The Be/X-ray binary LS 992/RX J0812.4-3114: Physical parameters and long-term variability
Reig, P. ; Negueruela, I. ; Buckley, D. A. H. ; et al. ; - ASI Sponsor
Feb - 1999
ISSN : 0004-6361 ;
journal : Astronomy and Astrophysics

Issue : 1
type: Article Journal

Abstract
We present the first long-term optical and infrared study of the optical counterpart to the source RX J0812.4-3114, an X-ray pulsar with a Be type companion. During the period covered by the observations the profile of some Balmer lines changed from absorption to emission and back again to absorption. Contemporaneously, the infrared magnitudes varied by more than 0.8 mag. This long-term variability is interpreted as the formation and subsequent dissipation of the Be stars disc. The building up of the disc ended up in an active X-ray state characterised by regular outbursts occurring at 80 day intervals. The overall duration of the formation/dissipation of the disc is found to be ≲ 4.3 years. Optical spectroscopic and infrared photometric observations were used to refine the spectral type of the primary (B0.2IV) and to monitor the circumstellar envelope around the Be star. UBVRI and uvbybeta photometric observations allowed the determination of the astrophysical parameters of the optical companion. Based on observations collected at the South African Astronomical Observatory, the European Southern Observatory, Chile (ESO N64.H-0059) and the Teide Observatory, Tenerife (Spain).

keywords : 3114,4,BINARIES: GENERAL,STARS: EMISSION-LINE,STARS: INDIVIDUAL: LS 992/RX J0812.4-3114,STARS: PULSARS: GENERAL,X-RAYS: STARS,be,binaries,emission-,general,individual,line,ls 992,pulsars,rx j0812,stars,x-rays