- ID:
- ivo://CDS.VizieR/J/A+A/578/A128
- Title:
- VI light curves of NGC4590 variables
- Short Name:
- J/A+A/578/A128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyse 20 nights of CCD observations in the V and I bands of the globular cluster M68 (NGC 4590), using these to detect variable objects. We also obtained electron-multiplying CCD (EMCCD) observations for this cluster in order to explore its core with unprecedented spatial resolution from the ground. We reduced our data using difference image analysis, in order to achieve the best possible photometry in the crowded field of the cluster. In doing so, we showed that when dealing with identical networked telescopes, a reference image from any telescope may be used to reduce data from any other telescope, which facilitates the analysis significantly. We then used our light curves to estimate the properties of the RR Lyrae (RRL) stars in M68 through Fourier decomposition and empirical relations. The variable star properties then allowed us to derive the cluster's metallicity and distance. M68 had 45 previously confirmed variables, including 42 RRL and 2 SX Phoenicis (SX Phe) stars. In this paper we determine new periods, and search for new variables, especially in the core of the cluster where our method performs particularly well. We detect an additional 4 SX Phe stars, and confirm the variability of another star, bringing the total number of confirmed variable stars in this cluster to 50. We also used archival data stretching back to 1951 in order to derive period changes for some of the single-mode RRL stars, and analyse the significant number of double-mode RRL stars in M68. Furthermore, we find evidence for double-mode pulsation in one of the SX Phe stars in this cluster. Using the different classes of variables, we derived values for the metallicity of the cluster of [Fe/H]=-2.07+/-0.06 on the ZW scale, or -2.20+/-0.10 on the UVES scale, and found true distance moduli 15.00 +/- 0.11 mag (using RR0 stars), 15.00+/-0.05mag (using RR1 stars), 14.97+/-0.11mag (using SX Phe stars), and 15.00+/-0.07mag (using the M_V_-[Fe/H] relation for RRL stars), corresponding to physical distances of 10.00+/-0.49, 9.99+/-0.21, 9.84+/-0.50 and 10.00+/-0.30kpc, respectively. Thanks to the first use of difference image analysis on time-series observations of M68, we are now confident that we have a complete census of the RRL stars in this cluster.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/765/71
- Title:
- VI light curves of RRL stars in M31
- Short Name:
- J/ApJ/765/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first evidence that Oosterhoff type II globular clusters exist in the Andromeda galaxy (M31). On the basis of time-series photometry of the moderately metal-poor ([Fe/H]~-1.6dex) M31 globular cluster G11, obtained with the Wide Field Planetary Camera 2 on board the Hubble Space Telescope, we detected and derived periods for 14 RR Lyrae stars, of which five are found to lie inside the cluster tidal radius. They include three fundamental-mode (RRab) and two first-overtone (RRc) pulsators, with average periods <P_ab_>=0.70 days, and <P_c_>=0.40 days, respectively. These mean periods and the position of the cluster variable stars in the period-amplitude and period-metallicity diagrams all suggest that G11 is likely to be an Oosterhoff type II globular cluster. This appears to be in agreement with the general behavior of Milky Way globular clusters with similar metallicity and horizontal branch morphology.
- ID:
- ivo://CDS.VizieR/J/AJ/126/2954
- Title:
- VI light curves of Sand 986 in M67
- Short Name:
- J/AJ/126/2954
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have discovered that the star S986 in the old open cluster M67 has detectable total eclipses of depth 0.08mag for the primary eclipse and 0.011mag for the secondary eclipse (in I only). We confirm the detection of a third star in spectra contributing (11.5+/-1.5)% of the total light in V band. The radial velocity of the third star indicates that it is a cluster member, but it is unclear whether it is physically associated with the eclipsing binary.
- ID:
- ivo://CDS.VizieR/J/AcA/66/131
- Title:
- VI light curves of SMC and LMC RR Lyrae
- Short Name:
- J/AcA/66/131
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We present the largest collection of RR Lyrae stars in the Magellanic System and in its foreground. The sample consists of 45451 RR Lyr stars, of which 39082 were detected toward the Large Magellanic Cloud and 6369 toward the Small Magellanic Cloud. We provide long-term time-series photometric measurements collected during the fourth phase of the Optical Gravitational Lensing Experiment (OGLE-IV). We discuss several potential astrophysical applications of our collection: investigation of the structure of the Magellanic Clouds and the Galactic halo, studies of the globular clusters in the Magellanic System, analysis of double-mode RR Lyr stars, and search for RR Lyr stars in eclipsing binary systems.
- ID:
- ivo://CDS.VizieR/J/AcA/60/17
- Title:
- VI light curves of SMC classical Cepheids
- Short Name:
- J/AcA/60/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The seventh part of the OGLE-III Catalog of Variable Stars (OIII-CVS) consists of 4630 classical Cepheids in the Small Magellanic Cloud (SMC). The sample includes 2626 fundamental-mode (F), 1644 first-overtone (1O), 83 second-overtone (2O), 59 double-mode F/1O, 215 double-mode 1O/2O, and three triple-mode classical Cepheids. For each object basic parameters, multi-epoch VI photometry collected within 8 or 13 years of observations, and finding charts are provided in the OGLE Internet archive.
