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Bursts from GS 1826-238: a clocked thermonuclear flashes generator

P. Ubertini·A. Bazzano·M. Cocchi·L. Natalucci·J. Heise·J. M. Muller·J. J. M. in 't Zand
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Abstract

The transient X-ray source GS 1826-238 was monitored during five different observing periods between August 1996 and October 1998 with the BeppoSAX Wide Field Camera instrument in the framework of a deep observation of the Galactic Center region. A first detection of X-ray bursts from this source occurred, ruling out its previously suggested black hole candidacy and strongly suggesting the compact object to be a weakly magnetized neutron star. During the 2.5 years of monitoring, corresponding to ~2.0 Ms observing time, 70 bursts were detected from the source. We here report a quasi-periodicity of 5.76 h in the burst occurrence time which is present during all observations. This is the first example of quasi-periodic bursting over a period of years. It is in line with the history of a rather constant flux since the turn on in 1988 and points to a very stable accretion.

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P. Ubertini, A. Bazzano, M. Cocchi, L. Natalucci, J. Heise, J. M. Muller, J. J. M. in 't Zand. 1999-01-29. Bursts from GS 1826-238: a clocked thermonuclear flashes generator. https://doi.org/10.1086/311933

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