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D.E. Gruber (CASS/UCSD), Y. Rephaeli (CASS/UCSD \& Tel Aviv U.)
The nearby starburst galaxies M82 and NGC253 were monitored by RXTE during 1966 in a series of 30 observations each. The observation plan was designed to detect variability on all time scales up to 10 months. The >2.5 keV x-ray emission from NGC253 showed some significant variability from its average value of 1 mCrab, but no marked changes. The flux from M82, on the other hand, was fairly steady for the first 7 months at an average of 4 mCrab, but then doubled to 8 mCrab within three weeks, and stayed more or less at the new level. Spectra from both objects and at all times were thermal rather than power-law, and the temperature of the flaring component in M82 was lower by 25% than the previous emission. If at M82, the flare luminosity is several times 1040, which may indicate origin in a compact object of mass greater than a few M\odot.
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