Title: X to Gamma Ray deep observations of two X-ray Bursters.


Proposal ID: 0120207
Subject category: Compact Object
Principal investigator: Bazzano
Institute: CNR - Istituto di Astrofisica Spaziale

Abstract

We aim to investigate on a wider energy band, the spectral behaviour of two already detected reported hard X-ray bursters to better determine the spectral parameters (presence of an energy cut-off, reflection component etc.), study the accretion flow around the compact object and hence to firmly establish the still unclear emission origin. This as a part of long term programme started with BeppoSAX. The BeppoSAX and RossiXTE telescopes allowed for the first time to perform simultaneous high energy observations of classes of objects on a wide energy band. A high energy component in the spectra of X-Ray bursters, firstly discovered by SIGMA, has been detected with the NFIs (Narrow Field Instruments) on board BeppoSAX from at least 15 sources confirmning these objects as hard X-ray emitters. Similarity of Black Hole and Neutron Star spectra as well as variability when in "Low State" suggest the same mechanism to power the hard X-ray emission. Still controversial remain observational criteria to distinguish these two types of accreting systems apart from clear timing signature such as X-ray pulsation or X-ray bursts. We require total of 2 x 300 ksec to be spent on 2 bursters whose hard X-ray properties need for key investigation at high energy to disentangle their soft gamma ray emission processes: X1916-053 and X2127+119.