GRB 250507A
GCN Circular 40374
Subject
GRB 250507A: SVOM detection of a long burst
Date
2025-05-07T07:23:04Z (23 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
Z. Wang (GXU), Y. Liang (PMO), H. Yang, O. Godet (IRAP), P. Maggi (ObAS), D. Götz (CEA), L Xin (NAOC)
report on behalf of the SVOM mission team:
SVOM/ECLAIRs triggered on the gamma-ray burst GRB 250507A (SVOM burst-id sb25050703) starting at 2025-05-07T06:34:45.17 UTC (Tb).
The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network.
The burst was detected by the Count-Rate Trigger (CRT) and Image Trigger (IMT). A sequence of 10 alerts was produced. IMT provided the alert with the best signal-to-noise-ratio (SNR) of 10.65 in the 8-120 keV energy band over a time window of 40.96 seconds starting at Tb.
The localization of the best alert is R.A., Dec. 182.990, -23.615 degrees:
R.A. (J2000) = 12h11m57.6s
Dec. (J2000) = -23h36m54s
with a 90% confidence level (C.L.) radius of 7.5 arcmin (including systematic error of 2 arcmin added in quadrature).
SVOM slewed to the burst.
MXT began observing the field after the slew, starting at 2025-05-07T06:41:02 i.e. 377 s after Tb. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec 183.074, -23.598 degrees:
R.A. (J2000) = 12h12m17.76s
Dec. (J2000) = -23d35m52.8s
with a 90% C.L. radius of 30 arcseconds (including 25 arcseconds systematic error added in quadrature).
This location is 4.7’ from the ECLAIRs onboard position. This position may be improved as more data is received.
VT began observing the field after the slew. The analysis of the recorded images will be published in a future circular gathering information on the follow-up of the SVOM optical instruments.
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.
The Burst Advocate (BA) on shift for this burst is Ziqi Wang: ziqi.wang@st.gxu.edu.cn.
Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst.
GCN Circular 40376
Subject
GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
Date
2025-05-07T08:57:04Z (23 days ago)
Edited On
2025-05-07T13:09:06Z (23 days ago)
From
J.-G. Ducoin at CPPM <ducoin@cppm.in2p3.fr>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of J.-G. Ducoin at CPPM <ducoin@cppm.in2p3.fr>
Via
Web form
Jean-Grégoire Ducoin (CPPM), Alan M. Watson (UNAM), Fredd Alvarez (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), Z. Wang (GXU) and Y. Liang (PMO):
We imaged the field of the SVOM GRB 250507A (Wang et al., GCN 40374) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2025-05-07 06:36:04 to 07:34:42 UTC (from 79 to 3597 seconds after the trigger) and obtained 2560 seconds of exposure in the i filter.
The data were reduced and coadded with the COLIBRÍ pipeline and analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog and is not corrected for Galactic extinction.
In the stacked image, we do not detect any new source at the MXT source position (Wang et al., GCN 40374) down to the following 5-sigma limit (AB):
i > 22.3 mag
Further observations are ongoing.
We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams.
COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.
GCN Circular 40379
Subject
GRB 250507A: SVOM/VT optical upper limit
Date
2025-05-07T11:01:12Z (23 days ago)
From
Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>
Via
Web form
L. P. Xin, Y. L. Qiu, H. L. Li, C. Wu, Z. H. Yao, Y. N. Ma, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. T. Palmerio (CEA), Z. Q. Wang (GXU), Y. F. Liang (PMO), W. K. Zheng (UCB) report on behalf of the SVOM/VT instrument team.
After the trigger by SVOM/ECLAIRs at 2025-05-07T06:34:45 UT (SVOM burst-id sb25050703), SVOM performed an automatic slew on the burst. SVOM/VT began observing the field at 260 seconds after the SVOM trigger in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
With the downlinked X band data, no any uncataloged sources are detected in single or stacked imags within the errorbox of Eclairs or MXT (Wang et al., GCN 40374), compared to the Legacy survey.
The 3 sigma upper limits are derived below:
Mid_time | Exposure time | Band | Upper limit (AB)
550 sec | 10*50 sec | VT_B | 22.8
550 sec | 10*50 sec | VT_R | 22.7
1225 sec | 38*50 sec | VT_B | 23.2
1225 sec | 38*50 sec | VT_R | 23.1
This results are consistent with the report (J.-G. Ducoin et al. GCN 40376).
