GRB 240713A

SVOM/GRM team: Wen-Jun tan, Yong-Wei Dong, Jiang-Tao Liu, Shi-Jie Zheng, Jian-Chao Sun, Chen-Wei Wang, 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, Chen-Wei Wang, 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), Patrick Maeght (LUPM), Frédéric Piron (LUPM), 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 detected a weak long GRB 240713A at 2024-07-13T02:02:40 UT (T0) with on-ground blind search using event-by-event data downloaded through the X-band ground station, which also triggered SVOM/ECLAIRs (ECLAIRs team, GCN 36854
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 ) and Fermi/GBM Sub-threshold Observation(Fermi GBM team, GCN 36856
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 ).

The GRM light curve shows that this burst consists of multiple pulses with a duration of about 60 s.

The GRM light curve can be found here:
http://www.bursthub.cn//admin/static/svgrb240713A.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: Wen-Jun Tan (IHEP)(tanwj@ihep.ac.cn)

S. Guziy (IAA-CSIC), Y.-D. Hu (INAF-OAB),  A. J. Castro-Tirado, E. Fernandez-Garcia, I. Perez-Garcia, S.-Y. Wu, M. D. Caballero-Garcia, R. Sanchez-Ramirez  (IAA-CSIC) and I. Vico and I. Hermelo (CAHA) on behalf of a larger collaboration, report:

Following the detection of GRB 240713A by SVOM/ECLAIRs (Schanne et al. GCNC 36854), we triggered the 2.2m CAHA telescope (+ CAFOS) at the Calar Alto Observatory (Almeria, Spain). Images were gathered starting on Jul. 15 02:41:58 UT (i.e. ~ 2.0 days after trigger) in Sloan-griz and clear bands covering part (about 50%) of the error region. On the co-added clear band image (200 x 7 s), no optical transient is detected in the 16 arcmin diameter FOV, including the four EP candidates (Yang et al. GCNC 36859), down to 23.5 mag. This non-detection is consistent with the reports from Hello et al. (GCNC 36855), Sankar et al. (GCNC 36857), Turpin et al. (GCNC 36861), Jiang et al. (GCNC 36862), An et al. (GCNC 36863), Schneider et al. (GCNC 36864), Reguitti et al. (GCNC 36876), Konno et al. (GCNC 36880) and Oates et al. (GCNC 36889).

We thank the staff at Calar Alto observatory for their excellent support.

S. R. Oates (Lancaster U.) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 240713A
142 ks after the SVOM trigger (Schanne et al., GCN Circ. 36854
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 ).
No optical afterglow is found in the initial UVOT exposures.
The UVOT exposures include the positions of XRT sources 1 and 2, but
XRT source 3 is outside of the UVOT field of view (Perri et al., GCN 36884
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 ).
No optical source is found consistent with the XRT sources.

Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag
white            142975       156299        3969         >22.4

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.03 in the direction of the burst
(Schlegel et al. 1998).

M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), J.A. Kennea
(PSU), A. Tohuvavohu (U. Toronto), D.N. Burrows (PSU), J.P. Osborne (U.
Leicester), K.L. Page (U. Leicester), B. Sbarufatti (INAF-OAB) and P.A.
Evans (U. Leicester) reports on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the SVOM-detected
burst GRB 240713A in a series of observations tiled on the sky. The
total exposure time is 4.0 ks, distributed over 1 tiles; the maximum
exposure at a single sky location was 4.0 ks. The data were collected
between T0+142.7 ks and T0+156.3 ks, and are entirely in Photon
Counting (PC) mode. 

Three uncatalogued X-ray sources have been detected, however none of
them is above the RASS limit or shows definitive signs of fading. 
Source 3 is consistent in position and flux with EP J233058.2+015317,
identified by EP-FXT in their follow-up observations (GCN 36859
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 ). The
consistent flux between the two detections suggest that the source is
not fading. Moreover, source 3 is spatially consistent with a
catalogued 2MASS source (2MASS J23305766+0153156). 
Source 2 is spatially consistent and can be associated to a catalogued
quasar (SDSS J233053.58+014603.0). 
Therefore, at the present time we cannot identify which, if any, is the
afterglow. Details of these sources are given below:

Source 1:
  RA (J2000.0):  352.7279  =  23:30:54.70
  Dec (J2000.0): +1.9401  =  +01:56:24.5
  Error: 6.7 arcsec (radius, 90% conf.)
  Count-rate: (1.55 [+1.06, -0.76])e-3 ct s^-1	 
  Distance: 541 arcsec from SVOM position.

