First INTEGRAL observations of GRS 1915+105
Belloni, T.; Charles, P. A.; Rodriguez, J.; Fender, R. P.; Mirabel, I. F.; Dean, A. J.; Westergaard, N. J.; Lund, N.; Castro-Tirado, A.; Feroci, M.; Hakala, P.; Pooley, G. G.; Poutanen, J.; Wu, K.; Brandt, S.; Zdziarski, A. A.; King, A.; Vilhu, O.; Hunstead, R. W.; Durouchoux, Ph.; Hannikainen, D. C.; Mocœur, I.; Kaiser, C. R.
Finland, Switzerland, France, Denmark, Italy, Spain, United Kingdom, Netherlands, Australia, Poland
Abstract
We present data from the first of six monitoring Open Time observations of GRS 1915+105 undertaken with the orbiting INTEGRAL satellite. The source was clearly detected with all three X-ray and gamma-ray instruments on board. GRS 1915+105 was in a highly variable state, as demonstrated by the JEM X-2 and ISGRI lightcurves. These and simultaneous RXTE/PCA lightcurves point to a novel type of variability pattern in the source. In addition, we fit the combined JEM X-2 and ISGRI spectrum between 3-300 keV with a disk blackbody + powerlaw model leading to typical parameter values found earlier at similar luminosity levels. A new transient, IGR J19140+098, was discovered during the present observation.
Based on observations with INTEGRAL, an ESA project with instruments and science data center funded by ESA and member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, and Spain), the Czech Republic, and Poland and with the participation of Russia and the US.