1999/01/29 by P. Ubertini, A. Bazzano, M. Cocchi +5 · 2 citations
Earth and Planetary Sciences · Engineering · Physics and Astronomy · #Astrophysical Phenomena and Observations #High-pressure geophysics and materials #Mechanics and Biomechanics Studies #astro-ph
paper · pdf · doi:10.1086/311933
3 figures, accepted for publication in ApJ Letters
arxiv created 1999/01/29 · openalex publication_date 1999/03/20 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
The transient X-ray source GS 1826-238 was monitored during five different observing periods between 1996 August and 1998 October with the BeppoSAX Wide Field Camera instrument in the framework of a deep observation of the Galactic center region. During this time, 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 yr of monitoring, corresponding to ~2.0 Ms of observing time, 70 bursts were detected from the source. Here we report a quasi-periodicity of 5.76 hr in the burst occurrence time that 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.