notice that the model sequence does NOT strictly follow an orderly pattern in parameter space, because the present file was composed from several original files having their individual parameter sequences. The last model (#242) is the solar model. Note that the present file still contains 8 models (out of a total of 242) which have turbulent velocities vturb=5.00 km/s, but whose flux distributions have n o t actually been computed for this value of vturb (=5.00 km/s). Hence, for these models, the flux distributions given in the present file are erroneous and should not be used at all. It is suggested that the user d e l e t e them from the file altogether; for the user's convenience, these models are marked on the accompanying list. (1 data file). Title: The Spectrum of Sirius from 307 to 1040 NM Authors: Furenlid, I.; Westin, T.; Kurucz, R. L. Bibcode: 1995ASPC...81..615F Altcode: 1995lahr.conf..615F No abstract at ADS Title: Synthetic template spectra Authors: Kurucz, R. L. Bibcode: 1995HiA....10..407K Altcode: No abstract at ADS Title: The Kurucz Smithsonian Atomic and Molecular Database Authors: Kurucz, R. L. Bibcode: 1995ASPC...78..205K Altcode: 1995aapn.conf..205K No abstract at ADS Title: Atomic Line Data Authors: Kurucz, Robert; Bell, B. Bibcode: 1995KurCD..23.....K Altcode: No abstract at ADS Title: Atomic line list Authors: Kurucz, Robert L.; Bell, Barbara Bibcode: 1995all..book.....K Altcode: No abstract at ADS Title: The Solar Spectrum: Atlases and Line Identifications Authors: Kurucz, R. L. Bibcode: 1995ASPC...81...17K Altcode: 1995lahr.conf...17K No abstract at ADS Title: An Atomic and Molecular Data Bank for Stellar Spectroscopy Authors: Kurucz, R. L. Bibcode: 1995ASPC...81..583K Altcode: 1995lahr.conf..583K No abstract at ADS Title: The Kurucz (Smithsonian) atomic and molecular database Authors: Kurucz, R. L. Bibcode: 1995HiA....10..579K Altcode: No abstract at ADS Title: An Upper Limit for the Deuterium Abundance in the Halo Star HD 140283 Authors: Lubowich, D. A.; Pasachoff, Jay M.; Galloway, Robert P.; Kurucz, R. L.; Smith, Verne V. Bibcode: 1994AAS...185.9805L Altcode: 1994BAAS...26.1479L Because of the possible enhanced deuterium abundance of D/H = 2.5 10(-4) (the ISM D/H = 1.65x10(-5) ) recently reported in quasar absorption spectra, we searched for the D_alpha line at 6561 A in the metal-poor halo star HD 140283 (G2IV, [Fe/H] = -2.6; Teff= 5700K). We observed HD 140283 using the .9m KPNO coude feed and the 2.7m McDonald Observatory telescopes with echelle spectrographs having a resolution Delta lambda = .05 A/pixel with S/N= 200 and Delta lambda = .11 A/pixel with S/N = 600 respectively. We did not detect the D_alpha line and compared our results to model atmosphere calculations for this star. We estimate an upper limit of D/H < 1x10(-5) which is smaller than the primordial or and Early Galactic D/H = 8x10(-5) . Since D is destroyed via reactions with protons at T > 5x10(5) K, the atmospheric deuterium has probably been destroyed during the pre-main sequence convection phase. Because (7) Li, (9) Be, and (11) B have all been detected in this star (Li/H=1.5x10(-10) and B/H=2.9x10(-12) ) and Li is destroyed at T > 2.5x10(6) K, the temperature at the bottom of the pre-main sequence convection zone is 1x10(6) K < T < 2.5x10(6) .K Title: Cross-correlation radial-velocity techniques for rotating F stars. Authors: Nordstroem, B.; Latham, David W.; Morse, Jon A.; Milone, A. A. E.; Kurucz, R. L.; Andersen, J.; Stefanik, R. P. Bibcode: 1994A&A...287..338N Altcode: Data reduction techniques for cross-correlation determination of radial velocities for F stars using echelle spectra obtained with the Center for Astrophysics Digital Speedometers are described and evaluated. Synthetic spectra, calculated for a grid of spectral types and rotational velocities, are used to derive radial velocities for a large sample of nearby F stars with a wide range of rotational velocities. Using a grid of calculated spectra provides a set of noise-free templates on a consistent wavelength scale and allows a closer match between the rotational velocity of the object and that of the template spectrum than would be possible using observed spectra as templates. We describe the methods used to choose the template parameters for each star and the tests conducted to evaluate the accuracy of our procedure. Typically the random error of a single velocity measurement is in the range 0.7 to 3 km/s, depending primarily on the rotation of the star. The zero point of our velocity system has been established to an accuracy of better than 1km/s for the F stars. Title: Further Enhancements to the Wilson-Devinney Eclipsing Binary Modeling Code Authors: Milone, E. F.; Stagg, C. R.; Kallrath, J.; Kurucz, R. L. Bibcode: 1994AAS...184.0605M Altcode: 1994BAAS...26Q.867M The enhancements to the Wilson-Devinney code described earlier (see Milone et al., ApJS 79, 123, 1992 and Milone, ed., 'Light Curve Modeling of Eclipsing Binary Stars' 1993) have been extended to the 1993 version of the WD program and now involve the latest Kurucz atmospheres for a range of metallicities. Potentially all of Kurucz' models may be used to construct files of the ratio of the flux to blackbody curves for the passbands of interest, if the passband profiles are known. The version is called WD93K93. These improvements have also been extended to our simplex version, LC93KS, which permits a sweep of parameter space for deepest minimum and thus tests model uniqueness. Both codes now permit spot modeling although WD93K93 is restricted to 4 parameters on each of 2 spots. Future work will involve attempts to improve the convergence algorithms, global search capabilities, and efficiency. This work is being supported by Canadian NSERC and University of Calgary URGC Grants to EFM. Title: Atomic Data for Mn and Co. Authors: Kurucz, Robert Bibcode: 1994KurCD..21.....K Altcode: No abstract at ADS Title: Alpha Centauri A Revisited Authors: Furenlid, I.; Kurucz, R. L.; Meylan, T. Bibcode: 1994ASPC...64..560F Altcode: 1994csss....8..560F No abstract at ADS Title: Solar abundance model atmospheres for 0,1,2,4,8 km/s. Authors: Kurucz, Robert Bibcode: 1994KurCD..19.....K Altcode: No abstract at ADS Title: Atomic Data for Ca, Sc, Ti, V, and Cr. Authors: Kurucz, Robert Bibcode: 1994KurCD..20.....K Altcode: No abstract at ADS Title: Model atmospheres for Vega. Authors: Castelli, F.; Kurucz, R. L. Bibcode: 1994A&A...281..817C Altcode: We compared blanketed Local Thermodynamic Equilibrium (LTE) models for Vega computed both with the opacity distribution function (ODF) method and the opacity-sampling (OS) method. In the ODF case we used the ATLAS9 code with the new opacity data from Kurucz (1992). Model parameters for Vega depend on the amount of reddening and on the helium abundance. For E(B-V) ranging from 0.0 to 0.01, the effective temperature Teff is included between 9550K and 9650K. A lower limit for the graity is log g = 3.95, obtained for Teff = 9550K and solar He abundance. The metallicity is (M/H) = -0.5. The parameters were fixed by comparing the observed ultraviolet, visual, and near infrared flux distribution with the computed one and by comparing observed and computed Balmer profiles. A microturbulent velocity zeta = 2 km/s was assumed on the basis of previous spectroscopic works. In the OS case, we computed a model with parameters Teff = 9550K, log g = 3.95, zeta = 2 km/s, but with the real abundances of Vega, as derived from spectroscopic analyses. We used the ATLAS12 code (Kurucz 1993b). The comparison of the fluxes and Balmer profiles from the ATLAS9 and ATLAS12 models computed with the same Teff, log g, and zeta, but with different abundances for some elements has shown that they are almost identical, small differences occuring only in the ultraviolet. Therefore ATLAS9 fluxes can be used to predict colors of Vega. The more realistic ATLAS12 models should be used as starting point for abundance analyses and for spectrum synthesis. Title: Atomic Data for Fe and Ni. Authors: Kurucz, Robert Bibcode: 1994KurCD..22.....K Altcode: No abstract at ADS Title: Computation of Opacities for Diatomic Molecules Authors: Kurucz, Robert L. Bibcode: 1994LNP...428..282K Altcode: 1994mse..conf..282K; 1994IAUCo.146..282K No abstract at ADS Title: Synthetic Infrared Spectra Authors: Kurucz, R. L. Bibcode: 1994IAUS..154..523K Altcode: No abstract at ADS Title: A GHRS/HST Spectral Atlas of Sirius-A Authors: Wahlgren, G. M.; Johansson, Se.; Kurucz, R. L.; Leckrone, D. S. Bibcode: 1993AAS...183.1806W Altcode: 1993BAAS...25.1321W The Goddard High Resolution Spectrograph (GHRS) onboard the Hubble Space Telescope has been used to obtain a spectral atlas, covering the wavelength range 1270 - 3200 Angstroms , of the bright star Sirius-A (A1 V). The use of the GHRS first-order gratings provides spectral resolutions between R = 20000 - 35000; however, the rotational velocity (v sin i = 16 km sec(-1) ) limits the spectral resolution. The signal-to-noise ratio over most of the spectrum is approximately 200 by photon statistics. The data are being used to understand the ultraviolet line opacity in warm stars. As a result of this work a new model atmosphere for Sirius will be determined, along with corrections to its bolometric correction and elemental abundances. The spectrum also allows us to test and improve current atomic models. A by-product of our work will be more accurate wavelengths and oscillator strengths for the second spectra of the iron-peak elements that will serve as templates for studying the ultraviolet spectra, obtained at lower spectral resolutions, of other warm stars. Title: VizieR Online Data Catalog: Model atmospheres for Vega (Castelli+ 1994) Authors: Castelli, F.; Kurucz, R. L. Bibcode: 1993yCat..32810817C Altcode: Not Available (10 data files). Title: VizieR Online Data Catalog: Model Atmospheres (Kurucz, 1979) Authors: Kurucz, R. L. Bibcode: 1993yCat.6039....0K Altcode: This tape lists fluxes and temperature-mass relations for 1200 models. The first 284 models are from Kurucz, R.L., Ap.J. Supp., 40,1,1979 and are described there. Next are purely radiactive models for A and B stars with Teff 8000K to 20000K for [M/H] =-1.,-.5,+.5,+1. Finally are new improved convective models for 5500K to 8500K with [M/H]=+1.,+.5,0.,-.5,-1.,-1.5, -2.,-2.5,-3.,-9.99. Because the new models have not yet been published and because I am computing visible and infrared colors in various photometric systems, these new fluxes should not be used to publish colors without my agreement. For any other use these fluxes are in the public domain. The models are presented as ATLAS format input decks. The tape is recorded on 9 tracks at 1600 bpi in ASCII card images with 4000 character blocks. A sample program that reads the tape follows. I suggest that the user read the tape once and write a binary tape that can be read much more quickly. (1 data file). Title: The Mount Wilson Observatory Metallicity Index, C RV: Comparison with Other Photometric Systems Authors: Soon, W. H.; Zhang, Q.; Baliunas, S. L.; Kurucz, R. L. Bibcode: 1993ApJ...416..787S Altcode: A new spectrophotometric index, CRV, is assessed as a metallicity indicator for late-type stars. The index is the ratio of the measured photospheric fluxes in 20 Å wide passbands centered at 400t and 3901 Å. CRV correlates directly with the metallicity index, m1, of the Strömgren uvby system and with the metallicity index hk, of Anthony-Twarog et al. (1991).

