TITLE: GCN CIRCULAR NUMBER: 41176 SUBJECT: GRB 250727A: SVOM detection of a burst DATE: 25/07/27 11:55:37 GMT FROM: SVOM_group svomgroup@bao.ac.cn
J. X. Cao (GXU), W. J. Xie (NAOC), M. Brunet, J-L. Atteia (IRAP), M. G. Bernardini (INAF-OAB, LUPM), report on behalf of the SVOM mission team:
At 2025-07-27T10:55:41 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 250727A (SVOM burst-id sb25072701).
The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network.
The burst was only detected by the Image Trigger (IMT), which produced a sequence of 3 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 8.45 in the [8-50] keV energy band over a time window of 163.84 seconds starting at 2025-07-27T10:53:39.
The localization of the best alert is R.A., Dec. 355.7990, -81.1275 degrees: R.A. (J2000) = 23h43m11.76s Dec. (J2000) = -81d07m39.00s with a 90% confidence level (C.L.) radius of 9.33 arcmin (including systematic error of 2 arcmin added in quadrature).
The SVOM/ECLAIRs light curve showed a featureless structure with a T90 duration in the [5-120] keV energy band of about 70 (-14, +16) s.
This burst was also detected by SVOM/GRM with low significance.
No immediate slew was performed on this burst. A SVOM ToO has been requested.
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. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE.
The Burst Advocate (BA) on shift for this alert is Jiaxin Cao: cjx@st.gxu.edu.cn. Please contact the BA by email if you require additional information.
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