- ID:
- ivo://CDS.VizieR/III/176
- Title:
- RR Lyrae Metallicities
- Short Name:
- III/176
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog presents metal abundance, distance and radial velocity data on a sample of 302 ab-type RR Lyrae variables within about 2.5 kpc of the Sun. The metal abundance information was obtained from low-medium resolution spectra, using the pseudo-equivalent widths of the Ca II K line and the the H-delta, H-gamma and H-beta lines. The technique employed was similar to Preston's (1959ApJ...130..507P) {Delta}-S method, though significant differences exist; see the source reference for details. The data were calibrated to the Zinn & West (1984ApJS...55...45Z) globular cluster abundance scale. The photometry employed in the distance determinations was primarily taken from the General Catalog of Variable Stars (1985, hereafter GCVS4). Exceptions are noted in column 29; the letters match the footnotes in Table 10 of Layden (1994AJ....108.1016L). The minimum and maximum light photometry, and rise-time were combined following Barnes & Hawley (1986ApJ...307L...9B) to give an estimate of the intensity- averaged magnitude, i.e. the magnitude the star would have if it were not variable. When the GCVS4 quoted magnitudes in passbands other than V, the GCVS4 magnitudes were transformed to the V passband using the relations established in Layden (1994AJ....108.1016L). The interstellar absorption estimates are from Burstein & Heiles (1982AJ.....87.1165B), modified by a simple dust-distribution model. The distances were computed assuming the Mv(RR)-[Fe/H] relation of Carney, Storm & Jones (1992ApJ...386..663C). Radial velocities were measured from the spectra via cross-correlation with secondary velocity standards. The velocities from the individual spectra were fit with a standard radial velocity curve in the (phase, velocity) plane, to give an estimate of the systemic (center of mass) velocity of each star. The error in this value was estimated from the scatter about the best-fit velocity curve, and the quality of the spectra employed. Other methods were used to combine the individual velocities when the situation demanded (cm = 2,3 in column 70; see Layden (1994AJ....108.1016L) for details). The observed velocities were combined with values from the literature to produce a final, best estimate of the systemic radial velocity of each star, and its error.
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- ID:
- ivo://CDS.VizieR/J/A+A/330/515
- Title:
- RR Lyrae parallaxes & proper motions
- Short Name:
- J/A+A/330/515
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used HIPPARCOS proper motions and the method of Statistical Parallax to estimate the absolute magnitude of RR Lyrae stars. In addition we used the HIPPARCOS parallax of RR Lyrae itself to determine it's absolute magnitude. These two results are in excellent agreement with each other and give a zero-point for the RR Lyrae M_v_,[Fe/H] relation of 0.77+/-0.15 at [Fe/H]=-1.53. This zero-point is in good agreement with that obtained recently by several groups using Baade-Wesselink methods which, averaged over the results from the different groups, gives M_v_=0.73+/-0.14 at [Fe/H]=-1.53. Taking the HIPPARCOS based zero-point and a value of 0.18+/-0.03 for the slope of the M_v_,[Fe/H] relation from the literature we find firstly, the distance modulus of the LMC is 18.26+/-0.15 and secondly, the mean age of the Globular Clusters is 17.4+/-3.0 GYrs. These values are compared with recent estimates based on other "standard candles" that have also been calibrated with HIPPARCOS data. It is clear that, in addition to astrophysical problems, there are also problems in the application of HIPPARCOS data that are not yet fully understood.
- ID:
- ivo://CDS.VizieR/J/A+AS/125/313
- Title:
- RR Lyrae radial velocities and [Fe/H] I.
- Short Name:
- J/A+AS/125/313
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present systemic velocities and iron abundances for 56 RR Lyraes, the majority of which have been observed by the HIPPARCOS satellite. Comparison between our systemic velocities and previous values identifies several binary candidates only one of which, TU UMa, was previously suspected of being a binary. However, spectra of the unusual RR Lyrae BB Vir show no evidence of line doubling and hence do not support the recent claims that this star may have a Blue Horizontal Branch companion. Comparison between our abundances and previous determinations shows reasonable agreement except with the recent work of Layden (1994, Cat. <J/AJ/108/1016>) where we find systematic differences. Several of the stars included on the HIPPARCOS observing list as RR Lyraes are shown to be mis-classified. Of particular interest are the stars V363 Cas and AT And which, by analogy with XZ Cet, may be anomalous Cepheids.
- ID:
- ivo://CDS.VizieR/J/A+AS/125/321
- Title:
- RR Lyrae radial velocities and [Fe/H] II.