Using observations of 236 dwarfs and 140 giants combined with stellar atmosphere models (Kurucz 1991), we compared the sensitivity of the CRV, m1, and hk indices to metal abundance. We also studied the sensitivity of the CRV, C1, and hk indices to surface gravity. The effect of interstellar extinction on all the indices was also studied from published mean extinction laws.

We find that the CRV index is sensitive to the variation of metal abundance, [M], over the range examined (-5.0 ≲ [M] ≲ 0.5). CRV is also more sensitive than the m1 index at metal-poor conditions ([M] ≲ -2.0). The CRV index has the following advantages: (1) the passbands of CRV are dominated by Fe lines, which reduce the uncertainty that may be introduced by the presence of lines of α-process elements with enhanced abundances at metal-poor conditions; (2) the effect of interstellar reddening is limited because the two passbands are separated in wavelength by only 100 Å. We also find that the atmospheric models produce results that agree qualitatively with the trends of observed indices on stellar parameters such as effective temperature, metallicity, and surface gravity. Title: Cool stars : spectral energy distributions and model atmosphere fluxes. Authors: Morossi, C.; Franchini, M.; Malagnini, M. L.; Kurucz, R. L.; Buser, R. Bibcode: 1993A&A...277..173M Altcode: The main results of a program of systematic comparison between observed and computed spectral energy distributions of late G and K type solar chemical composition stars are illustrated. We built the observed energy distributions of eleven representative stars, from the ultraviolet to the infrared, starting from lUE archive data, supplemented by our own lUE observations, and data from the literature. Broad-band Johnson and DDO color indices, together with suitable calibrations, were used for estimating the basic stellar atmospheric parameters, i.e., effective temperature and surface gravity. Theoretical fluxes were computed for the appropriate parameters of each star, starting from a recent grid of atmosphere models.

While very good consistency between data and model predictions has been obtained in the optical and infrared, significant discrepancies were found in the ultraviolet.

We present semi-empirical models, based on the minimum temperature concept, obtained by modifying the temperature (versus optical depth) structure so as to mimic the effect of non-radiative heating in the upper photospheres of cool stars. The fluxes predicted by these models provide a fairly good description of the data not only in the visible and IR regions, but also in the ultraviolet region. Our results indicate that different values for the Tmin/Teff ratio, ranging from 0.76 (as in the Sun) up to 0.85 (θ Boo), are required to reproduce the observed ultraviolet fluxes of different stars. Title: A Critical List of Voigt-fitted Equivalent Width Measurements Based on the Solar Flux Spectrum Authors: Meylan, Thomas; Furenlid, Ingemar; Wiggs, Michael S.; Kurucz, R. L. Bibcode: 1993ApJS...85..163M Altcode: Equivalent widths of around 570 carefully selected absorption lines in the solar flux spectrum have been measured, using the Solar Flux Atlas from 296 to 1300 nm by Kurucz et al. (1984). The equivalent widths were derived from Voigt functions fitted to the selected line profiles in the Solar Flux Atlas. The measurements were used to determine two sets of solar log gf-values; one set is based on the solar model in the 1979 model grid by Kurucz and the other set on a similar 1990 solar model, also by Kurucz, using revised metal abundances by Anders and Grevesse (1989). The data provide a homogeneous, high-precision reference for studies of differential stellar abundances based on equivalent widths, using the solar flux spectrum as the standard. Title: The Nonsolar Abundance Ratios of Arcturus Deduced from Spectrum Synthesis Authors: Peterson, Ruth C.; Dalle Ore, Cristina M.; Kurucz, Robert L. Bibcode: 1993ApJ...404..333P Altcode: Using opacity distribution functions based on a newly expanded atomic and molecular line list, we have calculated a model atmosphere for Arcturus that reproduces the observed flux distribution. Individual line parameters in teh list were adjusted to match the solar spectrum in a preliminary way, in the regions 5000-5500 A, 6000-6500 A, and 7500-9000 A. The Arcturus model spectrum calculated with these adjustments reproduces well the profiles of all lines in the observed spectrum of the Griffin atlas for which the solar gf-values are well determined. The Arcturus model has an iron abundance (Fe/H) = -0.5 +/- 0.1, a temperature T(eff) = 4300 +/- 30 K, gravity log g = 1.5 +/- 0.15, and an overabundance of the light metals. The factor of two enhancement in Arcturus of O, Mg, Si, Ca, and Ti is similar to that of halo stars of much lower metallicity and velocity about the Galactic center. This enhancement significantly affects the ionization equilibria and opacities of Arcturus. Title: New calibration of the Vilnius photometric system. I. Effective temperatures and gravities of B-type stars. Authors: Straizys, V.; Kurucz, R. L.; Philip, A. G. D.; Valiagua, G. Bibcode: 1993BaltA...2..326S Altcode: 1993OAst....2..326S Color indices and reddening-free Q-parameters in the Vilnius photometric system of B-type stars of all luminosities and A-supergiants are calibrated in terms of effective temperature and surface gravity, using synthetic spectra of the newest Kurucz model atmospheres. The calibration is verified by comparing the photometrically determined effective temperatures and surface gravities with the most accurate spectroscopic data. Satisfactory agreement has been found, proving the accuracy of the calibration within +/- 0.02 to +/- 0.05 dex in log Te and +/- 0.2 to +/- 0.3 dex in log g. Title: Atomic data for opacity calculations. Authors: Kurucz, Robert Bibcode: 1993KurCD...1.....K Altcode: No abstract at ADS Title: ATLAS9 Stellar Atmosphere Programs and 2 km/s grid. Authors: Kurucz, Robert Bibcode: 1993KurCD..13.....K Altcode: No abstract at ADS Title: SYNTHE Spectrum Synthesis Programs and Line Data. Authors: Kurucz, Robert Bibcode: 1993KurCD..18.....K Altcode: No abstract at ADS Title: Diatomic Molecular Data for Opacity Calculations. Authors: Kurucz, Robert Bibcode: 1993KurCD..15.....K Altcode: No abstract at ADS Title: Opacities for Stellar Atmospheres: [-2.5a],[-3.0a],[-3.5a] +.4 alpha. Authors: Kurucz, Robert Bibcode: 1993KurCD..11.....K Altcode: No abstract at ADS Title: Atomic data for interpreting stellar spectra: isotopic and hyperfine data. Authors: Kurucz, R. L. Bibcode: 1993PhST...47..110K Altcode: The quality of solar, stellar, and interstellar observations is now so high that we can see physical effects that have been assumed to be insignificant. In natural isotopic mixtures essentially all atomic lines are asymmetric because of isotopic and hyperfine components. In astrophysics the effects of isotopic components have been generally ignored in the case of Ti, Cr, Fe and Ni. Ignoring isotopic splitting introduces systematic errors. It is imperative that laboratory measurements be made to determine the isotopic splitting of every energy level of every stable isotope of every atom and ion as is now routinely done for actinides and for diatomic molecules. Hyperfine splitting should be measured as well for those isotopes with nuclear spin. Computer programs for analyzing spectra including the hyperfine and isotopic splitting already exist. One now need the laboratory data. Title: Opacities for Stellar Atmospheres: [-4.0a],[-4.5a],[-5.0a] +.4 alpha Authors: Kurucz, Robert Bibcode: 1993KurCD..12.....K Altcode: No abstract at ADS Title: A New Opacity-Sampling Model Atmosphere Program for Arbitrary Abundances Authors: Kurucz, R. L. Bibcode: 1993ASPC...44...87K Altcode: 1993pvnp.conf...87K; 1993IAUCo.138...87K No abstract at ADS Title: Opacities for Stellar Atmospheres: [+0.5a],[+0.0a],[-0.5a] +.4 alpha. Authors: Kurucz, Robert Bibcode: 1993KurCD...9.....K Altcode: No abstract at ADS Title: Opacities for Stellar Atmospheres: [-5.0],[+0.0,noHe],[-0.5,noHe]. Authors: Kurucz, Robert Bibcode: 1993KurCD...8.....K Altcode: No abstract at ADS Title: Opacities for Stellar Atmospheres: Abundance Sampler. Authors: Kurucz, Robert Bibcode: 1993KurCD..14.....K Altcode: No abstract at ADS Title: Opacities for Stellar Atmospheres: [-0.1],[-0.2],[-0.3] Authors: Kurucz, Robert Bibcode: 1993KurCD...6.....K Altcode: No abstract at ADS Title: Opacities for Stellar Atmospheres: [-2.0],[-2.5],[-3.0]. Authors: Kurucz, Robert Bibcode: 1993KurCD...4.....K Altcode: No abstract at ADS Title: Models for VEGA Authors: Castelli, F.; Kurucz, R. L. Bibcode: 1993ASPC...44..496C Altcode: 1993IAUCo.138..496C; 1993pvnp.conf..496C No abstract at ADS Title: New atmospheres for modelling binaries and disks. Authors: Kurucz, R. L. Bibcode: 1993IAUCB..21...93K Altcode: The authors has used his newly calculated iron group line list together with earlier atomic and molecular line data, 58,000,000 lines total, to compute new opacities for the temperature range 2000K to 200000K. Calculations have been completed for a lot of of temperatures, pressures, microturbulent velocities and scaled solar abundances. The author has rewritten his model atmosphere program to use the new line opacities, additional continuous opacities, and an approximate treatment of convective overshooting. Thus far he has completed a grid of 7000 model atmospheres at 2 km/s for all the abundances, for the temperature range 3500K to 50000K, and for log g from 0.0 to 5.0. The models, fluxes, intensities, and colors are available on magnetic tape and will also be distributed on CD-ROMs. Title: Opacities for Stellar Atmospheres: [+0.1],[+0.2],[+0.3]. Authors: Kurucz, Robert Bibcode: 1993KurCD...5.....K Altcode: No abstract at ADS Title: Opacities for Stellar Atmospheres: [-0.5],[-1.0],[-1.5]. Authors: Kurucz, Robert Bibcode: 1993KurCD...3.....K Altcode: No abstract at ADS Title: Opacities for Stellar Atmospheres: [-3.5],[-4.0],[-4.5]. Authors: Kurucz, Robert Bibcode: 1993KurCD...7.....K Altcode: No abstract at ADS Title: Opacities for Stellar Atmospheres: [+0.0],[+0.5],[+1.0]. Authors: Kurucz, Robert Bibcode: 1993KurCD...2.....K Altcode: No abstract at ADS Title: Limbdarkening for 2 km/s grid (No. 13): [+1.0] to [-1.0]. Authors: Kurucz, Robert Bibcode: 1993KurCD..16.....K Altcode: No abstract at ADS Title: Opacities for Stellar Atmospheres: [-1.0a],[-1.5a],[-2.0a] +.4 alpha. Authors: Kurucz, Robert Bibcode: 1993KurCD..10.....K Altcode: No abstract at ADS Title: Limbdarkening for 2 km/s grid (No. 13): [+0.0] to [-5.0]. Authors: Kurucz, Robert Bibcode: 1993KurCD..17.....K Altcode: No abstract at ADS Title: SYNTHE spectrum synthesis programs and line data Authors: