X-Ray Timing in 1E 1740.7−2942 and GRS 1758−258

Abstract

We report on deep observations of the Galactic bulge sources 1E 1740.7-2942 and GRS 1758-258 with the Rossi X-Ray Timing Explorer. These objects form a class of two, showing radio jets, very hard spectra, and persistent emission. Here we show that their power spectra are also similar: flat-topped noise, breaking to a power law, with a pair of weak, harmonically spaced quasi-periodic oscillations above the break and an integrated rms variability of ~20%. We discuss to what extent these results can be considered support for the identification of both as black hole candidates.