Detection of the dwarf nova GK Persei with SVOM/ECLAIRs

ATel #17980; F. Cangemi (APC, France), S. Le Stum (APC, F), A. Coleiro (APC, F), H. Goto (RIKEN, Japan / CEA, France), L. Zhang (IHEP, China)
on 17 Aug 2026; 13:30 UT
Credential Certification: Floriane Cangemi (cangemi@apc.in2p3.fr)

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We report the detection of the dwarf nova GK Persei with SVOM/ECLAIRs (4-150 keV). The source was first detected by the ECLAIRs Quick Look Analysis on 2026 July 25 at a count rate of 6.95+/-0.67 counts/s (10-20 keV). Since then, the source has been repeatedly detected. An increase in the counting rate was detected continuously from August 7 to August 12, rising from 6.61+/-0.42 counts to 13.56+/-0.94 counts in the 10-20 keV energy band. The most recent detection was obtained on 2026 August 16 with a count rate of 6.98 +/-0.46 counts/s (10-20 keV). July 25 marks the first detection of this source by SVOM/ECLAIRs. The previous ECLAIRs observation in which the source was within the field of view was performed on 2026 July 19 (2618 s), but no significant detection was obtained.

A preliminary spectral analysis shows that the 2026 August 16 spectrum (exposure of 5481s) is well fitted (chi2/dof = 1.87/2) with a black body model (bbody), yielding a temperature of kT = 4.8 (+0.6 /-0.5) keV and a normalisation of norm = 0.011 +/- 0.002. The observed 4-50 keV flux is (9.3 +0.7 / -0.9) e-10 erg/cm2/s. All uncertainties are quoted at the 90% confidence level.

GK Persei underwent an optical outburst in early July 2026. The source was subsequently detected by MAXI on August 9 (ATel #17958). SVOM follow-up observations will continue as the source enters the ECLAIRs field of view. The previous recorded outburst of the source occurred in 2023 January (ATels #15858, and #15860).

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.