Flux and spectral variations of 1E1740.7$-$2942 over the years 2003$-$2012

Abstract

The black hole system 1E1740.7$-$2942 is usually the brightest hard X-ray source (above 20 keV) near the Galactic Center, but presents some epochs of low emission (below the INTEGRAL detection limit, for example). In this work, we present the results of studies on 1E1740.7$-$2942 over 10 years, using the instruments ISGRI/IBIS and JEM-X, both on board the INTEGRAL observatory. We fit the spectra with both the compTT and cutoffpl models. According to the fits and taking the mean value over the 10 years, we have obtained a plasma temperature in the range $\sim$20$-$90 keV, and an average powerlaw index of 1.41 ($\sigma$=0.25). We have also made a Lomb$-$Scargle periodogram of the flux in the 50$-$20keV band and found two tentative periods at 2.90 and 3.99days. We present here the preliminary results of this ongoing work.

10th INTEGRAL Workshop: "A Synergistic View of the High Energy Sky" - Integral2014,15-19 September 2014, Annapolis, MD, USA