Related papers: Delayed emission from luminous blue optical transi…
Luminous red nova transients, presumably from stellar coalescence, exhibit long-term precursor emission over hundreds of binary orbits, leading to impulsive outbursts with durations similar to a single orbital period. In an effort to…
The optical behaviour of the Be star in the high-mass X-ray transient A0535+26/HDE245770 shows that at periastron the luminosity is typically enhanced by 0.02 to a few tenths magnitude, and the X-ray outburst occurs eight days after the…
Observations of fast X-ray transients (FXRTs) with the Einstein Probe have successfully led to the discovery of some unusual extragalactic optical transients. EP241021a is a newly discovered FXRT that was featured by a significant bump…
We report the discovery of a luminous late-time source at the position of the fast blue optical transient (FBOT) AT2018cow on images taken by the Hubble Space Telescope (HST) at 714 d and 1136 d after its explosion. This source is detected…
Radio wavelengths offer a unique window into high-energy astrophysical phenomena that may be obscured or too rapidly evolving to be captured at other wavelengths. Leveraging data from the Very Large Array Sky Survey, we perform a systematic…
By definition transients are sudden events, some, like supernovae, are catastrophic, while others might be due to recurrent phenomena. The aim of studying transients is to reveal the physical conditions causing them, in this sense ideal…
We study the thermal and viscous stability of accretion flows in Low Mass Black Hole Binaries (LMBHBs). We consider a model in which an inner advection-dominated accretion flow (ADAF) is surrounded by a geometrically thin accretion disk,…
X-ray binaries are cauldrons of fundamental physical processes which appear along practically the whole electromagnetic spectrum. The sub-class of X-ray transient sources show multifrequency behaviour which deserve particular attention in…
Long $\rm \gamma$-ray bursts (GRBs) are produced by the dissipation of ultra-relativistic jets launched by newly-born black holes after the collapse of massive stars. Right after the luminous and highly variable $\gamma$-ray emission, the…
We report the discovery of fast variability of gamma-ray flares from blazar OJ 287. This blazar is known to be powered by binary system of supermassive black holes. The observed variability time scale T_var < 3-10 hr is much shorter than…
Recent observations presented in Cendes et al. (2024a) show that optically selected tidal disruption events (TDEs) commonly produce delayed radio emission that can peak years post-disruption. Here, we explore the multi-wavelength properties…
Highly eccentric binary systems appear in many astrophysical contexts, ranging from tidal capture in dense star clusters, precursors of stellar disruption by massive black holes, to high-eccentricity migration of giant planets. In a highly…
Observations of soft X-ray transients (SXTs) in quiescence have found that the binaries harboring black holes are fainter than those that contain a neutron star. Narayan and collaborators postulated that the faint X-ray emission from black…
We consider black hole formation in failed supernovae when a dense circumstellar medium (CSM) is present around the massive star progenitor. By utilizing radiation hydrodynamical simulations, we calculate the mass ejection of blue…
Extreme coronal line emitters (ECLEs) are objects showing transient high-ionization lines in the centers of galaxies. They have been attributed to echoes of high-energy flares of ionizing radiation, such as those produced by tidal…
We study the long-term evolution of ejecta formed in a binary neutron star (BNS) merger that results in a long-lived remnant NS by performing a hydrodynamics simulation with the outflow data of a numerical relativity simulation as the…
Observing the famous high-mass, eccentric X-ray and gamma-ray binary PSR B1259-63/LS 2883 with Chandra, we detected X-ray emitting clumps moving from the binary with speeds of about 0.1 of the speed of light, possibly with acceleration. The…
Blazars show variability on timescales ranging from minutes to years, the former being comparable to and in some cases even shorter than the light-crossing time of the central black hole. The observed gamma-ray lightcurves can be described…
The tidal disruption of a star by a supermassive black hole provides us with a rare glimpse of these otherwise dormant beasts. It has long been predicted that the disruption will be accompanied by a thermal `flare', powered by the accretion…
Recently two fast X-ray transients (XT1 and XT2) have been reported from the search in the Chandra Deep Field (CDF) data. Each transient shows an initial plateau lasting around hundreds to thousands seconds followed by a rapid decay in the…