GRB 250610B
GCN Circular 40719
Subject
GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
Date
2025-06-13T13:43:34Z (a year ago)
From
zengxt27@mail2.sysu.edu.cn
Via
Web form
Xiang-Tao Zeng, Duo-Le Cao, Chun Chen, Zhong-Nan Dong, Jia-Qi Lin, Wei-Sen Huang, Jin-Ji Li, Xia Li, Pu Lin, Hao-Nan Yang, Yan Yu, Hao-Ran Zhang, P H Thomas Tam, Rong-Feng Shen, Bin Ma (Sun Yat-sen University) report on behalf of the SYSU 80cm infrared telescope team:
We observed the field of GRB 250610B (Saccardi et. al., GCN 40671; Evans et. al., GCN 40679; Liang et. al., GCN 40681) using the Sun Yat-sen University 80cm infrared telescope with 51 x 20 s exposures in J band. The calculated position is RA. = 200.1744 deg, DEC = 31.1751 deg J2000, from SVOM observation. Our observations began at 2025-6-10 16:55:00 UTC, 22 minutes after the SVOM trigger.
We do not detect any counterpart at the position of the optical afterglow (Wang et al., GCN 40672, Gompertz et al., GCN 40674, Schneider et al., GCN 40676, Gompertz et al., GCN 40677, Li et al., GCN 40678, Brivio, et al., GCN 40687, Schneider, et al., GCN 40689, Adami, et al., GCN 40698), down to a 5-sigma depth of J~ 17 Vega magnitudes.
The SYSU 80cm infrared telescope is operated and managed by the Department of Astronomy, Sun Yat-sen University.
GCN Circular 40705
Subject
GRB 250610B: Swift-XRT refined Analysis
Date
2025-06-12T15:11:21Z (a year ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
P. D'Avanzo (INAF-OAB), J.A. Kennea (PSU), D.N. Burrows (PSU), M.A.
Williams (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U.
Leicester), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) and
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
We have analysed 5.0 ks of XRT data for GRB 250610B, from 2.9 ks to
105.7 ks after the SVOM/ECLAIRs trigger. The data are entirely in
Photon Counting (PC) mode. Using 2013 s of PC mode data and 2 UVOT
images, we find an enhanced XRT position (using the XRT-UVOT alignment
and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec =
200.17991, +31.10477 which is equivalent to:
RA (J2000): 13h 20m 43.18s
Dec(J2000): +31d 06' 17.2"
with an uncertainty of 2.8 arcsec (radius, 90% confidence).
The light curve can be modelled with a power-law decay with a decay
index of alpha=0.68 (+0.12, -0.10).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.86 (+0.33, -0.25). The
best-fitting absorption column is 3.1 (+7.7, -2.0) x 10^20 cm^-2,
consistent with the Galactic value of 1.1 x 10^20 cm^-2 (Willingale et
al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum is 3.5 x 10^-11 (3.7 x
10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 3.1 (+7.7, -2.0) x 10^20 cm^-2
Galactic foreground: 1.1 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index: 1.86 (+0.33, -0.25)
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00019863.
This circular is an official product of the Swift-XRT team.
GCN Circular 40699
Subject
GRB 250610B: Liverpool Telescope continued monitoring
Date
2025-06-12T12:54:32Z (a year ago)
Edited On
2025-06-12T13:39:04Z (a year ago)
From
Ben Gompertz at U of Birmingham <b.gompertz@bham.ac.uk>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Ben Gompertz at U of Birmingham <b.gompertz@bham.ac.uk>
Via
email
B. P. Gompertz (U. Birmingham), Dimple (U. Birmingham) and A. Bochenek (LJMU) report on behalf of a larger collaboration:
We continued follow-up observations of GRB 250610B (Saccardi et al., GCN 40671) for a second night with the IO:O camera on the 2m robotic Liverpool Telescope (LT). Observations began at 21:56:59 UT on 2025-06-11, ~29.4 hr after the SVOM/ECLAIRs trigger, and consisted of 8x180 s exposures in the SDSS r and i filters.
