Related papers: Primordial Globular Clusters, X-Ray Binaries & Cos…
The 26 long-duration gamma-ray bursts (GRBs) with known redshifts form a distinct cosmological set, selected differently than other cosmological probes such as quasars and galaxies. Since the progenitors are now believed to be connected…
The discovery of gravitationally lensed stellar clusters at high redshift with the James Webb Space Telescope (JWST) has revealed extremely compact, massive star-forming systems in galaxies at $z > 6$, providing a new window into early…
We present an analysis of low mass X-ray binaries (LMXBs) and globular clusters (GCs) in five galaxies using Chandra, and HST data. Of the 186 LMXBs within the optical fields 71 are in GCs, confirming that LMXBs are formed particularly…
The nature of ultraluminous X-ray sources (ULXs) is presently unknown. A possible explanation is that they are accreting intermediate mass black holes (IBHs) that are fed by Roche lobe overflow from a tidally captured stellar companion. We…
We model the evolution of the selected types of X-ray sources (both with BHs and NSs) for the star formation burst at the Galactic center. For the currently assumed starburst age of 4-7 millions years, our results are consistent with the…
Pinpointing the progenitors of long duration gamma-ray bursts (LGRBs) remains an extremely important question, although it is now clear that at least a fraction of LGRBs originate in the core collapse of massive stars in type Ic supernovae,…
We present a deep UBI CCD survey using the Palomar 5-m telescope of a sample of high X-ray luminosity, distant clusters selected from the ROSAT All-Sky Survey. The 10 clusters lie at z=0.22-0.28, an era where evolutionary effects have been…
Surface temperature distribution of horizontal-branch (HB) stars is very sensitive to age in old stellar systems, which makes it an attractive age indicator. In this paper, we present the recent revision of our model calculations for the HB…
We investigate the dependence of the low-mass X-ray binary (LMXB) population in early-type galaxies on stellar age, by selecting 20 massive nearby early-type galaxies from the Chandra archive occupying a relatively narrow range of masses…
Dark stars powered by dark matter annihilation have been proposed as the first luminous sources in the universe. These stars are believed to form in the central dark matter cusp of low-mass minihalos. Recent calculations indicate stellar…
A brief overview is given of X-ray observations of old clusters. Most X-ray sources in old open clusters are interacting binaries, formed via evolution of a primordial binary, and emitting X-rays because of magnetic activity; however, a…
Metal poor globular clusters (MPGCs) are a unique probe of the early universe, in particular the reionization era. Systems of globular clusters in galaxy clusters are particularly interesting as it is in the progenitors of galaxy clusters…
We present an estimation of lifetimes of massive galaxies with distinct UV colors at $0.5 \le z \le 2.5$ in the COSMOS/UltraVISTA field. After dividing the galaxy sample into subsamples of red sequence (RS), blue cloud (BC), and green…
It is often argued that young stellar clusters suffer a significant infant mortality that is partly related to the expulsion of dust and gas in their early phases caused by radiation pressure from hot stars and supernovae. Near-infrared…
We have recently presented observational evidence which suggests that the origin of the second generation (G2) stars in globular clusters (GCs) is due to the binary-mediated collision of primordial (G1) low-mass main-sequence (MS) stars.…
Globular clusters (GCs) effectively produce dynamically-formed low-mass X-ray binaries (LMXBs). Observers detect ~100 times more LMXBs per stellar mass in GCs compared to stars in the fields of galaxies. It has also been observationally…
Studies of nearby elliptical and S0 galaxies reveal that roughly half of the low mass X-ray binaries (LMXBs), which are luminous tracers of accreting neutron star or black hole systems, are in clusters. There is a surprising tendency of…
We here present our first attempt to use Globular Clusters as tracers of their parent galaxy's formation history. Globular Cluster Systems of most early-type galaxies feature two peaks in their optical colour distributions. Blue-peak…
Serving as the progenitors of electromagnetic and gravitational wave transients, massive stars have received renewed interest in recent years. However, many aspects of their birth and evolution remain opaque, particularly in the context of…
In low-metallicity environments, massive stars might avoid supernova explosion and directly collapse, forming massive (~25-80 solar masses) stellar black holes (MSBHs), at the end of their life. MSBHs, when hosted in young massive clusters,…