Source 2:
  RA (J2000.0):  352.7219  =  23:30:53.25
  Dec (J2000.0): +1.7664  =  +01:45:59.2
  Error: 7.4 arcsec (radius, 90% conf.)
  Count-rate: (1.63 [+1.13, -0.80])e-3 ct s^-1	 
  Distance: 626 arcsec from SVOM position.

Source 3:
  RA (J2000.0):  352.7404  =  23:30:57.69
  Dec (J2000.0): +1.8868  =  +01:53:12.6
  Error: 6.1 arcsec (radius, 90% conf.)
  Count-rate: (2.33 [+1.24, -0.94])e-3 ct s^-1	 
  Distance: 541 arcsec from SVOM position.
  Flux: (6.3 [+3.3, -2.5])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)

The results of the XRT-team automatic analysis of the tiled XRT
observations, including a position-specific upper limit calculator, are
available at https://www.swift.ac.uk/xrt_products/TILED_GRB00126.

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

A. Reguitti (INAF-OAB/INAF-OAPd), P. D'Avanzo, R. Brivio, M. Ferro, Y-D.Hu (INAF-OAB), A. Rossi (INAF-OAS), 
A. Melandri (INAF - OAR), L. Tomasella (INAF-OAPd) report on behalf of the CIBO collaboration:

We observed the field of GRB 240713A detected by SVOM/ECLAIR and Fermi/GBM (Schanne et al., GCN Circ. 36854
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 ; 
Burns et al., GCN Circ. 36856
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 ) from the INAF - Padova Astronomical Observatory located in Asiago (Italy) with the Schmidt 
telescope starting on 2023-07-14 at 00:06:36 UT (~ 22.07 hours after the burst) with the r filter.

No optical afterglow candidate is detected within the entire 1 deg x 1deg field of view of the telescope, which covers the whole 
error circle of SVOM/ECLAIR and the positions of the EP-FXT sources (Yang et al., GCN Circ. 36859
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 ), down to a 3sigma limiting 
magnitude of r ~ 20.7 (AB; calibrated against the PanSTARRS catalogue).

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

Swift has initiated a series of observations, tiled on the sky, of the
SVOM GRB 240713A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00126

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. The probability of finding
serendipitous sources, unrelated to the SVOM event is high: 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.

Benjamin Schneider (MIT), Geoffrey Mo (MIT), Viraj Karambelkar (Caltech), Robert Stein (Caltech), Danielle Frostig (MIT), Nathan Lourie (MIT), Tomas Ahumada (Caltech), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report:

We observed the SVOM/ECLAIRs localization region of GRB 240713A (Schanne et al, GCN 36854
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 ) and the possible sub-threshold signal of Fermi/GBM (Burns et al., GCN 36856
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 ) in the near-infrared J-band with the Palomar 1-m telescope, equipped with the 1-square degree WINTER camera (Lourie et al. 2020).

Our observations began at 2024-07-13T11:34:28 UTC (~9.5 hours after the GRB trigger) and consisted of 22 exposures of 120s before sunrise. The images were processed using the WINTER data reduction pipeline (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.10888436
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 ), with image subtraction performed relative to J-band images from the UKIRT Hemisphere survey (Dye et al., 2017).

Our observations covered 90% of the SVOM/ECLAIRs error circle and 8/10 of the EP/FXT soft X-ray afterglow candidates (Yang et al., GCN 36859
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 ). EP J233039.0+014426 and EP J233017.4+014339 were out of our field of view. In our stacked and subtracted images, we do not detect any new source to a depth of J ~ 19 mag (AB).

WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research.