We detect the optical counterpart (Schneider et al., GCN 40676; Gompertz et al., GCN 40677; Li et al., GCN 40678; Bochenek & Perley, GCN 40684; Qiu et al., GCN 40685; Schneider et al., GCN 40689; Breeveld & Williams, GCN 40691; Adami et al., GCN 40698) with AB magnitudes of r = 22.38 ± 0.13 (mid-time t0+1.23 days) and i = 22.13 ± 0.08 (mid-time t0+1.25 days).
Magnitudes are calibrated against nearby Pan-STARRS stars and are not corrected for Galactic extinction.
GCN Circular 40698
Subject
GRB 250610B: MISTRAL/T193 and T120 OHP further observations
Date
2025-06-12T11:57:50Z (a year ago)
From
Christophe Adami at LAM <christophe.adami@lam.fr>
Via
Web form
C. Adami (LAM/Pytheas/AMU), B. Schneider (LAM), A. de Ugarte Postigo (LAM), Y. Degot-Longui (Pytheas/OHP), J. Balcaen (Pytheas/OHP), S. Basa (LAM/OHP/Pytheas/AMU), E. Le Floc'h (CEA/Irfu), report on behalf of a larger collaboration:
We re-observed the field of the GRB 250610B (Saccardi et al., GCN 40671; Wang et al., GCN 40672; Gompertz et al., GCN 40674; Schneider et al., GCN 40676; Gompertz et al., GCN 40677; Li et al., GCN 40678; Evans et al., GCN 40679; Liang et al., GCN 40681; Wang et al., GCN 40682; Wang et al., GCN 40683; Bochenek et al., GCN 40684; Qiu et al., GCN 40685; Brivio et al., GCN 40687; Schneider et al., GCN 40689; Breeveld et al., GCN 40691; Hamburg et al., GCN 40692; Godet al., GCN 40695) using the T120cm and T193cm (MISTRAL instrument) telescopes at Observatoire de Haute-Provence (France). We obtained 60 minutes with MISTRAL and 75 minutes with the T120 CCD camera simultaneously in the r-band, from 2025-06-11 at 20:41 to 22:17 UTC (from 28.13 to 29.73 hr after the trigger).
In the stacked and combined image from both instruments, the optical counterpart is detected at a preliminary magnitude of:
r = 22.59 +/- 0.21 mag (AB)
The photometric calibration was performed using nearby stars from the PanStarrs catalog and the magnitude is not corrected for Galactic extinction.
We acknowledge the excellent support from Observatoire de Haute-Provence and in particular the students and professors from the summer camp OHP 2025 and the SOPHIE observer T. Llopis
GCN Circular 40695
Subject
GRB 250610B - SVOM/ECLAIRs refined analysis
Date
2025-06-12T07:39:53Z (a year ago)
From
ogodet@irap.omp.eu
Via
Web form
Authors: O. Godet (IRAP), A. Coleiro (APC), M.-G. Bernardini (INAF-OAB, LUPM), A. Saccardi (CEA), J. Rodriguez (CEA)
Using the event-by-event data downloaded through the X-band ground station, we report further analysis of ECLAIRs observations of GRB 250610B (SVOM burst-id sb25061018).
The burst that triggered ECLAIRs onboard (GCN #40671) consists of a single large peak with a duration of T90 = 108.25 -13.14 / +34.95 s in the 4-120 keV energy band.
The time-averaged spectrum from T0-10s to T0+80s (T0 = 2025-06-10T16:32:58 UTC) in the energy range 5-120 keV is best fitted by a cutoff powerlaw model with a photon index of 0.9 +/- 0.1 and a cutoff energy of 49 +14/-10 keV. This translates to a Epeak-value of 53 +16/-12 keV. These spectral parameters are consistent with those obtained by SVOM/GRM (GCN #40683). With this model, the total 4-120 keV fluence is (2.9 +0.1/-0.4)e-6 erg/cm^2.
All the quoted errors are given at the 68% confidence level.
