INTEGRAL observations of the X-ray burster 4U1850-087: first detection of hard X-ray emission extending above 50keV

Abstract

The X-ray burster 4U1850-087, located in the globular cluster NGC6712, is an ultracompact binary likely harbouring a degenerate companion.The source has been observed with INTEGRAL several times, during the monitoring of the Galactic plane, with an unprecedented exposure time. The broad-band spectrum (2-100 keV; INTEGRAL together with a quasi-simultaneous XMM-Newton observation) is well described with a disk-blackbody emission (kTin=0.8keV) together with a power-law (photon index of 2). We report here the first detection of hard X-ray emission from this source above 50 keV. A lower limit on the presence of a high energy cut-off can be placed at Ec>100keV.

To be published in the proceedings of the conference "The Multicoloured Landscape of Compact Objects and their Explosive Origins", eds.L.Burderi et al., held in Cefalu', Sicily (Italy), June 11-24, 2006. Submitted