- ID:
- ivo://CDS.VizieR/J/A+A/405/1095
- Title:
- Limb-darkening coefficients from ATLAS9 models
- Short Name:
- J/A+A/405/1095
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using up-to-date model atmospheres (Heiter et al. 2002A&A...392..619H) with the turbulent convection approach developed by Canuto, Goldman & Mazzitelli (1996ApJ...473..550C, CGM), quadratic, cubic and square root limb darkening coefficients (LDC) are calculated with a least square fit method for the Stroemgren photometric system. This is done for a sample of solar metallicity models with effective temperatures between 6000 and 8500K and with logg between 2.5 and 4.5. A comparison is made between these LDC and the ones computed from model atmospheres using the classical mixing length prescription with a mixing length parameter {alpha}=1.25 and {alpha}=0.5. For CGM model atmospheres, the law which reproduces better the model intensity is found to be the square root one for the u band and the cubic law for the v band. The results are more complex for the b and y bands depending on the temperature and gravity of the model. Similar conclusions are reached for Mixing Length Theory (MLT) {alpha}=0.5 models. As expected much larger differences are found between CGM and MLT with {alpha}=1.25. In a second part, the weighted limb-darkening integrals, b_ell_, and their derivatives with respect to temperature and gravity, are then computed using the best limb-darkening law. These integrals are known to be very important in the context of photometric mode identification of non-radial pulsating stars. The effect of convection treatment on these quantities is discussed and as expected differences in the b_ell_ coefficients and derivatives computed with CGM and MLT {alpha}=0.5 are much smaller than differences obtained between computations with CGM and MLT {alpha}=1.25. The limb darkening coefficients are given here for the u, v, b and y bands and for CGM models, MLT {alpha}=0.5 models and MLT {alpha}=1.25 models.
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- ID:
- ivo://CDS.VizieR/J/A+A/546/A14
- Title:
- Limb-darkening for CoRoT, Kepler, Spitzer
- Short Name:
- J/A+A/546/A14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The knowledge of how the specific intensity is distributed over the stellar disk is crucial for interpreting the light curves of extrasolar transiting planets, double-lined eclipsing binaries, and other astrophysical phenomena. To provide theoretical inputs for light curve modelling codes, we present new calculations of limb-darkening coefficients for the spherically symmetric PHOENIX models. The limb-darkening coefficients were computed by covering the transmission curves of Kepler, CoRoT, and Spitzer space missions, as well as the passbands of the Stromgren, Johnson-Cousins, Sloan, and 2MASS. These computations adopted the least-square method. In addition, we also calculated the linear and bi-parametric approximations by adopting the flux conservation method as an additional tool for estimating the theoretical error bars in the limb-darkening coefficients. Six laws were used to describe the specific intensity distribution: linear, quadratic, square root, logarithmic, exponential, and a more general one with 4 terms. The computations are presented for the solar chemical composition, with logg varying between 2.5 and 5.5 and effective temperatures between 1500K-4800K. The adopted Microturbulent velocity and the mixing-length parameters are 2.0km/s and 2.0, respectively. Model are for solar metallicity.
- ID:
- ivo://CDS.VizieR/J/A+A/552/A16
- Title:
- Limb-darkening for CoRoT, Kepler, Spitzer. II.
- Short Name:
- J/A+A/552/A16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an extension of our investigations on limb-darkening coefficients computed with spherical symmetrical PHOENIX models. The models investigated in this paper cover the range 5000K<=Teff<=10000K and complete our previous studies of low effective temperatures computed with the same code. The limb-darkening coefficients are computed for the transmission curves of the Kepler, CoRoT, and Spitzer space missions and the Stroemgren, Johnson-Cousins, Sloan, and 2MASS passbands. These computations were performed by adopting the least-squares method. We have used six laws to describe the specific intensity distribution: linear, quadratic, square root, logarithmic, exponential, and a general law with four terms. The computations are presented for the solar chemical composition and cover the range 3.0<=logg<=5.5. The adopted microturbulent velocity and the mixing-length parameter are 2.0km/s and 2.0.
- 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
- 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/AJ/146/21
- Title:
- LINEAR. II. Catalog of RR Lyrae stars
- Short Name:
- J/AJ/146/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of ~5000 RR Lyrae stars selected from the recalibrated LINEAR data set and detected at heliocentric distances between 5kpc and 30kpc over ~8000 deg^2^ of sky. The coordinates and light curve properties, such as period and Oosterhoff type, are made publicly available. We analyze in detail the light curve properties and Galactic distribution of the subset of ~4000 type ab RR Lyrae (RRab) stars, including a search for new halo substructures and the number density distribution as a function of Oosterhoff type. We find evidence for the Oosterhoff dichotomy among field RR Lyrae stars, with the ratio of the type II and I subsamples of about 1:4, but with a weaker separation than for globular cluster stars. The wide sky coverage and depth of this sample allow unique constraints for the number density distribution of halo RRab stars as a function of galactocentric distance: it can be described as an oblate ellipsoid with an axis ratio q=0.63 and with either a single or a double power law with a power-law index in the range -2 to -3. Consistent with previous studies, we find that the Oosterhoff type II subsample has a steeper number density profile than the Oosterhoff type I subsample. Using the group-finding algorithm EnLink, we detected seven candidate halo groups, only one of which is statistically spurious. Three of these groups are near globular clusters (M53/NGC 5053, M3, M13), and one is near a known halo substructure (Virgo Stellar Stream); the remaining three groups do not seem to be near any known halo substructures or globular clusters and seem to have a higher ratio of Oosterhoff type II to Oosterhoff type I RRab stars than what is found in the halo. The extended morphology and the position (outside the tidal radius) of some of the groups near globular clusters are suggestive of tidal streams possibly originating from globular clusters. Spectroscopic follow-up of detected halo groups is encouraged.
