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E. Chapman, R.M. Sambruna (George Mason University)
We present X-ray observations of the nearby TeV blazar Mrk 501 obtained in 1998 and 1999 with the Rossi X-ray Timing Explorer. We are using proprietary as well as archival RXTE data. In 1998, the source was observed starting February 25 every three days for two months, then daily in May and June, and finally with a more irregular sampling through September. In 1999, Mrk 501 was observed daily starting May 7 for a month, and with a more sparse sampling throughout June and July. We will discuss the results of a detailed timing and spectral analysis of both datasets. Large flux and spectral variations are observed at both epochs. The 2--20 keV PCA light curves show large-amplitude flux changes up to a factor 4 on timescales of one day. The flux changes are accompanied by spectral variations, with the well-known trend of flatter X-ray spectrum with increasing intensity, in agreement with a synchrotron origin for the X-ray flux. The results will be compared to models for X-ray emission from relativistic jets.
This work is supported by NASA grant NAG5-10244.