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S.S. Eikenberry (Cornell University), K. Matthews (Caltech), P.R. Blanco (UC San Diego), M. Muno, E.H. Morgan, R.A. Remillard (MIT)
We present simultaneous infrared and X-ray observations of the Galactic microquasar GRS 1915+105 using the Palomar 5-m telescope and Rossi X-ray Timing Explorer on July 10, 1998 UT. Over the course of 5 hours, we observed 6 faint infrared (2.2-micron) flares with peak amplitudes of ~0.6 mJy and durations of ~500 seconds. These flares are associated with X-ray soft-dip/soft-flare cycles, as opposed to the brighter infrared flares associated with X-ray hard-dip/soft-flare cycles seen in August 1997 by Eikenberry et al. (1998). Interestingly, the IR flares begin before the X-ray oscillations, implying an ``outside-in'' origin of the IR/X-ray cycle. We also show that the quasi-steady infrared excess in August 1997 is due to the pile-up of similar faint flares. We discuss the implications of this previously unknown flaring behavior for understanding jet formation in microquasars.
This research was funded in part by NASA's Office of Space Science.