Evidence for a black hole in the historical X-ray transient A 1524-61 (= KY TrA)
We present Very Large Telescope spectroscopy, high-resolution imaging, and time-resolved photometry of KY TrA, the optical counterpart to the X-ray binary A...
Evidence for inflows and outflows in the nearby black hole transient Swift J1727.8−162
We present 20 epochs of optical spectroscopy obtained with the GTC-10.4m telescope across the bright discovery outburst of the black hole candidate Swift J1727...
The RXTE All-Sky monitor shows new detections of the black hole binary, XTE J1118+480, reported to be in optical outburst (ATEL #383). The source is first seen...
First gravitational-wave burst GW150914: MASTER optical follow-up observations
The Advanced LIGO observatory recently reported the first direct detection of the gravitational waves (GWs) predicted by Einstein & Sitzungsber. We report on...
Follow-up Survey for the Binary Black Hole Merger GW200224_222234 Using Subaru/HSC and GTC/OSIRIS
The LIGO/Virgo detected a gravitational wave (GW) event, named GW200224_222234 (also known as S200224ca) and classified as a binary-black hole coalescence, on...
Furiously fast and red: sub-second optical flaring in V404 Cyg during the 2015 outburst peak
We present observations of rapid (sub-second) optical flux variability in V404 Cyg during its 2015 June outburst. Simultaneous three-band observations with the...
Galactic Black Hole Transient H1743-322 in transition to the hard state
Galactic black hole transient H1743-322 has been in outburst since UT 2009 May 26, (ATELs #2058, #2062). The RXTE PCA count rate has been dropping since 2009...
Gamma-ray observations of MAXI J1820+070 during the 2018 outburst
MAXI J1820+070 is a low-mass X-ray binary with a black hole (BH) as a compact object. This binary underwent an exceptionally bright X-ray outburst from 2018...