- 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]).
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Search Results
- 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/J/AJ/161/288
- Title:
- Stellar population in M53
- Short Name:
- J/AJ/161/288
- Date:
- 18 Jan 2022
- Publisher:
- CDS
- Description:
- We present results from a study of 94 red giant stars in the globular cluster M53. We use low-resolution spectra to measure the strength of CN and CH features at ~3800 and 4300{AA}, respectively. The strengths of these features are used to classify stars into a CN-enhanced and CN-normal population and to measure C and N abundances in all 94 stars. We find the red giant branch stars to be evenly split between the two populations identified, and observe the presence of CN-enhanced stars on the asymptotic giant branch. In addition, we identify five CH star candidates based on the strength of their CN and CH band features, and the presence of a P-branch in their CH band. We compare our identification of multiple populations to those based on the Na-O anticorrelation and pseudo-color indices in Hubble Space Telescope UV photometry, and find general agreement between all three methods. Our large sample size also allows us to study the radial distribution of each population, and we find that the CN-enhanced population is more centrally concentrated. We use our C and N measurements to compare the evolutionary changes in these elements as a function of magnitude between the two populations, and show that both populations experience similar evolutionary changes to the surface abundances of C and N. Finally, we calculate C+N+O abundances for each population and compare them to similar measurements made in M10; we find that in both clusters, CN-enhanced stars have a slightly enhanced C+N+O ({Delta}(C+N+O)~0.2dex).
- ID:
- ivo://CDS.VizieR/V/136
- Title:
- Teff and metallicities for Tycho-2 stars
- Short Name:
- V/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have created specialized target lists for radial velocity surveys that are biased toward stars that (1) possess planets and (2) are easiest to observe with current detection techniques. We use a procedure that uniformly estimates fundamental stellar properties of Tycho 2 stars, with errors, using spline functions of broadband photometry and proper motion found in Hipparcos/Tycho 2 and 2MASS. We provide estimates of effective temperature and distance for 2.4 million Tycho 2 stars that lack trigonometric distances. For stars that appear to be FGK dwarfs, we also derive [Fe/H] and identify unresolved binary systems with mass ratios 1.25<M1/M2<3.0. For FGK dwarfs with photometric error {sigma}_V_<0.05, or V<9, our temperature model gives a 1{sigma} error of {sigma}_T_=+58.7/-65.9K and our metallicity model gives a 1{sigma} error of {sigma}_[Fe/H]_=+0.13/-0.14dex. The binarity model can be used to remove 70% of doubles with 1.25<M1/M2<3.0 from a magnitude-limited sample of dwarfs at a cost of cutting 20% of the sample. Our estimates of distance and spectral type enable us to isolate 354,822 Tycho 2 dwarfs, 321,996 absent from Hipparcos, with giant contamination of 2.6% and 7.2%, respectively. Roughly 100,000 of these stars, not in Hipparcos, have sufficiently low photometric errors to retain 0.13-0.3dex [Fe/H] accuracy and 80-100K temperature accuracy (1{sigma}). Our metallicity estimates have been used to identify targets for N2K, a large-scale radial velocity search for hot jupiters, which has verified the errors presented here. The catalogs that we publish can be used to further large-scale studies of Galactic structure and chemical evolution and to provide potential reference stars for narrow-angle astrometry programs such as the Space Interferometry Mission and large-aperture optical interferometry.
- ID:
- ivo://CDS.VizieR/J/ApJ/892/31
- Title:
- Teff and metallicities of M dwarfs in APOGEE DR14
- Short Name:
- J/ApJ/892/31
- Date:
- 07 Mar 2022 13:23:27
- Publisher:
- CDS
- Description:
- M dwarfs have enormous potential for our understanding of structure and formation on both Galactic and exoplanetary scales through their properties and compositions. However, current atmosphere models have limited ability to reproduce spectral features in stars at the coolest temperatures (Teff<4200K) and to fully exploit the information content of current and upcoming large-scale spectroscopic surveys. Here we present a catalog of spectroscopic temperatures, metallicities, and spectral types for 5875 M dwarfs in the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and Gaia-DR2 surveys using The Cannon (Ness+ 2015, J/ApJ/808/16 ; Casey+ 2016, arXiv:1603.03040; Ho+ 2017, J/ApJ/836/5; Behmard+ 2019ApJ...876...68B): a flexible, data-driven spectral-modeling and parameter-inference framework demonstrated to estimate stellar-parameter labels (Teff, logg, [Fe/H], and detailed abundances) to high precision. Using a training sample of 87 M dwarfs with optically derived labels spanning 2860K<Teff<4130K calibrated with bolometric temperatures, and -0.5<[Fe/H]<0.5dex calibrated with FGK binary metallicities, we train a two-parameter model with predictive accuracy (in cross-validation) to 77K and 0.09dex respectively. We also train a one-dimensional spectral classification model using 51 M dwarfs with Sloan Digital Sky Survey optical spectral types ranging from M0 to M6, to predictive accuracy of 0.7 types. We find Cannon temperatures to be in agreement to within 60 K compared to a subsample of 1702 sources with color-derived temperatures, and Cannon metallicities to be in agreement to within 0.08 dex metallicity compared to a subsample of 15 FGK+M or M+M binaries. Finally, our comparison between Cannon and APOGEE pipeline (ASPCAP DR14) labels finds that ASPCAP is systematically biased toward reporting higher temperatures and lower metallicities for M dwarfs.
