Spectrophotometric follow-up of GU Mus, the (X-ray) Nova Muscae 1991

TL;DR

This study presents a detailed spectrophotometric follow-up of the X-ray nova GU Mus, analyzing optical light curves and spectral evolution to understand its behavior during the outburst and decline phases.

Contribution

It provides a comprehensive observational dataset and interprets the spectral line evolution in X-ray novae, offering insights into their physical processes.

Findings

Optical lightcurve shows typical X-ray nova features with secondary maxima.

Spectral lines such as Balmer and He II 4686 widen during decline.

Proposes a model explaining spectral line broadening during outburst decline.

Abstract

The spectrophotometric follow-up of the X-ray nova GU Mus (=GS 1124-68) is presented. We have analysed 128 B, V and R frames and 19 optical spectra, collected at ESO-La Silla, from the epoch of the discovery to January 1992. The optical lightcurve appears to be typical for a X-ray nova and exhibits secondary maxima in coincidence with the X-ray ones. The spectra show that Balmer and He II 4686 emission lines and the N III 4640 emission blend widen during the decline. A possible explanation of this behaviour is proposed and applied to the spectral evolution of other X-ray novae.