Given that the ECLAIRs calibration is still on-going, the above results shall be seen as 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: O. Godet (IRAP) (ogodet at irap.omp.eu)
GCN Circular 40692
Subject
Fermi GBM Sub-Threshold Detection of GRB 250610B
Date
2025-06-11T19:54:51Z (a year ago)
From
rhamburg@usra.edu
Via
Web form
R. Hamburg (USRA) reports on behalf of the Fermi-GBM Team:
The SVOM/ECLAIRs and SVOM/GRM instruments detected GRB 250610B on 2025-06-10T16:32:58 (GCN 40671). There was no Fermi-GBM onboard trigger around this event time. An automated, blind search for gamma-ray bursts below the onboard triggering threshold in Fermi-GBM identified no candidates.
The GBM Targeted Search [1], the most sensitive, coherent search for GRB-like signals in GBM data, identified a transient starting approximately 31 seconds after the SVOM/ECLAIRs trigger time, most significantly on the 16.384 s timescale and with a false alarm rate of 9.7e-5 Hz. Using the standard search protocol, the Targeted Search localization was found to be spatially consistent with the SVOM/ECLAIRs location. Additionally, the GBM Targeted Search transient was found with the highest significance using a "soft" spectrum (Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7) for a GRB. This is roughly consistent with the soft spectrum found by Wang et al. 2025 (GCN 40682).
[1] Goldstein et al. 2019 arXiv:1903.12597
GCN Circular 40691
Subject
GRB 250610B: Swift/UVOT Detection
Date
2025-06-11T15:39:28Z (a year ago)
From
Alice Breeveld at MSSL-UCL <a.breeveld@ucl.ac.uk>
Via
email
A.A. Breeveld (UCL-MSSL) and M.A. Williams (PSU) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 250610B
2 ks after the SVOM trigger (Saccardi et al., GCN Circ. 40671).
The optical source at the position of XRT source 1 (Evans et al., GCN Circ. 40679) seen by Schneider et al., (GCN Circ. 40676), Gompertz et al., (GCN Circ. 40677), Li et al., (GCN Circ. 40678), Bochenek et al., (GCN Circ. 40684) and Qiu et al. (GCN Circ. 40685) was also detected in the UVOT U-band filter and shows signs of fading.
Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag
u 2939 4660 1694 20.20 ± 0.15
u 8634 8923 285 20.50 ± 0.36
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.0104 in the direction of the burst (Schlegel et al. 1998).
GCN Circular 40689
Subject
GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
Date
2025-06-11T13:50:37Z (a year ago)
From
Benjamin Schneider at MIT <bschn@mit.edu>
Via
Web form
Benjamin Schneider (LAM), Diego López-Cámara (UNAM), Rosa L. Becerra (U Roma), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Fredd Alvarez (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Antonio de Ugarte Postigo (LAM), A. Saccardi (CEA), and J. Rodriguez (CEA):
We imaged the field of the SVOM GRB 250610B (Saccardi et al., GCN Circ. 40671) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2025-06-11 04:35 to 06:40 UTC (from 12.0 to 14.1 hours after the trigger) and obtained 32 minutes of exposure in each of the g, r and i filters.
The data were reduced and coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.
We detected the optical counterpart reported by Schneider et al., GCN Circ. 40676; Gompertz et al., GCN Circ. 40677; Li et al., GCN Circ. 40678; Bochenek et al., GCN Circ. 40684, and Qiu et al., GCN Circ. 40685 at preliminary magnitudes of:
g = 21.83 +/- 0.14
r = 21.56 +/- 0.10
i = 21.49 +/- 0.09
Our detections are consistent with the shallow decay reported by the SVOM/VT team (Qiu et al., GCN Circ. 40685) and imply a temporal decay index of ~0.6.
Further observations are planned.
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 40687
Subject
GRB 250610B: REM optical/NIR observations
Date
2025-06-11T11:49:21Z (a year 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) report on behalf of the REM team:
We observed the field of GRB 250610B detected by SVOM/ECLAIRs (Saccardi et al., GCN 40671) 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, and H bands, started on 2025 June 10 at 22:45:52 UT (i.e. 6.2 hr after the burst), and lasted for about 1 hour.
