- ID:
- ivo://CDS.VizieR/J/A+A/580/A10
- Title:
- New MnII energy levels
- Short Name:
- J/A+A/580/A10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The NIST database lists several MnI 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{AA} interval. We aimed to assign energy levels and loggf values to these lines. Semi-empirical line data for MnII 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 3050-10000{AA} region was also examined.
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- ID:
- ivo://CDS.VizieR/J/A+A/363/1081
- Title:
- Non-linear limb-darkening law for LTE models
- Short Name:
- J/A+A/363/1081
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new non-linear limb-darkening law, based on the Least-Squares Method (LSM), is presented. This law is able to describe the intensity distribution much more accurately than any of the old ones given that the differences I(model)-I(fitting) are of some order of magnitude smaller than those derived from other approximations. This new law shows several advantages: it represents well the intensity distribution, the flux is conserved with high accuracy and it permits the use of a single law for the whole HR Diagram since that the bi-parametric laws are only marginally valid in certain range of effective temperatures. The limb-darkening coefficients are computed for the 12 commonly used photometric bands u v b y U B V R I J H K. Bolometric and monochromatic calculations are also available. The computations are presented for 19 metallicities ranging from 10^-5^ up to 10^+1^ solar abundances, with log(g) varying between 0 and 5.0 and effective temperatures between 2000K-50000K. Results for microturbulent velocities of 0, 1, 2, 4, 8 km/s are also available. With this set of data it was possible to investigate, for the first time, the influence of such parameters in the limb-darkening. Limb-brightening, instead of limb-darkening, was detected for some models. It is shown that the limb-darkening coefficients derived using the Flux Conservation Method (FCM) do not describe very well the intensity distribution, mainly near the border of the disk. On the contrary, the present coefficients, based on the LSM, represent very well the function I({mu}) at any part of the disk for any filter or wavelength, log(g), effective temperature, metallicity and microturbulent velocity. The results are presented here as synthetic tables containing the limb-darkening coefficients. The 46 tables announced in the paper are also accessible as the "original.tar" file.
- ID:
- ivo://CDS.VizieR/J/A+A/401/657
- Title:
- Non-linear limb-darkening law for LTE models. II.
- Short Name:
- J/A+A/401/657
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As an extension of our previous investigations on stellar atmospheres (Claret, 2000, Cat. <J/A+A/363/1081>), the limb-darkening coefficients for the Geneva and Walraven photometric systems are presented for the first time using the ATLAS and PHOENIX models. They cover a wide range of values of logg, T_eff_, metallicities and microturbulent velocities. In addition to the traditional applications of limb-darkening coefficients, the present ones are now being used in the interpretation of phase shift of B and A-F type pulsating stars.
- ID:
- ivo://CDS.VizieR/J/A+A/428/1001
- Title:
- Non-linear limb-darkening law for LTE models. III.
- Short Name:
- J/A+A/428/1001
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Continuing our studies on stellar atmospheres (Claret, 2000, Cat. <J/A+A/363/1081>, 2003, Cat. <J/A+A/401/657>), we present in this paper the limb-darkening coefficients for the Sloan photometric system. The calculations cover a wide range of values of logg, T_eff_, metallicities and microturbulent velocities. The atmosphere models used are ATLAS and PHOENIX. In addition to the traditional applications of the limb-darkening coefficients, the present ones will be useful since the Sloan filters are now being used in the interpretation of light curves of extrasolar transiting planets, for example. The present calculations may also be useful, as a complement, for the Kepler mission, dedicated to the search for terrestrial planets.
- ID:
- ivo://CDS.VizieR/J/A+A/373/987
- Title:
- Non-LTE Ga abundance in HgMn stars
- Short Name:
- J/A+A/373/987
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present, for the first time, the Non-LTE gallium equivalent widths for the most prominent gallium transitions as identified in real spectra and in (hot) mercury-manganese star. The common feature of the departure coefficients is to decrease near the stellar surface, the collision rates are dominant in many cases and the Non-LTE equivalent widths are generally smaller. In particular, the abundance difference as derived from UV and visual lines is reduced. The photoionization cross sections were computed by means of standard R-matrix formalism.
- ID:
- ivo://CDS.VizieR/J/A+A/333/231
- Title:
- O-M stars model atmospheres
- Short Name:
- J/A+A/333/231
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Broad band colors and bolometric corrections in the Johnson-Cousins-Glass system (Bessell, 1990PASP..102.1181B; Bessell & Brett, 1988PASP..100.1134B) have been computed from synthetic spectra from new model atmospheres of Kurucz (1995a, priv. comm.), Castelli (1997, priv. comm.), Plez, Brett & Nordlund (1992A&A...256..551P), Plez (1995-97, priv. comm.), and Brett (1995A&A...295..736B, 1995A&AS..109..263B). These atmospheres are representative of larger grids that are currently being completed. We discuss differences between the different grids and compare theoretical color-temperature relations and the fundamental color temperature relations derived from: (a) the infrared-flux method (IRFM) for A-K stars (Blackwell & Lynas-Gray 1994A&A...282..899B; Alonso et al. 1996A&AS..117..227A) and M dwarfs (Tsuji et al. 1996A&A...305L...1T); (b) lunar occultations (Ridgway et al. 1980ApJ...235..126R) and (c) Michelson interferometry (Di Benedetto & Rabbia 1987A&A...188..114D; Dyck et al. 1996AJ....111.1705D; Perrin et al. 1998A&A...331..619P) for K-M giants, and (d) eclipsing binaries for M dwarfs. We also compare color-color relations and color-bolometric correction relations and find good agreement except for a few colors. The more realistic fluxes and spectra of the new model grids should enable accurate population synthesis models to be derived and permit the ready calibration of non-standard photometric passbands. As well, the theoretical bolometric corrections and temperature-color relations will permit reliable transformation from observed color magnitude diagrams to theoretical HR diagrams.
