GRB 240914A

SVOM/ECLAIRs commissioning team: Alexis Coleiro (APC), Stéphane Schanne, Frédéric Chateau, Nicolas Dagoneau, Hervé Le Provost (CEA), Olivier Godet, Laurent Bouchet, Sebastien Guillot, Juliette Alaux (IRAP), Tais Maiolino (LUPM), Karine Mercier, Marie-Claire Charmeau, Stefano Crepaldi (CNES)

SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), Jean-Luc Atteia (IRAP), Arnaud Claret (CEA), Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC), Andrea Goldwurm (APC), Diego Götz (CEA), Xu-Hui Han (NAOC), Cyril Lachaud (APC), En-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs.Paris), Jing Wang (NAOC), Chao Wu (NAOC), Li-Ping Xin (NAOC), Bing Zhang (UNLV)

report on behalf of the SVOM team:

During the commissioning phase, the SVOM/ECLAIRs telescope triggered and located GRB 240914A (sb24091403) an intermediate duration GRB or SGR at 2024-09-14T01:40:03.9 UT (T0).

The following information was received on the ground with by the SVOM VHF Alert Network:

The burst was detected by the Count-Rate Trigger (CRT) onboard ECLAIRs. The signal to noise ratio in the reconstructed image is 10.5 in the 8-50 keV energy band during a time window of 5.12 s starting at T0. The transient location is RA, DEC = 54.281, -35.027 (J2000). The statistical uncertainty on this position is 10.3 arcminutes, to which we recommend to add 10 arcminutes of systematic uncertainty in quadrature during the commissioning phase.

SVOM did not slew to the burst since automated slewing was not enabled.

We note that this position is about 10 arcminutes from NGC 1380.

The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), French Space Agency (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.

The SVOM point of contact for this burst is J-L Atteia: jean-luc.atteia@irap.omp.eu

L. Asquini, M. Landoni, P. D'Avanzo, S. Campana (INAF-Brera), C. Farias (ESO/ La Silla) report:


We observed the field of GRB 240914A (SVOM team, GCN Circ. 37495
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 ) with the ESO-NTT telescope equipped with EFOSC2 starting at 2024-09 14T08:38:49 UT (i.e. about 7 hours after the burst T0), during an on-site test run for the scheduler of the incoming SOXS instrument. 
Observations have been carried out in imaging mode with the Gunn r filter, pointing to the NGC 1380 galaxy position with a 4’ x 4’ field of view. 

Visual inspection with archival optical images of  NGC 1380 from the Legacy Survey shows no clear evidence for new transients. 

From preliminary photometry, we estimate a 3sigma limit of r ~ 22.5 mag (AB), for a region in the outskirts of the NGC 1380 galaxy. 

Further observations and analysis are ongoing. 

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a ToO observation of the SVOM/ECLAIRs GRB 240914A. 
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021716

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the SVOM/ECLAIRs event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a 
GCN Circular after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

This circular is an official product of the Swift-XRT team.

SVOM/GRM team: Chen-Wei Wang, Yong-Wei Dong, Jiang-Tao Liu, Shi-Jie Zheng, Jian-Chao Sun, Wen-Jun Tan, Jiang He, Min Gao, Hao-Xuan Guo, Yue Huang, Lu Li, Yong-Ye Li, Hong-Wei Liu, Xin Liu, Hao-Li Shi, Li-Ming Song, You-Li Tuo, Hao-Xi Wang, Jin Wang, Jin-Zhou Wang, Ping Wang, Rui-Jie Wang, Yu-Xi Wang, Bo-Bing Wu, Shao-Lin Xiong, Jian-Ying Ye, Yi-Tao Yin, Wen-Hui Yu, Fan Zhang, Li Zhang, Peng Zhang, Shuang-Nan Zhang, Wen-Long Zhang, Yan-Ting Zhang, Shu-Min Zhao, Xiao-Yun Zhao, Chao Zheng (IHEP), Maria-Grazia Bernardini (LUPM/INAF-OAB), Laurent Bouchet (IRAP), David Corre (CEA), Tais Maiolino (LUPM), Frédéric Piron (LUPM), Stéphane Schanne (CEA), Jingwei Wang (IAP)

SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), JeanLuc Attéia (IRAP), Arnaud Claret (CEA), Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC), Andrea Goldwurm (APC), Diego Götz (CEA), Xu-Hui Han (NAOC), Cyril Lachaud (APC), En-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs.Paris), Jing Wang (NAOC), Chao Wu (NAOC), Li-Ping Xin (NAOC), Bing Zhang (UNLV)

report on behalf of the SVOM team:

During the commissioning phase, the SVOM/GRM was triggered both in-flight and on-ground by a weak GRB 240914A (SVOM trigger reference: sb24091403) at 2024-09-14T01:40:03.9 UT (T0), which was also observed and located by SVOM/ECLAIRs（Alexis Coleiro et al., GCN 37495
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 ）.

The real-time alert data and light curves of SVOM/GRM were downlinked to the ground through the VHF system with low latency. With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a single pulse with a T90 of 4.6 s +3.1/-4.4 s.

The GRM light curve can be found here:
https://www.bursthub.cn/admin/static/svgrb240914A.png

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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS.

The SVOM point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang@ihep.ac.cn)

S. Dichiara (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U.
Leicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E.
Ambrosi  (INAF-IASFPA) , J.A. Kennea (PSU), D.N. Burrows (PSU) and P.A.
Evans (U. Leicester) reports on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the
SVOM/ECLAIRs-detected burst GRB 240914A, collecting 1.9 ks of Photon
Counting (PC) mode data between T0+36.3 ks and T0+42.4 ks. 

No uncatalogued X-ray sources have been detected. The 3-sigma upper
limit in the field ranges from ~0.005 to ~0.006 ct s^-1, corresponding
to a 0.3-10 keV observed flux of 1.9e-13 to 2.3e-13 erg cm^-2 s^-1
(assuming a typical GRB spectrum).

Three previously-catalogued X-ray sources have been detected, however
their status as catalogued objects makes them unlikely to be the
afterglow.

The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
https://www.swift.ac.uk/ToO_GRBs/00021716.

This circular is an official product of the Swift-XRT team.