Related papers: Exploring the Leo II dSph I.: The Variable Star Co…
We report the discovery of a large number of short-period variable stars in the dwarf irregular galaxy NGC6822, based on deep time-series imaging carried out with the ESO Very Large Telescope. In particular, we found a modest population of…
We use the pulsational properties of the RR Lyrae variables in the globular cluster NGC 1851 to obtain detailed constraints of the various sub-stellar populations present along its horizontal branch. On the basis of detailed synthetic…
We investigate the properties of the so-called BL Her stars, i.e., Population II Cepheids with periods shorter than 8 days, using updated pulsation models and evolutionary tracks computed adopting a metal abundance in the range of Z=0.0001…
A thorough analysis of the OGLE-II time-series photometry of the Large Magellanic Cloud bar supplemented by similar data from the MACHO database led us to the discovery of three Beta Cephei-type stars. These are the first known…
Classical pulsating stars such as Cepheid and RR Lyrae variables exhibit well-defined Period-Luminosity relations at near-infrared wavelengths. Despite their extensive use as stellar standard candles, the effects of metallicity on…
Draco dwarf Spheroidal galaxy (dSph) is one of the nearest and the most dark matter dominated satellites of the Milky Way. We obtained multi-epoch near-infrared (NIR, $JHK_s$) observations of the central region of Draco dSph covering a sky…
I point out that the Oosterhoff dichotomy for globular cluster and field RR Lyrae (RRL) stars may place the strongest constraints so far on the number of dwarf spheroidal-like protogalactic fragments that may have contributed to the…
We present deep Hubble Space Telescope single-star photometry of Leo A in B, V, and I. Our new field of view is offset from the centrally located field observed by Tolstoy et al. (1998) in order to expose the halo population of this galaxy.…
RR Lyrae stars in the bulge have been reported to be associated with the spheroidal, relatively metal-poor component. They offer a way to trace this component with precise distances. While a few studies of RR Lyrae spectra with medium/high…
The eleventh part of the OGLE-III Catalog of Variable Stars (OIII-CVS) contains 16836 RR Lyr stars detected in the OGLE fields toward the Galactic bulge. The total sample is composed of 11756 RR Lyr stars pulsating in the fundamental mode…
NGC 6441 is a bulge globular cluster with an unusual horizontal branch morphology and a rich population of RR Lyrae (RRL) and Type II Cepheid (T2C) variables that is unexpected for its relatively high metallicity. We present near-infrared…
The properties of RR Lyrae variables make them excellent probes of the formation and evolution of a stellar population. The mere presence of such stars necessitates an age greater than ~10 Gyr while their periods and amplitudes can be used…
The first calibrated broadband UBVI time-series photometry is presented for the RR Lyrae variable stars in NGC6656 (M22), with observations spanning a range of twenty-two years. We have also redetermined the variability types and periods…
Context. A number of RR Lyrae stars show variable mean magnitudes in the OGLE survey light curves of the Galactic bulge. Hitherto this phenomenon was not studied, as it was generally assumed to be related to problems with the photometry.…
Leo I is considered one of the youngest dwarf spheroidals (dSph) in the Local Group. Its isolation, extended star formation history (SFH), and recent perigalacticon passage (~1 Gyr ago) make Leo~I one of the most interesting nearby stellar…
We present the first period-luminosity and period-radius relation of Galactic RV Tauri variable stars. We have surveyed the literature for all variable stars belonging to this class and compiled the full set of their photometric and…
Context. Observational evidence has accumulated in the past years, showing that the Galactic bulge includes two populations, a metal poor and a metal rich one that, in addition to a different metallicity, show different alpha over iron…
New B, V, I photometry was obtained for a sample of 152 variables (125 RR Lyrae's, 4 anomalous Cepheids, 11 classical Cepheids, 11 eclipsing binaries and a delta Scuti star) in two regions near the bar of the Large Magellanic Cloud (LMC).…
We obtained a series of more than two hundred R-band CCD images for the crowded central (115"x77") region of the metal-poor globular cluster M15 with an angular resolution of 0.5"-0.9" in most images. Optimal image subtraction was used to…
This is the third in a series of papers studying the variable stars in old globular clusters in the Large Magellanic Cloud. The primary goal of this series is to look at how the characteristics and behavior of RR Lyrae stars in…