- ID:
- ivo://CDS.VizieR/J/A+A/594/A79
- Title:
- NGC 6121 turnoff and subgiant stars abundances
- Short Name:
- J/A+A/594/A79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The stellar abundances observed in globular clusters show complex structures, currently not yet understood. The aim of this work is to investigate the relations between the abundances of different elements in the globular cluster M4, selected for its uniform deficiency of iron, to explore the best models explaining the pattern of these observed abundances. Moreover, in turnoff stars, the abundances of the elements are not suspected to be affected by internal mixing. In M4, using low and moderate resolution spectra obtained for 91 turnoff (and subgiant) stars with the ESO FLAMESGiraffe spectrograph, we have extended previous measurements of abundances (of Li, C and Na) to other elements (C, Si, Ca, Sr and Ba), using model atmosphere analysis. We have also studied the influence of the choice of the microturbulent velocity. Firstly, the peculiar turnoff star found to be very Li-rich in a previous paper does not show any other abundance anomalies relative to the other turnoff stars inM4. Secondly, an anti-correlation between C and Na has been detected, the slope being significative at more than 3{sigma}. This relation between C and Na is in perfect agreement with the relation found in giant stars selected below the RGB bump. Thirdly, the strong enrichment of Si and of the neutron-capture elements Sr and Ba, already observed in the giants in M4, is confirmed. Finally, the relations between Li, C, Na, Sr and Ba constrain the enrichment processes of the observed stars. The abundances of the elements in the turnoff stars appear to be compatible with production processes by massive AGBs, but are also compatible with the production of second generation elements (like Na) and low Li produced by, for example, fast rotating massive stars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/141/81
- Title:
- NGC 2419 variable star population
- Short Name:
- J/AJ/141/81
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present B, V, and I CCD light curves for 101 variable stars belonging to the globular cluster NGC 2419, 60 of which are new discoveries, based on data sets obtained at the Telescopio Nazionale Galileo, the Subaru telescope, and the Hubble Space Telescope. The sample includes 75 RR Lyrae stars (38 RRab, 36 RRc, and one RRd), one Population II Cepheid, 12 SX Phoenicis variables, two delta Scuti stars, three binary systems, five long-period variables, and three variables of uncertain classification.
- ID:
- ivo://CDS.VizieR/J/AcA/66/31
- Title:
- NGC 3201 variable stars in NGC 3201
- Short Name:
- J/AcA/66/31
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The field of the globular cluster NGC 3201 was monitored between 1998 and 2009 in a search for variable stars. BV light curves were obtained for 152 periodic or likely periodic variables, fifty-seven of which are new detections. Thirty-seven newly detected variables are proper motion members of the cluster. Among them we found seven detached or semi-detached eclipsing binaries, four contact binaries, and eight SX Phe pulsators. Four of the eclipsing binaries are located in the turnoff region, one on the lower main sequence and the remaining two slightly above the subgiant branch. Two contact systems are blue stragglers, and another two reside in the turnoff region. In the blue straggler region a total of 266 objects were found, of which 140 are proper motion (PM) members of NGC 3201, and another nineteen are field stars. Seventy-eight of the remaining objects for which we do not have PM data are located within the half-light radius from the center of the cluster, and most of them are likely genuine blue stragglers. Four variable objects in our field of view were found to coincide with X-ray sources: three chromospherically active stars and a quasar at a redshift z~~0.5.
- ID:
- ivo://CDS.VizieR/J/MNRAS/499/4026
- Title:
- NGC 6254 variable stars VI light curves
- Short Name:
- J/MNRAS/499/4026
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Time-series VI CCD photometry of the globular cluster M10 (NGC 6254) is employed to perform a detailed identification, inspection of their light curves, their classification and their cluster membership, of all the known variables reported up to 2018. The membership analysis is based on the Gaia-DR2 positions and proper motions. The metallicity of the cluster is estimated based on the sole RRc star known in the cluster. The Fourier decomposition of its light curve leads to [Fe/H]_ZW_=-1.59+/-0.23dex. The mean cluster distance, estimated by several independent methods is 5.0+/-0.3kpc. A multi-approach search in a region of about 10x10arcmin^2^ around the cluster revealed three new variables, one SX Phe (V35) and two sinusoidal variables on the red giant branch of unclear classification (V36,V37). Modelling the HB stars is very sensitive to the stellar hydrogen shell mass, which surrounds the 0.50M_{sun}_ helium core. To match the full stretch of the HB population, a range of total mass of 0.56 to 0.62M_{sun}_ is required. These models support a distance of 5.35kpc and an age of about 13Gyrs, and hints to some individual variation of the mass loss on the upper RGB, perhaps caused by the presence of closed magnetic field in red giants.
