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Burst-properties as a function of mass accretion rate in GX 3+1

2003; EDP Sciences; Volume: 400; Issue: 2 Linguagem: Inglês

10.1051/0004-6361

1432-0746

P. R. den Hartog, J. J. M in 't Zand, E. Kuulkers, R. Cornelisse, J. Heise, A. Bazzano, M. Cocchi, L. Natalucci, P. Ubertini,

Mechanics and Biomechanics Studies

GX 3+1 is a low-mass X-ray binary that is persistently bright since its discovery in 1964.It was found to be an X-ray burster twenty years ago proving that the compact object in this system is a neutron star.The burst rate is so low that only 18 bursts were reported prior to 1996.The Wide Field Cameras on BeppoSAX have, through a dedicated monitoring program on the Galactic center region, increased the number of X-ray bursts from GX 3+1 by 61.Since GX 3+1 exhibits a slow (order of years) modulation in the persistent flux of about 50%, these observations opens up the unique possibility to study burst properties as a function of mass accretion rate for very low burst rates.This is the first time that bursts are detected from GX 3+1 in the high state.From the analysis we learn that all bursts are short with e-folding decay times smaller than 10 s.Therefore, all bursts are due to unstable helium burning.Furthermore, the burst rate drops sixfold in a fairly narrow range of 2-20 keV flux; we discuss possible origins for this.