We report intermediate resolution H alpha spectroscopy of the black hole candidate Nova Muscae 1991 during quiescence. We classify the companion star as a K3...

We present the results of the study of visible (UBVRIZ) intra-night microvariability in the blazar OJ 287. Useful observations (at least four integrations in a...

Observations of some quiescent black hole X-ray binaries have revealed an excess of mid-infrared (MIR) emission above that expected from their donor stars. In...

Polarization measurements of the microquasar Cygnus X-1 exist at γ-ray, X-ray, ultraviolet, optical and radio frequencies. The γ-ray emission has been shown to...

From the peak of a gravitational microlensing high-magnification event in the A component of QSO 2237+0305, which was accurately monitored by the Gravitational...

We report on UV and X-ray spectroscopy and broadband optical observations of the ultraluminous X-ray source in Holmberg II. Fitting various stellar spectral...

MAXI J1834–021 is a new X-ray transient discovered in February 2023. We analysed the spectral and timing properties of MAXI J1834–021 using NICER, NuSTAR and...

Phase-resolved spectroscopy of the newly discovered X-ray transient MAXI J0556-332 has revealed the presence of narrow emission lines in the Bowen region that...

SAX J1711.6-3808 is an X-ray transient in the Galactic bulge that was active from January through May of 2001 and whose maximum 1-200 keV luminosity was...