First results of IBIS/ISGRI Cygnus X-3 monitoring during INTEGRAL PV phase

Abstract

We report on preliminary results of IBIS/ISGRI serendipitous observations of Cygnus X-3 in the 15-100 keV energy range during the INTEGRAL Performance and Verification phase. This peculiar microquasar was inside IBIS/ISGRI field of view at a ~ 9^deg distance from the pointing direction during Cygnus X-1 staring observations in November and December 2002. We analyzed observations from 27 November 2002 to 8 December 2002 with an effective on source exposure time of ~ 300 ks. Cyg X-3 was always significantly detected in the 15-40 and 40-100 keV energy bands during single exposures lasting between 30 min and one hour. The source light curve shows the characteristic 4.8-hour modulation with a shape consistent with a standard template. The two light curves' phase zero have no measurable offset and their values are consistent with historical ephemeris. These results show that even at this early stage of the mission, IBIS/ISGRI is capable of producing high quality scientific results on highly off axis, relatively bright targets.

Based on observations with INTEGRAL, an ESA project with instruments and science data center funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain), Czech Republic and Poland, and with the participation of Russia and the USA.