Hard X-Ray Signature of Plasma Ejection in the Galactic Jet Source GRS 1915+105

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Abstract
Since its discovery in 1992, GRS 1915+105 has undergone numerous X-ray outbursts with luminosities ranging from 1037 to a few ×1038 ergs s-1 (20-100 keV). The radio counterpart sometimes exhibits optically thin flares (0.1-1 Jy) in the GHz frequency range associated with superluminal ejection of radio-emitting plasma. Here we examine the temporal and spectral evolution of the hard X-ray and radio emission of GRS 1915+105. We find, during a 1993 December to 1994 April spring outburst, an exceptionally high level of activity in the GHz band coupled with the appearance of several ejection events when compared to other monitoring results. Within the derived uncertainty of the ejection times and the subsequent appearance of radio flares, there appear to be decreases or dips in the hard X-ray flux anticorrelated with increases in radio emission. These observations suggest an interaction between the hard X-ray emission region and jet production, and they imply the redirection of accretion material into jets on timescales of days or less. Although jet production may occur at high accretion rates, other factors must be important, i.e., at times, something must "break" the correlative nature of the radio and X-ray bands. We also search for long-term periodicities in the X-ray data for evidence of a binary signature in light of recent suggestions that GRS 1915+105 may be a high-mass system.