- ID:
- ivo://CDS.VizieR/J/A+A/641/A44
- Title:
- Dwarfs, giants and supergiants Equivalent widths
- Short Name:
- J/A+A/641/A44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar population studies in the infrared (IR) wavelength range have two main advantages with respect to the optical regime: they probe different populations, because most of the light in the IR comes from redder and generally older stars and allow us to see through dust because the IR light is less affected by extinction. Our project investigates the sensitivity of various spectral features in the 1-5um wavelength range to the physical properties of stars (Teff, [Fe/H], logg) and aims to objectively define spectral indices that can characterize age and metallicity of unresolved stellar populations. We implemented a method that uses derivatives of the indices as functions of Teff, [Fe/H] of log g across the entire available wavelength range to reveal the most sensitive indices to these parameters and the ranges in which these indices work. Here, we complement the previous work in the I and K bands reporting a new system for Y, J, H and L atmospheric windows. We list the equivalent widths of these indices for the Infrared Telescope Facility (IRTF) spectral library stars.
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- ID:
- ivo://CDS.VizieR/J/A+A/640/A2
- Title:
- Dwarfs & giants surface brightness-colour relations
- Short Name:
- J/A+A/640/A2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Surface brightness-colour relations (SBCRs) are used to derive the stellar angular diameters from photometric observations. They have various astrophysical applications, such as the distance determination of eclipsing binaries or the determination of exoplanet parameters. However, strong discrepancies between the SBCRs still exist in the literature, in particular for early and late-type stars. We aim at calibrating new SBCRs as a function of the spectral type and the luminosity class of the stars. Our purpose is also to apply homogeneous criteria for the selection of the reference stars and on the basis of an exhaustive and up-to-date list of interferometric late-type targets. We implement criteria to select measurements in the JMMC Measured Diameters Catalog (JMDC). We then apply additional criteria on the photometric measurements used to build the SBCRs, together with stellar characteristics diagnostics. We build SBCRs for F5/K7-II/III, F5/K7-IV/V, M-II/III and M-V stars, with respective RMS of {sigma}_FV_=0.0022mag, {sigma}_FV_ =0.0044mag, {sigma}_FV_=0.0046mag, and {sigma}_FV_=0.0038mag. This results in a precision on the angular diameter of 1.0%, 2.0%, 2.1% and 1.7%, respectively. These relations cover a large V-K colour range of magnitude, from 1 to 7.5. Our work demonstrates that SBCRs are significantly dependent on the spectral type and the luminosity class of the star. Through a new set of interferometric measurements, we demonstrate the critical importance of the selection criteria proposed for the calibration of SBCR. Finally, using the Gaia photometry for our samples, we obtain (G-K) SBCRs with a precision on the angular diameter between 1.1% and 2.4%. By adopting a refined and homogeneous methodology we show that the spectral type and the class of the star should be considered when applying a SBCR. This is particularly important in the context of PLATO.
- ID:
- ivo://CDS.VizieR/J/ApJ/886/10
- Title:
- Dwarfs or giants? Stellar metallicities & distances
- Short Name:
- J/ApJ/886/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new fully data-driven algorithm that uses photometric data from the Canada-France Imaging Survey (CFIS; u), Pan-STARRS 1 (PS1; griz), and Gaia (G) to discriminate between dwarf and giant stars and to estimate their distances and metallicities. The algorithm is trained and tested using the Sloan Digital Sky Survey (SDSS)/SEGUE spectroscopic data set and Gaia photometric/astrometric data set. At [Fe/H]<-1.2, the algorithm succeeds in identifying more than 70% of the giants in the training/test set, with a dwarf contamination fraction below 30% (with respect to the SDSS/SEGUE data set). The photometric metallicity estimates have uncertainties better than 0.2dex when compared with the spectroscopic measurements. The distances estimated by the algorithm are valid out to a distance of at least ~80kpc without requiring any prior on the stellar distribution and have fully independent uncertainties that take into account both random and systematic errors. These advances allow us to estimate these stellar parameters for approximately 12 million stars in the photometric data set. This will enable studies involving the chemical mapping of the distant outer disk and the stellar halo, including their kinematics using the Gaia proper motions. This type of algorithm can be applied in the southern hemisphere to the first release of LSST data, thus providing an almost complete view of the external components of our Galaxy out to at least ~80kpc. Critical to the success of these efforts will be ensuring well-defined spectroscopic training sets that sample a broad range of stellar parameters with minimal biases. A catalog containing the training/test set and all relevant parameters within the public footprint of CFIS is available online.
