- ID:
- ivo://CDS.VizieR/J/AJ/138/1310
- Title:
- Variable stars in NGC 2257. I.
- Short Name:
- J/AJ/138/1310
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The variable stars in the Large Magellanic Cloud star cluster NGC 2257 are reinvestigated using photometry (to ~20th mag) of over 400 new B, V CCD images taken with the CTIO 0.9m telescope on 14 nights in 2007 December and 2008 January. New period searches have been made using two independent algorithms (CLEAN, Period04); the resultant periods of most of the stars are consistent with the pulsation periods derived previously, and where there are discrepancies these have been resolved. For the B and V light curves, accurate Fourier coefficients and parameters are given. Six new variable stars have been discovered (V45-50), including a bright candidate long-period variable star showing secondary oscillations (V45) and two anomalously bright RRc stars (V48 and V50), which are shown to be brightened and reddened by nearby red giant stars. Also discovered among the previously known variable stars are three double-mode RR Lyrae stars (V8, V16, and V34) and several Blazhko variables. Archival Hubble Space Telescope images and the photometry by Johnson et al. (Cat. J/ApJ/527/199) have been used to define better the properties of the most crowded variable stars. The total number of cluster variable stars now stands at forty-seven: 23 RRab stars, four of which show Blazhko amplitude variations; 20 RRc stars, one showing clear Blazhko variations and another showing possible Blazhko variations; the three RRd stars, all having the dominant period ~0.36 day and period ratios P1/P0 ~0.7450; and an LPV star located near the tip of the red giant branch. A comparison of the RRd stars with those in other environments shows them to be most similar to those in IC4499.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/416/2265
- Title:
- Variable stars in NGC 5024 (M53)
- Short Name:
- J/MNRAS/416/2265
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report CCD V and I time series photometry of the globular cluster NGC 5024 (M53). The technique of difference image analysis has been used which enables photometric precisions better than 10mmag for stars brighter than V~18.5mag even in the crowded central regions of the cluster. The high photometric precision has resulted in the discovery of two new RR1 stars and 13 SX Phe stars. A detailed identification chart is given for all the variable stars in the field of our images of the cluster. Periodicities were calculated for all RR Lyrae and SX Phe stars and a critical comparison is made with previous determinations.
- ID:
- ivo://CDS.VizieR/J/MNRAS/424/2722
- Title:
- Variable stars in NGC 5024 (M53)
- Short Name:
- J/MNRAS/424/2722
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed a careful investigation of the 74 candidate variable stars presented by Safonova & Stalin (2011AJ....142..179S) . For this purpose we used our data base of imaging and light curves from Arellano Ferro et al. (J/MNRAS/416/2265 and J/MNRAS/420/1333). We find that two candidates are known variable stars, eight candidates were discovered first by Arellano Ferro et al. (J/MNRAS/416/2265), but would not have been known to Safonova & Stalin (2011AJ....142..179S) at the time of their paper submission, while four candidates are new variables. Three of the new variables are SX Phe type and one is a semiregular (SR) type red giant variable. We also tentatively confirm the presence of true variability in two other candidates, and we are unable to investigate another four candidates because they are not in our data base. However, we find that the remaining 54 candidate variable stars are spurious detections where systematic trends in the light curves have been mistaken for true variability. We believe that the erroneous detections are caused by the adoption of a very low detection threshold used to identify these candidates.
- ID:
- ivo://CDS.VizieR/J/A+A/424/1101
- Title:
- Variable Stars in the field of {omega} Cen
- Short Name:
- J/A+A/424/1101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a photometric survey for variable stars in the field of the globular cluster Omega Centauri. The observed region was centered roughly on the cluster core and covered 644arcmin^2^. The cluster was monitored on 59 nights in 1999 and 2000. A total of 117 new variables were identified. Among them there are 16 RR Lyr-type stars, 35 SX Phe variables and 26 eclipsing binaries. A comprehensive catalog including all variable stars so far reported from the cluster field is presented. We list basic photometric properties and provide finding charts for a total of 392 objects. For 313 of them new BV light curves were obtained. The presented sample includes several interesting variables, such as SX Phe stars with extremely short periods of pulsation and several candidates for pulsating K giants. Optical counterparts to 9 X-ray sources detected by XMM and Chandra telescopes were identified: all of them are likely to be foreground variables not related to the cluster.
