- ID:
- ivo://CDS.VizieR/J/A+A/550/A70
- Title:
- Galactic and Magellanic Cloud Cepheids distance
- Short Name:
- J/A+A/550/A70
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The metallicity dependence of the Cepheid period-luminosity (PL) relation is of importance in establishing the extragalactic distance scale. The aim of this paper is to investigate the metallicity dependence of the PL relation in V and K, based on a sample of 128 Galactic, 36 Large Magellanic Cloud (LMC), and 6 Small Magellanic Cloud (SMC) Cepheids with individual Baade-Wesselink (BW) distances (some of the stars also have an Hubble Space Telescope (HST) based and Hipparcos parallax or are in clusters) and individually determined metallicities from high-resolution spectroscopy. Literature values of the V-band, K-band, and radial velocity data were collected for the sample of Cepheids. Based on a (V-K) surface-brightness relation and a projection factor, distances were derived from a BW analysis. Since 2008, additional radial velocity data has been obtained using the 1.2m Euler telescope located at the La Silla observatory (see Groenewegen 2008A&A...488...25G for a description of the data taking and data reduction). The new Radial Velocity (RV) data are presented in Table 3.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/625/A151
- Title:
- Galactic Bulge Type II Cepheids NIR data
- Short Name:
- J/A+A/625/A151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform parallel Lomb-Scargle and Generalized Lomb-Scargle periodogram analysis of the Ks-band time series of the VISTA Variables in the Via Lactea Survey, to detect periodicities. We take account of periods, light amplitudes, distances and proper motions to provide a classification of the candidate variables. We provide a catalog which will be the starting point for future spectroscopic surveys in the innermost regions of the Galaxy.
- ID:
- ivo://CDS.VizieR/J/A+A/381/32
- Title:
- Galactic Cepheid abundances
- Short Name:
- J/A+A/381/32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- File table1 contains information about the program stars and spectra . Note that we also added to our sample two distant Cepheids (TV Cam and YZ Aur) which were previously analyzed by Harris & Pilachowski (1984ApJ...282..655H). File table2 contains relative-to-solar averaged elemental abundances (i.e. [El/H]) for program stars. First column gives the name of the star, other columns list the abundance data for all investigated elements. File tablea1 contains an Appendix table with elemental abundances from individual ions (ions are listed in the first column). For each star the following information is given: relative-to-solar abundance of a given ion (i.e. [M/H]), sigma-value, number of the lines used in analysis, absolute abundance of a given ion (M/H) in the scale where logA(H)=12.00.
- 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.
- 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.
