SUMMARY OF PROPOSAL 42053 PROF. JONATHAN E. GRINDLAY PRESIDENT AND FELLOWS OF HARVARD COLLEGE USA USA 02138 CAMBRIDGE 440 HOLLYOKE CENTER, 1350 MASS AVE. E-mail: JOSH@CFA255.HARVARD.EDU Tel: (617)495-5501 Fax: (617)495-2900 Medium: 2GB8MM Subject: X-RAY BINARIES Title: ASCA SPECTROSCOPY OF BURSTERS DETECTED BY SIGMA Abstract: We propose to investigate the X-ray spectral properties of four bursters detected above 30 keV with SIGMA: GX354-0, SLX1732-304, KS1731-260 and A1742-294. All four sources have been poorly studied in the 1-10 keV band. We propose to obtain ASCA observations to constrain the origin of the hard X-ray emission, as required in particular for on-going theoretical investigations. Taking advantage of the high spectral resolution and extended energy coverage of ASCA, we will study the coupling between the cool blackbody-like radiation emitted at the neutron star surface and the Comptonizing corona (i.e. Compton cooling). This is required to understand the residual differences observed between black hole and neutron star systems, with respect to hard X-ray emission. Co-Is: 1 DIDIER BARRET CFA/HARVARD USA BARRET@BODEGA.HARVARD.EDU 617-496 3114 2 KAZUHISA MITSUDA ISAS JAPAN 3 HAJIME INOUE ISAS JAPAN Target Name PRI RA Dec Time TC Off GIS SIS_Cts Obs ------------------- --- -------- -------- ---- -- --- --- ------- --- GX354-0 0 262.9875 -33.8344 20 N N P 20.00000 1 REMARKS: DATA IN THE HARD X-RAY BAND FROM THE BATSE EXPERIMENT SLX1732-304 0 263.9458 -30.4819 20 N N P 6.00000 1 REMARKS: DATA IN THE HARD X-RAY BAND FROM THE BATSE EXPERIMENT REMARKS: DATA IN THE HARD X-RAY BAND FROM THE BATSE EXPERIMENT REMARKS: DATA IN THE HARD X-RAY BAND FROM THE BATSE EXPERIMENT