- ID:
- ivo://CDS.VizieR/J/MNRAS/493/1996
- Title:
- NGC 6712 variable stars VI light curves
- Short Name:
- J/MNRAS/493/1996
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of VI CCD time-series photometry of globular cluster NGC 6712. Our main goal is to study the variable star population as indicators of the cluster mean physical parameters. We employed the Fourier decomposition of RR Lyrae light curves to confirm that [Fe/H]_UVES_=-1.0+/-0.05 is a solid estimate. We estimated the reddening to the cluster as E(B-V)=0.35+/-0.04 from the RRab stars colour curves. The distance to the cluster was estimated using three independent methods which yielded a weighted mean distance <d>=8.1+/-0.2kpc. The distribution of RRab and RRc stars on the horizontal branch shows a clear segregation around the first overtone red edge of the instability strip, which seems to be a common feature in OoI-type cluster with a very red horizontal branch. We carried out a membership analysis of 60447 stars in our field of view (FoV) using the data from Gaia-DR2 and found 1529 likely members; we possess the light curves of 1100 among the member stars. This allowed us to produce a clean colour-magnitude diagram, consistent with an age of 12Gyr, and enabled us to discover close unresolved contaminants for several variable stars. From the proper motion analysis, we found evidence of non-member stars in the FoV of the cluster being tidally affected by the gravitational pull of the bulge of the Galaxy. We found that the RRab variable V6, shows a previously undetected Blazhko effect. Finally, we report 16 new variables of the EW-type (9) and SR-type (7).
- ID:
- ivo://CDS.VizieR/J/other/RMxAA/55.337
- Title:
- NGC 1261 variables VI light curves
- Short Name:
- J/other/RMxAA/55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Time-series VI CCD photometry of the globular cluster NGC 1261 is employed to study its variable star population. A membership analysis of most variables based on Gaia DR2 proper motions and colours was performed prior to the estimation of the mean cluster distance and metallicity. The light curves of the member RR Lyrae were Fourier decomposed to calculate their individual values of distance, [Fe/H], radius and mass. The I-band P-L for RR Lyrae stars was also employed. Our best estimates of the metallicity and distance of this Oo I cluster are [Fe/H]_ZW_=-1.42+/-0.05dex and d=17.2+/-0.4kpc. No mixture of fundamental and first overtone RR Lyrae stars in the either-or or bimodal region is seen in this cluster, as it seems to be the rule for Oo I clusters with a red horizontal branch. A multi-approach search in a region of about 10x10 arcmin^2^ around the cluster revealed no new variable stars within the limitations of our CCD photometry.
- ID:
- ivo://CDS.VizieR/J/MNRAS/402/226
- Title:
- NGC 5053 variables VrI light curves
- Short Name:
- J/MNRAS/402/226
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of CCD V, r and I time-series photometry of the globular cluster NGC 5053. New times of maximum light are given for the eight known RR Lyrae stars in the field of our images, and their periods are revised. Their V light curves were Fourier decomposed to estimate their physical parameters.
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/727
- Title:
- NGC 6229 variable VI light curves
- Short Name:
- J/MNRAS/452/727
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report an analysis of new V and I CCD time series photometry of the distant globular cluster NGC 6229. The principal aims were to explore the field of the cluster in search of new variables, and to Fourier decompose the RR Lyrae light curves in pursuit of physical parameters. We found 25 new variables: 10 RRab, 5 RRc, 6 SR, 1 CW, 1 SX Phe, and 2 that we were unable to classify. Secular period changes were detected and measured in some favourable cases. The classifications of some of the known variables were rectified. The Fourier decomposition of RRab and RRc light curves was used to independently estimate the mean cluster value of [Fe/H] and distance. From the RRab stars we found [Fe/H]_UVES_ =-1.31+/-0.01(statistical)+/-0.12(systematic) ([Fe/H]_ZW_=-1.42) and a distance of 30.0+/-1.5kpc, and from the RRc stars we found [Fe/H]_UVES_=-1.29+/-0.12 and a distance of 30.7+/-1.1kpc, respectively. Absolute magnitudes, radii and masses are also reported for individual RR Lyrae stars. Also discussed are the independent estimates of the cluster distance from the tip of the red giant branch, 34.9+/-2.4kpc and from the period-luminosity relation of SX Phe stars, 28.9+/-2.2kpc. The distribution of RR Lyrae stars in the horizontal branch shows a clear empirical border between stable fundamental and first overtone pulsators which has been noted in several other clusters; we interpret it as the red edge of the first overtone instability strip.
- ID:
- ivo://CDS.VizieR/J/AcA/66/307
- Title:
- NGC 362 variable V light curves
- Short Name:
- J/AcA/66/307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The field of the globular cluster NGC 362 was monitored between 1997 and 2015 in a search for variable stars. BV light curves were obtained for 151 periodic or likely periodic variable stars, over a hundred of which are new detections. Twelve newly detected variable stars are proper-motion members of the cluster: two SX Phe and two RR Lyr pulsators, one contact binary, three detached or semi-detached eclipsing binaries, and four spotted variable stars. The most interesting objects among these are the binary blue straggler V20 with an asymmetric light curve, and the 8.1d semidetached binary V24 located on the red giant branch of NGC 362, which is a Chandra X-ray source. We also provide substantial new data for 24 previously known variable stars.
- ID:
- ivo://CDS.VizieR/J/AJ/117/1313
- Title:
- NGC 6441 VI photometry
- Short Name:
- J/AJ/117/1313
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present time-series VI photometry of the metal-rich ([Fe/H]=-0.53) globular cluster NGC 6441. Our color-magnitude diagram shows that the extended blue horizontal branch seen in Hubble Space Telescope data exists in the outermost reaches of the cluster.
