Related papers: Variable stars in the open cluster NGC 6791 and it…
We present the results of a 2-epoch variability survey in the Hubble Deep Field with the goal of investigating the population of AGN to z=1. The primary data sets analyzed for galactic variability are the original HDF observations obtained…
The number of known periodic variables has grown rapidly in recent years. Thanks to its large field of view and faint limiting magnitude, the Zwicky Transient Facility (ZTF) offers a unique opportunity to detect variable stars in the…
We have surveyed a 6.5' x 6.5' field centered on the globular cluster M56 (NGC 6779) in search for variable stars. We have detected seven variables, among which two objects are new identifications. One of the new variables is an RR Lyrae…
We present a survey of variable stars detected in K2 Campaign 13 within the massive intermediate age ($\sim1$ Gyr) open cluster NGC 1817. We identify a complete sample of 44 red clump stars in the cluster, and have measured asteroseismic…
We present a CCD photometric survey for the search of variable stars in four open clusters namely Berkeley 69, King 5, King 7, and Berkeley 20. The time series observations were carried out for 1 and/or 2 nights for each of the clusters in…
The results of CCD photometric survey performed with the 90/180 cm Schmidt-Cassegrain Telescope of the Nicolaus Copernicus University Astronomical Observatory in Piwnice (Poland) and the 70/172 cm Schmidt Telescope of the National…
We report on the results of a long time photometric monitoring of the two metal poor Galactic globular clusters M22 and IC4499 searching for long period variables (LPVs) on the upper giant branch. We detected 22 new LPVs in the field of M22…
Motivated by the detection of a recent outburst of the massive luminous blue variable LMC-R71, which reached an absolute magnitude M_V = -9.3 mag, we undertook a systematic study of the optical variability of 1268 massive stars in the Large…
We present time-series VI photometry of the metal-rich ([Fe/H] = -0.53) globular cluster NGC 6441. Our color-magnitude diagram shows that the extended blue horizontal branch seen in Hubble Space Telescope data exists in the outermost…
We have searched for variable stars in deep V-band images of a field towards the Galactic plane in Carina. The images were taken with VIMOS instrument at ESO VLT during 4 contiguous nights in April 2005. We detected 348 variables among…
We present the first evidence of clear signatures of tidal distortions in the density distribution of the fascinating open cluster NGC 6791. We used deep and wide-field data obtained with the Canada-France-Hawaii-Telescope covering a 2x2…
Models of stellar structure and evolution can be constrained by measuring accurate parameters of detached eclipsing binaries in open clusters. Multiple binary stars provide the means to determine helium abundances in these old stellar…
We have conducted a 1.5 year-long variability study of the stars in the Cygnus OB2 association, the region in the northern hemisphere with the highest density of optically visible massive stars. The survey was conducted using four pointings…
Five fields located close to the center of the globular cluster NGC 104=47 Tuc were surveyed in a search for variable stars. We present V-band light curves for 42 variables. This sample includes 13 RR Lyr stars -- 12 of them belong to the…
We examine the photometric variability of stars in the M 67 field using Kepler/K2-Campaign-5 light curves. Variabilities and periods were determined for 639 stars. The mean photometric period of 28 single Sun-like members stars in M 67 is…
We present the results of a multi-wavelength (FUV to I-band) survey of the stellar populations of the globular cluster NGC 6752, using STIS, ACS and WFC3 on board the Hubble Space Telescope. We have confirmed that two previously identified…
We have searched for optical identifications for 39 Chandra X-ray sources that lie within the 1.9 arcmin half-mass radius of the nearby (d = 4.0 kpc), core-collapsed globular cluster, NGC 6752, using deep Hubble Space Telescope ACS/WFC…
NGC 7419 is a young open cluster notable for hosting five Red Supergiants and a high abundance of Classical Be (CBe) stars. CBe stars are main sequence non-supergiant B-type stars, which exhibit or have exhibited Balmer line emissions in…
Context. Stars that are members of stellar clusters are assumed to be formed at the same time and place from material with the same initial chemical composition. These additional constraints on the ensemble of cluster stars make these stars…
We have conducted a long-term V-band photometric monitoring of M33 on 95 nights during four observing seasons (2000 - 2003). A total number of 6418 lightcurves of bright objects in the range of 14 - 21 mag have been obtained. All…