- ID:
- ivo://CDS.VizieR/J/ApJ/681/311
- Title:
- Blue stragglers in NGC 2419
- Short Name:
- J/ApJ/681/311
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used a combination of ACS HST high-resolution and wide-field Subaru data in order to study the blue straggler star (BSS) population over the entire extension of the remote Galactic globular cluster NGC 2419. The BSS population presented here is among the largest ever observed in any stellar system, with more than 230 BSSs in the brightest portion of the sequence. The radial distribution of the selected BSSs is essentially the same as that of the other cluster stars.
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- ID:
- ivo://CDS.VizieR/J/AJ/119/1824
- Title:
- Caby photometry of {Omega} Centauri
- Short Name:
- J/AJ/119/1824
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new measurements of the metallicity of 131 RR Lyrae stars in the globular cluster {omega} Centauri, using the hk index of the Caby photometric system. The hk method has distinct advantages over {delta}S and other techniques in determining the metallicity of RR Lyrae stars and has allowed us to obtain the most complete and homogeneous metallicity data to date for the RR Lyrae stars in this cluster. For RR Lyrae stars in common with the {delta}S observations of Butler, Dickens, & Epps (1978ApJ...225..148B) and Gratton, Tornambe, & Ortolani (1986A&A...169..111G), we have found that our metallicities, [Fe/H]_hk_, deviate systematically from their {delta}S metallicity, while our [Fe/H]_hk_ for well-observed, field RR_ab_ stars are consistent with previous spectroscopic measurements.
- ID:
- ivo://CDS.VizieR/J/ApJ/816/L4
- Title:
- Candidate BHB stars in Ophiuchus stream
- Short Name:
- J/ApJ/816/L4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Ophiuchus stellar stream presents a dynamical puzzle: its old stellar populations (~12Gyr) cannot be reconciled with (1) its orbit in a simple model for the Milky Way potential and (2) its short angular extent, both of which imply that the observed stream formed within the last <1Gyr. Recent theoretical work has shown that streams on chaotic orbits may abruptly fan out near their apparent ends; stars in these fans are dispersed in both position and velocity and may be difficult to associate with the stream. Here we present the first evidence of such stream-fanning in the Ophiuchus stream, traced by four blue horizontal branch stars beyond the apparent end of the stream. These stars stand out from the background by their high velocities (v_los_>230km/s) against ~40 other stars: their velocities are comparable to those of the stream, but would be exceptional if they were unrelated halo stars. Their positions and velocities are, however, inconsistent with simple extrapolation of the observed cold, high-density portion of the stream. These observations suggest that stream-fanning may be a real, observable effect and, therefore, that Ophiuchus may be on a chaotic orbit. They also show that the Ophiuchus stream is more extended and hence dynamically older than previously thought, easing the stellar population versus dynamical age tension.
- ID:
- ivo://CDS.VizieR/J/ApJS/67/461
- Title:
- Candidate field horizontal-branch stars catalog
- Short Name:
- J/ApJS/67/461
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Coordinates and brightness estimates are presented for 4408 candidate field horizontal-branch stars selected using an objective-prism, interference-filter survey technique. The candidates lie primarily in the southern Galactic hemisphere, and are distributed in color over the range B-V from -0.2 to 0.40. Previous spectroscopic observation of a subset of these candidates indicates that roughly 85 percent of the catalog objects are bona fide members of the field blue horizontal branch. The remaining candidates include, in order of frequency, stars with main-sequence gravity which are likely to be a mix of metal-deficient turnoff stars and field blue stragglers, metallic line (Am) stars, A stars of near-solar metallicity, and high-luminosity or binary stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/161/147
- Title:
- Catalog of FHB stars aligned with HVCs
- Short Name:
- J/ApJS/161/147
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 430 field horizontal branch (FHB) stars, selected from the Hamburg/ESO Survey (HES), which fortuitously align with high column density neutral hydrogen (HI) high-velocity cloud (HVC) gas. These stars are ideal candidates for absorption-line studies of HVCs, attempts at which have been made for almost 40 years with little success. A parent sample of 8321 HES FHB stars (Christlieb et al., 2005, Cat. <J/A+A/431/143>) was used to extract HI spectra along each line of sight, using the HI Parkes All-Sky Survey (Putman et al., 2002, Cat. <J/AJ/123/873>). All lines of sight aligned with high-velocity HI emission with peak brightness temperatures greater than 120mK were examined. The HI spectra of these 430 probes were visually screened and cross-referenced with several HVC catalogs.