J. An, S.Q. Jiang, X. Liu, Z.P. Zhu, S.Y. Fu, L.B. He, D. Xu (NAOC), J.P.U. Fynbo (DAWN/NBI), N. Koivisto (NOT) report on behalf of a large collaboration:

We observed the field of GRB 240713A detected by SVOM/ECLAIRs (Schanne et al., GCN 36854
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 ) and by Fermi/GBM as a sub-threshold event (Burns et al., GCN 36856
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 ) using the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. 

Due to the constraints of the NOT's FOV and observational time window, we managed to observe three among the ten EP/FXT soft X-ray afterglow candidates (Yang et al., GCN 36859
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 ). Observation started at 2024-07-14T03:02:07, i.e., ~ 1.04 day after the SVOM trigger, and a series of 300 s in the Sloan r-band images were obtained.

No credible uncatalogued source or apparently brightening catalogued source was found at the positions of the three candidates. Preliminary results are as follows

Source | mid time | T-T0(d) |  U.L. (5 sigma)
----------------------------------------------------------
EP J233017.4+014339  | 2024-07-14T03:18:18 | 1.0525 | 24.0
EP J233012.2+015001  | 2024-07-14T03:52:33 | 1.0763 | 24.0
EP J233020.4+015231  | 2024-07-14T03:52:32 | 1.0763 | 24.0

calibrated with nearby PanSTARRS stars and not corrected for Galactic extinction.

S.Q. Jiang, S.Y. Fu, Z.P. Zhu, X. Liu, J. An, L.B. He, D. Xu (NAOC), J.Z. Liu (XAO) report on behalf of a large collaboration:

We observed the field of GRB 240713A detected by SVOM/ECLAIRs (Schanne et al., GCN 36854
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 ) and by Fermi/GBM as a sub-threshold event (Burns et al., GCN 36856
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 ) using the 50D, 100C telescopes of the JinShan project located at Altay, Xinjiang, China.

A series of Sloan r-, i-, and z- bands frames were obtained fro m 17:33:20 UT to 20:22:38.95 on 2024-07-13, i.e., starting 15.51 hr after the SVOM trigger time.

We didn't detect any credible new source at the positions of the ten X-ray afterglow candidates found by EP/FXT (Yang et al., GCN 36860
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 ), down to the following 5-sigma upper limits:

Source | R.A. | Dec. | Sloan-r | Sloan-i | Sloan-z |
--------------------------------------------------------
EP J233058.2+015317  | 352.7425 | 1.8879 | 22.0 | 19.7 | 20.0
EP J233023.3+015537  | 352.5970 | 1.9269 | 20.6 | 19.7 | 20.2
EP J233039.0+014426  | 352.6627 | 1.7404 | 22.0 | 19.7 | 20.0
EP J233020.4+015231  | 352.5850 | 1.8753 | 22.0 | 19.7 | 20.2
EP J233016.5+020124  | 352.5687 | 2.0232 | 20.6 | 19.7 | 20.2
EP J233017.4+014339  | 352.5724 | 1.7275 | 22.0 | 19.7 | N/A
EP J233012.2+015001  | 352.5509 | 1.8335 | 20.6 | 19.7 | 20.0
EP J233042.1+015623  | 352.6754 | 1.9397 | 20.6 | 19.7 | 20.0
EP J233002.5+015949  | 352.5104 | 1.9968 | 20.6 | 19.7 | 20.2
EP J232954.2+015030  | 352.4757 | 1.8416 | 20.6 | 19.7 | N/A

calibrated with nearby PanSTARRS stars and not corrected for Galactic extinction.

We acknowledge the excellent support from S.W Luo, M.M. Yang, Z. K. Feng, Q. C. Zhao and L.F. Huo for enabling these observations.

