- ID:
- ivo://CDS.VizieR/J/MNRAS/458/2307
- Title:
- gamma Dor stars spectroscopic survey
- Short Name:
- J/MNRAS/458/2307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic survey of known and candidate {gamma} Doradus stars. The high-resolution, high signal-to-noise spectra of 52 objects were collected by five different spectrographs. The spectral classification, atmospheric parameters (T_eff_, logg, {xi}), vsini and chemical composition of the stars were derived. The stellar spectral and luminosity classes were found between G0-A7 and IV-V, respectively. The initial values for T_eff_ and logg were determined from the photometric indices and spectral energy distribution. Those parameters were improved by the analysis of hydrogen lines. The final values of T_eff_, logg and {xi} were derived from the iron lines analysis. The T_eff_ values were found between 6000K and 7900K, while log g values range from 3.8 to 4.5dex. Chemical abundances and vsin i values were derived by the spectrum synthesis method. The vsini values were found between 5 and 240km/s. The chemical abundance pattern of {gamma} Doradus stars were compared with the pattern of non-pulsating stars. It turned out that there is no significant difference in abundance patterns between these two groups. Additionally, the relations between the atmospheric parameters and the pulsation quantities were checked. A strong correlation between the vsini and the pulsation periods of {gamma} Doradus variables was obtained. The accurate positions of the analysed stars in the Hertzsprung-Russell diagram have been shown. Most of our objects are located inside or close to the blue edge of the theoretical instability strip of {gamma} Doradus.
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Search Results
- ID:
- ivo://CDS.VizieR/V/117A
- Title:
- Geneva-Copenhagen Survey of Solar neighbourhood
- Short Name:
- V/117A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (from paper II, 2007) Ages, metallicities, space velocities, and Galactic orbits of stars in the Solar neighbourhood are fundamental observational constraints on models of galactic disk evolution. Understanding and minimising systematic errors and sample selection biases in the data is crucial for their interpretation. We aim to consolidate the calibrations of uvbyb photometry into T_eff_, [Fe/H], distance, and age for F and G stars and rediscuss the results of the Geneva-Copenhagen Survey (GCS, Nordstrom et al., 2004, paper I) in terms of the evolution of the disk. We use recent V-K photometry, angular diameters, high-resolution spectroscopy, Hipparcos parallaxes, and extensive numerical simulations to re-examine and verify the temperature, metallicity, distance, and reddening calibrations for the uvbyb system. We also highlight the selection effects inherent in the apparent-magnitude limited GCS sample. We substantially improve the T_eff_ and [Fe/H] calibrations for early F stars, where spectroscopic temperatures have large systematic errors. A slight offset of the GCS photometry and the non-standard helium abundance of the Hyades invalidate its use for checking metallicity or age scales; however, the distances, reddenings, metallicities, and age scale for GCS field stars require minor corrections only. Our recomputed ages are in excellent agreement with the independent determinations by Takeda et al. (2007ApJS..168..297T), indicating that isochrone ages can now be reliably determined. The revised G-dwarf metallicity distribution remains incompatible with closed-box models, and the age-metallicity relation for the thin disk remains almost flat, with large and real scatter at all ages sigma_intrinsic=0.20 dex). Dynamical heating of the thin disk continues throughout its life; specific in-plane dynamical effects dominate the evolution of the U and V velocities, while the W velocities remain random at all ages. When assigning thick and thin-disk membership for stars from kinematic criteria, parameters for the oldest stars should be used to characterise the thin disk.
- ID:
- ivo://CDS.VizieR/J/A+A/530/A138
- Title:
- Geneva-Copenhagen survey re-analysis
- Short Name:
- J/A+A/530/A138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a re-analysis of the Geneva-Copenhagen survey, benefiting from the infrared flux method to improve upon the accuracy of the derived stellar effective temperatures and using the latter to build a consistent and improved metallicity scale. Metallicities are calibrated on high-resolution spectroscopy and checked against four open clusters and a moving group, showing excellent consistency. The new temperature and metallicity scales provide a better match to theoretical isochrones, which are used for a Bayesian analysis of stellar ages. With respect to previous analyses, our stars are on average 100K hotter and 0.1dex more metal rich, shifting the peak of the metallicity distribution function around the solar value. From Stromgren photometry we are able to derive for the first time a proxy for [Fe] abundances, which enables for a tentative dissection of the chemical thin and thick disc. We find evidence for the latter being composed of an old, mildly but systematically alpha-enhanced population extending to super solar metallicities, in agreement with spectroscopic studies. Our revision offers the largest existing kinematically unbiased sample of the solar neighbourhood that contains full information on kinematics, metallicities and ages and thus provides better constraints on the physical processes relevant in the build-up of the Milky Way disc, enabling a better understanding of the Sun in a Galactic context.