Kurucz, Robert L. Bibcode: 1993sssp.book.....K Altcode: No abstract at ADS Title: A library of theoretical stellar flux spectra. I. Synthetic UBVRI photometry and the metallicity scale for F- to K-type stars. Authors: Buser, Roland; Kurucz, Robert L. Bibcode: 1992A&A...264..557B Altcode: Synthetic colors on the Johnson-Cousins standard UBVRI system of a grid of theoretical model atmosphere flux distributions for late-type stars are presented. These colors are based on new synthetic spectra calculated from the flux-constant, blanketed model atmospheres of Gustafsson et al. (1975) and Eriksson et al. (1979). The present calculations substantially reduce the systematic effects of the 'missing UV opacity' present in the synthetic colors computed by Bell & Gustafsson (1978) and by VandenBerg & Bell (1985), who employed the same models but different opacity source input. The new fluxes provide significantly improved theoretical representations of the observed two-color diagrams and the empirical temperature calibrations for F-, G-, and K-type stars of all luminosities and metallicities. The present models for F- to K-stars provide an extensive quasi-homogeneous grid of low-resolution theoretical flux spectra for a significant range in stellar parameters covering most of the observed HR diagram. Title: UV Spectra of K Type Stars from IUE Database Authors: Morossi, C.; Franchini, M.; Malagnini, M. L.; Kurucz, R. L. Bibcode: 1992ESOC...43..381M Altcode: 1992ald2.proc..381M No abstract at ADS Title: Atomic and Diatomic Molecular Opacities for Atmospheres and Envelopes Authors: Kurucz, R. L. Bibcode: 1992AAS...180.3202K Altcode: 1992BAAS...24Q.779K No abstract at ADS Title: Atomic and Molecular Data for Opacity Calculations Authors: Kurucz, R. L. Bibcode: 1992RMxAA..23...45K Altcode: I am attempting to produce line lists for all atoms and diatomic molecules that are important in stars. I collect all published data on spectrum analysis and oscillator strengths. I compute the energy levels, wavelengths, gf values, and damping constants that are not available from the literature. Line lists have been computed for diatomic molecules H2, CII, NH, OH, MgH, SiH, CN, C2, CO, SiO, and TiO, and for the iron group atoms Ca 1-IX to Ni 1-IX. These lists total 58 million lines. These calculations are being revised as new laboratory data become available. The work is being extended to other diatomic molecules, to lighter and heavier elements, and to higher stages of ionization. Key words: ATOMIC PROCESSES - MOLECULAR PROCESSES - TRANSITION PROBABILITIES Title: Remaining Line Opacity Problems for the Solar Spectrum Authors: Kurucz, R. L. Bibcode: 1992RMxAA..23..187K Altcode: We need high-resolution, high-signal-to-noise spectra of the sun with complete spectral coverage. The solar spectrum provides the insolation that controls the atmospheric chemistry of the earth and of all the solar system bodies. It is important for stellar astrophysics as the "standard" stellar spectrum because it can be observed better than that of any other star. It is important for understanding the sun, for it allows us to study the conditions and motions at its surface. It is an important high-temperature laboratory source for atomic and molecular spectroscopy. To interpret the spectrum we require accurate energy levels, accurate wavelengths, accurate gf values, accurate damping constants. We require hyperfine splitting, isotopic splitting, and Zeeman splitting. We require completeness in order to deconvolve blends. We need every level below the lowest ionization or dissociation energy. For molecules that is every vibrational and rotational level. Key words: ATOMIC PROCESSES - MOLECULAR PROCESSES - TRANSITION PROBABILITIES - SUN: SPECTRA Title: "Finding" the "missing" solar ultraviolet opacity. Authors: Kurucz, R. L. Bibcode: 1992RMxAA..23..181K Altcode: The author has computed new opacities for model stellar atmospheres and envelopes using a large grant of Cray computer time at the San Diego Supercomputer Center. The opacities include 58,000,000 atomic and diatomic molecular lines. Twelve-step distribution functions are tabulated for 56 temperatures in the range from 2000 K to 200000 K, for 21 log pressures from -2 to 8, for 1212 wavelength intervals from 10 to 10000 nm, for microturbulent velocities 0, 1, 2, 4, and 8 km/s, for scaled solar abundances [+1.0], [+0.5], [+0.3], [+0.2], [+0.1], [+0.0], [-0.1], [-0.2], [-0.3], [-0.5], [-1.0], [-1.5], [-2.0], [-2.5], [-3.0], [-3.5], [-4.0], [-4.5], [-5.0], and [+0.0, no He] (log abundance of elements heavier than helium relative to solar). Rosseland means are also tabulated for each case. The final files for each abundance require two 6250 bpi VAX backup tapes. The author is now distributing tape copies. He hopes to have CD-ROMs available in the near future. A solar photospheric model computed with the new opacities matches the observed energy distribution. Title: The Eclipsing Binary AI Phoenicis: New Results Based on an Improved Light Curve Analysis Program Authors: Milone, E. F.; Stagg, C. R.; Kurucz, R. L. Bibcode: 1992ApJS...79..123M Altcode: A revised atmospheres option based on the model developed by Kurucz (1979) together with empirical correction factors are used to model the parameters of AI Phe with the program of Wilson and Devinney (1971), employing a single temperature to parameterize all light curves from the UV to the IR, with better agreement with observation than previous attempts applying this mode. Improved precision in coupled luminosity-temperature determinations is obtained, especially in fitting to the ground-based UV. The present fittings to IUE data suggest nonlinear limb darkening for the primary component. The limb darkening of the hotter component in the far UV as it undergoes total eclipse is investigated and compared with Kurucz models. Title: Model Atmospheres for Population Synthesis Authors: Kurucz, R. L. Bibcode: 1992IAUS..149..225K Altcode: No abstract at ADS Title: Gedanken Astrophysics - the Universe Since Recombination Authors: Kurucz, R. L. Bibcode: 1992ComAp..16....1K Altcode: No abstract at ADS Title: The solar abundance of iron - A 'final' word. Authors: Biemont, E.; Baudoux, M.; Kurucz, R. L.; Ansbacher, W.; Pinnington, E. H. Bibcode: 1991A&A...249..539B Altcode: New accurate radiative lifetimes have been measured by a laser-induced-fluorescence technique for 12 selected levels of Fe(+) of astrophysical interest. These new results combined with recent theoretical transition probabilities provide another contribution in order to try to solve the controversy concerning the content of iron in the sun. The abundance value, A(Fe) = 7.54 +/-0.03, obtained from an extensive sample of Fe II lines, supports the 'low' value of the iron abundance, in agreement with the meteoritic result. Title: The SDSC Grid from [-5] to [+1] at 2 km/s Authors: Kurucz, R. L. Bibcode: 1991BAAS...23..967K Altcode: No abstract at ADS Title: A New Theoretical Model Photosphere Authors: Kurucz, R. L. Bibcode: 1991BAAS...23.1047K Altcode: No abstract at ADS Title: The solar spectrum. Authors: Kurucz, Robert L. Bibcode: 1991sia..book..663K Altcode: This chapter contains a discussion of what is known about the solar spectrum as a whole from the ultraviolet to the infrared. The data that are available are described and information is provided on how the reader can obtain paper or magnetic tape copies for particular applications, be it in atomic or molecular spectroscopy, or in solar, atmospheric, planetary, cometary or stellar physics. Title: New Opacity Calculations Authors: Kurucz, R. L. Bibcode: 1991ASIC..341..441K Altcode: 1991sabc.conf..441K No abstract at ADS Title: New Lines, New Models, New Colors Authors: Kurucz, Robert L. Bibcode: 1991ppag.conf...27K Altcode: 1991LDP....14...27K; 1991ppag.proc...27K No abstract at ADS Title: Binaries among the blue stragglers in M67. Authors: Milone, Alejandra A. E.; Latham, David W.; Kurucz, Robert L.; Morse, Jon A. Bibcode: 1991ASPC...13..424M Altcode: 1991fesc.book..424M The authors have used calculated spectra as templates to derive radial velocities for eleven of the classical blue stragglers in M67 by cross-correlations. The mean velocities for all eleven stars are close to the cluster mean, thus confirming their membership in the cluster. For the blue straggler F190 they derive a spectroscopic orbit with period 4.1829 d, eccentricity 0.21, and mass function 1.6×10-3Msun. Thus F190 is a good candidate for a blue straggler that resulted from mass transfer in a close binary. Several of the other blue stragglers show evidence for low-amplitude velocity variations. Title: Relative Abundance Determinations in Extremely Metal Poor Giants. II. Transition Probabilities and the Abundance Determinations Authors: Peterson, Ruth C.; Kurucz, Robert L.; Carney, Bruce W. Bibcode: 1990ApJ...350..173P Altcode: The abundances of Fe and other elements are determined for a star of intermediate metallicity and for nine extremely metal poor stars, including two members of the globular cluster M92 and CD -38 deg 245. The accuracy of the transition probabilities for Fe I and other elements is evaluated. The distribution of the abundances of other elements with respect to Fe is the same for most of the cases studied. Manganese is the only element that shows a different relative abundance in an extremely metal poor star. Title: High resolution ultraviolet stellar spectroscopy from space observations: What atomic physics and astrophysics can do for each other Authors: Leckrone, D. S.; Johansson, Se.; Kurucz, R. L.; Adelman, S. J. Bibcode: 1990asos.conf....3L Altcode: No abstract at ADS Title: Why I study the solar spectrum Authors: Kurucz, R. L. Bibcode: 1990asos.conf...20K Altcode: No abstract at ADS Title: High Resolution Ultraviolet Stellar Spectroscopy From Space Observatories - Atomic Physics and Astrophysics Authors: Leckrone, D. S.; Johansson, S.; Kurucz, R. L.; Adelman, S. J. Bibcode: 1989BAAS...21.1198L Altcode: No abstract at ADS Title: Reducing Photometry by Computing Atmospheric Transmission Authors: Kurucz, Robert L. Bibcode: 1989LNP...341...55K Altcode: 1989ies..conf...55K The transmission spectrum of the earth's atmosphere at every observatory can be computed if monitors are set up to determine the atmospheric structure and the abundance versus height of components that vary, such as water vapor and particulates. Photometric observations can be modelled and reduced using the measured instrumental bandpasses and the computed transmission. This method of reduction will greatly improve the quality of infrared photometry and may even be relevant in the visible where ozone, oxygen dimer, and water vapor affect photometric bandpasses. Here I describe the beginning of my work on