Shot Noise in USA lightcurves of Black Hole Transient XTE J1118+480

We investigate the behavior of the new transient black hole candidate XTE J1118+480 using shot noise models in the time domain. Using light curves from the Unconventional Stellar Aspect experiment (USA) and RXTE, we model the emission as a superposition of shots. Individual structures in the light curve are fit to template functions. The results are compared to a similar analysis performed on light curves from Cygnus X-1. In both sources, the preferred shape is one with an exponential rise and decay (not necessarily symmetric.) Preliminary results indicate that the characteristic timescale for XTE J1118+480 is around 10 times as long as for Cygnus X-1. Templates are fit both to large, isolated events using light curves integrated into constant-width time bins and to overlapping events using Bayesian blocks. This work was supported by Department of Energy contract DE-AC03-768SF00515, the Office of Naval research, and the NASA Applied Information Systems Research Program.