Low-mass X-ray binaries are systems in which a star transfers matter onto a compact object—either a black hole or a neutron star—producing energetic outbursts. During these events, their optical spectra provide a way to study extreme processes of accretion and matter ejection. While some spectroscopic features have been analysed in detail (e.g., revealing disc expansion and the presence of optical winds), the appearance of broad absorptions in the optical regime has traditionally been neglected. In this work, we present the first systematic study of these broad absorptions. We carry out the

In the standard Lambda cold dark matter (Lambda-CDM) cosmology, galaxies grow by gradually accreting material and through mergers with other galaxies. This scenario successfully explains many large-scale cosmic structures, yet it struggles to account for the existence of numerous massive spiral galaxies in the local Universe that lack a prominent central bulge, pure disc systems, in the local Universe. Understanding how these galaxies form and survive is also essential for placing our own Galaxy, the Milky Way, into context, as it also hosts a low-mass bulge. In this study, we analyse 22

Dormant black holes in X-ray transients can be identified by the presence of broad Hα emission lines from quiescent accretion discs. Unfortunately, short-period cataclysmic variables can also produce broad Hα lines, especially when viewed at high inclinations, and are thus a major source of contamination. Here we compare the full width at half maximum (FWHM) and equivalent width (EW) of the Hα line in a sample of 20 quiescent black hole transients and 354 cataclysmic variables (305 from SDSS I to IV) with secure orbital periods (Porb) and find that: (1) FWHM and EW values decrease with Porb