this approach. Title: Effects of CO molecules on the outer solar atmosphere - Dynamical models with opacity distribution functions Authors: Muchmore, D.; Ulmschneider, P.; Kurucz, R. L. Bibcode: 1988A&A...201..138M Altcode: Carbon monoxide can be an important cooling agent in late-type stars. This paper expands previous theoretical work by extending the frequency set used in the radiation calculations, employing opacity distribution functions for the infrared bands of CO and 19 frequency points for the H(-) continuum. It is found that the net cooling rate due to CO decreases by a factor of about 3 due to the large optical depths in the line cores. The influence of the 2.2-micron CO band is small compared to the effect of the 4.6-micron band. An atmospheric structure with a sharp drop of the temperature in the outer photosphere, where CO cooling sets in, was found again. This temperature drop occurs higher in the atmosphere and is less steep than in the simpler models but is nevertheless steep enough to be convectively unstable. When CO cooling sets in, surface temperatures drop to very low values (T less than 3000 K) for radiative equilibrium models, even without including the effects of other molecules. Title: Line-Blanketing in Theoretical Model Atmospheres for f, g, and K-Type Stars Authors: Buser, R.; Kurucz, R. L. Bibcode: 1988IAUS..132..531B Altcode: The authors have computed improved flux distributions from Gustafsson et al.'s (1979) extensive grids of theoretical model atmospheres for late-type (F-K) giant and dwarf stars. The massive list of atomic opacity sources used for the hotter Kurucz models was also employed in calculating the cooler spectra. For both the giant and the dwarf models, the resulting synthetic UBVRI photometry provides excellent matches to the spectroscopic calibrations of the observed metallicity and temperature scales based on the ultraviolet excesses, δ(U-B), and the BVRI colors, respectively. The authors conclude that the atomic line-blanketing accounts for the largest fraction of the systematic UV discrepancy existing between observations and earlier model calculations. Title: The Distances to RR Lyrae Variables Authors: Jones, Rodney V.; Carney, Bruce W.; Latham, David W.; Kurucz, Robert L. Bibcode: 1988IAUS..126..589J Altcode: No abstract at ADS Title: The Metallicity Distribution Function of Halo Dwarfs and Globular Clusters Authors: Laird, J. B.; Rupen, M. P.; Carney, B. W.; Latham, D. W.; Kurucz, R. L. Bibcode: 1988IAUS..126..517L Altcode: Metallicities have been determined for a chemically unbiased sample of field halo dwarf stars. Their metallicity distribution function is similar to the predictions of a simple model of chemical evolution, but somewhat different from that of globular clusters. Title: Yet another Progress Report - New Model Atmospheres Soon Authors: Kurucz, R. L. Bibcode: 1988nds..conf...25K Altcode: 1988LDP.....9...25K No abstract at ADS Title: Yet another Progress Report - New Models Soon Authors: Kurucz, R. L. Bibcode: 1988csa..proc..139K Altcode: 1988LDP....10..139K No abstract at ADS Title: Semiempirical Determination of Feii Oscillator Strengths Authors: Kurucz, R. L. Bibcode: 1988ASSL..138...41K Altcode: 1988IAUCo..94...41K; 1988pffl.proc...41K The "missing ultraviolet opacity" is caused by lines of iron group elements that go to excited configurations that have not yet been seen in the laboratory. For the first 10 ions the author computes allowed and forbidden transition arrays for all known even and odd configurations plus as many predicted configurations as he can fit in the computer. A-sums, Stark and van der Waals broadening constants, and the Lande g value are computed for each energy level. Title: OH and CH Continuous Opacity in Solar and Stellar Atmospheres Authors: Kurucz, Robert L.; van Dishoeck, Ewine F.; Tarafdar, S. P. Bibcode: 1987ApJ...322..992K Altcode: Continuous absorption cross sections of OH and CH have been computed for the temperature range 1000K to 9000K. Both OH and CH produce significant ultraviolet opacity in the Sun and cool stars. CH is also significant in the visible at 400 nm. Title: A Survey of Proper-Motion Stars. II. Extracting Metallicities from High-Resolution, Low S/N Spectra Authors: Carney, Bruce W.; Laird, John B.; Latham, David W.; Kurucz, Robert L. Bibcode: 1987AJ.....94.1066C Altcode: The authors discuss the calculations of a grid of high-resolution synthetic spectra covering λλ5150 - 5250, Teff = 4750, 5000, ..., 6500K, [M/H] = +0.5, 0, ..., -3.0, and gravities of log g = 4.5 or 4.0. They describe a method using χ2 fits with these spectra as templates in the determination of mean line strengths from observed spectra. The authors estimate metallicities for 48 stars whose abundances have been previously determined from high-resolution, high-S/N spectra and conventional fine-analysis techniques. None of the observed spectra are high S/N, yet they result in metallicities with internal scatter of typically 0.1 dex. Comparison with published fine analyses shows excellent agreement (-0.03±0.02 dex) for metal-poor stars, and a small systematic error at higher abundances, which is easily corrected. Metallicities with σ < 0.2 dex are still obtained even when S/N is as low as 3. Title: The Baade-Wesselink Method and the Distances to RR Lyrae Stars. III. The Field Star SW Draconis Authors: Jones, Rodney V.; Carney, Bruce W.; Latham, David W.; Kurucz, Robert L. Bibcode: 1987ApJ...314..605J Altcode: The authors have obtained simultaneous BV and JHK photometry and radial velocities of typical accuracies of 1 km s-1 for the moderately metal-rich ([Fe/H] ≈ -0.75) RRab star SW Draconis. They have used these data and the surface brightness variation of the Baade-Wesselink method to derive <MV> = +0.94±0.15 mag for this star. The phasing problem encountered earlier recurs for SW Dra when the B-V index is employed. The authors find that SW Dra is only 0.06±0.10 mag fainter than the very metal-poor ([Fe/H] ≈ -2.2) star X Ari, so that the two stars have essentially the same luminosity within the uncertainty despite their large differences in metallicity.The implication of this result upon the derived ages of globular clusters is discussed. Title: The Baade-Wesselink Method and the Distances to RR Lyrae Stars. II. The Field Star X ARIETIS Authors: Jones, Rodney V.; Carney, Bruce W.; Latham, David W.; Kurucz, Robert L. Bibcode: 1987ApJ...312..254J Altcode: VR and JHK photometry and radial velocities with typical accuracies of 1 km/sec for the metal-poor RR Lyrae field star X Arietis. These data, along with unpublished UVBY photometry, have been used to derive the distance to X Ari using two variations of the Baade-Wesselink method. The possibility of photospheric velocity gradients that might distort the value of the systemic velocity and cause a phase shift was examined, and it was found that no gradient exists in the part of the stellar atmosphere considered. The phasing problem previously noted for VY Ser by Carney and Latham (1984) also occurs for X Ari when optical photometry is used to compute the effective temperatures, but not when the V - K color index is used. Possible causes of these phase shifts are discussed, and it is concluded that X Ari has an aggregate average V magnitude of 0.73-1.03 mag on the basis of the V - K results. Title: Atmospheres for population II stars. Authors: Kurucz, Robert L. Bibcode: 1987fbs..conf..129K Altcode: 1987IAUCo..95..129K; 1987LDP.....8..129K Recent theoretical models of stellar atmospheres are examined in a brief critical review, with a focus on population II stars. Consideration is given to numerical errors, physically inconsistent modeling of convection, inadequate treatment of structural equilibrium, arbitrarily selected microturbulent velocities and He abundances, and underestimated Fe-group line opacities. Tables illustrating the complexity of the model computations and listing corrected values of key parameters are provided. Title: The Distances and Absolute Magnitudes of RR Lyrae Variables Authors: Jones, R. V.; Carney, B. W.; Latham, D. W.; Kurucz, R. L. Bibcode: 1986BAAS...18..912J Altcode: No abstract at ADS Title: A New Sunspot Umbral Model and Its Variation with the Solar Cycle Authors: Maltby, P.; Avrett, E. H.; Carlsson, M.; Kjeldseth-Moe, O.; Kurucz, R. L.; Loeser, R. Bibcode: 1986ApJ...306..284M Altcode: Semiempirical model atmospheres are presented for the darkest parts of large sunspot umbrae, regions have called umbral cores. The approach is based on general-purpose computational procedures that are applicable to different types of stellar atmospheres. It is shown that recent umbral intensity measurements of the spectral energy distribution may be accounted for by an umbral core atmospheric model that varies with time during the solar cycle; the observed center-limb variation can be accounted for by the properties of the model. Three umbral core models are presented, corresponding to the early, middle, and late phases of the solar cycle. These three models also may be regarded as having the properties of dark, average, and bright umbral cores respectively. The effects of atomic, opacity, and abundance data uncertainties on the model calculations are briefly discussed. For comparison, a new reference model for the average quiet solar photosphere is given. Title: Theoretical UVBY beta Indices Authors: Lester, J. B.; Gray, R. O.; Kurucz, R. L. Bibcode: 1986ApJS...61..509L Altcode: The authors present theoretical photometric indices on the Strömgren and β systems for the published and unpublished grids of Kurucz. The indices have been placed on the standard systems using the ultraviolet and visual energy distributions of the secondary spectrophotometric standards. The common practice of using a single standard star to effect the transformation of the computed indices to the standard system is shown to produce systematic errors. Title: The empirical BC versus T EFF scale for non-supergiant O9-G5 stars. Authors: Malagnini, M. L.; Morossi, C.; Rossi, L.; Kurucz, R. L. Bibcode: 1986A&A...162..140M Altcode: By the analysis of observed energy distributions extending from the UV to the IR, the effective temperature, the gravity and the bolometric correction for a representative sample of nonsupergiant and not chemically peculiar O9-G5 stars are derived in a self-consistent way. The new, improved relationship between the bolometric correction and the effective temperature is then compared to the theoretical or observed ones previously published. The method used permits the derivation of angular diameters for the stars, with an uncertainty on the same order as the errors quoted for interferometric measurements. The importance of these results in the calibration of stellar parameters is