- ID:
- ivo://CDS.VizieR/J/AJ/160/90
- Title:
- Stellar parameters for 13196 Kepler dwarfs
- Short Name:
- J/AJ/160/90
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The rotational evolution of cool dwarfs is poorly constrained after ~1-2Gyr due to a lack of precise ages and rotation periods for old main-sequence stars. In this work, we use velocity dispersion as an age proxy to reveal the temperature-dependent rotational evolution of low-mass Kepler dwarfs and demonstrate that kinematic ages could be a useful tool for calibrating gyrochronology in the future. We find that a linear gyrochronology model, calibrated to fit the period-Teff relationship of the Praesepe cluster, does not apply to stars older than around 1Gyr. Although late K dwarfs spin more slowly than early-K dwarfs when they are young, at old ages, we find that late K dwarfs rotate at the same rate or faster than early-K dwarfs of the same age. This result agrees qualitatively with semiempirical models that vary the rate of surface-to-core angular momentum transport as a function of time and mass. It also aligns with recent observations of stars in the NGC6811 cluster, which indicate that the surface rotation rates of K dwarfs go through an epoch of inhibited evolution. We find that the oldest Kepler stars with measured rotation periods are late K and early M dwarfs, indicating that these stars maintain spotted surfaces and stay magnetically active longer than more massive stars. Finally, based on their kinematics, we confirm that many rapidly rotating GKM dwarfs are likely to be synchronized binaries.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/899/62
- Title:
- Stellar parameters from the 1st release of the MaSTar
- Short Name:
- J/ApJ/899/62
- Date:
- 14 Mar 2022 07:12:49
- Publisher:
- CDS
- Description:
- We report the stellar atmospheric parameters for 7503 spectra contained in the first release of the Mapping Nearby Galaxies at Apache Point Observatory survey (MaNGA) stellar library (MaStar) in Sloan Digital Sky Survey DR15. The first release of MaStar contains 8646 spectra measured from 3321 unique stars, each covering the wavelength range 3622-10354{AA} with a resolving power of R~1800. In this work, we first determined the basic stellar parameters: effective temperature (Teff), surface gravity (logg), and metallicity ([Fe/H]), which best fit the data using an empirical interpolator based on the Medium-resolution Isaac Newton Telescope library of empirical spectra (MILES), as implemented by the University of Lyon Spectroscopic analysis Software package. While we analyzed all 8646 spectra from the first release of MaStar, since MaStar has a wider parameter-space coverage than MILES, not all of these fits are robust. In addition, not all parameter regions covered by MILES yield robust results, likely due to the nonuniform coverage of the parameter space by MILES. We tested the robustness of the method using the MILES spectra itself and identified a proxy based on the local density of the training set. With this proxy, we identified 7503 MaStar spectra with robust fitting results. They cover the range from 3179 to 20517K in effective temperature (Teff), from 0.40 to 5.0 in surface gravity (logg), and from -2.49 to +0.73 in metallicity ([Fe/H]).
- ID:
- ivo://CDS.VizieR/J/AJ/159/287
- Title:
- Stellar parameters in Ophiuchus Stream with MMT
- Short Name:
- J/AJ/159/287
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new kinematic data for the Ophiuchus stellar stream. Spectra have been taken of member candidates at the Multiple Mirror Telescope (MMT) using Hectospec, Hectochelle, and Binospec, which provide more than 1800 new velocities. Combined with proper-motion measurements of stars in the field by the Gaia-DR2 catalog, we have derived stream membership probabilities, resulting in the detection of more than 200 likely members. These data show the stream extends to more than three times the length shown in the discovery data. A spur to the main stream is also detected. The high-resolution spectra allow us to resolve the stellar velocity dispersion, found to be 1.6{+/-}0.3km/s.
- ID:
- ivo://CDS.VizieR/J/A+A/475/1003
- Title:
- Stellar parameters of G and K giant stars
- Short Name:
- J/A+A/475/1003
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a spectroscopic analysis of 366 G and K giant stars. For 112 stars this is the first spectroscopic analysis. The stars were selected for a radial velocity survey, which is currently carried out at Lick observatory, using the Coude Auxiliary Telescope in conjunction with the Hamilton Echelle spectrograph. For each star a high signal to noise spectrum is available, which is used for the present analysis. The Teff, logg and iron abundance are determined by imposing excitation and ionisation equilibrium through stellar models. The micro turbulence is obtained by requiring no dependence of Fe I against equivalent width. The rotational velocity is obtained from a comparison with data from Gray (1989ApJ...347.1021G) and the macro turbulence is derived using Gray (2005PASP..117..711G).