Given the bright X-ray counterpart (Wang et al., GCN 40374), and the deep optical upper limit at the early phase of the burst, near infrared observations are encouraged to investigate the nature of the burst.
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.
GCN Circular 40380
Subject
GRB 250507A: REM optical/NIR observations
Date
2025-05-07T12:09:00Z (23 days ago)
From
Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it>
Via
Web form
R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB), M. De Pasquale (Univ. of Messina) report on behalf of the REM team:
We observed the field of GRB 250507A detected by SVOM/ECLAIRs (Wang et al., GCN 40374) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, and K bands, started on 2025 May 07 at 06:45:31 UT (i.e. about 11 minutes after the burst), and lasted for about 2 hours.
From preliminary inspection, we do not detect any possible counterpart inside the SVOM/MXT error circle down to the following 3sigma limits:
r > 19.3 (AB; calibrated against the Pan-STARRS catalogue),
at a mid-time of 33 minutes after the trigger;
H > 16.0 (Vega; calibrated against the 2MASS catalogue),
at a mid-time of 32 minutes after the trigger.
GCN Circular 40381
Subject
GRB 250507A: refined SVOM/MXT data analysis
Date
2025-05-07T14:04:48Z (23 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
P. Maggi (ObAS), D. Götz (CEA), H. Goto (Kanazawa University/CEA), M. Moita (CEA), C. Plasse (CEA), F. Robinet (IJCLab), C. Van Hove (IJCLab) report of behalf of the SVOM/MXT Team:
GRB 250507A (Wang et al. GCN 40374) was observed by SVOM/MXT after an automatic SVOM slew, starting at T0 = 2025-05-07T06:40:59.951 (374s after trigger time Tb). MXT observed during the first orbit for 2.1 ks effective exposure.
Using the full X-band dataset, we measure a complex light curve with two flares of 150 to 200s duration, followed by a rapid decay with a temporal index of -4.1+/-0.2 at times t+T0>400s. The source is no longer detected at t+T0>1200s and hence we restricted the analysis below to the first 20 min of data.
The X-ray source located at R.A., Dec 183.066, -23.5928 degrees:
R.A. (J2000) = 12h12m15.8s
Dec. (J2000) = -23d35m34.12s
with a 90% C.L. radius of 37 arcseconds (including 35 arcseconds systematic error added in quadrature)
The spectrum is modelled with an absorbed power law. Using the average spectrum of the first 1200s of MXT data, the absorption column NH is 5.2 +/-0.5 x 1e22 /cm2 (90% C.L. uncertainties) and a rather soft photon index of 3.6 +/- 0.2. The time-averaged observed flux is 4.5 x 1e-10 ergs/cm^2/s but the count rate varies by a factor 100 between peak at t+T0=160s and t+T0=1200s.
Follow-up observations at other wavelengths are encouraged.
The Space 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. MXT was developed jointly by CEA, CNES, University of Leicester, IJCLab and MPE.
The SVOM point of contact for this burst is:z iqi.wang@st.gxu.edu.cn.
Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst.
GCN Circular 40385
Subject
GRB 250507A: follow-up observation with EP-FXT
Date
2025-05-07T15:44:09Z (23 days ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
M. H. Zhang, H. Sun (NAO, CAS), Y. J. Zhang (THU), W. Yuan (NAO, CAS) on behalf of the Einstein Probe (EP) team:
EP-FXT performed a follow-up observation of GRB 250507A at 2025-05-07T07:33:50 (UTC), about 1 hour after the SVOM/ECLAIRs trigger (Wang et al., GCN # 40374).
An uncatalogued X-ray source (EPF_J121215.7−233519) was detected within the ECLAIRs error circle, and is potentially associated with GRB 250507A.
Preliminary analysis of this source was automatically conducted, with the following results:
RA (J2000): 183.0647 deg
Dec (J2000): -23.5883 deg
Flux: 4.91 x 10^-13 erg/cm^2/s (observed, 0.5-10 keV)
Flux_error: 1.54 x 10^-13 erg/cm^2/s (1 sigma)
The position uncertainty of the above source is about 10 arcsec in radius (90% C.L. statistical and systematic).
We note that this source is spacially consistent with the one reported by SVOM/MXT (Maggi et al., GCN # 40381). The flux measured by EP-FXT shows a rapid decline of more than two orders of magnitude compared to the MXT measurements over a timescale of approximately 50 minutes, consistent with the rapid decay reported previously.