- ID:
- ivo://CDS.VizieR/J/A+A/572/A69
- Title:
- Opacities of magnetized neutron stars
- Short Name:
- J/A+A/572/A69
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- There is observational evidence that central compact objects (CCOs) in supernova remnants have moderately strong magnetic fields B~10^11^G. Meanwhile, available models of partially ionized hydrogen atmospheres of neutron stars with strong magnetic fields are restricted to B>~10^12^G. Extension of the applicability range of the photosphere models to lower field strengths is complicated by a stronger asymmetry of decentered atomic states and by the importance of excited bound states. We extend the equation of state and radiative opacities, as presented in previous papers for 10^12^G<~B<~10^15^G, to weaker fields. We constructed analytical fitting formulae for binding energies, sizes, and oscillator strengths for different bound states of a hydrogen atom moving in moderately strong magnetic fields and calculate an extensive database for photoionization cross sections of such atoms. Using these atomic data, in the framework of the chemical picture of plasmas we solved the ionization equilibrium problem and calculated thermodynamic functions and basic opacities of partially ionized hydrogen plasmas at these field strengths. Then plasma polarizabilities were calculated from the Kramers-Kronig relation, and the radiative transfer equation for the coupled normal polarization modes was solved to obtain model spectra. An equation of state and radiative opacities for a partially ionized hydrogen plasma are obtained at magnetic fields B, temperatures T, and densities {rho} typical for atmospheres of CCOs and other isolated neutron stars with moderately strong magnetic fields. The first- and second-order thermodynamic functions, monochromatic radiative opacities, and Rosseland mean opacities are calculated and tabulated, considering partial ionization, for 3x10^10G<~B<~10^12^G, 10^5^K<~T<~10^7^K, and a wide range of densities. Atmosphere models and spectra are calculated to verify the applicability of the results and to determine the range of magnetic fields and effective temperatures where the incomplete ionization of the hydrogen plasma is important.
- ID:
- ivo://CDS.VizieR/J/MNRAS/418/114
- Title:
- Opacity-sampling models of Mira variables
- Short Name:
- J/MNRAS/418/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present four model series of the CODEX dynamical opacity-sampling models of Mira variables with solar abundances, designed to have parameters similar to {omicron} Cet, R Leo and R Cas. We demonstrate that the CODEX models provide a clear physical basis for the molecular shell scenario used to explain interferometric observations of Mira variables. We show that these models generally provide a good match to photometry and interferometry at wavelengths between the near-infrared and the radio, and make the model outputs publicly available. These models also demonstrate that, in order to match visible and infrared observations, the Fe-poor silicate grains that form within 3 continuum radii must have small grain radii and therefore cannot drive the winds from O-rich Mira variables.
- ID:
- ivo://CDS.VizieR/J/MNRAS/399/699
- Title:
- Parameters of atmospheres of white dwarfs
- Short Name:
- J/MNRAS/399/699
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is possible to reliably identify white dwarfs (WDs) without recourse to spectra, instead using photometric and astrometric measurements to distinguish them from main-sequence stars and quasars. WDs' colours can also be used to infer their intrinsic properties (effective temperature, surface gravity, etc.), but the results obtained must be interpreted with care. The difficulties stem from the existence of a solid angle degeneracy, as revealed by a full exploration of the likelihood, although this can be masked if a simple best-fitting approach is used. Conversely, this degeneracy can be broken if a Bayesian approach is adopted, as it is then possible to utilize the prior information on the surface gravities of WDs implied by spectroscopic fitting. The benefits of such an approach are particularly strong when applied to outliers, such as the candidate halo and ultracool WDs identified by Vidrih et al. A reanalysis of these samples confirms their results for the latter sample, but suggests that most of the halo candidates are thick-disc WDs in the tails of the photometric noise distribution.
- ID:
- ivo://CDS.VizieR/J/A+A/430/223
- Title:
- Parameters of cool companions of sdB stars
- Short Name:
- J/A+A/430/223
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis of a high-resolution, high-quality sample of optical spectra for 76 subdwarf B (sdB) stars from the ESO Supernova Ia Progenitor Survey (SPY, Napiwotzki et al., 2001A&A...367..973N). Effective temperature, surface gravity, and photospheric helium abundance are determined simultaneously by fitting the profiles of hydrogen and helium lines using synthetic spectra calculated from LTE and NLTE model atmospheres. We perform a detailed comparison of our measurements with theoretical calculations, both for single star evolution and for binary population synthesis models of close binary evolution.
