- 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.
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Search Results
- 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/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/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/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/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/BaltA/14/1
- Title:
- Vilnius photometry in a Cam area
- Short Name:
- J/BaltA/14/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The paper gives the results of seven-color CCD photometry in the Vilnius system of 1376 stars down to 15.5mag in the area of the Galactic equator (l=146{deg}, b=+2.6{deg}) in Camelopardalis. Photometric spectral and luminosity classes, interstellar extinctions and distances of the stars are determined.
- ID:
- ivo://CDS.VizieR/J/BaltA/13/555
- Title:
- Vilnius photometry in NGC 2395
- Short Name:
- J/BaltA/13/555
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The area of the open cluster NGC 2395 in Gemini is investigated by CCD photometry in the Vilnius seven-color system. Magnitudes, color indices, photometric spectral types, color excesses, interstellar extinctions and distances are determined for the 163 stars down to V=15.75mag in the 25' diameter area.
- ID:
- ivo://CDS.VizieR/J/A+A/590/A21
- Title:
- Vilnius photometry near Sh 2-205
- Short Name:
- J/A+A/590/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of CCD photometry in the seven-color Vilnius system for 302 stars in the 12x12 arcmin area in the vicinity of the dark cloud TGU H942 P7. Observational data were obtained in 2015-2016 with the 1.8m VATT telescope of the Vatican observatory on Mt Graham, Arizona. Using the Koenig & Leisawitz (2014ApJ...791..131K) classification scheme we identified 88 YSOs in this area. The majority of them are concentrated in dust clump P7 and the infrared cluster FSR 655. The other compact group of YSOs is located at RA=03:54:56, DEC=+53:45. These stars are probably members of small infrared cluster which we call SCB1.
- ID:
- ivo://CDS.VizieR/J/BaltA/14/179
- Title:
- Vilnius photometry of NGC 1647 area
- Short Name:
- J/BaltA/14/179
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The area of the open cluster NGC 1647 in Taurus is investigated by CCD photometry in the Vilnius seven-color system. Magnitudes and color indices are determined for 433 stars down to V=15.0mag in the 45arcmin diameter area. For 252 of them photometric spectral and luminosity classes, interstellar reddenings, extinctions and distances are obtained. According to the CDS WEBDA database, 89 of them have a high cluster membership probability. Their mean distance from the Sun is 555+/-74pc, excluding four stars which seem to be field stars. The main sequence starts at spectral class B7 V which corresponds to a cluster age of about 150 million years. Cluster members show a differential interstellar extinction ranging from 0.8 to 1.8mag. The mean extinction of the cluster stars is 1.12+/-0.25mag. Interstellar extinction in the area is dominated by the Taurus dark cloud complex at 160pc. Color excesses of individual stars correlate well with the 100um dust thermal emission intensity. The cluster shape is investigated by counting stars down to K=15.6mag and is found to be elongated in the direction roughly perpendicular to the Milky Way, with the flattening 0.4.
