Related papers: The Star Formation Region NGC 6530: distance, ages…

Recent studies have started to cast doubt on the assumption that most stars are formed in clusters. Observational studies of field stars and star cluster systems in nearby galaxies can lead to better constraints on the fraction of stars…

Using Hubble Space Telescope (HST) ACS/WFC data we present the photometry and spatial distribution of resolved stellar populations in the outskirts of NGC 2915, a blue compact dwarf with an extended HI disc. These observations reveal an…

Here we have obtained the {\it BVRI CCD} photometry down to a limiting magnitude of $V \sim$ 20 for the southern poorly studied open cluster NGC 6631. It is observed from the {\it 1.88 m} Telescope of Kottamia Observatory in Egypt. About…

We present the results of CCD UBVRI observations of the open cluster NGC 6811 obtained on 18th July 2012 with the 1m telescope at the T\"UB\.ITAK National Observatory (TUG). Using these photometric results, we determine the structural and…

We use photometric and spectroscopic observations of the detached eclipsing binaries V40 and V41 in the globular cluster NGC 6362 to derive masses, radii, and luminosities of the component stars. The orbital periods of these systems are…

We present a uniform analysis of the stellar initial mass function (IMF) from integrated light spectroscopy of 15 compact stellar systems (11 globular clusters in M31 and 4 ultra compact dwarfs in the Virgo cluster, UCDs) and two brightest…

We study star clusters in two fields in the nearby spiral galaxy M83 using broad and narrow band optical imaging taken with the WFC3 on-board HST. We present results based on several different catalogs of star clusters in an inner and outer…

We present high-dispersion spectra of two extremely massive star clusters in galactic merger remnants. One cluster, W30, is located in the ~500 Myr old merger remnant NGC 7252 and has a velocity dispersion and effective radius of…

We demonstrate the feasibility of detecting directly low mass stars in unresolved super-star clusters with ages < 10 Myr using near-infrared spectroscopy at modest resolution (R ~ 1000). Such measurements could constrain the ratio of high…

Photographic photometries of 789 stars in the region of the open clusters NGC1750 and NGC1758 are derived from a set of 8 photometric plates. According to the astronomical data including proper motions, positions and membership…

Sensitive imaging X-ray observations of young stellar clusters (YSCs, ages less than about 10 Myr) are valuable tools for the acquisition of an unbiased census of cluster members needed for Initial Mass Function (IMF) studies. Several dozen…

We present results from ACS and WFPC observations in the low luminosity galaxy NGC 45. We identified 28 young star cluster candidates. While the exact values of age, mass, and extinction depend somewhat on the choice of SSP models, we find…

We present deep Hubble Space Telescope/Wide Field and Planetary Camera 2 photometry of the young HD 97950 star cluster in the giant H {\sc ii} region NGC 3603. The data were obtained in 1997 and 2007 permitting us to derive membership based…

A cluster intermediate in age between the Pleiades (150 Myr) and the Hyades (600 Myr) is needed to probe the rotational evolution, especially the transition between fast and slow rotation that occurs between the two ages. We study the rich…

The newly installed Wide Field Camera 3 (WFC3) on the Hubble Space Telescope has been used to obtain multi-band images of the nearby spiral galaxy M83. These new observations are the deepest and highest resolution images ever taken of a…

We show that one can obtain a good fit to the measured main sequence mass function (MF) of a large sample of Galactic clusters (young and old) with a tapered Salpeter power law distribution function with an exponential truncation. The…

NGC 663 is a young, moderately rich open cluster, known to contain one of the largest fractions of Be stars among all galactic clusters. In this work we present CCD uvby-beta photometry for stars in its central area. We have used these data…

The detached eclipsing binary V20 in the old, metal--rich open cluster NGC 6791 is studied in order to determine highly accurate masses and radii of its components. This allows the cluster age to be established with high precision, using…

The ACS and NICMOS have been used to obtain new HST images of NGC 4038/4039 ("The Antennae"). These new observations allow us to better differentiate compact star clusters from individual stars, based on both size and color. We use this…

NGC6231 is a massive young star cluster, near the center of the Sco OB1 association. While its OB members are well studied, its low-mass population has received little attention. We present high-spatial resolution Chandra ACIS-I X-ray data,…