D. Turpin (CEA Paris-Saclay), Vincent Robert (IMCCE), C. Adami, S. Basa (LAM/Pytheas/AMU), A. de Ugarte Postigo (OCA/LAM), S. D. Vergani (GEPI, Obs. de Paris), B. Schneider (MIT), E. Le Floc'h, D. Götz, F. Schussler (CEA Paris-Saclay), M. Dennefeld (IAP) report on behalf of a larger collaboration:

We observed the field of GRB 240713A (Schanne et al., GCN 36854
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 ) also possibly detected by Fermi-GBM as a sub-threshold event (Burns et al., GCN 36856
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 ) using the T120cm telescope at Observatoire de Haute-Provence (France). A total of 8 single exposures between 400-500 seconds (3200 sec in total) were obtained in the R-band from 00:27:57.12 UT to 01:35:28.71 on 2024-07-14 (mid-time ~22.98h after the SVOM ECLAIRs trigger time). Note that our field of view (FoV) could only partially cover the ECLAIRs error box so we perfomed single observations with a quite large dithering in order to cover ~80% of the ECLAIRs error box. This results in an sky position dependency of our exposure time in the combined frame.

In the combined frame, after subtracting with the PanSTARRS DR1 catalog, we did not detect any optical counterpart consistent with the non detection reported by (Hello et al., GCN 36855
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 ; Sankar et al., GCN 36857
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 ). We measure a limiting magnitude of R > 21.7 (5 sigma) where we obtained the longest exposures in the stacked frame.

At the positions of the x-ray sources found by EP/FXT (Yang et al., GCN 36860
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 ), we derive the following optical upper limits in R-band:

Source | R.A. | Dec. | OHP/T120 U.L (5 sigma)
----------------------------------------------------------
EP J233058.2+015317  | 352.7425 | 1.8879 | 21.3
EP J233023.3+015537  | 352.5970 | 1.9269 | 21.7
EP J233039.0+014426  | 352.6627 | 1.7404 | Not in our FoV
EP J233020.4+015231  | 352.5850 | 1.8753 | 21.8
EP J233016.5+020124  | 352.5687 | 2.0232 | 21.4
EP J233017.4+014339  | 352.5724 | 1.7275 | Not in our FoV
EP J233012.2+015001  | 352.5509 | 1.8335 | 21.8
EP J233042.1+015623  | 352.6754 | 1.9397 | 21.7
EP J233002.5+015949  | 352.5104 | 1.9968 | 21.3
EP J232954.2+015030  | 352.4757 | 1.8416 | 21.3

The photometric calibration was performed using nearby stars from the Gaia DR3 Synphot catalog and magnitudes are not corrected for Galactic extinction.

We acknowledge the Observatoire de Haute Provence staff for their excellent support.

This was a duplicate submission of GCN 36859
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 .

J. Yang (NJU), Q. Y. Wu, M. J. Liu, X. Pan, Z. X. Ling, C. C. Jin, W. Yuan, Y. Liu, C. Zhang, W. Chen, H. Q. Cheng, C. Z. Cui, D. W. Fan, H. B. Hu, J. W. Hu, M. H. Huang, D. Y. Li, H. Y. Liu, Z. Z. Lv, T. Y. Lian, X. Mao, H. W. Pan, H. Sun, W. X. Wang, Y. L. Wang, S. X. Wen, X. P. Xu, Y. F. Xu, H. N. Yang, M. Zhang, W. D. Zhang, W. J. Zhang, Z. Zhang, D. H. Zhao (NAOC, CAS), J. Guan, C. K. Li, Y. Chen, S. M. Jia, W. W. Cui, H. Feng, D. W. Han, W. Li, C. Z. Liu, F. J. Lu, L. M. Song, J. Wang, J. J. Xu, J. Zhang, S. N. Zhang, H. S. Zhao, X. F. Zhao (IHEP, CAS), E. Kuulkers, A. Santovincenzo (ESA), P. O'Brien (Univ. of Leicester), K. Nandra, A. Rau (MPE), B. Cordier (CEA) on behalf of the Einstein Probe team

Following the detection of the GRB 240713A reported by ECLAIRs on board SVOM (Schanne et al., GCN 36854
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 ), which also shows a possible sub-threshold signal in Fermi/GBM data (Burns et al., GCN 36856
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 ), we performed an observation of GRB 240713A with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation began at 2024-07-13T15:23:28 (UTC), about 13.3 hours after the detection of SVOM/ECLAIRs. The exposure time is about 6.8 ks. Through the preliminary analysis of the EP-FXT data, we found 10 X-ray sources within the SVOM/ECLAIRs localization error box (10 arcmin centered on RA, Dec = 352.59, 1.88), which are detailed as follows. The positions are given with an uncertainty of 30 arcsec (radius, 90% C.L. statistical and systematic). The 0.5 - 10 keV flux is derived from the FXT-B data if the source is detected by both FXT-A and FXT-B.

