- ID:
- ivo://CDS.VizieR/VI/154
- Title:
- Limb-darkening for Space Mission GAIA
- Short Name:
- VI/154
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- In the past few years, the number of space missions with astrophysical purposes has increased, with COROT, KEPLER, MOST and more recently TESS. Two of the most important complementary tools for these missions are the gravity and limb-darkening coefficients, hereafter GDC and LDC. For the missions mentioned above, many calculations are available to be used in several branches of stellar physics: synthetic light curves of eclipsing binaries and planetary transits, stellar diameters, line profiles in rotating stars, etc. see Claret & Bloemen (2011, Cat. J/A+A/529/A75), Claret et al. (2014, Cat. J/A+A/567/A3), Claret (2017, Cat. J/A+A/600/A30) and Claret (2018, Cat. J/A+A/618/A20). However, as noted by Zhou et al. (2018, AJ, submitted), these coefficients are not available for the GAIA mission. The main objective of this Research Note is to provide the theoretical calculations of the LDC and GDC for GAIA. We use two stellar atmosphere models: ATLAS (plane-parallel) and PHOENIX with spherical symmetry (Husser et al. 2013). The specific intensity distribution was fitted using five approaches: linear, quadratic, square root, logarithmic, and a more general one with four terms. These grids cover 19 metallicities ranging from 10^-5^ up to 10^+1^ solar abundances, 0<=logg<=6.0 and 1500K<=Teff<=50000K. The calculations of the gravity-darkening coefficients were performed for all plane-parallel ATLAS models. https://doi.org/10.3847/2515-5172/aaffdf
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/618/A20
- Title:
- Limb-darkening for TESS, Kepler, Corot, MOST
- Short Name:
- J/A+A/618/A20
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- One of the biggest problems we can encounter while dealing with the limb-darkening coefficients for stellar atmospheric models with spherical symmetry is the difficulty of adjusting both the limb and the central parts simultaneously. In particular, the regions near the drop-offs are not well reproduced for most models, depending on Teff, log g, or wavelength. Even if the law with four terms is used, these disagreements still persist. Here we introduce a new method that considerably improves the description of both the limb and the central parts and that will allow users to test models of stellar atmospheres with spherical symmetry more accurately in environments such as exoplanetary transits, eclipsing binaries, etc.
- ID:
- ivo://CDS.VizieR/J/A+A/600/A30
- Title:
- Limb-darkening for TESS satellite
- Short Name:
- J/A+A/600/A30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new gravity and limb-darkening coefficients for a wide range of effective temperatures, gravities, metallicities, and microturbulent velocities. These coefficients can be used in many different fields of stellar physics as synthetic light curves of eclipsing binaries and planetary transits, stellar diameters, line profiles in rotating stars, and others.
- ID:
- ivo://CDS.VizieR/J/A+A/494/403
- Title:
- Low temperature Rosseland opacities
- Short Name:
- J/A+A/494/403
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We provide low temperature opacity data that incorporate varied abundances of the elements carbon and nitrogen. In the temperature range that we focus at, molecules are the dominant opacity source. Our dataset spans a large metallicity range and shall deliver the necessary input data for stellar evolution models as well as other applications. We conduct chemical equilibrium calculations in order to evaluate the partial pressures of neutral atoms, ions and molecules. Based on a large dataset containing atomic line and continuum data, and, most importantly, a plethora of molecular lines, we subsequently calculate Rosseland mean opacity coefficients. This is done not only for a number of different metallicities, but also for varied abundances of the isotopes ^12^C and ^14^N at each metallicity. The molecular data comprise the main opacity sources at either an oxygen-rich or carbon-rich chemistry. We tabulate the opacity coefficients as a function of temperature and, basically, density. Already within a certain chemistry regime an alteration in the carbon abundance causes, due to the special role of the CO molecule, considerable changes in the Rosseland opacity. The transition from a scaled solar (i.e. oxygen-rich) mixture to the carbon-rich regime results in opacities that can, at low temperatures, be orders of magnitude different compared to the initial situation. The reason is that different molecular absorbers make up the mean opacity in either case. A varying abundance of nitrogen has less pronounced effects but, nevertheless, cannot be neglected.