- ID:
- ivo://CDS.VizieR/J/MNRAS/427/1153
- Title:
- Stellar parameters of giants in {omega} Cen
- Short Name:
- J/MNRAS/427/1153
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have determined stellar parameters and abundances for 221 giant branch stars in the globular cluster omega Centauri. A combination of photometry and lower-resolution spectroscopy was used to determine temperature, gravity, metallicity, [C/Fe], [N/Fe] and [Ba/Fe]. These abundances agree well with those found by previous researchers and expand the analysed sample of the cluster. k-means clustering analysis was used to group the stars into four homogeneous groups based upon these abundances. These stars show the expected anticorrelation in [C/Fe] to [N/Fe]. We investigated the distribution of CN-weak/strong stars on the colour-magnitude diagram. Asymptotic giant branch stars, which were selected from their position on the colour-magnitude diagram, were almost all CN-weak. This is in contrast to the red giant branch where a large minority were CN-strong. The results were also compared with cluster formation and evolution models. Overall, this study shows that statistically significant elemental and evolutionary conclusions can be obtained from lower resolution spectroscopy.
- ID:
- ivo://CDS.VizieR/J/A+A/517/A3
- Title:
- Stellar parameters of Kepler early-type targets
- Short Name:
- J/A+A/517/A3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar pulsation offers a unique opportunity to constrain the intrinsic parameters of stars and to unveil their inner structure. Kepler satellite is collecting a huge amount of data of unprecedent photometric precision, that will allow us to test theory and obtain a very precise tomography of stellar interiors. Aiming at providing the stars' fundamental parameters (Teff, logg, vsini, and luminosity) which are needed for computing asteroseismic models and interpreting Kepler data, we report spectroscopic observations of 23 early-type Kepler asteroseismic targets and 13 other stars in the Kepler field, but not selected to be observed. The cross-correlation with template spectra was used for measuring the radial velocity with the aim of identifying non-single stars. Spectral synthesis has been performed in order to derive the stellar parameters for our target stars. State-of-art LTE atmospheric models have been computed. For all the stars of our sample, we derive the radial velocity, Teff, logg, vsini, and luminosities. Further, for 12 stars, we perform a detailed abundance analysis of 20 species; for 16, we could derive only the [Fe/H] ratio. A spectral classification has been also performed for 17 stars in the sample. We found two double-lined spectroscopic binaries, HIP96299 and HIP98551, the former of which is an already known eclipsing binary, and two single-lined spectroscopic binaries, HIP97254 and HIP97724. We also report two suspected spectroscopic binaries, HIP92637 and HIP96762, and the detection of a possible variability of the radial velocity of HIP96277. Two of our program stars turn out to be chemically peculiar, namely HIP93941, which we classify as B2 He-weak, and HIP96210, which we classify as B6Mn. Finally, we find that HIP93522, HIP93941, HIP93943, HIP96210 and HIP96762, are very slow rotators (vsini<20km/s) which makes them very interesting and promising targets for an asteroseismic modeling.
- ID:
- ivo://CDS.VizieR/J/AJ/159/193
- Title:
- Stellar parameters of ~30000 LAMOST DR1 M dwarfs
- Short Name:
- J/AJ/159/193
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- M-dwarfs are the most common type of star in the Galaxy, and because of their small size are favored targets for searches of Earth-sized transiting exoplanets. Current and upcoming all-sky spectroscopic surveys, such as the Large Sky Area Multi Fiber Spectroscopic Telescope (LAMOST), offer an opportunity to systematically determine physical properties of many more M dwarfs than has been previously possible. Here, we present new effective temperatures, radii, masses, and luminosities for 29678 M dwarfs with spectral types M0-M6 in the first data release (DR1) of LAMOST. We derived these parameters from the supervised machine-learning code, The Cannon, trained with 1388 M-dwarfs in the Transiting Exoplanet Survey Satellite Cool Dwarf Catalog that were also present in LAMOST with high signal-to-noise ratio (>250) spectra. Our validation tests show that the output parameter uncertainties are strongly correlated with the signal-to-noise of the LAMOST spectra, and we achieve typical uncertainties of 110K in T_eff_(~3%), 0.065R_{sun}_(~14%) in radius, 0.054M_{sun}_(~12%) in mass, and 0.012L_{sun}_(~20%) in luminosity. The model presented here can be rapidly applied to future LAMOST data releases, significantly extending the samples of well-characterized M dwarfs across the sky using new and exclusively data-based modeling methods.