stressed and their relevance for a direct comparison between the theoretical and the observational HR diagrams is briefly mentioned. Title: Chromospheric flare models. Authors: Avrett, E. H.; Machado, M. E.; Kurucz, R. L. Bibcode: 1986lasf.conf..216A Altcode: The calculations presented provide insights on how the observed chromospheric flare spectrum is produced. The results also suggest numerous improvements that should be made in the model calculations in order to interpret observations in better detail. The upper chromospheric contribution to white light flare emission is due to H, not H-, but H- plays an important role deeper in the atmosphere, and there could be a temperature enhancement in the deeper layers as a result of enhanced radiation produced in the upper chromosphere. Further work is needed to account for the important radiative processes, as well as time-dependent and kinetic processes, that affect the lower atmosphere in solar flares. Title: Theoretical stellar energy distributions. Authors: Kurucz, R. L. Bibcode: 1986HiA.....7..827K Altcode: The author's work on model stellar atmospheres is reviewed. In this context, the shortcomings that still exist in stellar atmosphere models are stressed, including numerical errors and errors in the treatment of convection, non-LTE, microturbulent velocity, abundances, and opacity. Models for A and B stars can be produced that reproduce the Balmer, Paschen, and Brackett continua and the Balmer line wings. This implies that even if the physical parameters that characterize the model for a given star are somewhat off, the temperature-pressure structure must be correct in the continua and line-wing-forming layers. Improved models will have a similar structure, but perhaps a somewhat different effective temperature and gravity. Title: Effective temperature and bolometric correction for HD 61421, HD 87901, HD 159561, HD 216956. Authors: Malagnini, M. L.; Morossi, C.; Rossi, L.; Kurucz, R. L. Bibcode: 1985A&A...152..117M Altcode: The effective temperature and the bolometric correction for four normal non-supergiant stars are determined from visible spectrophotometry, IUE data and Kurucz' models. The method applied does not require any a priori knowledge of the apparent angular diameter of the star. The excellent agreement of the results with those obtained by using the apparent angular diameter measured with the stellar interferometer at Narrabry Observatory demonstrates the soundness of the present approach. The paper shows how it is possible to overcome the limitation of direct measurement of angular diameters. Title: Chromosphere flare models Authors: Avrett, E. H.; Kurucz, R. L.; Machado, M. E. Bibcode: 1985smm..conf.....A Altcode: Further calculated results based on the F1 and F2 chromospheric models of Machado et al. (1980) are presented in addition to results from a model with enhanced temperatures relative to the weak-flare model F1 in the upper photosphere and low chromosphere, and from a model with enhanced temperatures relative to the strong flare model F2 in the upper chromosphere. The coupled equations of statistical equilibrium and radiative transfer for H, H(-), He I-II, C I-IV, Si I-II, Mg I-II, Fe, Al, O I-II, Na, and Ca II are solved, and the overall absorption and emission of radiation by lines throughout the spectrum are determined by means of a reduced set of opacities taken from a compilation of over 10 million lines. Semiempirical models show that the white light flare continuum may arise by extreme chromospheric overheating, as well as by an enhancement of the minimum temperature region. Title: Book-Review - Solar Flux Atlas from 296 TO 1300-NM Authors: Kurucz, R. L.; Furenlid, I.; Brault, J.; Testerman, L. Bibcode: 1985S&T....70...38K Altcode: No abstract at ADS Title: Photospheric Limb Darkening Signatures of Global Structure Variations Authors: Petro, L. D.; Foukal, P. V.; Kurucz, R. L. Bibcode: 1985SoPh...98...23P Altcode: Observations of short-term irradiance variations and consideration of mechanisms of the solar activity cycle suggest the possibility of long-term variation of the solar flux. Since the limb darkening is sensitive to effective temperature and convective efficiency, observations of the solar limb darkening may provide a useful means to detect and study long-term global variations. The limb-darkening responses to impulsive variation (in depth) of the source function, to effective temperature variation, and to convection variations are presented. For the variations considered, the limb-darkening variation is approximately linearly proportional to the associated parameters. The minimum detectable amplitude of those parametric variations is derived as a function of observational noise. Given our demonstrated errors of observation, single-parameter sensitivies are 3 K for effective temperature variation and 0.007 for local mixing-length variation for year to year changes at 99% confidence. Title: Investigation of Photospheric Limb-Darkening Variation Between 1980 and 1985 Authors: Petro, L. D.; Foukal, P. V.; Rosen, W. A.; Pierce, A. K.; Kurucz, R. L. Bibcode: 1985BAAS...17..644P Altcode: No abstract at ADS Title: Progress on Solar Opacity Authors: Kurucz, Robert L. Bibcode: 1985BAAS...17..640K Altcode: No abstract at ADS Title: Effective temperature and bolometric correction for HD 61421, HD 87901, HD 159561, and HD 216956. Authors: Malagnini, M. L.; Morossi, C.; Rossi, L.; Kurucz, R. L. Bibcode: 1985SSNew...7...16M Altcode: No abstract at ADS Title: The empirical B.C. (Bolometric Correction) versus Teff scale for non-supergiant O9 - G5 stars. Authors: Malagnini, M. L.; Morossi, C.; Rossi, L.; Kurucz, R. L. Bibcode: 1985SSNew...7...17M Altcode: No abstract at ADS Title: Steps toward a physical calibration of UBV photometry. Authors: Buser, R.; Kurucz, R. L. Bibcode: 1985IAUS..111..513B Altcode: The large data base of photoelectric measurements on the Johnson UBV system has been a primary source of information in many fields of astrophysical interest. The availability of UBV data for virtually all types of stars known to make up the stellar populations in galaxies requires a continued effort toward establishing a fully physical calibration of these data in order to propagate effectively the improving knowledge on stellar evolution and stellar atmospheres (i.e., the HR diagram) through the observations relevant to the structure and evolution of the galaxies. One of the major links in this long chain of scientific progress is provided by the synthesis of stellar photometric properties from theoretical model atmospheres. This paper will briefly address some of the basic problems involved in the synthetic color calculations and discuss the theoretical calibration of UBV photometry as obtained from various grids of model atmospheres covering a large range of stellar types. Title: A study of solar photospheric limb-darkening variations Authors: Petro, L. D.; Foukal, P. V.; Rosen, W. A.; Kurucz, R. L.; Pierce, A. K. Bibcode: 1984ApJ...283..426P Altcode: The authors have obtained regular observations of photospheric limb darkening, using the McMath Solar Telescope, to study possible slow changes in the global temperature structure, in Teff, and in the ultraviolet continuum flux from the quiet Sun. This paper reports on the analysis of data obtained on 15 days between 1980 September and 1982 December in a continuum window at λ4451. There are no variations of global limb darkening exceeding 0.1% at the 99% confidence level. The implications of these measurements for slow changes in solar luminosity, convection zone structure, and ultraviolet flux are discussed. Title: New Models of the Solar Temperature Minimum Region and Low Chromosphere Authors: Avrett, E. H.; Kurucz, R. L.; Loeser, R. Bibcode: 1984BAAS...16..450A Altcode: No abstract at ADS Title: Solar flux atlas from 296 to 1300 nm Authors: Kurucz, Robert L.; Furenlid, Ingemar; Brault, James; Testerman, Larry Bibcode: 1984sfat.book.....K Altcode: No abstract at ADS Title: Solar Cycle Temperature Variations in Sunspots Authors: Maltby, P.; Albregtsen, F.; Moe, O. Kjeldseth; Kurucz, R.; Avrett, E. Bibcode: 1984LNP...193..176M Altcode: 1984csss....3..176M The observed umbra/photosphere intensity ratio varies from the beginning to the end of each solar cycle by ∼ 30% at 1.6 μm and by factors > 2 at visible wavelengths. We present the intensity ratios measured in 10 wavelength bands extending from 0.387 to 2.35 μ m for 22 large sunspots observed during the period 1968-82, thus covering most of solar cycles 20 and 21. These results together with new observations of umbral limb darkening, and available data on photospheric absolute intensities, are used to estimate the dependence of the relative umbral intensity, and the absolute umbral intensity, on wavelength, heliocentric angle, and phase of the solar cycle. These umbral intensities are used to determine preliminary sunspot models which show the temperature as a function of depth in early, mid-, and late phases of the solar cycle. In the model calculations we use an extensive new compilation of atomic and molecular line data, allowing us to carry out the analysis by means of a detailed synthesis of the observed spectral bands. Title: Variation of Solar Limb Darkening Authors: Petro, L. D.; Foukal, P. V.; Rosen, W. A.; Kurucz, R. L.; Pierce, A. K. Bibcode: 1983BAAS...15..951P Altcode: No abstract at ADS Title: CD - 38 245, A Very Low-Metallicity Giant Authors: Peterson, R. C.; Carney, B. W.; Kurucz, R. L. Bibcode: 1983BAAS...15..923P Altcode: No abstract at ADS Title: Synthesis of old systems populations and input metallicities. Authors: Capuzzo-Dolcetta, R.; Kurucz, R.; Rossi, L. Bibcode: 1983MmSAI..54..829C Altcode: Problems encountered in generating synthetic spectra for old Population II stellar systems are discussed. The significance of selecting stellar atmospheres with appropriate metallicities for stars of temperatures over 10,000 K is emphasized. Comparisons of metallicity curves demonstrate that a low metallicity energy distribution is approximated well by solar composition models, except for a specific far-UV interval and at a 1550 A wavelength, where metal blends occur. Title: Photospheric and sunspot models from high-resolution spectrum synthesis. Authors: Avrett, E. H.; Kurucz, R. L. Bibcode: 1983ITABO..59...43A Altcode: Kurucz has recently compiled data for a list of 1.7×107 atomic and molecular lines. This list includes most of the lines seen in the solar spectrum. The authors use the line list and a standard photospheric model to calculate the detailed photospheric spectrum in the wavelength band 386 - 388 nm. The calculated spectrum is shown to be in good agreement with high-resolution observations, duplicating most