- ID:
- ivo://CDS.VizieR/J/A+A/601/A112
- Title:
- GES iDR4 Mg-Al anticorrelation in GCs
- Short Name:
- J/A+A/601/A112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use Gaia-ESO Survey iDR4 data to explore the Mg-Al anti-correlation in globular clusters, that were observed as calibrators, as a demonstration of the quality of Gaia-ESO Survey data and analysis. The results compare well with the available literature, within 0.1~[-] or less, after a small (compared to the Minternal spreads) offset between the UVES and the GIRAFFE data of 0.10-0.15dex was taken into account. In particular, we present for the first time data for NGC 5927, one of the most metal-rich globular clusters studied in the literature so far with [Fe/H]=-0.49dex, that was included to connect with the open cluster regime in the Gaia-ESO Survey internal calibration. The extent and shape of the Mg-Al anti-correlation provide strong constraints on the multiple population phenomenon in globular clusters. In particular, we studied the dependency of the Mg-Al anti-correlation extension with metallicity, present-day mass, and age of the clusters, using GES data in combination with a large set of homogenized literature measurements. We find a dependency with both metallicity and mass, that is evident when fitting for the two parameters simultaneously, but no significant dependency with age. We confirm that the Mg-Al anti-correlation is not seen in all clusters, but disappears for the less massive or most metal-rich ones. We also use our dataset to see whether a normal anti-correlation would explain the low [Mg/{alpha}] observed in some extragalactic globular clusters, but find that none of the clusters in our sample can reproduce it, and more extreme chemical compositions (like the one of NGC 2419) would be required. We conclude that GES iDR4 data already meet the requirements set by the main survey goals, and can be used to study in detail globular clusters even if the analysis procedures were not specifically designed for them.
- ID:
- ivo://CDS.VizieR/J/A+A/601/A70
- Title:
- GES: pre-main-sequence clusters [Fe/H]
- Short Name:
- J/A+A/601/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The radial metallicity distribution in the Galactic thin disc represents a crucial constraint for modelling disc formation and evolution. Open clusters allow us to derive both the radial metallicity distribution and its evolution over time. In this paper we perform the first investigation of the present-day radial metallicity distribution based on [Fe/H] determinations in late type members of pre-main-sequence clusters. Because of their youth, these clusters are therefore essential for tracing the current inter-stellar medium metallicity. We used the products of the Gaia-ESO Survey analysis of 12 young regions (age<100Myr), covering Galactocentric distances from 6.67 to 8.70kpc. For the first time, we derived the metal content of star forming regions farther than 500pc from the Sun. Median metallicities were determined through samples of reliable cluster members. For ten clusters the membership analysis is discussed in the present paper, while for other two clusters (Chamaeleon I and Gamma Velorum) we adopted the members identified in our previous works. All the pre-main-sequence clusters considered in this paper have close-to-solar or slightly sub-solar metallicities. The radial metallicity distribution traced by these clusters is almost flat, with the innermost star forming regions having [Fe/H] values that are 0.10-0.15dex lower than the majority of the older clusters located at similar Galactocentric radii. This homogeneous study of the present-day radial metallicity distribution in the Galactic thin disc favours models that predict a flattening of the radial gradient over time. On the other hand, the decrease of the average [Fe/H] at young ages is not easily explained by the models. Our results reveal a complex interplay of several processes (e.g. star formation activity, initial mass function, supernova yields, gas flows) that controlled the recent evolution of the Milky Way.
- ID:
- ivo://CDS.VizieR/J/MNRAS/444/2251
- Title:
- G0-G3 main-sequence stars with V<15
- Short Name:
- J/MNRAS/444/2251
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The basic stellar atmospheric parameters (effective temperature, surface gravity and global metallicity) were determined simultaneously for a sample of 233 stars, limited in magnitude (V<15), with spectral types between G0 and G3 and luminosity class V (main sequence). The analysis was based on spectroscopic observations collected at the Observatorio Astrofisico Guillermo Haro and using a set of Lick-like indices defined in the spectral range 3800-4800{AA}. An extensive set of indices computed in a grid of theoretical spectra was used as a comparison tool in order to determine the photospheric parameters. The method was validated by matching the results from spectra of the asteroids Vesta and Ceres with the Sun parameters. The main results were as follows: (i) the photospheric parameters were determined for the first time for 213 objects in our sample and (ii) a sample of 20 new super-metal-rich star candidates was found.
- ID:
- ivo://CDS.VizieR/J/A+A/584/A46
- Title:
- GIRAFFE Inner Bulge Survey (GIBS). II.
