1E 1740.7-2942: Temporal and spectral evolution from INTEGRAL and RXTE observations
Capitanio, F.; Bird, A. J.; Ubertini, P.; Malizia, A.; Bazzano, A.; Cadolle Bel, M.; Mirabel, I. F.; Natalucci, L.; De Cesare, G.; Farinelli, R.; Zdziarski, A. A.; Goldwurm, A.; Winkler, C.; Smith, D. M.; del Santo, M.; Bezayiff, N.
Italy, Poland, United States, United Kingdom, France, Netherlands
Abstract
We present results of the monitoring of the black hole candidate 1E 1740.7-2942 with INTEGRAL, in combination with simultaneous observations by RXTE. We concentrate on broad-band spectra from INTEGRAL/IBIS and RXTE/PCA instruments. During our observations, the source spent most of its time in the canonical low/hard state with the measured flux variation within a factor of two. In 2003 September the flux started to decline and in 2004 February it was below the sensitivity level of the INTEGRAL and RXTE instruments. Notably, during the decline phase the spectrum changed, becoming soft and typical of black-hole binaries in the intermediate/soft state.
Based on observations with INTEGRAL, an ESA project with instruments and science data centre funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain), Czech Republic and Poland, and with participation of Russia and the USA.