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R. K. Jain, C. D. Bailyn (Yale University), J. A. Orosz (The Pennsylvania State University), J. E. McClintock (Center for Astrophysics), R. A. Remillard (Center for Space Research, MIT)
We present results of an optical monitoring campaign for the newly discovered X-ray transient XTE J1550-564. Since the discovery of XTE J1550-564 by the RXTE satellite on Sept 7 1998, we have monitored the source in the optical using the YALO 1m telescope in Chile. Based on our observations from Sept 9 to Oct 27 1998, the optical counterpart was discovered at V = 16.7 (IAUC 7009). The optical brightness has been falling steadily except for a mild flare of ~ 0.2 magnitudes which peaked approximately 1 day after the ~6.8 crab X-ray flare (IAUC 7019). We resumed observations from Jan 3, 1999 and have continued observing on a nightly basis. The light curve from 1999 is dramatically different from what was found in 1998. The object was approximately 0.5 magnitudes brighter during 1999 compared to the peak brightness of the optical flare. Furthermore, the optical light curve is essentially flat, exhibiting minimal decay over time. We also present light curves for Aql X-1 obtained by the Yale 1m telescope from June 19 to November 28, 1998. Between September 15 and Sept 25 1998, there was an optical mini-outburst which was not followed by an X-ray outburst.
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