- 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.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/426/1475
- Title:
- CaT in 903 globular clusters
- Short Name:
- J/MNRAS/426/1475
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Although the colour distribution of globular clusters in massive galaxies is well known to be bimodal, the spectroscopic metallicity distribution has been measured in only a few galaxies. After redefining the calcium triplet index-metallicity relation, we use our relation to derive the metallicity of 903 globular clusters in 11 early-type galaxies. This is the largest sample of spectroscopic globular cluster metallicities yet assembled. We compare these metallicities with those derived from Lick indices finding good agreement. In six of the eight galaxies with sufficient numbers of high-quality spectra we find bimodality in the spectroscopic metallicity distribution. Our results imply that most massive early-type galaxies have bimodal metallicity as well as colour distributions. This bimodality suggests that most massive early-type galaxies experienced two periods of star formation.
- ID:
- ivo://CDS.VizieR/J/ApJS/115/185
- Title:
- 3C 390.3 BVRI and H photometry
- Short Name:
- J/ApJS/115/185
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results of a ground-based optical monitoring campaign on 3C 390.3 in 1994-1995 are presented. The broadband fluxes (B, V, R, and I), the spectrophotometric optical continuum flux F_{lambda}_(5177{AA}), and the integrated emission-line fluxes of H{alpha}, H{beta}, H{gamma}, He I 5876, and He II {lambda}4686 all show a nearly monotonic increase with episodes of milder short-term variations superposed. The amplitude of the continuum variations increases with decreasing wavelength (4400-9000{AA}). The optical continuum variations follow the variations in the ultraviolet and X-ray with time delays, measured from the centroids of the cross-correlation functions, typically around 5 days, but with uncertainties also typically around 5 days; zero time delay between the high-energy and low-energy continuum variations cannot be ruled out. The strong optical emission lines H{alpha}, H{beta}, H{gamma}, and He I {lambda}5876 respond to the high-energy continuum variations with time delays typically about 20 days, with uncertainties of about 8 days. There is some evidence that He II {lambda}4686 responds somewhat more rapidly, with a time delay of around 10 days, but again, the uncertainties are quite large (~8 days). The mean and rms spectra of the H{alpha} and H{beta} line profiles provide indications for the existence of at least three distinct components located at +/-4000 and 0km/s relative to the line peak. The emission-line profile variations are largest near line center.
- ID:
- ivo://CDS.VizieR/J/AJ/137/236
- Title:
- CC Com and BV Dra light curves
- Short Name:
- J/AJ/137/236
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on O-C curves, we present detailed period investigations of two weak-contact binaries CC Com and BV Dra. It is found that the periods of these two binaries have varied in a cyclic variation way superposed on a secular period change. The periods and amplitudes of the cyclic variations are P_3_=23.6(+/-0.4)yr and A=0.0028(+/-0.0003)d for CC Com and P_3_=23.8(+/-0.6)yr and A=0.0029(+/-0.0003)d for BV Dra.
- ID:
- ivo://CDS.VizieR/J/ApJ/628/729
- Title:
- CCD BVIc photometry of M10 stars
- Short Name:
- J/ApJ/628/729
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of the globular cluster M10 were taken at the Kitt Peak National Observatory (KPNO) 0.9 m telescope on the nights of UT dates 1995 May 6 and 9 using BVI filters. All frames were taken using a 2048x2048 pixel CCD with pixels covering 0.68 arcseconds on a side, for a total field of approximately 23.2 arcminutes on a side. The data were calibrated against Stetson (2000PASP..112..925S) standard stars. Additional high-resolution images were taken at the 3.6 m Canada-France-Hawaii Telescope (CFHT) on the night of UT date 1993 April 13 in BI filters. These observations used a 1200x1200 pixel CCD with pixels covering 0.11 arcseconds on a side, for a total field 2.2 arcminutes on a side, roughly centered on the cluster core. These data were calibrated against the KPNO data.
