- ID:
- ivo://CDS.VizieR/J/AJ/142/51
- Title:
- Galactic Cepheids abundance variations
- Short Name:
- J/AJ/142/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper reports on the spectroscopic investigation of 101 Cepheids in the Carina region. These Cepheids extend previous samples by about 35% in number and increase the amount of the Galactic disk coverage especially in the direction of l~~270{deg}. The new Cepheids do not add much information to the radial gradient, but provide a substantial increase in azimuthal coverage. We find no azimuthal dependence in abundance over an 80{deg} angle from the Galactic center in an annulus of 1kpc depth centered on the Sun. A simple linear fit to the Cepheid data yields a gradient d[Fe/H]/dR_G_=-0.055+/-0.003dex/kpc which is somewhat shallower than found from our previous, smaller Cepheid sample.
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- ID:
- ivo://CDS.VizieR/J/A+A/623/A116
- Title:
- Galactic Cepheids and RR Lyrae multiplicity. I.
- Short Name:
- J/A+A/623/A116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Classical Cepheids (CCs) and RR Lyrae stars (RRLs) are important classes of variable stars used as standard candles to estimate galactic and extragalactic distances. Their multiplicity is imperfectly known, particularly for RRLs. Astoundingly, only one RRL is convincingly demonstrated to be a binary as of today, TU UMa, out of tens of thousands of known RRLs. We aim at detecting the binary and multiple stars present in a sample of Milky Way CCs and RRLs. In the present article, we combine the Hipparcos and Gaia DR2 positions to determine the mean proper motion of the targets, and we search for proper motion anomalies (PMa) caused by close-in orbiting companions. We identify 57 CC binaries from PMa out of 254 tested stars, and 75 additional candidates, confirming the high binary fraction of these massive stars. For 28 binary CCs, we determine the companion mass by combining their spectroscopic orbital parameters and astrometric PMa. We detect 13 RRLs showing a significant PMa out of 198 tested stars, and 61 additional candidates. We determine that the binarity fraction of CCs is likely above 80%, while that of RRLs is at least 7%. The newly detected systems will be useful to improve our understanding of their evolutionary states. The discovery of a significant number of RRLs in binary systems also resolves the long-standing mystery of their extremely low apparent binarity fraction.
- ID:
- ivo://CDS.VizieR/J/A+AS/143/211
- Title:
- Galactic Cepheids BVRI photometry
- Short Name:
- J/A+AS/143/211
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a new version of the catalogue of distances and light-curve parameters for Galactic classical Cepheids. The catalogue lists amplitudes, magnitudes at maximum light, and intensity means for 455 stars in BVRI filters of the Johnson system and (RI)_C_ filters of the Cron-Cousins system. The distances are based on our new multicolour set of Period/Luminosity relations and on our Cepheid-based solution for interstellar extinction law parameters and are referred to an LMC distance modulus of 18.25.
- ID:
- ivo://CDS.VizieR/J/A+A/635/A33
- Title:
- Galactic classical Cepheids Per-Lbol-Rad
- Short Name:
- J/A+A/635/A33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Spectral energy distributions (SEDs) were constructed for a sample of 477 classical cepheids (CCs); including stars that have been classified in the literature as such but are probably not. The SEDs were fitted with a dust radiative transfer code. Four stars showed a large mid- or far-infrared excess and the fitting then included a dust component. These comprise the well-known case of RS Pup, and three stars that are (likely) Type-II cepheids (T2Cs), AU Peg, QQ Per, and FQ Lac. The infrared (IR) excess in FQ Lac is reported for the first time in this work. The remainder of the sample was fitted with a stellar photosphere to derive the best-fitting luminosity and effective temperature. Distance and reddening were taken from the literature. The stars were plotted in a Hertzsprung-Russell diagram (HRD) and compared to evolutionary tracks for cepheids and theoretical instability strips. For the large majority of stars, the position in the HRD is consistent with the instability strip for a CC or T2C. About 5% of the stars are outliers in the sense that they are much hotter or cooler than expected. A comparison to effective temperatures derived from spectroscopy suggests in some cases that the photometrically derived temperature is not correct and that this is likely linked to an incorrectly adopted reddening. Two three-dimensional reddening models have been used to derive alternative estimates of the reddening for the sample. There are significant systematic differences between the two estimates with a non-negligible scatter. In this work the presence of a small near-infrared (NIR) excess, as has been proposed in the literature for a few well-known cepheids, is investigated. Firstly, this was done by using a sample of about a dozen stars for which a mid-infrared spectrum is available. This data is particularly con straining as the shape of the observed spectrum should match that of the photosphere and any dust spectrum, both dust continuum and any spectral features of, for example, silicates or aluminium oxide. This comparison provides constraints on the dust composition, in agreement with a previous work in the literature. Secondly, the SEDs of all stars were fitted with a dust model to see if a statistically significant better fit could be obtained. The results were compared to recent work. Eight new candidates for exhibiting a NIR excess are proposed, solely based on the photometric SEDs. Obtaining mid-infrared spectra would be needed to confirm this excess. Finally, period-bolometric luminosity and period-radius relations are presented for samples of over 370 fundamental-mode CCs.
