Open AccessDetection of superhumps in XTE J1118+480 approaching quiescence
Author(s) -
Zurita C.,
Casares J.,
Shahbaz T.,
Wagner R. M.,
Foltz C. B.,
RodríguezGil P.,
Hynes R. I.,
Charles P. A.,
Ryan E.,
Schwarz G.,
Starrfield S. G.
Publication year - 2002
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2002.05450.x
Subject(s) - physics , light curve , astrophysics , amplitude , halo , precession , accretion disc , orbital period , orbital inclination , stars , astronomy , ellipsoid , black hole (networking) , accretion (finance) , binary number , optics , galaxy , link state routing protocol , computer network , routing protocol , routing (electronic design automation) , arithmetic , mathematics , computer science
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 P sh =0.17049(1) d i.e. 0.3 per cent longer than the orbital period. This implies a disc precession period P prec ∼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 H α profiles exhibit clear velocity variations with ∼500 km s −1 amplitude. We interpret this as the first spectroscopic evidence of an eccentric precessing disc.