From preliminary inspection, we do not detect any possible counterpart at the position of the optical afterglow (Schneider et al., GCN 40676; Gompertz et al., GCN 40677; Li et al., GCN 40678; Bochenek et al., GCN 40684; Qiu et al., GCN 40685) down to the following 3sigma limits:
r > 19.6 (AB; calibrated against the Pan-STARRS catalogue),
at a mid-time of 6.7 hr after the trigger;
H > 15.6 (Vega; calibrated against the 2MASS catalogue),
at a mid-time of 6.2 hr after the trigger.
GCN Circular 40685
Subject
GRB 250610B: SVOM/VT optical shallow decay
Date
2025-06-11T09:54:28Z (a year ago)
Edited On
2025-06-11T14:34:52Z (a year ago)
From
Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>
Via
Web form
Y. L. Qiu, H. L. Li, L. P. Xin, C. Wu, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, Y. N. Ma, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), A. Saccardi, J. Rodriguez, N. Dagoneau (CEA), C. Van Hove (IJCLab) report on behalf of the SVOM mission team.
SVOM/VT made a second ToO observation for GRB250610B (Saccardi et al., GCN 40671; Wang et al., GCN 40682; Wang et al, GCN 40683). The observation was performed in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
With more data, the brightness of the counterpart (Schneider et al., GCN 40676; Gompertz et al., GCN 40677; Li et al., GCN 40678; Bochenek et al., GCN 40684) was fading by about 0.6+/-0.1 mag in both band within 9 hours. The latest brightness is derived as follows:
Mid-time after the burst | exposure time| band | mag (AB) | mag err
-------------------------|--------------|------|----------|--------
9.53 hour | 14*70 sec | VT_B | 21.3 ｜ 0.1
9.50 hour | 12*70 sec | VT_R | 21.1 ｜ 0.1
Our photometry was not corrected for Galactic extinction.
We noticed that there is a faint blue source at the position of the counterpart in Legacy Surveys DR10 catalog with g=23.0 mag and r=22.75 mag. Considering the possible host galaxy's brightness and blue color，the photometry at later phase might be contaminated by the host galaxy's light, particularly in the VT_B band.
With the slow decaying behavior of X-ray emission (Evans et al., GCN 40679; Liang et al., GCN 40681) and optical at early phase, it is not an ordinary GRB event. More multiband follow-up and spectrum observations are encouraged.
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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC),CAS.
GCN Circular 40684
Subject
GRB 250610B: additional Liverpool Telescope optical observations
Date
2025-06-11T08:39:42Z (a year ago)
From
A. Bochenek at Liverpool John Moores University <a.m.bochenek@2023.ljmu.ac.uk>
Via
Web form
A. Bochenek and D. A. Perley (LJMU) report:
We observed the field of GRB 250610B (Saccardi et al., GCN 40671) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 4x100s exposures in the SDSS r’ and i’ filters starting at 2025-06-10 23:34:02 UT, approximately 7.0 hours after the trigger.
We report detections in stacked images in both filters at the position of the reported optical counterpart (Schneider et al., GCN 40676). The obtained magnitudes are r = 21.21 ± 0.11 and i = 21.14 ± 0.13, in line with previous optical observations (Schneider et al., GCN 40676; Gompertz et al., GCN 40677; Li et al., GCN 40678). The photometry was calibrated using nearby PanSTARRS secondary standards and was not corrected for extinction.
