The black hole X-ray binary (BHXB) GX 339-4 continues to fade in the optical, and has now reached its faintest optical flux since (at least) the start of its...
Hard-state Accretion Disk Winds from Black Holes: The Revealing Case of MAXI J1820+070
We report on a detailed optical spectroscopic follow-up of the black hole (BH) transient MAXI J1820+070 (ASASSN-18ey). The observations cover the main part of...
Hibernating black holes revealed by photometric mass functions
We present a novel strategy to uncover the Galactic population of quiescent black holes (BHs). This is based on a new concept, the photometric mass function...
High time resolution optical/X-ray cross-correlations for X-ray binaries: anticorrelations and rapid variability
Using simultaneous observations in X-rays and optical, we have performed a homogeneous analysis of the cross-correlation behaviours of four X-ray binaries...
High-precision optical polarimetry of the accreting black hole V404 Cyg during the 2015 June outburst
Our simultaneous three-colour (BVR) polarimetric observations of the low-mass black hole X-ray binary V404 Cyg show a small but statistically significant change...
Hubble spectroscopy of LB-1: Comparison with B+black-hole and Be+stripped-star models
Context. LB-1 (alias ALS 8775) has been proposed as either an X-ray dim B-type star plus black hole (B+BH) binary or a Be star plus an inflated stripped star...
Hβ spectroscopy of the high-inclination black hole transient Swift J1357.2−0933 during quiescence
Swift J1357.2−0933 is a transient low-mass X-ray binary hosting a stellar-mass black hole. The source exhibits optical dips and very broad emission lines during...
The INTEGRAL/EINSTEIN/ROSAT/NVSS objects IGR J17418-12122, 2E 1739.1-1210, 1RXS J174155.3-121157 and NVSS J174155-121201 have recently been suggested to be the...
Improved position of the new X-ray transient XTE J1637-498
Following the discovery of the new X-ray transient XTE J1637-498 (Atel #1699), we obtained a short (nearly 1 ksec) observation using the Swift/XRT in PC mode on...