- Short Name:
- J/A+AS/125/321
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the second of the papers devoted to derive radial velocities and iron abundances of field RR Lyraes observed by HIPPARCOS. Our abundances show good agreement with those in the literature obtained both from photometric ({DELTA}S index) and spectroscopic methods. Binary candidates and stars misclassified as RR Lyraes in the original HIPPARCOS list have been also identified.
- ID:
- ivo://CDS.VizieR/J/ApJS/246/8
- Title:
- RR Lyrae star candidates from SDSS-DR15
- Short Name:
- J/ApJS/246/8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the increase of known RR Lyrae stars, it is reliable to create classifiers of RR Lyrae stars based on their photometric data or combined photometric and spectroscopic data. Nevertheless the total number of known RR Lyrae stars is still too small compared with the large survey databases. So classification of RR Lyrae stars and other sources belongs to imbalanced learning. Based on Sloan Digital Sky Survey (SDSS) photometric and spectroscopic data, we apply cost-sensitive Random Forests fit for imbalanced learning to preselect RR Lyrae star candidates. Only with photometric data, u-g,g-r,r-i,i-z is the best input pattern. While also considering physical parameters (Teff, [Fe/H], log(g)), the optimal input pattern is Teff, [Fe/H], log(g), u-g,g-r,r-i,i-z, at this moment for cost-sensitive Random Forests, the performance metrics of completeness, contamination, and Matthews correlation coefficient are 0.975, 0.019, and 0.975, respectively. It indicates that adding stellar physical parameters is helpful for identifying RR Lyrae stars from other stars. We apply the best classifiers on the SDSS photometric data and combined photometric data with physical parameters to select RR Lyrae star candidates. Finally 11,041 photometric candidates with spectral type A and F are obtained, and then 304 candidates with physical parameters are selected out. Among the 304 candidates, a small part are HB stars, BS stars, RGB stars, and peculiar stars, and the rest are unknown in the Simbad database. These candidates may be used as the input catalog for time-series follow-up observations.
- ID:
- ivo://CDS.VizieR/J/ApJ/767/62
- Title:
- RR Lyrae stars BV photometry in UMa I
- Short Name:
- J/ApJ/767/62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed the first study of the variable star population of Ursa Major I (UMa I), an ultra-faint dwarf satellite recently discovered around the Milky Way (MW) by the Sloan Digital Sky Survey. Combining time series observations in the B and V bands from four different telescopes, we have identified seven RR Lyrae stars in UMa I, of which five are fundamental-mode (RRab) and two are first-overtone pulsators (RRc). Our V, B-V color-magnitude diagram of UMa I reaches V~23mag (at a signal-to-noise ratio of ~6) and shows features typical of a single old stellar population. The mean pulsation period of the RRab stars <P_ab_>=0.628, {sigma}=0.071 days (or <P_ab_>=0.599, {sigma}=0.032 days, if V4, the longest period and brightest variable, is discarded) and the position on the period-amplitude diagram suggest an Oosterhoff-intermediate classification for the galaxy. The RR Lyrae stars trace the galaxy horizontal branch (HB) at an average apparent magnitude of <V(RR)>=20.43+/-0.02mag (average on six stars and discarding V4), giving in turn a distance modulus for UMa I of (m-M)_0_=19.94+/-0.13mag, distance d=97.3_-5.7_^+6.0^kpc, in the scale where the distance modulus of the Large Magellanic Cloud is 18.5+/-0.1mag. Isodensity contours of UMa I red giants and HB stars (including the RR Lyrae stars identified in this study) show that the galaxy has an S-shaped structure, which is likely caused by the tidal interaction with the MW. Photometric metallicities were derived for six of the UMa I RR Lyrae stars from the parameters of the Fourier decomposition of the V-band light curves, leading to an average metal abundance of [Fe/H]=-2.29dex ({sigma}=0.06dex, average on six stars) on the Carretta et al. (2009, J/A+A/505/117) metallicity scale.
- ID:
- ivo://CDS.VizieR/J/A+A/578/A27
- Title:
- RV and [Fe/H] in 5 open clusters
- Short Name:
- J/A+A/578/A27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Open clusters are key to studying the formation and evolution of the Galactic disc. However, there is a deficiency of radial velocity and chemical abundance determinations for open clusters in the literature. Aims. We intend to increase the number of determinations of radial velocities and metallicities from spectroscopy for open clusters. We acquired medium-resolution spectra (R~8000) in the infrared region CaII triplet lines (~8500{AA}) for several stars in five open clusters with the long-slit IDS spectrograph on the 2.5m Isaac Newton Telescope (Roque de los Muchachos Observatory, Spain). Radial velocities were obtained by cross-correlation fitting techniques. The relationships available in the literature between the strength of infrared Ca ii lines and metallicity were also used to derive the metallicity for each cluster.
