Related papers: Response to Comment on "A Non-Interacting Low-Mass…
Most stellar remnants so far have been found in binary systems, where they interact with matter from their companions. Isolated neutron stars and black holes are difficult to find as they are dark, yet they are predicted to exist in our…
The existence of compact stellar remnants in the mass range $2-5\,M_{\odot}$ has long been debated. This so-called lower mass gap was initially suggested by the lack of low-mass X-ray binary observations with accretors about…
We discuss masses of stellar black holes found in binary systems and errors in their determination. The observed mass distribution has a broad shape within the range $4-16 M_\odot$ without visible concentration to some preferred value. On…
The state of the searches for isolated black holes, non-accreting black holes in binary systems and, finally, the accreting black holes in the X-ray binaries is presented. The third category is, by far, the most important source of…
Black hole - neutron star $(BH/NS)$ binaries are of interest in many ways: they are intrinsically multi-messenger systems, highly transient, radiate gravitational waves detectable by LIGO, and may produce $\gamma$-ray bursts. Although it…
Liu et al. (2019) recently reported the detection of a 68 [+11/-13] solar mass (Msun) black hole (BH) paired with an 8.2 [+0.9/-1.2] Msun B-type sub-giant star in the 78.9-day spectroscopic binary system LB-1. Such a black hole is over…
We investigate the relationship between the mass of the central supermassive black hole, M_bh, and the host galaxy luminosity, L_gal, in a sample of quasars from the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7). We use composite…
We present JWST MIRI/NIRSpec observations of the extremely red quasar SDSS J165202.64+172852.3 at z~3, one of the most luminous quasars known to date, driving powerful outflows and hosting a clumpy starburst, amidst several interacting…
We report the discovery of an exceptionally eccentric binary system, BE Lyncis (BE~Lyn), which might host a compact companion with mass $\gtrsim 2.5~M_{\odot}$. By combining TESS photometry with an extensive set of times of maximum light…
Optical spectra and images taken with the Baade 6.5 meter Magellan telescope confirm that 2XMM J123103.2+110648, a highly variable X-ray source with an unusually soft spectrum, is indeed associated with a type 2 (narrow-line) active nucleus…
The masses of compact objects like white dwarfs, neutron stars and black holes are fundamental to astrophysics, but very difficult to measure. We present the results of an analysis of subluminous B (sdB) stars in close binary systems with…
The majority of massive stars are found in close binaries which: (i) are prone to merge and (ii) are accompanied by another distant tertiary star (triples). Here, we study the evolution of the stellar post-merger binaries composed of the…
We present the results of a detailed non-LTE analysis of the UV and optical spectrum of the O6.5Iaf+ star HD153919 - the mass donor in the high-mass X-ray binary 4U1700-37. Given the eclipsing nature of the system these results allow us to…
Recently, a single-line spectroscopic binary, LTD064402+245919, has been discovered by Yang et al. Using data from LAMOST and ZTF, the unseen companion is estimated to have a mass of 1-3 $M_{\odot}$, orbiting a subgiant with orbital period…
The correlation between black hole mass and the stellar mass of the bulge of the host galaxy has attracted much attention ever since its discovery. While traditional investigations of this correlation have treated elliptical galaxies as…
We present the discovery of substellar-mass companions to three giant stars by the ongoing Penn State-Toru\'n Planet Search (PTPS) conducted with the 9.2 m Hobby-Eberly Telescope. The most massive of the three stars, K2-giant HD 240237, has…
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…
This article reviews the current status of black hole astrophysics, focusing on topics of interest to a physics audience. Astronomers have discovered dozens of compact objects with masses greater than 3 solar masses, the likely maximum mass…
This is the second of a series of papers that focuses on searching large sets of photometric light curves for evidence of close binaries with a dormant black hole, and, in some cases, a dormant neutron star. The detection of such a binary…
We report the discovery of the closest known black hole candidate as a binary companion to V723 Mon. V723 Mon is a nearby ($d\sim460\,\rm pc$), bright ($V\simeq8.3$~mag), evolved ($T_{\rm eff, giant}\simeq4440$~K, and $L_{\rm…