- ID:
- ivo://CDS.VizieR/J/A+A/645/A92
- Title:
- Dwarf spheroidal galaxies in CenA group
- Short Name:
- J/A+A/645/A92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dwarf spheroidal galaxies (dSphs) have been extensively investigated in the Local Group, but their low luminosity and surface brightness make similar work in more distant galaxy groups challenging. Modern instrumentation unlocks the possibility of scrutinizing these faint systems in other environments, expanding the parameter space of group properties. We use MUSE spectroscopy to study the properties of 14 known or suspected dSph satellites of Cen A. Twelve targets are confirmed to be group members based on their radial velocities. Two targets are background galaxies at ~50Mpc: KK 198 is a face-on spiral galaxy, and dw1315-45 is an ultra-diffuse galaxy with an effective radius of ~2300pc. The 12 confirmed dSph members of the Cen A group have old and metal-poor stellar populations and follow the stellar metallicity-luminosity relation defined by the dwarf galaxies in the Local Group. In the three brightest dwarf galaxies (KK 197, KKs 55, and KKs 58), we identify globular clusters, as well as a planetary nebula in KK197, although its association with this galaxy and/or the extended halo of Cen A is uncertain. Using four discrete tracers, we measure the velocity dispersion and dynamical mass of KK197. This dSph appears dark matter dominated and lies on the radial acceleration relation of star-forming galaxies within the uncertainties. It also is consistent with predictions stemming from modified Newtonian dynamics (MOND). Surprisingly, in the dwarf KK203 we find an extended H ring. Careful examination of Hubble Space Telescope photometry reveals a very low level of star formation at ages between 30-300Myr. The H{alpha} emission is most likely linked to a ~40Myr old supernova remnant, although other possibilities for its origin cannot be entirely ruled out.
- ID:
- ivo://CDS.VizieR/J/other/NatAs/5.707
- Title:
- Dwarf stars asteroseismic rotation rates
- Short Name:
- J/other/NatAs/5.
- Date:
- 17 Jan 2022 00:29:40
- Publisher:
- CDS
- Description:
- Studies using asteroseismic ages and rotation rates from star-spot rotation have indicated that standard age-rotation relations may break down roughly half way through the main sequence lifetime, a phenomenon referred to as weakened magnetic braking. Although rotation rates from spots can be difficult to determine for older, less active stars, rotational splitting of asteroseismic oscillation frequencies can provide rotation rates for both active and quiescent stars, and so can confirm whether this effect really takes place on the main sequence. We obtained asteroseismic rotation rates of 91 main sequence stars showing high signal-to-noise modes of oscillation. Using these new rotation rates, along with effective temperatures, metallicities and seismic masses and ages, we built a hierarchical Bayesian mixture model to determine whether the ensemble more closely agreed with a standard rotational evolution scenario, or one where weakened magnetic braking takes place. The weakened magnetic braking scenario was found to be 98.4% more likely for our stellar ensemble, adding to the growing body of evidence for this stage of stellar rotational evolution. This work presents a large catalogue of seismic rotation rates for stars on the main sequence, which opens up possibilities for more detailed ensemble analysis of rotational evolution with Kepler.
- ID:
- ivo://CDS.VizieR/J/A+A/658/A47
- Title:
- Dwarf stars limb-darkening coefficients
- Short Name:
- J/A+A/658/A47
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Stellar models applied to large stellar surveys of the Milky Way need to be properly tested against a sample of stars with highly reliable fundamental stellar parameters. We have established a program aiming to deliver such a sample of stars. Here we present new fundamental stellar parameters of nine dwarf stars that will be used as benchmark stars for large stellar surveys. One of these stars is the solar-twin 18Sco, which is also one of the Gaia-ESO benchmarks. The goal is to reach a precision of 1% in effective temperatures (Teff). This precision is important for accurate determinations of the full set of fundamental parameters and abundances of stars observed by the surveys. We observed HD131156 (xi Boo), HD146233 (18 Sco), HD152391, HD173701, HD185395 (theta Cyg), HD186408 (16 Cyg A), HD186427 (16 Cyg B), HD190360 and HD207978 (15 Peg) using the high angular resolution optical interferometric instrument PAVO at the CHARA Array. We derived limb-darkening corrections from 3D model atmospheres and determined Teff directly from the Stefan-Boltzmann relation, with an iterative procedure to interpolate over tables of bolometric corrections. Surface gravities were estimated from comparisons to Dartmouth stellar evolution model tracks. We collected spectroscopic observations from the ELODIE spectrograph and estimated metallicities ([Fe/H]) from a 1D non-local thermodynamic equilibrium (NLTE) abundance analyses of unblended lines of neutral and singly ionized iron. For eight of the nine stars we measure the Teff less than 1%, and for one star better than 2%. We determined the median uncertainties in log g and [Fe/H] as 0.015dex and 0.05dex, respectively. This study presents updated fundamental stellar parameters of nine dwarf stars that can be used as new set of benchmarks. All fundamental stellar parameters were based on consistently combining interferometric observations, 3D limb-darkening modelling and spectroscopic analysis. The next paper in this series will extend our sample to giants in the metal-rich range.