- ID:
- ivo://CDS.VizieR/J/A+A/654/A107
- Title:
- Catalogues of Blue Horizontal Branch Stars
- Short Name:
- J/A+A/654/A107
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Blue horizontal-branch stars evolve from low-mass stars that have completed their main-sequence lifetimes and undergone a helium flash at the end of their red-giant phase. As such, blue horizontal-branch stars are very old objects that can be used as markers in studies of the Galactic structure and formation history. To create a clean sky catalogue of blue horizontal-branch stars, we cross-matched the Gaia data release 2 (DR2) dataset with existing reference catalogues to define selection criteria based on Gaia DR2parameters. Following the publication of Gaia early data release 3 (EDR3), these methods were verified and subsequently applied to this latest release. Previous catalogues of blue horizontal-branch stars were developed using spectral analyses or were restricted to individual globular clusters. The purpose of this catalogue is to identify a set of blue horizontal-branch star candidates that have been selected using photometric and astrometric observations and exhibits a low contamination rate. This has been deemed important as the success of the Gaia mission has changed the way that targets are selected for large-scale spectroscopic surveys, meaning that far fewer spectra will be acquired for blue horizontal-branch stars in the future unless they are specifically targeted. We cross-matched reference blue horizontal-branch datasets with the Gaia DR2 database and defined two sets of selection criteria. Firstly, in Gaia DR2 - colour and absolute G magnitude space, and secondly, in Gaia DR2 - colour and reduced proper motion space. The main-sequence contamination in both subsets of the catalogue was reduced, at the expense of completeness, by concentrating on the Milky Way's Galactic halo, where relatively young main-sequence stars were not expected. The entire catalogue is limited to those stars with no apparent neighbours within 5 arcsec. These methods were verified and subsequently applied to theGaia Early Data Release 3 (EDR3). We present a catalogue, based on Gaia EDR3, of 57377 blue horizontal-branch stars. The Gaia EDR3 parallax was used in selecting 16794 candidates and the proper motions were used to identify a further 40583 candidates.
- ID:
- ivo://CDS.VizieR/J/ApJS/197/29
- Title:
- Chemical compositions of 11 RR Lyrae
- Short Name:
- J/ApJS/197/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed abundance study of 11 RR Lyrae ab-type variables: AS Vir, BS Aps, CD Vel, DT Hya, RV Oct, TY Gru, UV Oct, V1645 Sgr, WY Ant, XZ Aps, and Z Mic. High-resolution and high signal-to-noise ratio echelle spectra of these variables were obtained with the 2.5m du Pont telescope at the Las Campanas Observatory. We obtained more than 2300 spectra, roughly 200 spectra per star, distributed more or less uniformly throughout the pulsational cycles. A new method has been developed to obtain the initial effective temperatures of our sample stars at a specific pulsational phase. We find that the abundance ratios are generally consistent with those of similar metallicity field stars in different evolutionary states and throughout the pulsational cycles for RR Lyrae stars. TY Gru remains the only n-capture enriched star among the RRab in our sample.
- ID:
- ivo://CDS.VizieR/J/A+A/371/579
- Title:
- Empirical relations for cluster RR Lyrae
- Short Name:
- J/A+A/371/579
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Our former study on the empirical relations between the Fourier parameters of the light curves of the fundamental mode RR Lyrae stars and their basic stellar parameters has been extended to considerably larger data sets. The most significant contribution to the absolute magnitude M_V_ comes from the period P and from the first Fourier amplitude A_1_, but there are statistically significant contributions also from additional higher order components, most importantly from A_3_ and in a lesser degree from the Fourier phase phi_51_. When different colors are combined in reddening-free quantities, we obtain basically period-luminosity-color relations. From the standard deviations of the various regressions, an upper limit can be obtained on the overall inhomogeneity of the reddening in the individual clusters. This yields {sigma}_E(B-V)_<0.012mag, which also implies an average minimum observational error of {sigma}_V_>0.018mag.
- ID:
- ivo://CDS.VizieR/J/A+AS/107/445
- Title:
- Envelopes of oxygen-rich AGB stars
- Short Name:
- J/A+AS/107/445
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- (no description available)
- ID:
- ivo://CDS.VizieR/J/AJ/132/85
- Title:
- Equivalent width of 33 metal-poor RHB
- Short Name:
- J/AJ/132/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted spectrum analyses of 24 field metal-poor ([Fe/H]<-2) red horizontal-branch (RHB) stars identified in the HK objective-prism survey and 6 such stars in the globular cluster M15, based on high-quality spectra (R~40000, S/N~100) obtained with the Magellan Inamori Kyocera Echelle spectrograph at the Clay 6.5m telescope at Las Campanas Observatory. The atmospheric parameters of the RHB stars provide interesting bridges between turnoff stars of similar temperature and red giant branch (RGB) stars of similar gravity, and they permit investigations of abundance trends [X/Fe] versus [Fe/H] in a relatively unexplored region of the temperature-gravity plane. We find that the Teff, logg, vt, and [Fe/H] values determined from our spectra are consistent with expectations from literature spectroscopic studies of other evolved metal-poor stellar classes.