MJD (mid) T_mid-T_0 Filter Mag. (AB)
60836.98618 7.12 h r 21.21 ± 0.11
60836.99384 7.30 h i 21.14 ± 0.13
GCN Circular 40683
Subject
GRB 250610B: SVOM/GRM analysis
Date
2025-06-11T06:39:58Z (a year ago)
From
Chenwei Wang at IHEP <cwwang@ihep.ac.cn>
Via
Web form
SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: A. Saccardi, J. Rodriguez, N. Dagoneau (CEA)
Report on behalf of the SVOM team:
SVOM/GRM detected the burst GRB 250610B at 2025-06-10T16:32:58 UTC (T0), which is also detected by SVOM/ECLAIRs (A. Saccardi et al., GCN #40671) and Fermi/GBM (Yun Wang et al., GCN #40682)
With the event-by-event data downloaded through the X-band ground station, we conducted the standard analysis pipeline of GRB 250610B. The GRM light curve shows that this burst consists of a single pulse with a T90 of 94 +/-14 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb250610B.png
With the localization of ECLAIRs (RA=200.1831, DEC=31.1028), the time-averaged spectrum from T0-10 to T0+80 s is best fitted by a Blackbody function. The temperature, parameterized as kT, is 13 +/- 1 keV. The event fluence (10-1000 keV) in this time interval is (2.3 +/- 0.2)E-06 erg/cm^2.
The time-averaged spectrum can also be fitted by a power law function with an exponential high-energy cutoff adequately. The power law index is -1.2 +/- 0.5 and the cutoff energy, parameterized as Epeak, is 66 +15/-12 keV. The event fluence (10-1000 keV) in this time interval is (2.2 +/- 0.3)E-06 erg/cm^2. Thus GRB 250610B is consistent with Type II GRBs in the 'Amati' relation diagram, as shown at:
https://www.bursthub.cn//admin/static/grb250610B_amati.png
We note that the calibration of SVOM/GRM is undergoing thus these results are preliminary. Refined analysis will be reported later.
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/GRM point of contact for this burst is: Chen-Wei Wang (IHEP) (cwwang@ihep.ac.cn)
GCN Circular 40682
Subject
GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
Date
2025-06-11T03:32:59Z (a year ago)
From
Hao Zhou at Purple Mountain Observatory, CAS <haozhou@pmo.ac.cn>
Via
Web form
Yun Wang, Hao Zhou, Zhi-Ping Jin, Yi-Zhong Fan (PMO,CAS):
We report a possible sub-threshold detection of GRB 250610B by the Fermi Gamma-ray Burst Monitor (GBM). The burst was initially detected by SVOM/ECLAIRs (Saccardi et al., GCN 40671) at T0 = 2025-06-10 16:32:58 UTC. The reported position is R.A., Dec. 200.1831, 31.1028 degrees. Based on the poshist file, the GBM NaI detector with the smallest incident angle to the burst direction was nb.
We used the GBM Time-Tagged Event (TTE) data to extract the spectrum over the interval from T0–10 s to T0+80 s. The background was estimated from two intervals: T0–200 s to T0–100 s and T0+300 s to T0+400 s. We fitted the spectrum with a cutoff power-law model (dN/dE ~ (E^-alpha)*exp(-E/Ec)), obtaining alpha ~ -0.6 and a peak energy Ep=(2-alpha)*Ec ~ 55 keV. The energy flux in the 1–10000 keV band is estimated to be ~ 5.72e-9 erg/cm^2/s. The spectrum can be fitted with a blackbody model, yielding a temperature of kT ~13 keV and providing a better goodness of fit than a cutoff power-law model.
This is a test using RapidGBM (https://github.com/0neyun/RapidGBM), and the results presented here should be considered preliminary.
GCN Circular 40681
Subject
GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
Date
2025-06-11T02:44:20Z (a year ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
Y. F. Liang, Y. L. Hua (PMO, CAS), X. P. Xu, H. W. Pan(NAO, CAS), A. Saccardi, J. Rodriguez, N. Dagoneau (CEA), C. Van Hove (IJCLab) report on behalf of the Einstein Probe and SVOM team
We performed a follow-up observation of GRB 250610B (detected through offline search of SVOM/ECLAIRs, Saccardi et al, GCN #40671; followed by Swift/XRT, Evans et al. GCN #40679), with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation began at 2025-06-10T17:04:27 (T-TGRB ~ 1.9ks), and the exposure time is about 5.8 ks.
Only 1 uncatalogued source was detected both by FXTA and FXTB in the 90% localization error circle provided by SVOM/ECLAIRs (with a radius of 3.22 arcmin centered at RA, DEC = 200.1831 deg, +31.1028 deg), as listed below (the FXT flux is taken from FXTB module).
