GCN 44758: GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
2026-06-01T15:40:07.074Z | rev 0
M. Brunet, O. Godet (IRAP), D. Turpin (CEA) report on behalf of the SVOM/ECLAIRs team
The SVOM/ECLAIRs telescope detected a transient source, labelled GRB 260530C, starting at 2026-05-30T00:13:15.62 UTC (trigger time T0), through an on-ground search with the event-by-event data downloaded through the X-band ground station.
The burst was detected within several energy ranges and timescales. The best detection is obtained by the Image Trigger with a signal-to-noise ratio of 6.8 within 8-120 keV over a time window of 20.48 seconds starting at T0-20.48s.
The burst that triggered ECLAIRs onground shows a double peak structure. The burst duration is estimated to be around 25s in the 4-120 keV energy band through imaging.
The localization of the source is RA, Dec = 196.655, 26.384 degrees:
RA (J2000) = 13h 06m 37.2s
Dec (J2000) = 26d23m02.4s
with a 90% C.L. radius of 12.8 arcmin (including systematic error of 6 arcmin added in quadrature).
We note that no bright catalogued X-ray sources are found in the error box.
The time-averaged spectrum from T0-20.5 s to T0+4.5 s in the energy range 5-120 keV is best fitted by a powerlaw model with alpha = -1.10 +/- 0.16. With this model, the 4-120 keV fluence is (3.2 +0.3/-1.0) e-7 erg/cm^2 and the 4-120 keV photon flux is 0.26 +0.02/-0.08 ph/cm^2/s.
All the quoted errors are at the 68% confidence level.
A SVOM ToO observation has been requested to follow-up this trigger with both MXT and VT instruments. The results of these observations will be reported later in a future Circular.
The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC.
The SVOM/ECLAIRs point of contact for this burst is: Marius Brunet (IRAP) (marius.brunet at utoulouse.fr)