Source | R.A. | Dec. | FXT-A Significance | FXT-B Significance | Estimated Flux 
       |      |      |                    |                    |   (erg/s/cm^2) 
--------------------------------------------------------------------------------
EP J233058.2+015317  | 352.7425 | 1.8879 | 7.4 | 8.7 | 5.6 x 10^-14
EP J233023.3+015537* | 352.5970 | 1.9269 | 4.7 | 6.1 | 4.5 x 10^-14
EP J233039.0+014426* | 352.6627 | 1.7404 | 4.1 | 5.3 | 4.5 x 10^-14
EP J233020.4+015231  | 352.5850 | 1.8753 | 5.1 | 5.0 | 2.7 x 10^-14
EP J233016.5+020124  | 352.5687 | 2.0232 | 4.9 | 4.6 | 3.0 x 10^-14
EP J233017.4+014339  | 352.5724 | 1.7275 | <3.0 | 4.1 | 4.4 x 10^-14
EP J233012.2+015001  | 352.5509 | 1.8335 | <3.0 | 3.6 | 2.1 x 10^-14
EP J233042.1+015623  | 352.6754 | 1.9397 | <3.0 | 3.6 | 1.9 x 10^-14
EP J233002.5+015949  | 352.5104 | 1.9968 | 4.1 | <3.0 | 2.5 x 10^-14
EP J232954.2+015030  | 352.4757 | 1.8416 | 4.7 | <3.0 | 2.4 x 10^-14
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*Note: EP J233023.3+015537 is 15.9 arcsec away from a quasar named SDSS J233022.43+015527.2, and EP J233039.0+014426 is 5.0 arcsec away from another quasar SDSS J233038.79+014428.6. These two sources may be related to the two quasars.

The above observation was made with the EP-FXT instrument. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES.

A. Sankar. K, A. Aryan, Y. J. Yang, H.-Y. Hsiao, C.-S. Lin, T.-W. Chen (all NCU), S. Yang (HNAS), W.-J. Hou, C.-C. Ngeow, C.-H. Lai, M.-H. Lee, Y.-C. Pan, H.-C. Lin, J.-K. Guo (all NCUIA), S. J. Smartt (Oxford/QUB), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, J. Gillanders, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (IfA, University of Hawaii) report: 

We observed the field of the first probable GRB240713A Located On-Board SVOM by ECLAIRs (Schanne et al., GCN 36854
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 ) and followed by Hello et al. (GCN 36855
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 ) and Burns et al. (GCN 36856
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 ). We use the 40cm SLT at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al., 2024arXiv240609270C). The first SLT epoch of observations started at 16:02 UT on the 13th of July 2024 (MJD = 60504.668), 14 hrs after the SVOM trigger. 

We utilized the astroalign (Beroiz et al., 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al., 2022, ApJ, 935, 167) packages to align and stack the individual frames. 
We do not detect any evidence of a new uncatalogued source in our stacked frames having a Field of View (FoV) of around 13'.0 x 13'.0 centered at R.A. = 23:30:24.55 and Dec. = +01:52:50.9. Moreover, we utilized the python based package, AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform the PSF photometry on our stacked frame. The details of the observations and measured 3-sigma upper limit (in the AB system) are as follows:

Telescope | Filter | MJD (start) | t-t0 | Exposure | Magnitude | avg. Seeing | med. Airmass
SLT | r | 60504.668 | 15 hrs | 300 sec * 12 | > 20.5 | 2".27 | 1.69

The presented magnitudes are calibrated using the field stars from the Pan-STARRS1 catalog and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V) = 0.03 mag in the direction of the burst (Schlafly & Finkbeiner 2011).