-------------------------------------------------------------------------------------------------
Source name | RA | DEC | Estimated Flux | SNR | Dist from SVOM/ECLAIRs |
| deg | deg | (erg/s/cm^2) | | offset (in arcmin) |
EPF_J132043.1+310615 | 200.1795 | 31.1043 | 2.8(+/-0.2) x 10^-12 | 5.9 | 0.21 |
-------------------------------------------------------------------------------------------------
Note: * EPF_J132043.1+310615 was also detected by Swift/XRT (GCN #40679) in a ~2.0 ks observation, with a mean flux of ~3.9(+/-0.3)e-12 erg/s/cm^2, the position of this source is also associated with the Optical counterpart detected by SVOM/VT (Li et al. GCN #40678).
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.
GCN Circular 40679
Subject
GRB 250610B: Swift-XRT counterpart detection
Date
2025-06-10T23:55:14Z (a year ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
P.A. Evans (U. Leicester), J.A. Kennea (PSU), E. Ambrosi (INAF-IASFPA) , A.P.
Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB), D.N.
Burrows (PSU), S. Campana (INAF-OAB), M. Capalbi (INAF-OAR), A. D'Ai (INAF-IASFPA),
P. D'Avanzo (INAF-OAB), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), M. Ferro
(INAF-OAB), A. Melandri (INAF-OAR), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester), M. Perri (SSDC & INAF-OAR), C. Salvaggio (INAF-OAB), T. Sbarrato
(INAF-OAB), B. Sbarufatti (INAF-OAB), M.A. Williams (PSU) report on behalf of the
Swift-XRT team:
Swift-XRT has performed follow-up observations of the SVOM/ECLAIRs-detected source
GRB 250610B, collecting 2.0 ks of Photon Counting (PC) mode data between T0+2.8 ks
and T0+8.9 ks after the trigger. A likely counterpart has been found consistent with
the optical detection (GCN Circ. 40676, 40677 and 40678). The details of this source
are:
Source 1 (SWIFT J132043.2+310614):
==================================
RA (J2000.0): 200.1802 = 13h 20m 43.25s
Dec (J2000.0): +31.1040 = +31d 06' 14.4"
Error: 3.7 (arcsec, radius, 90% confidence).
Detect flag: GOOD
Distance: 4.3 arcmin from the SVOM/ECLAIRs position.
Mean rate: 0.1084 +/- 0.0084 ct s^-1
Mean flux: (3.91 +/- 0.30)e-12 erg cm^-2 s^-1
Peak rate: 0.134 +/- 0.022 ct s^-1
Peak flux: (4.85 +/- 0.81)e-12 erg cm^-2 s^-1
ECF: 3.61e-11 erg cm^-2 ct^-1, assuming NH=1.44e+20 cm^-2,
gamma=1.78; determined from a spectral fit.
XMM UL: 2.4e-12 erg cm^-2 s^-1, (0.3-10 keV)
so the source is 3.0-sigma above this 3-sigma upper limit.
There is no evidence for fading.
All fluxes are 0.3-10 keV, observed. For all flux conversions and comparisons with
catalogues and upper limits from other missions, we assumed a power-law spectrum
with NH=3x10^20 cm^-2 and photon index (Gamma)=1.7 unless otherwise stated.
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/SVOM.
This circular is an officicial product of the Swift-XRT team.
GCN Circular 40678
Subject
GRB 250610B: SVOM/VT optical counterpart
Date
2025-06-10T23:35:24Z (a year ago)
From
Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>
Via
Web form
H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, Y. N. Ma, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), A. Saccardi, J. Rodriguez, N. Dagoneau (CEA), C. Van Hove (IJCLab) report on behalf of the SVOM mission team.
SVOM performed a Target of Opportunity observation of GRB 250610B detected by SVOM/Eclairs (Saccardi et al., GCN 40671). SVOM/VT began observing the field at 2025-06-10 17:04:26 UTC, 0.52 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
An uncatalogued source, compared to legacy survey, is found using VT X-band data, within the error box of Swift/XRT1 at R.A., Dec 200.179739, 31.10496 degrees:
RA (J2000) = 13:20:43.1
Dec (J2000) = +31:06:17.9
with an uncertainty of 0.5 arcsec.
