INTEGRAL high energy behaviour of 4U 1812-12

¹ Istituto di Astrofisica Spaziale e Fisica Cosmica – INAF, via del Fosso del Cavaliere 100, 00133 Roma, Italy e-mail: Antonella.Tarana@rm.iasf.cnr.it
² Istituto di Astrofisica Spaziale e Fisica Cosmica – INAF, via E. Bassini 15, 20133 Milano, Italy
³ Department of Physics and Astronomy, Southampton University, SO17 1BJ Southampton, UK

Received: 26 July 2005
Accepted: 21 October 2005

Abstract

The low mass X-ray binary system 4U 1812-12 was monitored with the INTEGRAL observatory in the period 2003-2004 and with BeppoSAX on April 20, 2000. We report here on the spectral and temporal analysis of both persistent and burst emission. The full data set confirms the persistent nature of this burster, and reveals the presence of emission up to 200 keV. The persistent spectrum is well described by a comptonization (CompTT) model plus a soft blackbody component. The source was observed in a hard spectral state with a 1-200 keV luminosity of  erg s^-1 and and no meaningful flux variation has been revealed, as also confirmed by a 2004 RXTE observation. We have also detected 4 bursts showing double peaked profiles and blackbody spectra with temperatures ranging from 1.9 to 3.1 keV.