Related papers: Persistent and Transient Blank Field Sources
We report the initial results of deep eROSITA monitoring of the "magnificent seven" isolated neutron stars (INSs). Thanks to a combination of high count statistics and good energy resolution, the eROSITA datasets unveil the increasingly…
We review the formation and evolution of compact binary stars consisting of white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and BHs are thought to be the primary astrophysical sources of gravitational waves (GWs)…
The relatively large number of nearby radio-quiet and thermally emitting isolated neutron stars (INSs) discovered in the ROSAT All-Sky Survey, dubbed the ``Magnificent Seven'' (M7), suggests that they belong to a formerly neglected major…
A new type of high-energy binary systems has been revealed by the INTEGRAL satellite. These sources are in the course of being unveiled by means of multi-wavelength optical, near- and mid-infrared observations. Among these sources, two…
We consider transient behavior in low-mass X-ray binaries. In short-period neutron-star systems (orbital period less than ~ 1d) irradiation of the accretion disk by the central source suppresses this except at very low mass transfer rates.…
Deep, near-infrared imaging surveys have been motivated by the desire to study the rest-frame optical properties and stellar content of galaxies at high redshift. Here we briefly review their history, and illustrate one application, using…
Relativistic axions can be readily produced in a broad variety of transient sources, such as axion star bosenova explosions, supernovae or even evaporating primordial black holes. We develop a general framework describing the resulting…
Among the most explored directions in the study of dense stellar systems is the investigation of the effects of the retention of supernova remnants, especially that of the massive stellar remnant black holes (BHs), in star clusters. By…
The group of 7 thermally emitting and radio-quiet isolated neutron stars (INSs) discovered by ROSAT constitutes a nearby population which locally appears to be as numerous as that of the classical radio pulsars. So far, attempts to enlarge…
Sterile neutrinos with masses in the keV range are viable candidates for the warm dark matter. We analyze existing data for the extragalactic diffuse X-ray background for signatures of sterile neutrino decay. The absence of detectable…
Ground based optical observations have yielded considerable information on the statistics of damped-lyman alpha systems. In particular these systems are known to be the dominant repository of the observed neutral gas at high redshift.…
Cosmological nucleosynthesis calculations imply that many of the baryons in the Universe must be dark. We discuss the likelihood that some of these dark baryons may reside in the discs or halos of galaxies. If they were in the form of…
We report on follow-up observations with XMM-Newton, the FORS2 instrument at the ESO-VLT, and FAST, aiming to characterise the nature of five thermally emitting isolated neutron star (INS) candidates recently discovered from searches in the…
The past decades have witnessed a lot of progress in gravitational lensing with two main targets: stars and galaxies (with active galactic nuclei). The success is partially attributed to the continuous luminescence of these sources making…
Recent studies on dwarf galaxies reveal that some of them harbor a massive black hole (BH), which is believed to have a similar mass of the Supermassive BH "seeds" at early times. The origin and growth of the primitive BHs are still open…
A new type of high-energy binary system has been revealed by the INTEGRAL satellite. These sources are being unveiled by means of multi-wavelength optical, near- and mid-infrared observations. Among these sources, two distinct classes are…
We present initial results from a program aimed at establishing a network of hot DA white dwarfs to serve as spectrophotometric standards for present and future wide-field surveys. These stars span the equatorial zone and are faint enough…
We summarize the quiescent X-ray observations of transient low-mass X-ray binaries. These observations show that, in quiescence, binaries containing black holes are fainter than those containing neutron stars. This has triggered a number of…
We show that stable disk accretion should be very rare among low-mass X-ray binaries and cataclysmic variables whose evolution is driven by the nuclear expansion of the secondary star on the first giant branch. Stable accretion is confined…
While the number of stellar-mass black holes detected in X-rays or as gravitational wave sources is steadily increasing, the known population remains orders of magnitude smaller than predicted by stellar evolution theory. A significant…