- ID:
- ivo://CDS.VizieR/J/MNRAS/494/4110
- Title:
- DW Cnc H{alpha} and HeI RV curves
- Short Name:
- J/MNRAS/494/4110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present extensive radial velocity observations of the intermediate polar DW Cnc during its 2018-2019 low state. We show that the 86 min signal associated with the orbital period is strong in our radial velocity analysis, power spectrum search, and in our Doppler tomography. However, we find that the velocity modulation associated with the 70 min beat period and the 38 min spin cycle is dramatically weaker than that previously observed. We put forward two interpretations for this change. The first is that a sudden drop into a low state detected in 2018-2019 caused an episode of low mass transfer from the companion, thus inhibiting the lighthouse effect produced by the rebound emission. The second is that this is a consequence of a rare outburst detected in 2007 by Crawford et al. (2008, J. Am. Assoc. Var. Star Obs., 36, 60). We find this post-outburst hypothesis to be less likely. If the first scenario is correct, we predict that DW Cnc will recover its intermediate polar characteristics. A new ephemeris is presented by combining Patterson et al. (2004PASP..116..516P) radial velocities with ours.
4738. DX Eri variability
- ID:
- ivo://CDS.VizieR/J/A+A/309/787
- Title:
- DX Eri variability
- Short Name:
- J/A+A/309/787
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of nearly simultaneous monitoring of uvby light and HeI667.81nm line-profile variations of the equatorial Be star DX Eri in November 1991. They are analysed along with numerous uvby photometry in the period 1986-1995.
- ID:
- ivo://CDS.VizieR/J/ApJ/689/919
- Title:
- Dynamical evolution of globular clusters
- Short Name:
- J/ApJ/689/919
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We test the hypothesis that metal-poor globular clusters form within disk galaxies at redshifts z>3. We calculate the orbits of model clusters in the time-variable gravitational potential of a Milky Way-sized galaxy, using the outputs of a cosmological N-body simulation. We find that at present the orbits are isotropic in the inner 50kpc of the Galaxy and preferentially radial at larger distances. All clusters located outside 10kpc from the center formed in satellite galaxies, some of which are now tidally disrupted and some of which survive as dwarf galaxies. Mergers of the progenitors lead to a spheroidal spatial distribution of model clusters, although it is more extended than that of Galactic metal-poor clusters and has a somewhat shallower power-law slope of the number density profile, {gamma}~2.7. The combination of two-body relaxation, tidal shocks, and stellar evolution drives the evolution of the cluster mass function from an initial power law to a peaked distribution, in agreement with observations. However, not all initial conditions and not all evolution scenarios are consistent with the observed mass function of the Galactic globular clusters. We find that our best-fitting models require the average cluster density, M/R^3^_h_, to be constant initially for clusters of all mass and to remain constant with time. However, these models do not explain the observed decrease of the mean density with galactocentric distance. Both synchronous formation of all clusters at a single epoch (z=4) and continuous formation over a span of 1.6Gyr (between z=9 and 3) are consistent with the data. For both formation scenarios, we provide online catalogs of the main physical properties of model clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/771/85
- Title:
- Dynamical masses of z~2 quiescent galaxies
- Short Name:
- J/ApJ/771/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using stellar kinematics measurements, we investigate the growth of massive, quiescent galaxies from z~2 to today. We present X-Shooter spectra from the UV to NIR and dynamical mass measurements of five quiescent massive (>10^11^M_{sun}_) galaxies at z~2. This triples the sample of z>1.5 galaxies with well-constrained ({delta}{sigma}<100km/s) velocity dispersion measurements. From spectral population synthesis modeling we find that these galaxies have stellar ages that range from 0.5 to 2Gyr, with no signs of ongoing star formation. We measure velocity dispersions (290-450km/s) from stellar absorption lines and find that they are 1.6-2.1 times higher than those of galaxies in the Sloan Digital Sky Survey at the same mass. Sizes are measured using GALFIT from Hubble Space Telescope Wide Field Camera 3 H_160_ and UDS K-band images. The dynamical masses correspond well to the spectral energy distribution based stellar masses, with dynamical masses that are ~15% higher.