We present an optical spectroscopic study of the black hole X-ray transient V4641 Sgr (=SAX J1819.3-2525) covering the 1999, 2002, and 2004 outbursts. The spectra were taken over 22 different epochs during the low-luminosity phases that follow the sharp and bright outburst peaks displayed by the system. The data reveal the frequent presence of wind

The physical interpretation of the spectral line polarization produced by the joint action of the Hanle and Zeeman effects offers a unique opportunity to obtain empirical information about hidden aspects of solar and stellar magnetism. To this end, it is important to achieve a complete understanding of the sensitivity of the emergent spectral line

The resonant scattering solar spectrophotometer `Mark-I', designed and build at the University of Birmingham (UK) and located at the Observatorio del Teide (Spain), has been continuously in operation for the past 38 years. During this period of time, it has provided high-precision measurements of the radial velocity of the Sun as a star, which has

We discuss some of our current knowledge of the mass distribution of DA and non-DA stars using various methods for measuring white dwarf masses including spectroscopic, trigonometric parallax, and gravitational redshift measurements, with a particular emphasis on the problems encountered at the low end of the cooling sequence where energy transport

We obtained 16 VLT/X-shooter observations of GX 339‑4 in quiescence during the period 2016 May–September and detected absorption lines from the donor star in its NIR spectrum. This allows us to measure the radial velocity curve and projected rotational velocity of the donor for the first time. We confirm the 1.76 day orbital period and we find that

We present the first infrared light curve of GRO J0422+32, and use it along with R-band data and published I- and Cousins R_c-band data to constrain the inclination of the system to be between 10 deg and 26 deg, implying that the black hole mass is greater than ~15Msolar. Remodeling the data with a 30 per cent accretion disc contamination level