INTEGRAL high-energy monitoring of the X-ray burster KS 1741-293

KS 1741-293, discovered in 1989 by the X-ray camera TTM on the Kvant module of the Mir space station and identified as an X-ray burster, had not been detected in the hard X-ray band until the advent of the INTEGRAL observatory. Moreover, this source has recently been the object of scientific discussion, being also associated with a nearby extended radio source that in principle could be the supernova remnant produced by the accretion-induced collapse in the binary system. Our long-term monitoring with INTEGRAL, covering the period from 2003 February to 2005 May, confirms that KS 1741-293 is transient in the soft and hard X-ray bands. When the source is active, from a simultaneous JEM-X and IBIS data analysis, we provide a wide-band spectrum from 5 to 100 keV, which can be fitted by a two-component model a multiple blackbody for the soft emission and a Comptonized or a cut-off power-law model for the hard component. Finally, by the detection of two X-ray bursters with JEM-X, we confirm the bursting nature of KS 1741-293, including this source in the class of hard-tailed X-ray bursters. 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), the Czech Republic and Poland, and with the participation of Russia and the USA. E-mail giovanni.decesare@iasf-roma.inaf.it ‡ INAF personnel resident at ASDC.