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).
GCN Circular 40389
Subject
GRB 250507A: Swift-XRT refined Analysis
Date
2025-05-07T22:02:18Z (23 days ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore
(U. Leicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E.
Ambrosi (INAF-IASFPA) , M. A. Williams (PSU), S. Dichiara (PSU), J.A.
Kennea (PSU) and P.A. Evans (U. Leicester) reports on behalf of the
Swift-XRT team:
We have analysed 1.8 ks of XRT data for GRB 250507A, from 7.4 ks to
12.5 ks after the SVOM/ECLAIRs trigger. The data are entirely in
Photon Counting (PC) mode. We detect an uncatalogued X-ray source
within the SVOM/ECLAIRs 90% C.L. error region (GCN #40374) at RA, Dec =
183.06416, -23.5888 which is equivalent to:
RA (J2000): 12h 12m 15.40s
Dec (J2000): -23d 35' 19.6"
with an uncertainty of 4.2 arcsec (radius, 90% confidence). This
position is 15.6 arcsec from the SVOM/MXT position (GCN #40381) and 2.5
arcsec from the source detected by EP-FXT (GCN #40385).
The source has a mean count rate of 2.6e-02 ct/sec and a flux of
1.11 (+0.21, -0.20) × 10^-12 erg cm^-2 s^-1 (0.3-10 keV); we cannot
determine at the present time whether it is fading. However, the
decrease in flux compared to the SVOM/MXT observation suggests this
source is the afterglow.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00019769.
This circular is an official product of the Swift-XRT team.
GCN Circular 40400
Subject
GRB 250507A: KAIT optical upper limit
Date
2025-05-08T18:37:31Z (22 days ago)
From
Weikang Zheng at UC Berkeley <weikang@berkeley.edu>
Via
email
WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and
Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, observed the field of SVOM GRB 250507A (Wang
et al., GCN 40374) starting at 06:37:30, May 07 UT, 165 seconds
after the burst. Observations were performed in 3 x 3 tiling mode,
and a set of clear (roughly R) filter images were obtained.
Preliminary analysis do not reveal any new optical counterpart
candidate within the X-ray afterglow error circles (Maggi et al.,
GCN 40381; Zhang et al., GCN 40385; Osborne et al., GCN 40389),
neither in single image, nor in the co-add images. We estimate
the limiting magnitude of our coadd image to be ~20.0 mag at a
mid-time of 15.0 minutes after the burst, consistent with the
upper limit reported by other groups (Ducoin et al., GCN 40376;
Xin et al., GCN 40379; Brivio et al., GCN 40380)
GCN Circular 40413
Subject
GRB 250507A: J-band observations with WINTER
Date
2025-05-10T03:12:44Z (20 days ago)
From
Geoffrey Mo at MIT <gmo@mit.edu>
Via
Web form
Geoffrey Mo (MIT), Tomas Ahumada (Caltech), Benjamin Schneider (LAM), Viraj Karambelkar (Caltech), Robert Stein (UMD), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report:
We observed the field of GRB 250507A (Wang et al., GCN 40374) in the near-infrared J-band with the Palomar 1-m telescope, equipped with the 1-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024).
Observations were triggered automatically and began at 2025-05-09T05:54:11 UTC (1.97 days after the GRB), consisting of 15 x 120 s exposures. The images were processed using the WINTER data reduction pipeline implemented with mirar
(https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565).
We do not detect any uncataloged sources in the SVOM/MXT (Wang et al., GCN 40374; Maggi et al., GCN 40381), EP-FXT (Zhang et al., GCN 40385), or Swift-XRT (Osborne et al., GCN 40389) localizations after visual comparison to archival PanSTARRS-1 (Chambers et al. 2016) y-band imaging. This is consistent with observations by Ducoin et al., GCN 40376; Xin et al., GCN 40379; Brivio et al., GCN 40380; and Zheng et al., GCN 40400. We obtain the following 5-sigma upper limit: J ~ 19.5 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.
GCN Circular 40414
Subject
GRB 250507A: J-band observations with WINTER (duplicate submission)
Date
2025-05-10T03:13:29Z (20 days ago)
Edited On
2025-05-12T13:34:50Z (18 days ago)
From
Geoffrey Mo at MIT <gmo@mit.edu>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov>
Via
Web form
This is a duplicate submission of GCN 40413.