TITLE: GCN CIRCULAR NUMBER: 40816 SUBJECT: sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis DATE: 25/06/24 11:04:07 GMT FROM: ogodet@irap.omp.eu
Authors: O. Godet (IRAP), N. Dagoneau (CEA), F. Cangemi (APC), M. Brunet (IRAP), L. Zhang (IHEP), Y.-D. Hu (GXU), X.-L. Chen (YNU)
Using the event-by-event data downloaded through the X-band ground station, we report further analysis of ECLAIRs observations of the event sb25061207 that we confirm to be a GRB (GRB 250612D) based on the detection of a fading afterglow in both visible (GCN #40707) and X-rays (GCN #40718).
The burst that triggered ECLAIRs onboard (GCN #40697) displays a faint and soft emission with most photons emitted below 20 keV. The duration of this event is around 32 s in the 4-20 keV energy band.
The time-averaged spectrum from T0-32s to T0 (T0 = 2025-06-12T10:27:22 UTC) in the energy range 5-20 keV is best fitted by a powerlaw model with a photon index = 1.7 +/-0.3. With this model, the total 4-120 keV fluence is (7.4 +0.3/-4.2)e-7 erg/cm^2.
All the quoted errors are at the 68% confidence level.
We note that the calibration of SVOM/ECLAIRs is undergoing thus these results are preliminary.
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: Olivier Godet (IRAP) (ogodet at irap.omp.eu)
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