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- ID:
- ivo://CDS.VizieR/J/A+A/470/585
- Title:
- NGC 2682 uvby-Hbeta photometry
- Short Name:
- J/A+A/470/585
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Following deep astrometric and photometric study of the cluster NGC 2682 (M 67), we are able to accurately determine its fundamental parameters. Being an old and rich cluster, M 67 is relevant for the analysis of the Galactic disk evolution. M 67 is well studied but lacks a wide and deep Stroemgren photometric study. The brightest stars of the open cluster M 67 were used as uvby-Hbeta standard stars in our studies of NGC 1817 and NGC 2548, and the extension of the field covered, as well as the number of observations, allowed us to obtain the best set of Stroemgren data ever published for this cluster. We discuss the results of our CCD uvby-Hbeta intermediate-band photometry, covering an area of about 50'x50' down to V~19. Moreover, a complete membership segregation based on astrometric and photometric criteria is obtained. The photometric analysis of a selected sample of stars yields a reddening value of E(b-y)=0.03+/-0.03, a distance modulus of V_0_-M_V_=9.7+/-0.2 and [Fe/H]=0.01+/-0.14. Through isochrone fitting we found an age of logt=9.6+/-0.1 (4.2+/-0.2Gyr). A clump of approximately 60 stars around V=16, (b-y)=0.4 could be interpreted as a population of pre-cataclysmic variable stars (if members), or as a stream of field G-type stars placed at twice the distance of the cluster (if non-members).
- 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/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/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/419/2379
- Title:
- NGC 6866 variables V and I light curves
- Short Name:
- J/MNRAS/419/2379
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a variability search in the intermediate-age open cluster NGC 6866 from 29 nights over two observing seasons. We find 28 periodic variables, of which 19 are newly identified. The periods of these variables, which have V magnitudes from 11.5 to 19.3mag, range from ~48min to 37d. We detected several {delta} Scuti stars, some of which are of high amplitude, as well as {gamma} Doradus and rotational variables, and eclipsing binaries. In order to study the physical properties of the cluster, we obtained UBVRI photometry of all the stars on a good photometric night. The radial distribution of the stellar surface density shows that the cluster has a radial extent of about 7-arcmin ( ~3pc) with a peak density of 5.7+/-0.7stars/arcmin^2^ at the cluster centre. The colour-colour diagram indicates a reddening of E(B-V)=0.10mag towards NGC 6866. A distance of ~1.47kpc and an age of ~630Myr are estimated from the colour-magnitude diagram using the theoretical isochrones of solar metallicity.
- 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.