- ID:
- ivo://CDS.VizieR/J/A+AS/110/329
- Title:
- LTE model atmospheres coeff.
- Short Name:
- J/A+AS/110/329
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Linear, quadratic and square root limb-darkening coefficients have been computed by means of least squares fits to model atmospheres by Kurucz (1991) with the main purpose of facilitating the analysis of light curves of eclipsing binaries. Results are compared with previously published values using the same of different models and various fitting procedures.
- ID:
- ivo://CDS.VizieR/J/A+A/374/265
- Title:
- LTE spectrum synthesis in magnetic atmospheres
- Short Name:
- J/A+A/374/265
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Files table4.dat contain calculated Stokes IQUV local line profiles of Fe II 4923.9 shown in Fig. 4 of this paper. Profile sets are provided for 0.1, 5 and 20kG magnetic fields, with vector orientation {psi}=40{deg}, {phi}=0{deg}, disc centre and eps_fe_=4.6.
- ID:
- ivo://CDS.VizieR/J/other/AstBu/74.66
- Title:
- Main sequence magnetic stars properties
- Short Name:
- J/other/AstBu/74
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We reconsidered the previous studies of properties of magnetic stars based on the latest data on average surface magnetic fields of 177 stars. New, corrected results have been obtained that allow a better understanding of the phenomenon of magnetic chemically peculiar stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/207/15
- Title:
- M dwarf flare spectra
- Short Name:
- J/ApJS/207/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a homogeneous analysis of line and continuum emission from simultaneous high-cadence spectra and photometry covering near-ultraviolet and optical wavelengths for 20 M dwarf flares. These data were obtained to study the white-light continuum components at bluer and redder wavelengths than the Balmer jump. Our goals were to break the degeneracy between emission mechanisms that have been fit to broadband colors of flares and to provide constraints for radiative-hydrodynamic (RHD) flare models that seek to reproduce the white-light flare emission. New model constraints are presented for the time evolution among the hydrogen Balmer lines and between CaII K and the blackbody continuum emission. We calculate Balmer jump flux ratios and compare to the solar-type flare heating predictions from RHD models. The model ratios are too large and the blue-optical ({lambda}=4000-4800{AA}) slopes are too red in both the impulsive and gradual decay phases of all 20 flares. This discrepancy implies that further work is needed to understand the heating at high column mass during dMe flares.
- ID:
- ivo://CDS.VizieR/J/A+AS/109/263
- Title:
- M dwarfs model photospheres. II.
- Short Name:
- J/A+AS/109/263
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a table of new "classical" model photospheres for M dwarfs computed with an extensive set of atomic and molecular opacities treated with the accurate and realistic opacity sampling technique. The models of this grid are described and analysed in a companion paper (Brett 1995, A&A, in press)
- ID:
- ivo://CDS.VizieR/J/A+A/635/A161
- Title:
- Measured atmospheric parameters of NGC6397 stars
- Short Name:
- J/A+A/635/A161
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent work has used spectra of ~5000 stars in NGC 6397 that were extracted from a MUSE mosaic to determine the atmospheric parameters for these stars by fitting the spectra against the Goettingen Spectral Library. A significant change in metallicity between the turn off and the red giant branch was found and was discussed as a possible manifestation of predicted effects of atomic diffusion. However, the small amplitude of the effect and inconsistency with earlier measurements call for more attention before this result is interpreted. Systematic effects due to the interpolation or to the synthetic spectra cannot be ruled out at this level of precision. We reanalyze the data with : the ELODIE and MILES reference libraries in order to assess the robustness of the result. These empirical libraries have a finer metallicity coverage down to approximately the cluster metallicity turn-off. Methods. We used the ULySS full-spectrum fitting package, together with the library interpolators to remeasure the three atmospheric parameters effective temperature, surface gravity, and [Fe/H] metallicity. We find a very low [Fe/H] dispersion along the isochrone (0.07dex), consistent with our error estimate (0.05dex). However, the [Fe/H] trend is not reproducible. This shows that the data have the potential to reveal patterns of the magnitude of the expected physical effects, but the analysis methods need to be refined to cull systematic effects that currently dominate the patterns.