- ID:
- ivo://CDS.VizieR/J/AJ/151/82
- Title:
- The 4 brightest red giants in the UFD galaxy Ret 2
- Short Name:
- J/AJ/151/82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ultra-faint dwarf (UFD) galaxy Reticulum 2 (Ret 2) was recently discovered in images obtained by the Dark Energy Survey (Diehl et al. 2014SPIE.9149E..0VD). We have observed the four brightest red giants in Ret 2 at high spectral resolution using the Michigan/Magellan Fiber System. We present detailed abundances for as many as 20 elements per star, including 12 elements heavier than the Fe group. We confirm previous detection of high levels of r-process material in Ret 2 (mean [Eu/Fe]=+1.69+/-0.05) found in three of these stars (mean [Fe/H]=-2.88+/-0.10). The abundances closely match the r-process pattern found in the well-studied metal-poor halo star CS 22892-052. Such r-process-enhanced stars have not been found in any other UFD galaxy, though their existence has been predicted by at least one model. The fourth star in Ret 2 ([Fe/H]=-3.42+/-0.20) contains only trace amounts of Sr ([Sr/Fe]=-1.73+/-0.43) and no detectable heavier elements. One r-process enhanced star is also enhanced in C (natal [C/Fe]~+1.1). This is only the third such star known, which suggests that the nucleosynthesis sites leading to C and r-process enhancements are decoupled. The r-process-deficient star is enhanced in Mg ([Mg/Fe]=+0.81+/-0.14), and the other three stars show normal levels of {alpha}-enhancement (mean [Mg/Fe]=+0.34+/-0.03). The abundances of other {alpha} and Fe-group elements closely resemble those in UFD galaxies and metal-poor halo stars, suggesting that the nucleosynthesis that led to the large r-process enhancements either produced no light elements or produced light-element abundance signatures indistinguishable from normal supernovae.
- ID:
- ivo://CDS.VizieR/J/AJ/155/116
- Title:
- The globular cluster M14.II. Variable stars
- Short Name:
- J/AJ/155/116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present time-series BVI photometry for the Galactic globular cluster NGC 6402 (M14). The data consist of ~137 images per filter, obtained using the 0.9 and 1.0 m SMARTS telescopes at the Cerro Tololo Inter-American Observatory. The images were obtained during two observing runs in 2006-2007. The image-subtraction package ISIS, along with DAOPHOT II/ALLFRAME, was used to perform crowded-field photometry and search for variable stars. We identified 130 variables, eight of which are new discoveries. The variable star population is comprised of 56 ab-type RR Lyrae stars, 54 c-type RR Lyrae, 6 type II Cepheids, 1 W UMa star, 1 detached eclipsing binary, and 12 long-period variables. We provide Fourier decomposition parameters for the RR Lyrae, and discuss the physical parameters and photometric metallicity derived therefrom. The M14 distance modulus is also discussed, based on different approaches for the calibration of the absolute magnitudes of RR Lyrae stars. The possible presence of second-overtone RR Lyrae in M14 is critically addressed, with our results arguing against this possibility. By considering all of the RR Lyrae stars as members of the cluster, we derive <P_ab_>=0.589 days. This, together with the position of the RR Lyrae stars of both Bailey types in the period-amplitude diagram, suggests an Oosterhoff-intermediate classification for the cluster. Such an intermediate Oosterhoff type is much more commonly found in nearby extragalactic systems, and we critically discuss several other possible indications that may point to an extragalactic origin for this cluster.
