Related papers: A0620-00 revisited: a black-hole transient case-st…
IGR J11215-5952 is a hard X-ray transient source discovered in April 2005 with INTEGRAL and a confirmed member of the new class of High Mass X-ray Binaries, the Supergiant Fast X-ray Transients (SFXTs). Archival INTEGRAL data and RXTE…
We describe our monitoring strategy which best exploits the sensitivity and flexibility of Swift to study the long-term behaviour of Supergiant Fast X-ray Transients (SFXTs). We present observations of the recent outbursts from two objects…
We analyzed optical/X-ray quasi-simultaneous light curves of Aql X-1, obtained by MAXI (Monitor of All-sky X-ray Image), ZTF (Zwicky Transient Facility) and LCO (Las Cumbres Observatory) in about 3.6 years from 2016, for understanding…
We show that the 1996 outburst of the X-ray binary transient system GRO J1655-40 can be explained by the standard dwarf-nova type disc instability, followed by an episode of enhanced mass transfer from the secondary if the mass transfer…
MAXI J1820+070 is a low-mass black hole X-ray binary system with high luminosity in both optical and X-ray bands during the outburst periods. We present extensive photometry in X-ray, ultraviolet, and optical bands, as well as…
Research into OJ 287 has been ongoing for many years. In 2020 April-June, this source underwent the second highest X-ray outburst (second only to the 2016-2017 outburst) and the mechanism of this outburst is still under debate. In this…
Many black hole X-ray transients are in a low state for several decades until an outburst occurs. We interpret this outburst behaviour as a marginal occurrence of a dwarf nova type disk instability in the cool outer accretion disk. We…
We present optical spectroscopy and optical and infrared photometry of the neutron star soft X-ray transient Aql X--1 during its X-ray outburst of August 1997. By modelling the X-ray, optical, and IR light curves, we find a 3 day delay…
MAXI J1813-095 is an X-ray transient discovered during an outburst in 2018. We report on X-ray and optical observations obtained during this event, which indicate that the source is a new low-mass X-ray binary. The outburst lasted ~70 d and…
We have taken optical and infrared observations during the 2002 outburst of the soft X-ray transient, 4U 1543-47. A secondary maximum occurs in the lightcurves during the outburst decline. This feature is much stronger at infrared…
We present high time-resolution ULTRACAM optical and NOTCam infrared observations of the edge-on black hole X-ray transient Swift J1357.2-0933. Our data taken in 2012 and 2013 show the system to be at its pre-outburst magnitude and so the…
The observations and theory of the exciting new class of galactic black hole X-ray transients is reviewed. Seven of these systems have measured mass functions or mass estimates in excess of stable neutron stars, making them excellent black…
We present the results of Rossi X-ray Timing Explorer observations of GS 1354-644 during a modest outburst in 1997-1998. The source is one of a handful of black hole X-ray transients that are confirmed to be recurrent in X-rays. A 1987…
The last decade has seen a significant gain in both space and ground-based monitoring capabilities, producing vastly better coverage of BH X-ray binaries during their (rare) transient events. This interval included two of the three…
We study the evolution of the temporal properties of MAXI 1820+070 during the 2018 outburst in its hard state from MJD 58190 to 58289 with Insight-HXMT in a broad energy band 1-150 keV. We find different behaviors of the hardness ratio, the…
AT 2019avd is a nuclear transient detected from infrared to soft X-rays, though its nature is yet unclear. The source has shown two consecutive flaring episodes in the optical and the infrared bands and its second flare was covered by X-ray…
We probe the properties of the transient X-ray pulsar MAXI J1409$-$619 through \textit{RXTE} and \textit{Swift} follow up observations of the outburst in 2010. We are able to phase connect the pulse arrival times for the 25 days episode…
The optical counterpart of the transient, millisecond X-ray pulsar SAX J1808.4-3658 was observed in four colours (BVRI) for five weeks during the 2005 June-July outburst. The optical fluxes declined by ~2 magnitudes during the first 16 days…
In 2004, SGR 1806-20 underwent a period of intense and long-lasting burst activity that included the giant flare of 27 December 2004 -- the most intense extra-solar transient event ever detected at Earth. During this active episode, we…
We report on X-ray observations made with the Rossi X-ray Timing Explorer of the black hole candidate (BHC) transient XTE J1650-500 at the end of its first, and currently only, outburst. By monitoring the source at low luminosities over…