E. Burns (LSU), P. Veres (UAH), and C. M. Hui (MSFC) report on behalf of the Fermi-GBM Team:

SVOM detected a probable GRB (Schanne et al. 2024, GCN 36854
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 ) at 02:02:40 UT on July 13, 2024. There was no Fermi-GBM onboard trigger around the event.

The GBM targeted search [1], the most sensitive, coherent search for short GRB-like signals, did not find any significant signal with the default short GRB search settings. However, extending the window durations up to 32.768s identified a coherent transient signal with a S/N of 8.0 from the same region of the sky and temporal window as identified by the SVOM ECLAIRs telescope. The extended signal was found with the “soft” spectral template. We note that we have not yet carefully characterized transients on this timescale with this search. Overall, we believe this to be a valid GBM signal of the SVOM/ECLAIRs GRB and encourage follow-up confirmation.

[1] Goldstein et al. 2019 arXiv:1903.12597
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P. Hello (IJCLAB), T. Hussenot-Desenonges (IJCLAB), N. Kochiashvili (AbAO), R. Strausbaugh (EIU), C. Andrade (UMN), S. Antier (OCA), M. Coughlin (UMN), P-A Duverne (APC),  N. Guessoum (AUS), S. Karpov (FZU), T. Pradier (Unistra/IPHC), D. Turpin (CEA-Saclay/Irfu), X.-H. Han (NAOC), A. Klotz (CNRS-OMP-IRAP), M. Boer, S. Gervasoni, C. Limonta, A. De Ugarte-Postigo (OCA), K. Noysena, M. Sun (NARIT) on behalf of the GRANDMA collaboration.

TAROT together with GRANDMA, partner of the SVOM collaboration, performed follow-up in response to the GRB240713A detected by ECLAIRs (GCN36854
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 , Schanne et al.) on 2024-07-13 at 10:23:36 UTC (MJD 60504.43925, 8.5h after T0) with TAROT-TCH followed by TRT-SBO telescopes (observations to be received soon).

TAROT-TCH data have been reduced by a single data processing pipeline STDPIPE (Karpov et al., 2022). We do not find any optical counterpart within the ECLAIRs localization error box (10 arcmin centered on RA, Dec = 352.59, 1.88 (J2000)). We estimated an upper limit of the image at 18.4 in r-band (5 sigma).

Further GRANDMA data on this event will be available at https://skyportal-icare.ijclab.in2p3.fr/public/sources/GRB240713A/version/9906c481cae20d4b32d7be3e4afdb05e.

We thank SVOM for useful communication. We use the Skyportal application (skyportal.io) to monitor our observational campaign.

GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 49, 5518). 

Stéphane Schanne (CEA), Olivier Godet (IRAP) on behalf of the ECLAIRs collaboration 

and 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)

GRB240713A : The First probable GRB Located On-Board SVOM by ECLAIRs.

On July 13 2024, 02:02:40 (UTC, TimeTb) the ECLAIRs telescope on board SVOM triggered and located an apparent gamma-ray burst during the commissioning phase.

The on-board trigger produced real-time alerts, but their prompt sending to ground is not yet enabled, such that they were received after delay. The spacecraft did not autonomously slew to the burst since automated slewing is not yet enabled.

The burst is seen in the Count-Rate Trigger (CRT) and the Image Trigger (IMT). The best detection is given by IMT with a signal to noise of 9.7 in the 8-120 keV energy band on a time window of 40.96 s starting at TimeTb. The location is RA, Dec = 352.59, 1.88 (J2000). This is about 28.5 degrees off the ECLAIRs optical axis in the partially coded field of view. The SVOM attitude control system is still undergoing calibration, but we estimate that the location accuracy is within 10 arcmin (radius).

We caution that due to solar activity the particle environment is currently perturbed on low Earth orbit. However, the quality of the images produced let us be confident on the reality of this transient event.

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. ECLAIRs was developped jointly by APC, CEA, CNES and IRAP.

The SVOM points of contact for this burst are Stéphane Schanne (s.schanne@cea.fr) and Olivier Godet (ogodet@irap.omp.eu).