The source is detected in both VT_R and VT_B, and was fading by 0.3 mag in 2 orbits, the magnitudes are:
Mid-time after the burst | exposure time (s) | band | mag (AB) | mag err
--------------------|-------------------|------|----------|--------
1.234 hour | 70 | VT_B | 20.7 ｜ 0.1
1.234 hour | 70 | VT_R | 20.3 ｜ 0.1
This position and the brightness is consistent with the reports (Schneider et al., GCN 40676, Gompertz et al., GCN 40677)
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Centre 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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.
The Burst Advocate (BA) on shift for this alert is Andrea Saccardi@cea.fr.
GCN Circular 40677
Subject
GRB 250610B: LT detection of the optical counterpart
Date
2025-06-10T23:30:06Z (a year ago)
From
Ben Gompertz at U of Birmingham <b.gompertz@bham.ac.uk>
Via
email
B. P. Gompertz (U. Birmingham), Dimple (U. Birmingham), A. Martin-Carrillo (UCD) and G. Corcoran (UCD) report on behalf of a larger collaboration:
We initiated follow-up observations of GRB 250610B (Saccardi et al., GCN 40671) with the IO:O camera on the 2m robotic Liverpool Telescope (LT). Observations began at 22:24:56 UT, ~5.85 hr after the SVOM/ECLAIRs trigger, and consisted of 7x120 s and 10x120 s exposures in the SDSS g and i filters, respectively.
We detect the optical counterpart (Schneider et al., GCN 40676) with AB magnitudes of g = 21.38 ± 0.11 and i = 21.02 ± 0.06. Magnitudes are calibrated against nearby Pan-STARRS stars and are not corrected for Galactic extinction.
GCN Circular 40676
Subject
GRB 250610B: OHP/T120 optical counterpart candidate
Date
2025-06-10T23:26:37Z (a year ago)
Edited On
2025-06-11T14:35:11Z (a year ago)
From
Benjamin Schneider at MIT <bschn@mit.edu>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Benjamin Schneider at MIT <bschn@mit.edu>
Via
Web form
B. Schneider (LAM), A. de Ugarte Postigo (LAM), C. Adami (LAM/Pytheas/AMU), J.P Troncin (Pytheas/OHP), A. Martin-Carrillo (UCD), S. Basa (LAM/OHP/Pytheas/AMU), E. Le Floc'h (CEA/Irfu), K. Siellez (Institute of Astrophysics in Paris / UTas) report on behalf of a larger collaboration:
We observed the field of the GRB 250610B (Saccardi et al., GCN 40671) using the T120cm telescope at Observatoire de Haute-Provence (France). We obtained 30 minutes of exposure in the r-band starting at 20:31:03.29 UT on 2025-06-10 (3.97 hr after the trigger).
In the stacked image, we detected a new source not visible in the Legacy Survey and consistent with the XRT #1 error at RA, Dec 200.1796, +31.1047 which is equivalent to:
RA(J2000) = 13:20:43.11
Dec(J2000) = +31:06:16.8
with an uncertainty of 0.5 arcsec.
The preliminary magnitude derived for that source is:
r = 20.96 +/- 0.15 mag (AB)
The photometric calibration was performed using nearby stars from the SDSS catalog and the magnitude is not corrected for Galactic extinction.
We acknowledge the excellent support from Observatoire de Haute-Provence and in particular the students and professors from the summer camp OHP 2025.
GCN Circular 40674
Subject
GRB 250610B: GOTO optical upper limit
Date
2025-06-10T21:43:38Z (a year ago)
From
Ben Gompertz at U of Birmingham <b.gompertz@bham.ac.uk>
Via
email
B. P. Gompertz, D. O’Neill, D. Steeghs, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, A. Kumar, B. Godson, D. K. Galloway, V. Dhillon, P. O'Brien, G. Ramsay, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, and J. Casares report on behalf of the GOTO collaboration:
We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022; Dyer et al. 2024) in response to the SVOM/ECLAIRS detected GRB 250610B (Saccardi et al., GCN 40671).
