- ID:
- ivo://CDS.VizieR/J/A+A/443/413
- Title:
- VIKs photometry of NGC4365 globular clusters
- Short Name:
- J/A+A/443/413
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This table lists VIKs photometry for compact objects in the giant Virgo elliptical NGC 4365. The majority of these objects are globular clusters. V and I magnitudes are measured on images taken with the FORS1 instrument on the ESO Very Large Telescope, while the K magnitudes are from the SOFI imager on the ESO New Technology Telescope. No correction for foreground extinction has been applied to the photometry in the table.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/434/1220
- Title:
- Vi light curves of NGC6333 variables
- Short Name:
- J/MNRAS/434/1220
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report CCD V and I time series photometry of the globular cluster NGC 6333 (M9). The technique of difference image analysis has been used, which enables photometric precision better than 0.05mag for stars brighter than V~19.0mag, even in the crowded central regions of the cluster. The high photometric precision has resulted in the discovery of two new RRc stars, three eclipsing binaries, seven long-term variables and one field RRab star behind the cluster. A detailed identification chart and equatorial coordinates are given for all the variable stars in the field of our images of the cluster. Our data together with the literature V-data obtained in 1994 and 1995 allowed us to refine considerably the periods for all RR Lyrae stars. The nature of the new variables is discussed. We argue that variable V12 is a cluster member and an Anomalous Cepheid. Secular period variations, double-mode pulsations and/or the Blazhko-like modulations in some RRc variables are addressed. Through the light-curve Fourier decomposition of 12 RR Lyrae stars we have calculated a mean metallicity of [Fe/H]_ZW_=-1.70+/-0.01(statistical)+/-0.14(systematic) or [Fe/H]_UVES_=-1.67+/-0.01(statistical)+/-0.19(systematic). Absolute magnitudes, radii and masses are also estimated for the RR Lyrae stars. A detailed search for SX Phe stars in the Blue Straggler region was conducted but none were discovered. If SX Phe exist in the cluster then their amplitudes must be smaller than the detection limit of our photometry. The colour-magnitude diagram has been corrected for heavy differential reddening using the detailed extinction map of the cluster of Alonso-Garcia et al. (2012, Cat. J/AJ/143/70). This has allowed us to set the mean cluster distance from two independent estimates; from the RRab and RRc absolute magnitudes, we find 8.04+/-0.19 and 7.88+/-0.30kpc, respectively.
- 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.
- 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/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.
- ID:
- ivo://CDS.VizieR/J/AcA/63/429
- Title:
- VI light curves of 10 variables in NGC288
- Short Name:
- J/AcA/63/429
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A search for variable stars in the globular cluster NGC 288 was carried out using a time-series of CCD images in the V and I filters. The photometry of all stellar sources in the field of view of our images, down to V~19mag, was performed using difference image analysis (DIA). For stars of~15mag, measurement accuracies of ~8mmag and ~10mmag were achieved for V and I respectively. Three independent search strategies were applied to the 5525 light curves but no new variables were found above the threshold limits characteristic of our data set. The use of older data from the literature combined with the present data allowed the refinement of the periods of all known variables. Fourier light curve decomposition was performed for the RRab and the RRc stars to obtain an estimate of [Fe/H]_ZW_=-1.62+/-0.02 (statistical) +/-0.14 (systematic). A true distance modulus of 14.768+/-0.003mag (statistical) +/-0.042mag (systematic), or a distance of 8.99+/-0.01kpc (statistical) +/-0.17kpc (systematic) was calculated from the RRab star. The RRc star predicts a discrepant distance about one kiloparsec shorter but it is possibly a Blazhko variable. An independent distance from the P-L relationship for SX Phe stars leads to a distance of 8.9+/-0.3kpc. The SX Phe stars V5 and V9 are found to be double mode pulsators.
- ID:
- ivo://CDS.VizieR/J/A+A/458/767
- Title:
- Vilnius photometry on M92
- Short Name:
- J/A+A/458/767
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD observations of the northern globular cluster M 92 were obtained in the PXYVS colors of the Vilnius photometric system. The results for 230 stars in an area centered on the cluster and for 178 stars in an area west of the cluster down to V=17.0mag are presented. After a brief outline of the data pathway from observations to reduction via IRAF and a discussion of the photometric errors, the [Fe/H] ratio of the globular cluster M 92 is determined by multicolor PXYVS Vilnius photometry.
- ID:
- ivo://CDS.VizieR/J/AJ/123/279
- Title:
- VI Photometry and Variables in NGC 3201
- Short Name:
- J/AJ/123/279
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Globular Cluster NGC 3201 was monitored for the existence of variable stars with 16.5<V<20 and 0.2days<period<5days. The files v*.dat contain time-series photometry data in V and I for the 14 variables detected in the field of NGC 3201. Only V6 (a blue straggler contact binary) is a member of the cluster. Due to its low-latitude position, interstellar extinction is present across the field of the cluster. The file phot.dat contains VI photometry data on the monitored stars. These data are NOT corrected for extinction. The variables V7, V8, and V9 were discovered during a follow-up observing run with a different telescope and therefore do not lie in the field covered by phot.dat. Variables V1-V9 are contact system eclipsing binaries, V10 is an RR Lyrae, V11 a semi-detached Algol type binary, V12 a detached binary system, and V13 and V14 are unclassified variable systems.
- ID:
- ivo://CDS.VizieR/J/A+A/533/A36
- Title:
- VI photometry and velocity map of NGC 6388
- Short Name:
- J/A+A/533/A36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from ground based VLT/FLAMES spectroscopy in combination with HST data for the globular cluster NGC 6388. The aim of this work is to probe whether this massive cluster hosts an intermediate-mass black hole at its center and to compare the results with the expected value predicted by the M-{sigma} scaling relation.