- Short Name:
- J/A+A/584/A46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate metallicity and {alpha}-element abundance gradients along a Galactic longitude strip, at latitude b~-4{deg}, with the aim of providing observational constraints for the structure and origin of the Milky Way bulge. High-resolution (R~22500) spectra for 400 Kgiants, in four fields within -4.8{deg}<~b<~-3.4{deg} and -10{deg}<~l<~+10{deg}, were obtained within the GIRAFFE Inner Bulge Survey (GIBS) project. To this sample we added another ~400 stars in Baade's Window at (l,b)=(1{deg},-4{deg}), observed with the identical instrumental configuration: FLAMES GIRAFFE in Medusa mode with HR13 setup. All target stars lie within the red clump of the bulge colour-magnitude diagram, thus minimising contamination from the disc or halo stars. The spectroscopic stellar surface parameters were derived with an automatic method based on the GALA code, while the [Ca/Fe] and [Mg/Fe] abundances as a function of [Fe/H] were derived through a comparison with the synthetic spectra using MOOG. We constructed the metallicity distributions for the entire sample, and for each field individually, in order to investigate the presence of gradients or field-to-field variations in the shape of the distributions.
- ID:
- ivo://CDS.VizieR/J/ApJ/781/124
- Title:
- Granulation model for 508 KIC stars
- Short Name:
- J/ApJ/781/124
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A large fraction of cool, low-mass stars exhibit brightness fluctuations that arise from a combination of convective granulation, acoustic oscillations, magnetic activity, and stellar rotation. Much of the short-timescale variability takes the form of stochastic noise, whose presence may limit the progress of extrasolar planet detection and characterization. In order to lay the groundwork for extracting useful information from these quasi-random signals, we focus on the origin of the granulation-driven component of the variability. We apply existing theoretical scaling relations to predict the star-integrated variability amplitudes for 508 stars with photometric light curves measured by the Kepler mission. We also derive an empirical correction factor that aims to account for the suppression of convection in F-dwarf stars with magnetic activity and shallow convection zones. So that we can make predictions of specific observational quantities, we performed Monte Carlo simulations of granulation light curves using a Lorentzian power spectrum. These simulations allowed us to reproduce the so-called flicker floor (i.e., a lower bound in the relationship between the full light-curve range and power in short-timescale fluctuations) that was found in the Kepler data. The Monte Carlo model also enabled us to convert the modeled fluctuation variance into a flicker amplitude directly comparable with observations. When the magnetic suppression factor described above is applied, the model reproduces the observed correlation between stellar surface gravity and flicker amplitude. Observationally validated models like these provide new and complementary evidence for a possible impact of magnetic activity on the properties of near-surface convection.
- ID:
- ivo://CDS.VizieR/J/ApJ/736/L25
- Title:
- Habitability of Kepler planetary candidates
- Short Name:
- J/ApJ/736/L25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This Letter outlines a simple approach to evaluate habitability of terrestrial planets by assuming different types of planetary atmospheres and using corresponding model calculations. Our approach can be applied for current and future candidates provided by the Kepler mission and other searches. The resulting uncertainties and changes in the number of planetary candidates in the habitability zone (HZ) for the Kepler 2011 February data release are discussed. To first order, the HZ depends on the effective stellar flux distribution in wavelength and time, the planet albedo, and greenhouse gas effects. We provide a simple set of parameters which can be used for evaluating future planet candidates from transit searches.
- ID:
- ivo://CDS.VizieR/J/AJ/155/119
- Title:
- HATSouth-K2 C7 transiting/eclipsing systems
- Short Name:
- J/AJ/155/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the result of a campaign to monitor 25 HATSouth candidates using the Kepler space telescope during Campaign 7 of the K2 mission. We discover HATS-36b (EPIC 215969174b, K2-145b), an eccentric (e=0.105+/-0.028) hot Jupiter with a mass of 3.216+/-0.062 M_J_ and a radius of 1.235+/-0.043 R_J_, which transits a solar-type G0V star (V=14.386) in a 4.1752-day period. We also refine the properties of three previously discovered HATSouth transiting planets (HATS-9b, HATS-11b, and HATS-12b) and search the K2 data for TTVs and additional transiting planets in these systems. In addition, we also report on a further three systems that remain as Jupiter-radius transiting exoplanet candidates. These candidates do not have determined masses, however pass all of our other vetting observations. Finally, we report on the 18 candidates that we are now able to classify as eclipsing binary or blended eclipsing binary systems based on a combination of the HATSouth data, the K2 data, and follow-up ground-based photometry and spectroscopy. These range in periods from 0.7 day to 16.7 days, and down to 1.5 mmag in eclipse depths. Our results show the power of combining ground-based imaging and spectroscopy with higher precision space-based photometry, and serve as an illustration as to what will be possible when combining ground-based observations with TESS data.