- ID:
- ivo://CDS.VizieR/J/AJ/156/300
- Title:
- Velocity and light curve analysis of three PPNe
- Short Name:
- J/AJ/156/300
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained contemporaneous light, color, and radial velocity data for three proto-planetary nebulae (PPNe) over the years 2007 to 2015. The light and velocity curves of each show similar periods of pulsation, with photometric periods of 42 and 50 days for IRAS 17436+5003, 102 days for IRAS 18095+2704, and 35 days for IRAS 19475+3119. The light and velocity curves are complex with multiple periods and small, variable amplitudes. Nevertheless, at least over limited time intervals, we were able to identify dominant periods in the light, color, and velocity curves and compare the phasing of each. The color curves appear to peak with or slightly after the light curves while the radial velocity curves peak about a quarter of a cycle before the light curves. Similar results were found previously for two other PPNe, although for them the light and color appeared to be in phase. Thus, it appears that PPNe are brightest when smallest and hottest. These phase results differ from those found for classical Cepheid variables, where the light and velocity differ by half a cycle, and are hottest at about average size and expanding. However, they do appear to have similar phasing to the larger-amplitude pulsations seen in RV Tauri variables. Presently, few pulsation models exist for PPNe, and these do not fit the observations well, especially the longer periods observed. Model fits to these new light and velocity curves would allow masses to be determined for these post-AGB objects, and thereby provide important constraints to post-AGB stellar evolution models of low- and intermediate-mass stars.
- ID:
- ivo://CDS.VizieR/J/AJ/158/51
- Title:
- VR CCD photometry of variable stars in the GC NGC 4147
- Short Name:
- J/AJ/158/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a search for variable stars in a region of the globular cluster NGC 4147 based on photometric observations with a 4Kx4K CCD imager mounted at the axial port of the recently installed 3.6 m Devasthal optical telescope (DOT) at Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, India. We performed time series photometry of NGC 4147 in the V and R bands, and identified 42 periodic variables in the region of NGC 4147, 28 of which have been detected for the first time. Seventeen variable stars are located within the half-light radius ~<0.48', of which 10 stars are newly identified variables. Two of the 10 variables are located within the core radius ~<0.09'. Based on their location in the V/(V-R) color-magnitude diagram and variability characteristics, seven, eight, five, and one newly identified probable member variables are classified as RRc, EA/E, EW, and SX Phe, respectively. The metallicity of NGC 4147 estimated from the light curves of RRab and RRc stars with the help of Fourier decomposition is found to be characteristic of Oosterhoff II. The distance derived using the light curves of RRab stars is consistent with that obtained from the observed V/(V-R) color-magnitude diagram.
- ID:
- ivo://CDS.VizieR/J/AJ/159/220
- Title:
- WOCS LXXIX. M48. I. WIYN/Hydra spectra for M48 stars
- Short Name:
- J/AJ/159/220
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- WIYN/Hydra spectra (R~13500, signal-to-noise=50-1000/pixel) of a 400{AA} region around Li 6708{AA} are used to determine radial and rotational velocities for 287 photometrically selected candidate members of the open cluster M48. The sample ranges from turnoff A stars to late-K dwarfs and eight giants. We combine our radial velocity (V_RAD_) measurements and power spectrum analysis with parallax and proper motion data from Gaia DR2 to evaluate membership and multiplicity. We classify 152 stars as single cluster members, 11 as binary members, 16 as members of uncertain multiplicity, 56 as single nonmembers, 28 as single "likely" nonmembers, two as single "likely" members, one as a binary "likely" member, five as binary nonmembers, 10 as "likely" members of uncertain multiplicity, three as nonmembers of uncertain multiplicity, and three as "likely" nonmembers of uncertain multiplicity. From a subsample of 95 single members, we derive V_RAD_=8.512{+/-}0.087km/s ({sigma}_{mu}_, and {sigma}=0.848km/s). Using 16 isolated Fe I lines for a subsample of 99 single members (that have {sigma}_Teff_<75K (from 10 colors from UBVRI), vsini<25km/s, and well-behaved Fe I lines), [Fe/H]M48=-0.063{+/-}0.007dex ({sigma}_{mu}_). [Fe/H] is independent of Teff over an unprecedentedly large range of 2500K. The minimum cluster binary fraction is 11%-21%. M48 exhibits a clear but modest broadening of the main-sequence turnoff, and there is no correlation between color and vsini.