individual line features and matching broad-band and maximum absolute line intensities. The results suggest that the sunspot 386 - 388 nm intensities are formed in the sunspot temperature-minimum region, and that the observed ≡3350K brightness temperature in this band is close to the sunspot minimum temperature value. Title: Waht should zero metal red giants look like ? Authors: Dantona, F.; Kurucz, R.; Mazzitelli, I.; Rossi, L. Bibcode: 1983MmSAI..54..129D Altcode: Evolutionary modelling of zero metal stars of 0.9-1.0 solar masses is presented. Attention is focused on the evolution of a 0.8 solar mass star and a 1.0 solar mass star up to the helium flash, which will be an order of magnitude less luminous than that expected of a Population II red giant. It is found that zero metal giant in the hydrogen shell burning stage are never more luminous than 250 solar luminosities. The average color of the zero metal giants is calculated to be B-V = 0.5-0.6, significantly bluer than Population II giants, and therefore easily discernable at visible wavelengths. Title: A study of convective model stellar atmospheres using a modified mixing-length theory Authors: Lester, J. B.; Lane, M. C.; Kurucz, R. L. Bibcode: 1982ApJ...260..272L Altcode: The ATLAS model atmosphere program is modified to incorporate two recently proposed changes to the standard mixing-length theory of convection. These changes are (1) the use of horizontally averaged opacity in place of the opacity at the average horizontal temperature and (2) the use of a variable mixing length. The resulting changes in the structure of the atmosphere are studied by systematically varying effective temperature, surface gravity, and composition. It is found that the modified model atmospheres exhibit the following changes: (1) convection transports a smaller fraction of the total flux; (2) the convection zone is generally narrower, and the variation of F(conv)/F(total) with depth is smoother; (3) the temperature is higher in the convective region; (4) the model is brighter in the spectral region between 1500 and 2000 A; and (5) there are small, systematic flux differences in the visual spectral region. Title: Variations in photospheric limb darkening as a diagnostic of changes in solar luminosity Authors: Rosen, W. A.; Foukal, P. V.; Kurucz, R. L.; Pierce, A. K. Bibcode: 1982ApJ...253L..89R Altcode: The paper reports on photospheric limb-darkening measurements obtained with the McMath Solar Telescope in July, September, and October 1980 as part of a continuing program to investigate possible long-term variations in the photospheric emergent flux. A total of 243 usable full-diameter scans were recorded over seven days in the clean continuum window at 4451-25 A. The limb darkening was found to decrease significantly between September 25 and 26. It is suggested that this decrease was caused by a decrease of the temperature gradient in the upper photosphere in the region above approximately tau(5000) = 0.5. The small increase in effective temperature that might accompany this limb-darkening variation is estimated using a standard radiative equilibrium photospheric model. Title: Measurement of the oscillator strengths and autoionization widths of the neutral-aluminum multiplet 3s2 3p2 P0 - 3s 3p2 2P Authors: Lombardi, G. G.; Cardon, B. L.; Kurucz, R. L. Bibcode: 1981ApJ...248.1202L Altcode: The hook method is used in conjunction with absorption equivalent width measurements to determine the oscillator strengths and line widths of the Al I multiplet 3s2 3p2 P0 - 3s 3p2 2P at 176 nm. Autoionization is found to be the dominant decay channel for the two levels of the 3p2 2P term, with autoionizing widths of 4.0 and 0.87 x 10 to the 10th/sec for J of 3/2 and 1/2, respectively. The van der Waals scattering cross section for the Al I transition at 176.91 nm by He is determined to be (1.3 + or - 0.3) x 10 to the -14th sq cm at 2400 K, and a solar spectrum calculation centered at 176 nm shows that the Al I features are possible diagnostic probes of (1) solar non-LTE processes, and (2) the temperature minimum and structure of the lower chromosphere. Title: Solar Spectrum Synthesis. I. A Sample Atlas from 224 to 300 nm Authors: Kurucz, Robert L.; Avrett, Eugene H. Bibcode: 1981SAOSR.391.....K Altcode: We have developed sophisticated computer programs for determining solar and stellar atmospheric structure through the analysis of spectra. These programs allow us to treat the spectrum as a whole and to draw much stronger conclusions than would be apparent from individual spectral features. For a given LTE or non-LTE model atmosphere, the programs compute the emergent flux or the specific intensity at up to 20 angles. The spectrum can be broadened by macroturbulence and rotation; it can be modified by transmission through the Earth's atmosphere; it can be convolved with the instrumental profile; and it can finally be plotted together with the observed spectrum with each line labeled. In the opacity calculation, the lines are broadened by radiative, Stark, and van der Waals damping, and they can have isotopic and hyperfine splitting, autoionization, partial redistribution, or be merged into a continuum. The departure coefficients for ions treated in non-LTE in the model atmosphere calculation can be used in the spectrum synthesis programs for all lines of these ions, and highly ionized lines can be treated in the coronal approximation. The model atmosphere can have depth-dependent doppler shifts corresponding to large-scale motions. Using the Vernazza, Avrett, and Loeser models for the average quiet sun, we have computed theoretical solar spectra that include all available atomic and molecular line data. In this atlas we compare with the best available observed spectra in the 224- to 300-nm wavelength range, namely, the Kohl, Parkinson, and Kurucz (Harvard) center and limb rocket spectra in the range 224 to 300 nm; the Allen, McAllister, and Jefferies (Hawaii) disk center rocket spectrum for 268 to 293 nm; and the Brault and Testerman disk center spectrum taken at Kitt Peak for 294 to 300 nm. We also compare the observed spectra with each other. The existing spectra are noisy and do not have adequate resolution, so that it is difficult or impossible to identify weak features, to resolve blends, to study velocity fields, to search for variability; or to do any of the projects that can be routinely done in the visible where high quality spectra are available. Because the ultraviolet spectrum provides diagnostics for the upper photosphere, the temperature minimum, and the chromosphere, our understanding of these regions of the solar atmosphere is seriously impaired. One-half the lines in the observed spectrum are not identified. The overall level of the calculation lies considerably above the observed. The discrepancy is caused mainly by missing atomic and molecular lines and possibly by errors in the measured continuum opacities. Laboratory spectral analyses are seriously incomplete, especially for the iron group atoms and for high J and V molecular levels of CO, SiO, and the hydrides. Any model atmosphere or non-LTE rate calculation that depends directly on available ultraviolet opacities should not be trusted. Title: An Improved Theoretical Solar Photospheric Model Authors: Kurucz, R. L. Bibcode: 1981BAAS...13..888K Altcode: No abstract at ADS Title: Photospheric Limb Darkening as a Ground-based Diagnostic for Variations in the Solar Effective Temperature Authors: Rosen, W. A.; Foukal, P. V.; Kurucz, R.; Pierce, A. K. Bibcode: 1981BAAS...13..551R Altcode: No abstract at ADS Title: Semiempirical Calculation of gf Values, IV: Fe II Authors: Kurucz, Robert L. Bibcode: 1981SAOSR.390.....K Altcode: Slater parameters, eigenvalues, eigenvectors, and scaled Thomas-Fermi-Dirac wavefunctions have been computed for all known configurations of Fe II. The complete transition array has been computed, together with partial sums required for radiative, Stark, and van der Waals damping constants. A listing of the 431, 933 strongest lines is available on magnetic tape. A subset of that listing containing 22, 547 lines between observed energy levels is presented here. Comparisons are made with other published lifetime and gf value data. Title: A table of semiempirical gf values. Pt 4: FeII Authors: Kurucz, R. L. Bibcode: 1981tsgv.book.....K Altcode: No abstract at ADS Title: Solar Spectrum Synthesis I. A sample atlas from 224 to 300 NM Authors: Kurucz, Robert L.; Avrett, Eugene H. Bibcode: 1981ssss.book.....K Altcode: No abstract at ADS Title: Model Atmospheres for Globular Cluster Stars Authors: Kurucz, R. L. Bibcode: 1981apgc.conf..289K Altcode: 1981IAUCo..68..289K; 1981LDP.....2..289K No abstract at ADS Title: Semiemprical calculation of gf values Authors: Kurucz, Robert L. Bibcode: 1980AIPC...63..163K Altcode: 1980susp.conf..163K Because of the large scatter in my gf values in comparison to laboratory values which was well demonstrated by Wiese in his presentation, I am going to spend most of my time explaining the reasons for the scatter so that you will not worry unduly about using my calculations. Then I will mention my spectrum synthesis programs in passing and finally I will talk about future calculations that will provide oscillator strength data for Ni, Co, and Fe in supernova spectra. Title: Si0 in the Ultraviolet Solar Spectrum Authors: Kurucz, R. L. Bibcode: 1979BAAS...11Q.710K Altcode: No abstract at ADS Title: Sample Spectral Atlas for Sirius Authors: Kurucz, Robert L.; Furenlid, Ingemar Bibcode: 1979SAOSR.387.....K Altcode: We present a sample spectral atlas of Sirius for the region 354 to 440 nm in which we show a photographic spectrum that resolves the line profiles and has a small-scale signal to noise better than 300. The atlas also shows a calculated spectrum that demonstrates our capabilities in spectrum synthesis. We are able to compute a spectrum, broaden it with microturbulence and rotation, transmit it through the atmosphere, convolve it with the instrumental profile, plot it together with the observed spectrum, and label each line. This approach to analyzing stellar spectra has a number of advantages over working with lists of line identifications or equivalent widths or individual line profiles: (1) The reader gets an immediate impression of the quality of the data and of blending, and many lines that appear to be single are shown to be blends. (2) The reader can much better estimate the continuum level and the total blocking to check model atmosphere predictions and assess the reliability of an abundance determined from any given line. (3) Determinations of stellar parameters and abundances can be based on all the data, not just on a small sample. (4) The reader gets an intuitive "feel" for the data and for the properties of the star, which is missing in other approaches. (5) All the data are presented and the reader who disagrees with our treatment can reanalyze them. Our programs can be used to analyze existing and future ground-based, balloon, rocket, and satellite observations of the sun and stars. For Sirius we plot a roughly photometric spectrum at 10 nm/panel, then at 5 nm/panel with a comparison rotationally broadened calculated spectrum, then at 0.8 nm/panel with comparison unbroadened and rotationally broadened calculated spectra and line identifications. No attempt has yet been made to fit the calculated spectra to the observed spectrum. The observed spectrum has been only roughly normalized to the calculated spectrum to make it photometric. From the sample spectrum it is clear that Sirius is strongly underabundant in Ca, contrary to earlier studies, and that its abundances are roughly consistant with other metallic line stars although not extreme. There is no region of the spectrum shown here that is not produced by overlapping lines. Title: Model atmospheres for G, F, A, B, and O stars. Authors: Kurucz, R. L. Bibcode: 1979ApJS...40....1K Altcode: A grid of LTE model atmospheres is presented for effective temperatures ranging from 5500 to 50,000 K, gravities from the main sequence down to the radiation-pressure limit, and abundances solar, 1/10 solar, and 1/100 solar. The models were computed by use of a statistical distribution-function representation of the opacity of almost a million atomic lines. For each model the temperature structure, fluxes, UBV and uvby colors, bolometric correction, and Balmer line profiles are tabulated. The solar-abundance models are compared with narrow-, intermediate-, and wide-band photometry and found to be in good agreement with the observations for effective temperatures above 8000 K. Excellent agreement exists with the spectrophotometry and Balmer line profiles of Vega. A small systematic error in the colors of late A and F stars is probably due to an overstimate of convection in weakly convective models. This error does not seem to affect greatly the use of the predicted colors for differential studies. The solar model has approximately a 2% error in the V flux because molecular lines were not included. Title: High resolution atmospheric transmission calculations down to 28.7 km in the 200-243-nm spectral range (TE) Authors: Cann, M. W. P.; Evans, W. F. J.; Kohl, J. L.; Kurucz, R.; Parkinson, W. H.; Reeves, E. M.; Nicholls, Ralph W. Bibcode: 1979ApOpt..18..964C Altcode: Decrease in stratospheric ozone absorption and increase in oxygen absorption with decreasing wavelength combine to produce a window of maximum atmospheric transmission near 210 nm. Since solar radiation in this spectral region dissociates molecular oxygen, the deep atmospheric penetration at this wavelength is of particular aeronomical interest. High resolution calculations of the transmittance down to 28.65 km were made for the 200-243-nm spectral range in this window region, in support of a stratospheric balloon flight from Fort Churchill in July 1974. The calculations were made by dividing the atmosphere into layers which were chosen so that each could be assumed homogeneous; optical depths were calculated separately for each of these layers and then summed to obtain the over-all transmittance of the atmosphere. Absorption by molecular oxygen (line and continuum) and by ozone was included, as well as extinction through Rayleigh scattering by air molecules. The calculated transmittances were combined with high altitude (above 100-km) rocket measurements of the sun-center spectrum and center-to-limb variations to give residual high resolution solar spectral flux for several altitudes and solar zenith angles. Title: Theoretical Colors for Helium Rich Cepheids. Authors: Whitaker, R. W.; Kurucz, R. L. Bibcode: 1979BAAS...11..438W Altcode: No abstract at ADS Title: A progress report on theoretical photometry. Authors: Kurucz, R. L. Bibcode: 1979DudOR..14..363K Altcode: No abstract at ADS Title: A systematic investigation of multicolor photometric system. III. Theoretical UBV colors and the temperature scale for early-type stars. Authors: Buser, R.; Kurucz, R. L. Bibcode: 1978A&A....70..555B Altcode: Summary. We present synthetic UBV colors for early- type stars computed from a new grid of blanketed model atmospheres by Kurucz (1978), and from the revised response functions by Buser (1978). Excellent agreement with Johnson's (1966) mean `intrinsic' U-B and B - V colors for main sequence stars is obtained. The theoretical effective temperature scale and the bolometric corrections agree well with the empirical results found by Code et al. (1976). Key words: stars: early-type - blanketed model atmospheres - effective temperature scale - bolometric corrections - synthetic UBV colors. Title: Solar Spectrum Synthesis Authors: Kurucz, R. L. Bibcode: 1978BAAS...10..658K Altcode: No abstract at ADS Title: A theoretical analysis of uvby photometry. Authors: Relyea, L. J.; Kurucz, R. L. Bibcode: 1978ApJS...37...45R Altcode: Theoretical Stromgren uvby and Johnson-Morgan UBV colors have been calculated from the Kurucz (1978) grid of model atmospheres for G, F, A, B, and O stars, and calibrated to the standard systems using a model atmosphere for Vega with an effective temperature of 9400 K and log g = 3.95. The resultant color-color grids are analyzed, and the usefulness of the photometric systems for derivation of atmospheric effective temperature, surface gravity, and abundance is assessed. For the uvby system, excellent agreement between the models and observations is obtained for effective temperatures of at least 8500 K, and photometric grids for use in reducing observations are presented. A discrepancy is found for effective temperatures below 8500 K, and possible sources of error are discussed. For the UBV system, because of nonlinear transformations, no accurate system calibration is presented. Title: Center and limb solar spectrum in high spectral resolution 225.2 NM to 319.6 NM Authors: Kohl, John L.; Parkinson, William H.; Kurucz, Robert L. Bibcode: 1978clss.book.....K Altcode: 1978QB551.K63...... The atlas has been designed to fulfill the need in solar and stellar astronomy, in aeronomy, and in space science for a convenient reference source that provides a detailed and accurate record of the measured solar ultraviolet spectrum in high spectral resolution for the wavelength range from 225.2 nm to 319.6 nm. The atlas also contains a preliminary synthetic solar spectrum with a legend for identifying and describing the features of the synthetic spectrum. Attention is given to aspects of instrumentation, the radiometric calibration, the wavelength scale, background noise random fluctuations and data filtering, intermittent noise, the observational conditions, the experimental uncertainty, the atlas format, references, tables, and plots. Title: Theoretical stellar chromospheres of late type stars. II. Temperature minima. Authors: Ulmschneider, P.; Schmitz, F.; Renzini, A.; Cacciari, C.; Kalkofen, W.; Kurucz, R. Bibcode: 1977A&A....61..515U Altcode: The theory of heating by short period acoustic waves is applied to predict the height of shock formation and the acoustic flux at the base of the chromosphere for stars with effective temperatures of 4000 to 6500 K and log g of 2 to 4. These predictions are compared with heights of temperature minima and with chromospheric radiation losses computed from semiempirical models. Title: The rotational velocity and barium abundance of Sirius. Authors: Kurucz, R. L.; Traub, W. A.; Carleton, N. P.; Lester, J. B. Bibcode: 1977ApJ...217..771K Altcode: We have measured the Ba ii 649.69 nm line profile in Sirius using a PEPSIOS interferometer. We find a projected rotational velocity V sin i of 16 + 1 km 1; a heliocentric radial velocity of -8.6 + 0.4km 1; and a log Ba abundance of -8.18 + 0.15 relative to all atoms by number (3.87 if log H = 12), which is greater than the solar abundance by 1.76 + 0.18. Subject headings: stars: abundances stars: individual - stars: rotation Title: The ultraviolet spectra of Alpha Aquilae and Alpha Canis Minoris. Authors: Morton, D. C.; Spinrad, H.; Bruzual A., G.; Kurucz, R. L. Bibcode: 1977ApJ...212..438M Altcode: Scans of Alpha Aql (A7 IV, V) and Alpha CMi (F5 IV-V) obtained with the Copernicus satellite spectrometer over the wavelength range from 2100 to 3200 A are presented along with a spectrum of the integrated solar disk over the same range procured during a calibrated rocket flight. About 1500 fairly strong absorption lines in the Alpha CMi spectrum between 2400 and 2961 A are identified by comparison with a solar atlas and by using a theoretical spectrum synthesized from a blanketed LTE model with an effective temperature of 6500 K and a surface gravity of 10,000 cm/sec per sec. The Mg II resonance doublet at 2795.528 and 2802.704 A is found to be present in all three stars together with a discontinuity at 2635 A due to Fe II, Fe I, Cr I, and Mn II. It is concluded that the Mg II resonance lines and the 2635-A continuum break would be the best spectral features for estimating the redshift of a galaxy observed at low resolution provided the redshift is not less than about 0.75. Title: The Fourth Positive System of Carbon Monoxide Authors: Kurucz, Robert L. Bibcode: 1976SAOSR.374.....K Altcode: For the Fourth Positive system of CO we present tables of energy levels, Frank-Condon factors, r-centroids, transition moments, line wavelengths, and gf values. Title: Stellar model chromospheres. V. Alpha Centauri A (G2 V) and Alpha Centauri B (K1 V). Authors: Ayres, T. R.; Linsky, J. L.; Rodgers, A. W.; Kurucz, R. L. Bibcode: 1976ApJ...210..199A Altcode: Models for the upper photospheres and lower chromospheres of Alpha Centauri A and B are derived from high-dispersion spectrograms of the Ca II K-line emission cores and damping wings. Effective temperatures, surface gravities, and ages consistent with the measured broadband colors, metallicities, and absolute magnitudes are estimated for the two stars. The spectrograms are calibrated by fitting the far-wing K profiles with synthetic fluxes based on radiative-equilibrium models, and the model atmospheres are obtained through a partial-redistribution analysis of the line cores and damping wings. These models are compared with those previously proposed for Procyon, Arcturus, and the sun. Many features in all the models are found to be quite similar, and some evidence suggests that Alpha Cen A may be significantly older and more evolved than the sun, even though both stars exhibit similar chromospheric properties. Title: Solar Ultraviolet Spectrum Synthesis. Authors: Kurucz, R. L. Bibcode: 