XTE J1118+480 near Quiescence
ATel #428; C. Zurita, J. Casares, T. Muñoz-Darias, P. RodrÃguez-Gil, I. G. MartÃnez-Pais, T. Shahbaz (Instituto de AstrofÃsica de Canarias) and M. A. P. Torres, P. Zhao, D. Steeghs, M. R. Garcia (Harvard-Smithsonian Center for Astrophysics)
on 28 Feb 2005; 02:16 UT
Credential Certification: Manuel Torres (mtorres@cfa.harvard.edu)
Subjects: Optical, Binary, Black Hole, Transient
Following our optical monitoring of the halo black-hole candidate XTE J1118+480 (ATELs #383, #402, #424), we have obtained time-resolved R-band photometry with the ESA 1-m OGS telescope at the Spanish Observatorio del Teide and with the FLWO 1.2m telescope on Mt. Hopkins. Our observations show that the source has settled into a near-quiescence level, about 0.6-mag brighter than in true quiescence (R~18.9; IAUC # 7868 ). The light curve obtained on 2005 UT Feb 25.90-26.27 is consistent with a double-humped ellipsoidal modulation with an orbital period of 0.17+/-0.01 d and a ~0.35 mag peak-to-peak amplitude. Additionally, the light curve is distorted from a pure ellipsoidal variation suggesting the presence of superhumps, like those observed in the near-quiescence state at the end of the 2000 outburst (Zurita et al. 2002, MNRAS, 333, 791).
