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"Clocked" Bursts From GS 1826-238

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

We report on the long term monitoring of the GINGA transient source GS 1826-238 performed with the BeppoSAX Wide Fiels Camera (WFC) instrument, during four different observing campaigns covering October 1996 - September 1999. WFC detection of type-I bursting activity from the source ruled out its proposed black hole candidacy and clearly suggested the compact object related to GS 1826-238 to be a weakly magnetized neutron star. The analysis of the arrival times of the observed 78 bursts lead to the discovery of a recurrence of ~5.75 hours with a spread of 38 minutes (FWHM) along more than 3 years monitoring data (Ubertini et al., 1999). We performed a more detailed analysis of the whole available data, and evidence of shortening of the recurrence time, together with a drastic narrowing in the spread (down to a few minutes) was observed on a one year time scale. Possible relation with the source X-ray persistent emission is discussed.

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M. Cocchi, A. Bazzano, L. Natalucci, P. Ubertini, J. Heise, J. J. M. in 't Zand, J. M. Muller, M. J. S. Smith. 2000-03-22. "Clocked" Bursts From GS 1826-238. https://doi.org/10.1063/1.1303203

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