Long-Term Optical Variability of the Black Hole Binary XTE J1118+480
Abstract
We compare multicolor light curves of the black hole binary XTE J1118+480 obtained at Mount Laguna Observatory during the 2003 observing season to light curves obtained from the JKT on La Palma February 2001. In this presentation we highlight two features. First, the source was about 0.5 magnitudes fainter in 2003 than it was in 2001, indicating the true "quiescent" had not yet been reached in 2001 (this point has been noted elsewhere by others). Therefore previous estimates of the distance should be revised. Second, the 2003 light curves are dominated by ellipsoidal variability of the companion star, whereas the 2001 light curves show additional periodic or quasiperiodic variability superimposed on the underlying ellipsoidal modulation. The main signals detected have periods of ≈ 0.042 days and ≈ 0.715 days and amplitudes of ≈ 0.1 mag. Surprisingly, we do not detect any distortion related to the "superhump" (P sh=0.17049 days, Zurita et al. 2002). We characterize these extra modulations and discuss possible origins of them.
- Publication:
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American Astronomical Society Meeting Abstracts
- Pub Date:
- December 2004
- Bibcode:
- 2004AAS...20517203F