- 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.
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Search Results
- 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.
- ID:
- ivo://CDS.VizieR/J/AJ/131/2538
- Title:
- VI Photometry of globular cluster Palomar 11
- Short Name:
- J/AJ/131/2538
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new photometry for the Galactic thick-disk globular cluster Palomar 11 extending well past the main-sequence turnoff in the V and I bands.
- ID:
- ivo://CDS.VizieR/J/MNRAS/343/665
- Title:
- VI photometry of globular cluster systems
- Short Name:
- J/MNRAS/343/665
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have studied the globular cluster systems of seven giant, edge-on spiral galaxies using Hubble Space Telescope imaging in V and I. The galaxy sample covers the Hubble types Sa to Sc, allowing us to study the variation of the properties of globular cluster systems along the Hubble sequence.
- ID:
- ivo://CDS.VizieR/J/A+A/581/A13
- Title:
- VI photometry of globular ESO 37-1
- Short Name:
- J/A+A/581/A13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the Milky Way, most globular clusters are highly conspicuous objects that were found centuries ago. However, a few dozen of them are faint, sparsely populated systems that were identified largely during the second half of the past century. One of the faintest is ESO 37-1 (E 3) and as such it remains poorly studied, with no spectroscopic observations published so far although it was discovered in 1976. We investigate the globular cluster E3 in an attempt to better constrain its fundamental parameters. Spectroscopy of stars in the field of E3 is shown here for the first time. Deep, precise VI CCD photometry of E3 down to V~26mag is presented and analysed. Low-resolution, medium signal-to-noise ratio spectra of nine candidate members are studied to derive radial velocity and metallicity. Proper motions from the UCAC4 catalogue are used to explore the kinematics of the bright members of E3. Isochrone fitting indicates that E3 is probably very old, with an age of about 13Gyr; its distance from the Sun is nearly 10kpc. It is also somewhat metal rich with [Fe/H]=-0.7. Regarding its kinematics, our tentative estimate for the proper motions is ({mu}_{alpha}*cos{delta}, {mu}_{delta}_=(-7.0+/-0.8, 3.5+/-0.3)mas/yr (or a tangential velocity of 382+/-79km/s) and for the radial velocity 45+/-5km/s in the solar rest frame. E3 is one of the most intriguing globular clusters in the Galaxy. Having an old age and being metal rich is clearly a peculiar combination, only seen in a handful of objects like the far more conspicuous NGC 104 (47 Tucanae). In addition, its low luminosity and sparse population make it a unique template for the study of the final evolutionary phases in the life of a star cluster. Unfortunately, E3 is among the most elusive and challenging known globular clusters because field contamination severely hampers spectroscopic studies.
- ID:
- ivo://CDS.VizieR/J/MNRAS/423/2260
- Title:
- VI photometry of M15 core
- Short Name:
- J/MNRAS/423/2260
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-resolution I-band imaging of the core of the globular cluster M15 obtained at the 2.5-m Nordic Optical Telescope with FastCam, a low readout noise L3CCD-based instrument. Short exposure times (30ms) were used to record 200000 images (512x512 pixels each) over a period of 2h and 43min. The lucky imaging technique was then applied to generate a final image of the cluster centre with full width at half-maximum ~0.1arcsec and 13x13arcsec^2^ field of view. We obtained a catalogue of objects in this region with a limiting magnitude of I=19.5. I-band photometry and astrometry are reported for 1181 stars. This is the deepest I-band observation of the M15 core at this spatial resolution.
- ID:
- ivo://CDS.VizieR/J/A+A/366/498
- Title:
- VI photometry of M33 star clusters
- Short Name:
- J/A+A/366/498
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have detected 102 star clusters in M 33, from 35 deep Hubble Space Telescope (HST) WFPC2 fields taken from our program and from the HST archive. Twenty-eight fields have V and I band imaging, and an additional seven fields are imaged in a single V filter. Eighty-two of the clusters were previously unknown. Integrated photometry reveals that 25 clusters have (V-I) colors typical of those found in Galactic globular clusters (only ten of these objects were previously known). Our discovery of 15 new globular cluster candidates increases previous estimates of the old cluster population in M 33 by ~60%. An additional eleven objects (only two were previously known) have colors expected for intermediate age clusters. The new clusters have a range of ages from 6 million years to >15Gyrs, and masses between 10^2^M_{sun}_-10^6^M_{sun}_, although these parameters are estimated from only one color.