- ID:
- ivo://CDS.VizieR/J/ApJ/837/54
- Title:
- Variable stars in the globular cluster DDO 216-A1
- Short Name:
- J/ApJ/837/54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We confirm that the object DDO 216-A1 is a substantial globular cluster at the center of Local Group galaxy DDO 216 (the Pegasus dwarf irregular), using Hubble Space Telescope ACS imaging. By fitting isochrones, we find the cluster metallicity [M/H]=-1.6+/-0.2, for reddening E(B-V)=0.16+/-0.02; the best-fit age is 12.3+/-0.8Gyr. There are ~30 RR Lyrae variables in the cluster; the magnitude of the fundamental mode pulsators gives a distance modulus of 24.77+/-0.08 --identical to the host galaxy. The ratio of overtone to fundamental mode variables and their mean periods make DDO 216-A1 an Oosterhoff Type I cluster. We find a central surface brightness of 20.85+/-0.17 F814W mag/arcsec^2^, a half-light radius of 3.1" (13.4pc), and an absolute magnitude M814=-7.90+/-0.16 (M/M_{sun}_~10^5^). King models fit to the cluster give the core radius and concentration index, r_c_=2.1"+/-0.9" and c=1.24+/-0.39. The cluster is an "extended" cluster somewhat typical of some dwarf galaxies and the outer halo of the Milky Way. The cluster is projected <~30pc south of the center of DDO 216, unusually central compared to most dwarf galaxy globular clusters. Analytical models of dynamical friction and tidal destruction suggest that it probably formed at a larger distance, up to ~1kpc, and migrated inward. DDO 216 has an unexceptional specific cluster frequency, S_N_=10. DDO 216 is the lowest-luminosity Local Group galaxy to host a 10^5^M_{sun}_ globular cluster and the only transition-type (dSph/dIrr) galaxy in the Local Group with a globular cluster.
- ID:
- ivo://CDS.VizieR/J/A+AS/128/19
- Title:
- Variable stars in 47 Tuc fields 104A-E
- Short Name:
- J/A+AS/128/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD photometry for 42 variables from the field of 47 Tuc = NGC 104 is presented. VI photometry for a large set of stars from the surveyed fields is also given.
- ID:
- ivo://CDS.VizieR/J/A+A/651/A47
- Title:
- Variable stars in VVV globulars. II.
- Short Name:
- J/A+A/651/A47
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- The Galactic globular clusters (GGCs) located in the inner regions of the Milky Way suffer from high extinction that makes their observation challenging. High densities of field stars in their surroundings complicate their study even more. The VISTA Variables in the Via Lactea (VVV) survey provides a way to explore these GGCs in the near-infrared where extinction effects are highly diminished. We conduct a search for variable stars in several inner GGCs, taking advantage of the unique multi-epoch, wide-field, near-infrared photometry provided by the VVV survey. We are especially interested in detecting classical pulsators that will help us constrain the physical parameters of these GGCs. In this paper, the second of a series, we focus on NGC 6656 (M 22), NGC 6626 (M 28), NGC 6569, and NGC 6441; these four massive GGCs have known variable sources, but quite different metallicities. We also revisit 2MASS-GC 02 and Terzan 10, the two GGCs studied in the first paper of this series. We present an improved method and a new parameter that efficiently identify variable candidates in the GGCs. We also use the proper motions of those detected variable candidates and their positions in the sky and in the color-magnitude diagrams to assign membership to the GGCs. We identify and parametrize in the near-infrared numerous variable sources in the studied GGCs, cataloging tens of previously undetected variable stars. We recover many known classical pulsators in these clusters, including the vast majority of their fundamental mode RR Lyrae. We use these pulsators to obtain distances and extinctions toward these objects. Recalibrated period-luminosity-metallicity relations for the RR Lyrae bring the distances to these GGCs to a closer agreement with those reported by Gaia, except for NGC 6441, which is an uncommon Oosterhoff III GGC. Recovered proper motions for these GGCs also agree with those reported by Gaia, except for 2MASS-GC 02, the most reddened GGC in our sample, where the VVV near-infrared measurements provide a more accurate determination of its proper motions.
- ID:
- ivo://CDS.VizieR/J/AcA/63/91
- Title:
- V-band light curves of variables in M80
- Short Name:
- J/AcA/63/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a search for variable stars in the globular cluster M 80. Application of the image subtraction method to the ground-based times-series of CCD frames resulted in finding nine new RR Lyr stars, six of the RRc and three of the RRab type, and four SX Phe variables.
- ID:
- ivo://CDS.VizieR/J/AJ/127/980
- Title:
- vby and BVI photometry of Omega Cen giants
- Short Name:
- J/AJ/127/980
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained photometric observations in a 182arcmin^2 area, 25' to the north of the center of the globular cluster {omega} Centauri. The Stroemgren vby and broadband BI filters were used to obtain measurements for some 2500 stars. Preliminary examinations of parts of the data have been presented previously (Hughes & Wallerstein, 2000, Cat. <J/AJ/119/1225>; Hughes, Wallerstein, & van Leeuwen, 2002, in ASP Conf. Ser. 265, 73). Here we present the complete data set, study the giant branches, and use the B-I color index as a tool for assessing the ages of the populations within {omega} Cen.
- ID:
- ivo://CDS.VizieR/J/AJ/131/814
- Title:
- VCC 1087 globular cluster system
- Short Name:
- J/AJ/131/814
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the globular cluster (GC) system of the nucleated dwarf elliptical galaxy VCC 1087 in the Virgo Cluster based on Keck LRIS spectroscopy and archival Hubble Space Telescope Advanced Camera for Surveys imaging. We estimate that VCC 1087 hosts a total population of 77+/-19 GCs, which corresponds to a relatively high V-band specific frequency of 5.8+/-1.4. The g_475_-z_850_ color distribution of the GCs shows a blue (metal-poor) peak with a tail of redder (metal-rich) clusters similar in color to those seen in luminous elliptical galaxies.