- ID:
- ivo://CDS.VizieR/J/PAZh/39/942
- Title:
- Galactic classical Cepheids properties
- Short Name:
- J/PAZh/39/942
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on our compiled catalogue of positions, velocities, ages, and abundances of nine chemical elements for 221 classical Cepheids, we analyze the dependences of the relative abundances of alpha-elements as well as rapid and slow neutron capture elements on metallicity, space velocity components, and Galactocentric distance.
- ID:
- ivo://CDS.VizieR/J/MNRAS/492/3408
- Title:
- Galactic disc RR Lyrae stars
- Short Name:
- J/MNRAS/492/3408
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a kinematical study of 314 RR Lyrae stars in the solar neighbourhood using the publicly available photometric, spectroscopic, and Gaia DR2 astrometric data to explore their distribution in the Milky Way. We report an overdensity of 22 RR Lyrae stars in the solar neighbourhood at a pericentre distance of between 5 and 9kpc from the Galactic Centre. Their orbital parameters and their chemistry indicate that these 22 variables share the kinematics and the [Fe/H] values of the Galactic disc, with an average metallicity and tangential velocity of [Fe/H]=-0.60dex and v_theta_=241km/s, respectively. From the distribution of the Galactocentric spherical velocity components, we find that these 22 disc-like RR Lyrae variables are not consistent with the Gaia Sausage (Gaia-Enceladus), unlike almost half of the local RR Lyrae stars. Chemical information from the literature shows that the majority of the selected pericentre-peak RR Lyrae variables are alpha-poor, a property shared by typically much younger stars in the thin disc. Using the available photometry, we rule out a possible misclassification with the known classical and anomalous Cepheids. The similar kinematic, chemical, and pulsation properties of these disc RR Lyrae stars suggest they share a common origin. In contrast, we find that the RR Lyrae stars associated with the Gaia- Enceladus based on their kinematics and chemical composition show a considerable metallicity spread in the old population (approximately 1dex).
- ID:
- ivo://CDS.VizieR/J/AZh/95/54
- Title:
- Galactic-field RR Lyrae abundances and kinematics
- Short Name:
- J/AZh/95/54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Data of our compiled catalog containing the positions, velocities, and metallicities of 415 RR Lyrae variable stars and the relative abundances [el/Fe] of 12 elements for 101 RR Lyrae stars, including four {alpha} elements (Mg, Ca, Si, and Ti), are used to study the relationships between the chemical and spatial-kinematic properties of these stars. In general, the dependences of the relative abundances of {alpha} elements on metallicity and velocity for the RR Lyrae stars are approximately the same as those for field dwarfs. Despite the usual claim that these stars are old, among them are representatives of the thin disk, which is the youngest subsystem of the Galaxy. Attention is called to the problem of low metallicity RR Lyrae stars. Most RR Lyrae stars that have the kinematic properties of thick disk stars have metallicities [Fe/H]<-1.0 and high ratios [{alpha}/Fe]~=0.4, whereas only about 10% of field dwarfs belonging to the so-called "low-metallicity tail" have this chemical composition. At the same time, there is a sharp change in [{alpha}/Fe] in RR Lyrae stars belonging just to the thick disk, providing evidence for a long period of formation of this subsystem. The chemical compositions of SDSS J1707+58, V455 Oph, MACHO176.18833.411, V456 Ser, and BPS CS 30339-046 do not correspond to their kinematics. While the first three of these stars belong to the halo, according to their kinematics, the last two belong to the thick disk. It is proposed that they are all most likely extragalactic, but the possible appearance of some of them in the solar neighborhood as a result of the gravitational action of the bar on field stars cannot be ruled out.