1976BAAS....8..502K Altcode: No abstract at ADS Title: The Possible Role of Radiative Acceleration in Supporting Extended Atmospheres in be Stars Authors: Kurucz, R. L.; Schild, R. E. Bibcode: 1976IAUS...70..377K Altcode: No abstract at ADS Title: Line Blanketing in VEGA and Sirus Authors: Kurucz, R. L. Bibcode: 1976sao..rept.....K Altcode: A theoretical model and spectrum calculation for Vega is discussed. The abundance of carbon is approximately -3.8, which is 0.3 lower than the old solar value and supports Mount and Linsky's newer value. The oxygen abundance is approximately -3.5. Assuming that Vega has solar abundances, the solar oxygen abundance appears to have been overestimated by 0.3 in the log. Other abundances appear to be solar. For Sirius the calculations do not agree with the observed spectrum. Line opacity is considerably underestimated, notably in third-spectrum iron group lines. Carbon is underabundant relative to Vega by 0.2 in the log. Nitrogen is unchanged. Oxygen is enhanced by 0.3. Heavier elements are enhanced by 1.0 in the log. Calibration yields 1.3E-10 ergs/sq cm/s/nm for each U1 Copernicus count at 130 nm. Title: a Progress Report on Theoretical Four-Dimensional Photometry of F a, and B Stars Authors: Kurucz, Robert L. Bibcode: 1975mpth.conf..271K Altcode: 1975mpth.proc..271K No abstract at ADS Title: A table of semiempirical gf values. Pt 1: Wavelengths: 5.2682 NM to 272.3380 nm; Pt 2: Wavelengths: 272.3395 NM to 599.3892 nm; Pt 3: Wavelengths: 599.4004 NM to 9997.2746 NM Authors: Kurucz, R. L.; Peytremann, E. Bibcode: 1975SAOSR.362.....K Altcode: 1975tsgv.book.....K; 1975SAOSR.362....3K; 1975SAOSR.362....0K We tabulate gf values for 265,587 atomic lines selected from the line data used by Kurucz, Peytremann, and Avrett (1974) to calculate line-blanketed model atmospheres. These data are especially useful for line identification and spectral synthesis in solar and stellar spectra. Except for 10,000 lines taken from the literature, the gf values have been calculated semiempirically by using scaled Thomas-Fermi-Dirac radial wavefunctions and eigenvectors found through least-squares fits to observed energy levels. Included in the calculation were the first five or six stages of ionization for sequences up through nickel. Published gf values have been included for elements heavier than nickel. The tabulation is restricted to lines with wavelengths less than 10 μm. Title: Semiempirical Calculation of gf Values, Iii: Interstellar Lines of the Iron Group Authors: Kurucz, R. L. Bibcode: 1974SAOSR.360.....K Altcode: Iron-group gf values are tabulated for lines that might appear in the interstellar medium. Title: Semiempirical Calculation of gf values, II: Fe I(3d+4s)8 - (3d+4s)7 4p Authors: Kurucz, Robert L. Bibcode: 1974SAOSR.359.....K Altcode: No abstract at ADS Title: Semiempirical calculation of gf values, II: Fe I (3d+4s)8-(3d+4s)74p. Authors: Kurucz, R. L. Bibcode: 1974SAOSR.359....9K Altcode: No abstract at ADS Title: Stellar Spectral Synthesis in the Ultraviolet Authors: Kurucz, Robert L. Bibcode: 1974ApJ...188L..21K Altcode: A computer program for spectral synthesis has been developed, based on a list of data for atomic lines described by Kurucz, Peytremann, and Avrett. To demonstrate the usefulness of this program, we present a sample calculation of the region around the C w resonance doublet at 155 nm, which is a feature in rocket and satellite spectra of B stars. The calculation indicates that the observed feature is a blend of many lines in addition to C iv, so that detailed calculations are necessary for the correct interpretation of the observational data. Subject headings: atmospheres, stellar-line profiles-ultraviolet Title: Report on the Celescope ultraviolet observations from the OAO 2 satellite and associated research at the Smithsonian Astrophysical Observatory. Authors: Avrett, E.; Davis, R.; Deutschman, W.; Haramundanis, K.; Kurucz, R.; Payne-Gaposchkin, C.; Peytremann, E.; Schild, R. Bibcode: 1974spre.conf..515A Altcode: No abstract at ADS Title: Blanketed model atmospheres for early-type stars Authors: Kurucz, Robert L.; Peytremann, Eric; Avrett, Eugene H. Bibcode: 1974bmae.book.....K Altcode: 1974QB843.E2K37.... No abstract at ADS Title: Report on the Celescope ultraviolet observations from the OAO-2 satellite and associated research at the Smithsonian Astrophysical Observatory. Authors: Avrett, E.; Davis, R.; Deutschman, W.; Haramundanis, K.; Kurucz, R.; Payne-Gaposchkin, C.; Peytremann, E.; Schild, R. Bibcode: 1974rnuo.confC...2A Altcode: No abstract at ADS Title: A Preliminary Theoretical Line-Blanketed Model Solar Photosphere Authors: Kurucz, Robert L. Bibcode: 1974SoPh...34...17K Altcode: A preliminary theoretical solar model is presented that produces closer agreement with observation than has been heretofore possible. The qualitative advantages and shortcomings of this model are discussed and projected improvements are outlined. Title: Semiempirical Calculation of gf Values: sc II (3d+4s)2 - (3d+4s) 4p, a Detialed Example Authors: Kurucz, R. L. Bibcode: 1973SAOSR.351.....K Altcode: A semiempirical procedure for calculating gf values is developed in detail. A program written by R. D. Cowan is used to produce LS transition arrays and electrostatic and spin-orbit matrices. Transition integrals are evaluated with scaled Thomas- Fermi-Dirac wavefuntions following Warner. Eigenvectors are found through a least-squares procedure that fits computed eigenvalues to observed energy levels, and then the eigenvectors are used to transform the LS transition array to the observed coupling scheme. Throughout the discussion, examples are given for Sc II (3d+4s)2 - (3d+4s) 4p. The final computed gf values are compared to laboratory measurements. Title: Line-Blanketed Model Atmospheres. Authors: Kurucz, Robert Louis Bibcode: 1973PhDT.........4K Altcode: No abstract at ADS Title: Atlas: a Computer Program for Calculating Model Stellar Atmospheres Authors: Kurucz, R. L. Bibcode: 1970SAOSR.309.....K Altcode: The computer program ATLAS calculates model stellar atmospheres in radiative and convective equilibrium for the complete range of stellar temperatures. The apporximations used limit the program to plane-parallel, horizontally homogeneous, stedy-state, nonmoving atmospheres with energy and abundances constant with depth. The program has been written to allow detailed statistical equillibrium calculations, but only hydrogen continua and H- are coded at present. Most of the published continuous opacities and hydrogen lines have been included, and provision is made for adding others easily. There is also provision for treating line opacity as line absorption distribution functions. In Sections 2 through 7, we discuss all aspects of model atmosphere calculations in considerable detail. These include the radiation field, statistical equilibrium, thermodynamic properties, opacity, convection, and the temperature correction. In Sections 8 and 9, we discuss the computer program itself, by going first through a sample calculation and second through a technical discussion of the program coding and operation. The program was written in FORTRAN IV and is essentially machine independent. A listing is available on magnetic tape. Title: Atlas: A computer program for calculating model stellar atmospheres Authors: Kurucz, R. L. Bibcode: 1970acpc.book.....K Altcode: No abstract at ADS Title: A Matrix Method for Calculating the Source Function, Mean Intensity, and Flux in a Model Atmosphere Authors: Kurucz, Robert L. Bibcode: 1969ApJ...156..235K Altcode: The integrals for the mean intensity and flux are expressed as the multiplication of the source-function vector by matrix representations of the integral operators. This method leads to a rapid solution of the integral equation for the source function and to an efficient calculation of the mean intensity and flux Title: The Grid of Model Stellar Atmospheres from 50,000° to 11,000° Authors: Kurucz, R. Bibcode: 1969tons.conf..375K Altcode: No abstract at ADS Title: The Rocket Ultraviolet Spectra of a Stars Authors: Maran, Stephen P.; Kurucz, Robert L.; Strom, K. M.; Strom, Stephen E. Bibcode: 1968ApJ...153..147M Altcode: A synthetic spectrum covering the wavelength range 2000-3000 A has been computed for a tempera- ture and surface gravity appropriate to a main-sequence early A star. The strongest lines and also those of potential value in discussing nucleosynthesis problems are tabulated Title: Effects of Line Blanketing on the Solar Windows Authors: Carbon, Duane; Gingerich, Owen; Kurucz, Robert Bibcode: 1968SoPh....3...55C Altcode: The increasingly high flux predicted to the violet of 4500 Å by many model solar atmospheres stands in contradiction to the observations. Since one possible cause of the disagreement is that the solar `windows' by which the observed continuum is established might be obscured by line wings, we have made detailed calculations of these narrow spectral regions. With the exception of a few windows affected by the wings of Balmer lines, those redward of the Balmer discontinuity appear free of line blanketing. Even the assumption that the ultraviolet continuum is depressed 5% by unseen lines not included in our calculations leaves substantial disagreements between the models and observations. The discrepancies could perhaps be explained by a veil of weak lines across the ultraviolet spectrum. Title: Statistical Procedure for Computing Line-Blanketed Model Stellar Atmospheres. Authors: Strom, S. E.; Kurucz, R. Bibcode: 1966AJ.....71S.181S Altcode: In order to treat the problem of line blanketing in computing model stellar atmospheres we have developed a modified picket-fence approach. We divide the frequency range between the Lyman limit and 44 000 A into 16 separate regions and for each of these regions we compute at 34 optical depths a function N (H). This function descril~es the number distribution of the ratio of line to continuum opacity H. It is computed using a compilation of transition probabilities and excitation potentials for 28 500' spectral lines. The function N(H) is used to choose five values of H for each frequency region. Corresponding to each H is the fraction W of the particular frequency region occupied by opacity ratios equal to or less than H. The values of H and W for each frequency region and the continuum opacities are then used as input to a modified version of the stellar atmosphere program discussed by Strom and Avrett (Astrophys. J. Siippl. 12,1, 1965). We have tested the numerical accuracy of our program by comparing with the results obtained by Avrett for a grey atmosphere and a simple picket- fence absorption coefficient. Finally, we discuss the use of this program for the analysis of Procyon.