Beppo-SAX observation of the burster GS 1826-238 Original Research Article

One of the most intriguing features of the burster GS 1826-238 is the peculiar stability of its bursting behaviour over more than 3 years of observations by the Wide Field Cameras on board BeppoSAX. In fact, the source exhibits a type-I X-ray burst every ∼ 6 hours, and the burst wait times are constant within a few minutes for events spanning up to 6 months apart. In order to better study the physical parameters of GS 1826-238 in connection with its quasi-periodic bursting activity, a BeppoSAX-NFI observation was performed in Autumn 1999. The source was thus studied during consecutive bursts with wide band and sensitive instruments for the first time. Preliminary results of our analysis are presented. In particular, the possible observation of an occasional transition to pure helium burning regime is discussed.