Related papers: A Quasar microlensing event towards J1249+3449?

The discovery of a terrestrial-mass free-floating planet candidate in the light curve of the star TIC 107150013 observed by the Transiting Exoplanet Survey Satellite (TESS) has recently been announced. A short-duration (~0.5 day),…

The quasar OJ~287 has shown large flares since 1888, following a pattern that arises in a supermassive black hole binary when the secondary hits the accretion disk of the primary, and releases a hot bubble of gas at every disk crossing. A…

We present an imaging study of the black hole binary candidate SDSS J1536+0441 (z=0.3893), based on deep, high resolution VzK images collected at the ESO/VLT. The images clearly show an asymmetric elongation, indicating the presence of a…

We report that the Sloan Digital Sky Survey quasar SDSS J165043.44+425149.3 is gravitationally lensed into two images, based on observations obtained with the WIYN 3.5 m telescope at the Kitt Peak National Observatory. The lensed quasar, at…

I present an optical characterization of the Galactic X-ray transient source MAXI J1957$+$032. This system flares by a factor of $\gtrsim10^{4}$ every few-hundred days, with each flare lasting $\sim5$ days. I identify its quiescent…

We present simulated results of quasi-periodic flares generated by the inelastic collisions of a star bound to a super-massive black hole (SMBH) and its attendant accretion disc. We show that the behavior of the quasi-periodicity is…

We announce the discovery of a quasar behind the disk of M31, which was previously classified as a remarkable nova in our neighbour galaxy. The paper is primarily aimed at the outburst of J004457+4123 (Sharov 21), with the first part…

We present the main results of the first long-term spectrophotometric monitoring of the ``Einstein cross'' Q2237+0305 and of the single-epoch spectra of the lensed quasar J1131-1231. From October 2004 to December 2006, we find that two…

The high-mass microquasar Cygnus X-1, the best-established candidate for a stellar-mass black hole in the Galaxy, has been detected in a flaring state at very high energies (VHE), E > 200 GeV, by the Atmospheric Cherenkov Telescope MAGIC.…

Anomalous flux ratios between quasar images are suspected to be caused by substructures in lens galaxies. We present new deep and high resolution H and Ks imaging of the strongly lensed quasar SDSS J0924+0219 obtained using the ESO VLT with…

We consider the gravitational magnification of light for binary systems containing two compact objects: white dwarfs, a white dwarf and a neutron star or a white dwarf and a black hole. Light curves of the flares of the white dwarf caused…

Context. Multiwavelength studies of transients in actively accreting supermassive black holes have revealed that large-amplitude variability is frequently linked to significant changes in the optical spectra -- a phenomenon known as…

Microlensing studies of quasars can reveal dark matter lumps over a broad mass spectrum; we highlight the importance of monitoring quasars which are seen through the halos of low-redshift galaxies. For these configurations microlensing by…

It has long been suggested that supermassive black holes in non-active galaxies might be tracked down by occasional tidal disruptions of stars on nearly radial orbits. A tidal disruption event would reveal itself by a luminous flare of…

We report the discovery of the first known probable case of a physical triple quasar (not a gravitational lens). A previously known double system, QQ 1429-008 at z = 2.076, is shown to contain a third, fainter QSO component at the same…

We present observations of an optically-faint quasar, RD J114816.2+525339, discovered from deep multi-color observations of the field around the z = 6.42 quasar SDSS J1148+5251. The two quasars have a projected separation of 109 arcsec and…

Very deep ESO/VLT FORS1 and ISAAC images, as well as HST NICMOS2 data are used to infer the nature of the quasar pair LBQS 1429-0053 A and B, either a binary quasar or a doubly-imaged lensed quasar. Direct search of a putative lensing…

Recently, the discovery of a Venus-mass planet orbiting a brown-dwarf host in a binary system was reported from the analysis of the microlensing event OGLE-2013-BLG-0723. We reanalyze the event considering the possibility of other…

We present an analysis of microlensing event OGLE-2016-BLG-0693, based on the survey-only microlensing observations by the OGLE and KMTNet groups. In order to analyze the light curve, we consider the effects of parallax, orbital motion, and…

We present the discovery of four gravitationally lensed quasars selected from the spectroscopic quasar catalog of the Sloan Digital Sky Survey. We describe imaging and spectroscopic follow-up observations that support the lensing…