- ID:
- ivo://CDS.VizieR/J/AJ/146/101
- Title:
- LINEAR. III. Catalog of periodic variables
- Short Name:
- J/AJ/146/101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the construction of a highly reliable sample of ~7000 optically faint periodic variable stars with light curves obtained by the asteroid survey LINEAR across 10000deg^2^ of the northern sky. The majority of these variables have not been cataloged yet. The sample flux limit is several magnitudes fainter than most other wide-angle surveys; the photometric errors range from ~0.03mag at r=15 to ~0.20mag at r=18. Light curves include on average 250 data points, collected over about a decade. Using Sloan Digital Sky Survey (SDSS) based photometric recalibration of the LINEAR data for about 25 million objects, we selected ~200000 most probable candidate variables with r<17 and visually confirmed and classified ~7000 periodic variables using phased light curves. The reliability and uniformity of visual classification across eight human classifiers was calibrated and tested using a catalog of variable stars from the SDSS Stripe 82 region and verified using an unsupervised machine learning approach. The resulting sample of periodic LINEAR variables is dominated by 3900 RR Lyrae stars and 2700 eclipsing binary stars of all subtypes and includes small fractions of relatively rare populations such as asymptotic giant branch stars and SX Phoenicis stars. We discuss the distribution of these mostly uncataloged variables in various diagrams constructed with optical-to-infrared SDSS, Two Micron All Sky Survey, and Wide-field Infrared Survey Explorer photometry, and with LINEAR light-curve features. We find that the combination of light-curve features and colors enables classification schemes much more powerful than when colors or light curves are each used separately. An interesting side result is a robust and precise quantitative description of a strong correlation between the light-curve period and color/spectral type for close and contact eclipsing binary stars ({beta} Lyrae and W UMa): as the color-based spectral type varies from K4 to F5, the median period increases from 5.9hr to 8.8hr. These large samples of robustly classified variable stars will enable detailed statistical studies of the Galactic structure and physics of binary and other stars and we make these samples publicly available.
- ID:
- ivo://CDS.VizieR/J/ApJS/244/3
- Title:
- Linear structural param. of SDSS+UKIDSS+WISE gal.
- Short Name:
- J/ApJS/244/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate measurements of galaxy structure are prerequisites for quantitative investigation of galaxy properties or evolution. Yet galaxy inclination, through projection and varying dust effects, strongly affects many commonly used metrics of galaxy structure. Here we demonstrate that collapsing a galaxy's light distribution onto its major axis gives a "linear brightness profile" that is unaffected by projection. In analogy to widely used half-light radius and concentrations, we use two metrics to describe this light distribution: x_50_, the linear distance containing half of the galaxy's luminosity, and c_x_=x_90_/x_50_, the ratio between the 90% light distance and the 50% light distance. In order to minimize the effects of dust, we apply this technique to a diverse sample of galaxies with moderately deep and high-resolution K-band imaging from the UKIDSS Large Area Survey. Using simulated galaxy images, we find that while our measurements are primarily limited by the surface brightness in the outer parts of galaxies, most local galaxies have high enough surface brightnesses to result in reliable measurements. When applied to real data, our metrics vary from face-on to edge-on by typically ~5% in c_x_ and ~12% in x_50_, representing factors of several to 10 improvement over existing optical and some infrared catalog measures of galaxy structure. We release a sample of 23804 galaxies with inclination-independent and dust-penetrated observational proxies for stellar mass, specific star formation rate, half-light size, and concentration.
- ID:
- ivo://CDS.VizieR/J/MNRAS/450/4301
- Title:
- Line list for red giants in open clusters
- Short Name:
- J/MNRAS/450/4301
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have observed high-dispersion echelle spectra of red giant members in the five open clusters (OCs) NGC 1342, NGC 1662, NGC 1912, NGC 2354 and NGC 2447 and determined their radial velocities and chemical compositions. These are the first chemical abundance measurements for all but NGC 2447. We combined our clusters from this and previous papers with a sample drawn from the literature for which we remeasured the chemical abundances to establish a common abundance scale. With this homogeneous sample of OCs, we study the relative elemental abundances of stars in OCs in comparison with field stars as a function of age and metallicity. We find a range of mild enrichment of heavy (Ba-Eu) elements in young OC giants over field stars of the same metallicity. Our analysis supports that the youngest stellar generations in cluster might be underrepresented by the solar neighbourhood field stars.