Targeted observations were performed with GOTO-North centred at 2025-06-10 21:13:20 UT (+4.66h post trigger). Observations consisted of 4x90s exposures in the GOTO L-band (400-700 nm).
Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations. We detect no new sources within the ECLAIRS localisation region down to a 3-sigma limiting magnitude of L > 19.92 AB mag.
GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC).
GCN Circular 40672
Subject
GRB 250610B : SVOM/GWAC-F60A and F50 observations
Date
2025-06-10T18:53:15Z (a year ago)
From
Weikang Zheng at UC Berkeley <weikang@berkeley.edu>
Via
email
J. Wang, W. L. Dong, L. P. Xin(NAOC), L. J. Chen(GXU), Y. G. Yang(HNU), X.
H. Han, C. WU, Y. L. Qiu, H. L. Li, X .M. Lu, R. S. Zhang, Y. Xu, L. Huang,
H. B. Cai, Y. J. Xiao, P. P. Zhang, L. Lan, W. J. Xie, Z. H. Yao, J. Y.
Wei(NAOC), X. G. Wang, E. W. Liang(GXU) and W. Zheng (UCB) report on behalf
of the SVOM follow-up team:
We observed the field of SVOM GRB 250610B (Saccardi et al., GCN 40671) with
the GWAC-F60A and GWAC-F50 at Xinglong Observatory, China. F60A started
observing at 2025-06-10T17:14:17.39 UTC with a set of 34 images in R-band.
F50 started observing at 2025-06-10T17:14:17.39 UTC and with a set of 9
images in R-band.
After coadding the images, we do not find any uncatalog candidate within
the SVOM/ECLAIRs error box. We estimate the upper limit of 16.0 mag for
GWAC-F60A at mid time of 54.5 minutes after brust, and upper limit of 17.5
mag for GWAC-F50 at mid time of 54.0 minutes after brust.
Two 60cm GWAC-F60(A/B) are operated by Guangxi University and NAOC, CAS, at
Xinglong Observatory, China. The field of view is 19*19 arcmin. The 50cm
telescope (F50A) is operated by Huaibei Normal University and NAOC, CAS, at
Xinglong Observatory, China. The field of view is 27*27 arcmin.
GCN Circular 40671
Subject
GRB 250610B: SVOM detection of a long burst
Date
2025-06-10T17:27:30Z (a year ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
A. Saccardi, J. Rodriguez, N. Dagoneau (CEA), C. Van Hove (IJCLab) report on behalf of the SVOM mission team.
At 2025-06-10T16:32:58 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 250610B (SVOM burst-id sb25061018).
The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network.
The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 40 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 30.55 in the [8-50] keV energy band over a time window of 81.92 seconds starting at 2025-06-10T16:33:19.
The localization of the best alert is R.A., Dec. 200.1831, 31.1028 degrees:
R.A. (J2000) = 13h20m43.94s
Dec. (J2000) = 31d06m10.04s
with a 90% confidence level (C.L.) radius of 3.22 arcmin (including systematic error of 2 arcmin added in quadrature).
The ECLAIRs light curve may show a double narrow peak structure with a T90 duration of about 134.368 (-13.465 +23.518) s.
The ECLAIRs peak count rate was ~496.6503 ± 191.3858 counts/sec in the band [20-50] keV, ~5.6 seconds after the trigger.
This burst was also detected by SVOM/GRM with a significance of 14.30.
The GRM light curve showed a single broad peak structure with a T90 duration of about 69.237 (-6.343 +6.558) s.
The GRM peak count rate was ~470.4469 ± 82.6942 counts/sec in the band [4-5000] keV, ~34.4 seconds after the trigger.
A SVOM ToO has been executed for follow-up and started to observe at 2025-06-10T16:59 UTC.
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. GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE.
The Burst Advocate (BA) on shift for this alert is Andrea Saccardi: andrea.saccardi@cea.fr.
Please contact the BA by email if you require additional information.