- ID:
- ivo://CDS.VizieR/J/ApJ/763/32
- Title:
- Galactic halo RRab stars from CSS
- Short Name:
- J/ApJ/763/32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present analysis of 12227 type-ab RR Lyraes (RRLs; ~9400 are newly discovered) found among the 200 million public light curves in Catalina Surveys Data Release 1. These stars span the largest volume of the Milky Way ever surveyed with RRLs, covering ~20000deg^2^ of the sky (0{deg}<{alpha}<360{deg}, -22{deg}<{delta}<65{deg}) to heliocentric distances of up to 60kpc. Each of the RRLs is observed between 60 and 419 times over a six-year period. Using period finding and Fourier fitting techniques we determine periods and apparent magnitudes for each source. We find that the periods are generally accurate to {sigma}=0.002% in comparison to 2842 previously known RRLs and 100 RRLs observed in overlapping survey fields. We photometrically calibrate the light curves using 445 Landolt standard stars and show that the resulting magnitudes are accurate to ~0.05mag using Sloan Digital Sky Survey (SDSS) data for ~1000 blue horizontal branch stars and 7788 RRLs. By combining Catalina photometry with SDSS spectroscopy, we analyze the radial velocity and metallicity distributions for >1500 of the RRLs. Using the accurate distances derived for the RRLs, we show the paths of the Sagittarius tidal streams crossing the sky at heliocentric distances from 20 to 60kpc. By selecting samples of Galactic halo RRLs, we compare their velocity, metallicity, and distance with predictions from a recent detailed N-body model of the Sagittarius system. We find that there are some significant differences between the distances and structures predicted and our observations.
- ID:
- ivo://CDS.VizieR/J/AZh/79/510
- Title:
- Galactic orbits of RR Lyrae variable stars
- Short Name:
- J/AZh/79/510
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used published, high-accuracy, ground-based and satellite proper-motion measurements, a compilation of radial velocities, and photometric distances to compute the spatial velocities and Galactic orbital elements for 174 RR Lyrae (ab) variable stars in the solar neighborhood. The computed orbital elements and published heavy-element abundances are used to study relationships between the chemical, spatial, and kinematic characteristics of nearby RR Lyrae variables. We observe abrupt changes of the spatial and kinematic characteristics at the metallicity [Fe/H]~-0.95 and also when the residual spatial velocities relative to the LSR cross the critical value V_res_~290km/s.
- ID:
- ivo://CDS.VizieR/J/PASP/111/57
- Title:
- Galactic reddening maps
- Short Name:
- J/PASP/111/57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate maps of Galactic reddening are important for a number of applications, such as mapping the peculiar velocity field in the nearby universe. Of particular concern are systematic errors which vary slowly as a function of position on the sky, as these would induce spurious bulk flow. We have compared the reddenings of Burstein & Heiles (BH, 1982, Cat. <J/AJ/87/1165>) and those of Schlegel, Finkbeiner, & Davis (1998ApJ...500..525S, SFD) to independent estimates of the reddening, for Galactic latitudes |b|>10{deg}. Our primary source of Galactic reddening estimates comes from comparing the difference between the observed B-V colors of early-type galaxies, and the predicted B-V color determined from the B-V-Mg_2_ relation. We have fitted a dipole to the residuals in order to look for large-scale systematic deviations. There is marginal evidence for a dipolar residual in the comparison between the SFD maps and the observed early-type galaxy reddenings. If this is due to an error in the SFD maps, then it can be corrected with a small (13%) multiplicative dipole term. We argue, however, that this difference is more likely to be due to a small (0.01mag) systematic error in the measured B-V colors of the early-type galaxies. This interpretation is supported by a smaller, independent data set (globular cluster and RR Lyrae stars), which yields a result inconsistent with the early-type galaxy residual dipole. BH reddenings are found to have no significant systematic residuals, apart from the known problem in the region 230{deg}<l<310{deg}, -20{deg}<b<20{deg}.
