GCN Circular 45129
Subject
GRB 260704A: SVOM/ECLAIRs refined analysis
Event
Date
2026-07-10T07:41:16Z (2 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
GRB 260704A: SVOM/ECLAIRs refined analysis
Wenjin Xie (NAOC), Marius Brunet (IRAP), Olivier Godet (IRAP), Floriane Cangemi (APC), Xiao Tian (GXU), Yehao Cheng (YNU) report on behalf of the SVOM/ECLAIRs team
Using the event-by-event data downloaded through the X-band ground station, we report further analysis of SVOM/ECLAIRs observations of GRB 260704A (SVOM burst-id sb26070403 – GCN 45072, trigger time T0 = 2026-07-04T03:41:05 UTC).
The burst shows a multiple peak lightcurve, with a precursor between T0-41s and T0 s, and a main pulse from T0+105 s to T0+160 s. The burst duration is T90 = 166 +10/-7 s in the 4-120 keV energy band.
Considering the main pulse data, the refined burst localization we obtained is R.A., Dec = 318.631, -25.532 degrees :
R.A. (J2000) = 21h14m31.44s
Dec. (J2000) = -25d31m55.20s
with a 90% confidence level (C.L.) radius of 5.2 arcmin (including systematic error of 2 arcmin added in quadrature).
We note that the refined ECLAIRs central position is 4.33 arcmin from the X-ray counterpart position mentioned by the SVOM/MXT (W.J. Xie et al., GCN Circ. 45072) , and 4.79 from the position provided by EP/FXT (Y.-H. I. Yin et al., GCN Circ. 45078).
The time-averaged spectrum from T0-41 s to T0 s (precursor) in the 5-120 keV energy range is best fitted by a powerlaw model with best-fit parameters alpha = -2.71 +/- 0.31. the 4-120 keV fluence is 1.7 +0.1/-0.7 erg/cm² (photon flux is 0.29 +0.01/-0.11 ph/cm²/s) .
For the main pulse, the time-averaged spectrum from from T0+105 s to T0+160 s in the 5-120 keV energy range is best fitted by a powerlaw model with alpha = -1.96 +/- 0.12, the 4-120 keV fluence is 6.1 +0.5/-0.7 erg/cm² (photon flux is 0.48 +0.01/-0.05 ph/cm²/s) .
The values of the photon index may imply that the peak energy of the burst is less than 5 keV. If so, GRB 260704A shall be classified as an X-ray flash
The SVOM/ECLAIRs point of contact for this burst is: Wenjin XIE (NAOC) (xiewj@bao.ac.cn)