- ID:
- ivo://CDS.VizieR/J/AJ/158/56
- Title:
- Stellar parameters of M and K dwarfs
- Short Name:
- J/AJ/158/56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Empirical correlations between stellar parameters such as rotation or radius and magnetic activity diagnostics require estimates of the effective temperatures and the stellar radii. The aim of this study is to propose simple methods that can be applied to large samples of stars in order to derive estimates of the stellar parameters. Good empirical correlations between red/infrared colors (e.g., (R-I)_C_) and effective temperatures have been well established for a long time. The more recent (R-I)_C_ color-T_eff_ correlation using the data of Mann et al. (2015, J/ApJ/804/64, hereafter M15) and Boyajian et al. (2012, J/ApJ/757/112, hereafter B12) shows that this color can be applied as a temperature estimate for large samples of stars. We find that the mean scatter in T_eff_ relative to the (R-I)_C_-T_eff_ relationship of B12 and M15 data is only +/-3{sigma}=44.6 K for K dwarfs and +/-3{sigma}=39.4 K for M dwarfs. These figures are small and show that the (R-I)_C_ color can be used as a first-guess effective temperature estimator for K and M dwarfs. We derive effective temperatures for about 1910 K and M dwarfs using the calibration of (R-I)_C_ color-T_eff_ from B12 and M15 data. We also compiled T_eff_ and metallicity measurements available in the literature using the VizieR database. We determine T_eff_ for 441 stars with previously unknown effective temperatures. We also identified 21 new spectroscopic binaries and one triple system from our high-resolution spectra.
- ID:
- ivo://CDS.VizieR/II/237
- Title:
- Stellar Photometry in Johnson's 11-color system
- Short Name:
- II/237
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue gives photometric data in the UBVRIJHKLMN colors and some additional information. Data for the JHKLMN bands come from NASA Ref. Pub. 1294 (1993). More complete information is found in Wisconsin Astrophysics 504 (1993) The effective wavelength of the Johsnon filters are: U = 360 nm B = 450 nm V = 555 nm R = 670 nm I = 870 nm J = 1.2 um H = 1.62um K = 2.2 um L = 3.5 um M = 5.0 um N = 9.0 um
- ID:
- ivo://CDS.VizieR/J/A+A/568/A119
- Title:
- Stellar physical parameters for young stars
- Short Name:
- J/A+A/568/A119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A uvbyH{beta} Stromgren photometric survey covering 16 square degrees in the anticenter direction was carried out using the Wide Field Camera at the Isaac Newton Telescope. Physical parameters like stellar distances and extinctions for the young stars of our survey are presented here. We developed a new method for deriving physical parameters from Stromgren photometry and also implemented and tested it. This is a model-based method that uses the most recent available stellar atmospheric models and evolutionary tracks to interpolate in a 3D grid of the unreddened indexes [m1], [c1] and H{beta}. Distances derived from both this method and the classical pre-Hipparcos calibrations were tested against Hipparcos parallaxes and found to be accurate. Furthermore, a shift in the atmospheric grids in the range Teff=[7000,9000]K was detected and a correction is proposed. The two methods were used to compute distances and reddening for around 12000 OBA-type stars in our Stromgren anticenter survey. Data from the IPHAS and 2MASS catalogs were used to complement the detection of emission line stars and to break the degeneracy between early and late photometric regions. We note that photometric distances can differ by more than 20%, those derived from the empirical calibrations being smaller than those derived with the new method, which agree better with the Hipparcos data.
