Abstract
We present the results of our monitoring of the halo black hole soft X-ray transient (SXT) XTE J1118+480 during its decline to quiescence. The system has decayed 0.5 mag from 2000 December to its present near-quiescent level at R ≃ 18.65 (2001 June). The ellipsoidal light curve is distorted by an additional modulation that we interpret as a superhump of Psh = 0.17049(1) d i.e. 0.3 per cent longer than the orbital period. This implies a disc precession period Pprec ∼ 52 d. After correcting the average phase-folded light curve for veiling, the amplitude difference between the minima suggests that the binary inclination angle lies in the range i = 71-82°. However, we urge caution in the interpretation of these values because of residual systematic contamination of the ellipsoidal light curve by the complex form of the superhump modulation. The orbital-mean Hα profiles exhibit clear velocity variations with ∼ 500 km s-1 amplitude. We interpret this as the first spectroscopic evidence of an eccentric precessing disc.
Original language | English (US) |
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Pages (from-to) | 791-799 |
Number of pages | 9 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 333 |
Issue number | 4 |
DOIs | |
State | Published - Jul 11 2002 |
Keywords
- Accretion, accretion discs
- Binaries: close
- Stars: individual: XTE J1118+480
- X-rays: stars
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science