SVOM/ECLAIRs confirmation of GS 1826-238's return to a clocked burster state
ATel #17251; M. Brunet (IRAP, France), A. Coleiro (APC, F), S. Guillot (IRAP, F), J. Rodriguez (CEA, F), F. Cangemi (APC, F), L. Zhang (IHEP, China)
on 27 Jun 2025; 15:48 UT
Credential Certification: Alexis Coleiro (alexis.coleiro@u-paris.fr)
Subjects: X-ray, Binary, Neutron Star, Transient
GS 1826-238 (aka the Clocked Burster), has recently been seen to return to a ''clocked burster'' state as reported from NinjaSat observations (ATel #17245).
The source was in the field-of-view of the SVOM/ECLAIRs coded-mask instrument (4-150 keV) three times between June 21 and June 26, 2025, with a total exposure of approximately 49 ks.
During these observations, ECLAIRs detected six Type-I X-ray bursts through an offline search with the event-by-event data downloaded via the X-band ground station. Three of these bursts showed recurrence intervals of approximately 1.6 hours, confirming that GS 1826-238 have indeed entered a clocked burster state as already suggested by NinjaSat observations (ATel #17245).
The centers of the 2.5-second time windows during which the burst onsets were detected are listed below:
- 2025-06-21T07:51:28
- 2025-06-21T09:36:21
separated by 1.75 h.
- 2025-06-25T18:44:42
- 2025-06-25T20:19:10
- 2025-06-25T21:55:53
separated by 1.57h and 1.61h respectively.
For reference, during an 80-second window covering the rise and decay phases of the burst detected on 2025-06-25 at 21:55:53, the 4-20 keV energy flux was measured at 9.3(+/-0.7)e-9 erg/s/cm^2, assuming a bbody spectral model.
As previously reported in ATel #
17245, the observed recurrence periods are among the shortest ever observed for this source in its clocked burster state. Continued follow-up observations are encouraged.
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. ECLAIRs was developed jointly by APC, CEA, CNES and IRAP. MXT has been developed jointly by CNES, CEA, IJCLab, University of Leicester and MPE.