- ID:
- ivo://CDS.VizieR/J/AcA/61/217
- Title:
- VI light curves of SMC long-period variables
- Short Name:
- J/AcA/61/217
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The thirteenth part of the OGLE-III Catalog of Variable Stars (OIII-CVS) contains 19 384 long-period variables (LPVs) detected in the Small Magellanic Cloud. The sample is composed of 352 Mira stars, 2222 semiregular variables (SRVs) and 16 810 OGLE Small Amplitude Red Giants (OSARGs). Sources are divided into oxygen-rich and carbon-rich stars. The catalog includes time-series VI photometry obtained between 1997 and 2009.
- ID:
- ivo://CDS.VizieR/J/AcA/60/165
- Title:
- VI light curves of SMC RR Lyrae
- Short Name:
- J/AcA/60/165
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The ninth part of the OGLE-III Catalog of Variable Stars (OIII-CVS) comprises RR Lyr stars in the Small Magellanic Cloud (SMC). Our sample consists of 2475 variable stars, of which 1933 pulsate in the fundamental mode (RRab), 175 are the first overtone pulsators (RRc), 258 oscillate simultaneously in both modes (RRd) and 109 stars are suspected second-overtone pulsators (RRe). 30 objects are Galactic RR Lyr stars seen in the foreground of the SMC.
- ID:
- ivo://CDS.VizieR/J/AcA/60/91
- Title:
- VI light curves of SMC type II Cepheids
- Short Name:
- J/AcA/60/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The eighth part of the OGLE-III Catalog of Variable Stars (OIII-CVS) contains type II Cepheids in the Small Magellanic Cloud (SMC). The sample consists of 43 objects, including 17 BL Her, 17 W Vir and 9 RV Tau stars (first examples ever found in the SMC). Seven stars have been classified as peculiar W Vir stars - a recently identified subclass of type II Cepheids. These stars have distinctive light curves, are brighter and bluer than the ordinary W Vir variables. We confirm that a large fraction of the peculiar W Vir stars are members of binary systems.
- ID:
- ivo://CDS.VizieR/J/A+A/398/541
- Title:
- VI light-curves of the variable stars in M13
- Short Name:
- J/A+A/398/541
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- VI light-curves of variable stars in the globular cluster M13 are presented. They are based on the CCD observations carried out at the Bialkow station of the Wroclaw University Observatory using 60-cm reflecting telescope and the CCD camera. A 6x4 arcmin-squared field of view covering the core of the cluster was observed through V and I_C filters of the Johnson-Kron-Cousins UBV(RI)_C system. About 300 frames in both filters were taken during 23 nights between 2001 February 27 and August 1. The CCD images were analyzed with the DAOPHOT profile-fitting software and Image Subtraction Method. The main result of this study is discovery of five RR Lyrae and one SX Poenicis stars. Moreover we detect non-radial pulsations in RRc star v36. We also comment the variability of all observed suspected variable stars in M13.
- ID:
- ivo://CDS.VizieR/J/A+A/369/862
- Title:
- VI light curves of the variable stars in M92
- Short Name:
- J/A+A/369/862
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results of a search for variable stars in the central region of the Oosterhoff II type globular cluster M 92 are presented. Out of the 28 variable and suspected variable stars listed in the Catalogue of Variable Stars in Globular Clusters (Clement, 1997, Cat. <V/97>) only two were not observed. Surprisingly, almost half of the observed suspected variables did not show any evidence of variability. Only one out of the 11 candidate RR Lyrae variables of Kadla et al. (1983PZ.....21..827K) appeared to be variable. Moreover, variable V7, until now classified as an RR Lyrae star with a period of about 0.515d, turned out to be of the BL Herculis type, with the period approximately twice that long. In addition, six new variables were found in the very core of the cluster: four of the RR Lyrae and the remaining two of the SX Phoenicis type. RRc variable V11 shows changes in the light curve shape. Due to the aliasing problems, however, we can state only that this star is biperiodic. There is a possibility that V11 belongs to the new group of recently discovered double-period RRc variables pulsating in non-radial mode. Altogether, light curves were obtained for 20 variable stars. The total number of known RR Lyrae stars in M92 equals now 17, 11 of type RRab and the remaining 6, RRc. The CCD observations presented here were carried out at the Bialkow station of the Wroclaw University Observatory with the same equipment as that described by Kopacki & Pigulski (1995AcA....45..753K). Two 6x4arcmin^2^ fields of view, one centred approximately on the core of M92 and the other shifted about 2.5arcmin north and 2.6arcmin east, were observed through V and I_c_ filters of the Johnson-Kron-Cousins UBV(RI)_c_ system. The observations were carried out in two seasons: on 9 nights between 1998 July 20 and September 1, and on 17 nights between 2000 May 4 and June 20. During the 1998 season only a few frames of the second field were taken. The main field, centred on the core of the cluster, was observed during both seasons.