- ID:
- ivo://CDS.VizieR/J/ApJ/608/243
- Title:
- CCD BVI photometry of M12 stars
- Short Name:
- J/ApJ/608/243
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The observations were done on the nights of UT dates 1995 May 6 and 9 by using the Kitt Peak National Observatory (KPNO) 0.9 m telescope. The file contains BVI data of the globular cluster M12. All frames were taken using a 2048x2048 pixel CCD with pixels covering 0.68 arcseconds on a side, for a total field of approximately 23.2 arcminutes on a side. The data were calibrated against Stetson (2000PASP..112..925S) standard stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/365/110
- Title:
- CCD BVI photometry of 3 open clusters
- Short Name:
- J/MNRAS/365/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present BVI photometry for poorly known southern hemisphere open clusters: NGC 2425, Haffner 10 and Czernik 29. We have calculated the density profile and established the number of stars in each cluster. The colour-magnitude diagrams of the objects show a well-defined main sequence. However, the red giant clump is present only in NGC 2425 and Haffner 10. For these two clusters we estimated the age as 2.5+/-0.5Gyr assuming metallicity of Z=0.008. The apparent distance moduli are in the ranges 13.2<(m-M)_V<13.6 and 14.3<(m-M)_V<14.7, while heliocentric distances are estimated to be 2.9<d<3.8kpc and 3.1<d<4.3kpc, respectively for NGC 2425 and Haffner 10. The angular separation of 2.4deg (150pc at mean distance) may indicate a common origin of the two clusters.
- ID:
- ivo://CDS.VizieR/J/AJ/127/958
- Title:
- CCD BV photometry on Omega Cen
- Short Name:
- J/AJ/127/958
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present wide-field and high-precision BV and Ca and Stroemgren by photometry of {omega} Centauri, which represents one of the most extensive photometric surveys to date for this cluster. The member stars of {omega} Cen are well discriminated from foreground Galactic field stars in the hk[=(Ca-b)-(b-y)] versus b-y diagram. The resulting "cleaned" color-magnitude diagram (CMD) has allowed us to obtain an accurate distribution of the red horizontal-branch (HB) and the asymptotic giant branch stars.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A137
- Title:
- CCD B,V,R,I,Ha photometry of 3C120
- Short Name:
- J/A+A/620/A137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- At the Universitaetssternwarte Bochum near Cerro Armazones we have monitored the Seyfert-1 galaxy 3C 120 between September 2014 and March 2015 in BVRI and a narrow band filter covering the redshifted H{alpha} line; in addition we obtained a single con-temporary spectrum with FAST at Mt. Hopkins. Compared to earlier epochs 3C 120 is about a factor of three brighter, allowing us to study the shape of the broad line region (BLR) and the dust torus in a high luminosity phase. The analysis of the light curves yields that the dust echo is rather sharp and symmetric in contrast to the more complex broad H{alpha} BLR echo. We investigate how far this supports an optically thick bowl-shaped BLR and dust torus geometry as proposed by Kawaguchi & Mori (2010ApJ...724L.183K) and Goad et al. (2012MNRAS.426.3086G). The comparison with several parameterizations of these models supports the following geometry: the BLR clouds lie inside the bowl closely above the bowl rim, up to a half covering angle 0{deg}<theta<40{deg} (measured against the equatorial plane). Then the BLR is spread over many isodelay surfaces, yielding a smeared and structured echo as observed. Furthermore, if the BLR clouds shield the bottom of the bowl rim against radiation from the nucleus, the hot dust emission comes essentially from the top edge of the bowl (40{deg}<theta< 45{deg}). Then, for small inclinations as for 3C120, the top dust edge forms a ring which largely coincides with a narrow range of isodelay surfaces, yielding the observed sharp dust echo. The scale height of the BLR increases with radial distance from the black hole. This leads to luminosity dependent foreshortening effects of the lag. We discuss implications and possible corrections of the foreshortening for the black hole mass determination and consequences for the lag (size) - luminosity relationships and the difference to interferometric torus sizes.
- ID:
- ivo://CDS.VizieR/J/MNRAS/425/3085
- Title:
- CCD CT1 data of stars in the field of B119
- Short Name:
- J/MNRAS/425/3085
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present for the first time Washington CT_1_ photometry for 11 unstudied or poorly studied candidate star clusters. The selected objects are of small angular size, contain a handful of stars, and are projected towards the innermost regions of the Small Magellanic Cloud (SMC). The respective colour-magnitude diagrams (CMDs) were cleaned of the unavoidable star field contamination by taking advantage of a procedure which makes use of variable size CMD cells. This method has shown to be able to eliminate stochastic effects in the cluster CMDs caused by the presence of isolated bright stars, as well as to make a finer cleaning in the most populous CMD regions. Our results suggest that nearly one-third of the studied candidate star clusters would appear to be genuine physical systems.