- ID:
- ivo://CDS.VizieR/J/AJ/123/2490
- Title:
- RV and [Fe/H] of M31 globular cluster system
- Short Name:
- J/AJ/123/2490
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the ultimate aim of distinguishing between various models describing the formation of galaxy halos (e.g., radial or multiphase collapse and random mergers), we have completed a spectroscopic study of the globular cluster system of M31. We present the results of deep intermediate-resolution fiber-optic spectroscopy of several hundred of the M31 globular clusters using the Wide Field Fibre Optic Spectrograph at the William Herschel Telescope in La Palma, Canary Islands. These observations have yielded precise radial velocities (+/-12km/s) and metallicities (+/-0.26dex) for over 200 members of the M31 globular cluster population out to a radius of 1.5{deg} from the galaxy center. Many of these clusters have no previous published radial velocity or [Fe/H] estimates, and the remainder typically represent significant improvements over earlier determinations. We present analyses of the spatial, kinematic, and metal abundance properties of the M31 globular clusters.
- ID:
- ivo://CDS.VizieR/J/ApJ/769/107
- Title:
- RVs and [Fe/H] of star members of NGC 6388
- Short Name:
- J/ApJ/769/107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By combining high spatial resolution and wide-field spectroscopy performed, respectively, with SINFONI and FLAMES at the ESO/VLT we measured the radial velocities of more than 600 stars in the direction of NGC 6388, a Galactic globular cluster which is suspected to host an intermediate-mass black hole. Approximately 55% of the observed targets turned out to be cluster members. The cluster velocity dispersion has been derived from the radial velocity of individual stars: 52 measurements in the innermost 2", and 276 stars located between 18" and 600". The velocity dispersion profile shows a central value of ~13km/s, a flat behavior out to ~60" and a decreasing trend outward. The comparison with spherical and isotropic models shows that the observed density and velocity dispersion profiles are inconsistent with the presence of a central black hole more massive than ~2000M_{sun}_. These findings are at odds with recent results obtained from integrated light spectra, showing a velocity dispersion profile with a steep central cusp of 23-25km/s at r<2" and suggesting the presence of a black hole with a mass of ~1.7x10^4^M_{sun}_. We also found some evidence of systemic rotation with amplitude A_rot_~8km/s in the innermost 2" (0.13pc), decreasing to A_rot_=3.2km/s at 18"<r<160".
- ID:
- ivo://CDS.VizieR/J/MNRAS/475/1609
- Title:
- RV variability in NGC 2516 and NGC 2422
- Short Name:
- J/MNRAS/475/1609
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multi-epoch, high-dispersion, optical spectra obtained with the Michigan/Magellan Fiber System of 126 and 125 Sun-like stars in the young clusters NGC 2516 (141Myr) and NGC 2422 (73Myr). We determine stellar properties including radial velocity (RV), Teff, [Fe/H], [{alpha}/Fe], and the line-of-sight rotation rate, v_r_sin(i), from these spectra. Our median RV precision of 80m/s on individual epochs that span a temporal baseline of 1.1yr enables us to investigate membership, stellar binarity, and search for sub-stellar companions. We determine membership probabilities and RV variability probabilities for our sample along with candidate companion orbital periods for a select subset of stars. We identify 81 RV members in NGC 2516, 27 spectroscopic binaries (17 previously identified as photometric binaries), and 16 other stars that show significant RV variability after accounting for average stellar jitter found to be at the 74m/s level. In NGC 2422 we identify 57 members, 11 spectroscopic binaries, and 3 other stars that show significant RV variability after accounting for an average jitter of 138m/s. We use Monte Carlo simulations to verify our stellar jitter measurements, determine the proportion of exoplanets and stellar companions to which we are sensitive, and estimate companion mass limits for our targets. We also report mean cluster metallicity, velocity, and velocity dispersion based on our member targets and identify 58 non-member stars as RV variables - 24 of which have RV amplitudes that imply stellar or brown-dwarf mass companions. Finally, we note the discovery of a separate RV clustering of stars in our NGC 2422 sample.
