GRB 250702C, GRB 250702E, GRB 250702B, GRB 250702D, EP250702a
GCN Circular 42145
Subject
GRB 250702B/EP250702a: JWST/NIRCam Observations
Date
2025-10-07T18:49:45Z (5 days ago)
From
Huei Sears at Rutgers University <huei.sears@rutgers.edu>
Via
Web form
H. Sears (Rutgers University), P. K. Blanchard (Harvard), R. Chornock (UC Berkeley), Nayana AJ (UC Berkeley), T. Ahumada (Caltech), K. D. Alexander (Arizona), I. Andreoni, A. Anumarlapudi, J. Carney (UNC), J. Freeburn (UNC), O. Graur (Portsmouth), X. J. Hall (CMU), E. Hammerstein (UC Berkeley), S. W. Jha (Rutgers), M. Kasliwal (Caltech), T. Laskar (Utah), R. Margutti (UC Berkeley), B. O’Connor (CMU), D. Pasham (MIT), I. Sfaradi (UC Berkeley), and Y. Yao (UC Berkeley) report:
We obtained imaging of the field of GRB 250702B/EP250702a (GCNs 40883, 40886, 40890, 40906) with JWST/NIRCam under DD program 9447 (PI: H. Sears) starting at 2025-Oct-05 02:05:52 UT (~ 95 days post Fermi Gamma-ray trigger). The images were taken in the F150W, F200W, F277W, F356W, and F444W filters with exposure times of 10,049; 5024; 5024; 5024; and 5024 s, respectively.
The host galaxy of the transient has a complex morphology in the short-wavelength filters, F150W and F200W. The prominent separation between two brighter nuclear regions seen in the Hubble Space Telescope (HST) F160W imaging (A. Levan et al. 2025, ApJL, 990, L28; J. Carney et al. 2025, arXiv: 2509.22784) is also visible at these shorter wavelengths. In the long wavelength filters, however, the galaxy has a smooth profile, including near the nucleus. This morphology supports the interpretation that the host is a single system with a prominent dust lane in a disk viewed nearly edge-on. Visual inspection reveals emission near the position of the transient in F150W and F200W that is not apparent in the longer wavelength filters. This excess emission is coincident with the excess flux noted in the HST F160W imaging (A. Levan et al. 2025, ApJL, 990, L28; J. Carney et al. 2025, arXiv: 2509.22784). The associated color and morphology suggests emission from an underlying star-forming region rather than solely from the transient.
We use GALFIT to subtract two Sérsic components for the long-wavelength + F200W filters and one component for the F150W filter. To place limits on any transient flux, we additionally include one point source component in all filters fixed at the location of the HAWK-I H+K source as reported in A. Levan et al. 2025, ApJL, 990, L28; R.A. (J2000) = 18h 58m 45.s 57, decl. (J2000) = –07d 52 26.2. While the excess flux noticed in the F150W and F200W imaging is ~0.15’’ offset from the HAWK-I position, we believe this is likely to be due to imprecise absolute astrometry. For completeness, we report photometry for the transient at both locations. At the HAWK-I location, we report preliminary host-galaxy subtracted, 3-sigma upper-limits of m_F444W > 25.5 AB, m_F356W > 25.7 AB, m_F277W > 26.2 AB, m_F200W > 27.8 AB, and m_F150W > 28.6 AB (faint with high uncertainty). If, instead, we force the location of the transient to be at the excess flux noted in F150W and F200W, we report preliminary detections of m_F200W = 27.97 +/- 0.32 AB and m_F150W = 29.01 +/- 0.43 AB and find similar limits in the long-wavelength filters. Of note, these magnitudes are not corrected for Galactic nor host extinction.
Further analysis is ongoing.
We thank STScI staff members Alison Vick, Ben Sunnquist, and the entire JWST team for the successful implementation of this DD program.
GCN Circular 41767
Subject
GRB 250702B: Late time Chandra observations
Date
2025-09-09T20:42:37Z (a month ago)
From
Rob Eyles-Ferris at U of Leicester <raje1@leicester.ac.uk>
Via
Web form
R. A. J. Eyles-Ferris (U of Leicester), A. J. Levan (Radboud and Warwick), A. Martin-Carrillo (UCD), P. T. O’Brien (U of Leicester), M. De Pasquale (Univ. Messina), B. P. Gompertz (U. Birmingham), T. Laskar (Utah), D. B. Malesani (DAWN/NBI and Radboud), J. C. Rastinejad (Maryland), S. Schulze (Northwestern), N. R. Tanvir (U of Leicester), P. G. Jonker (Radboud) and D. Watson (DAWN/NBI) report on behalf of a larger collaboration:
We observed the position of the gamma-ray and X-ray transient GRB 250702B/EP250702a (Fermi GBM Team, GCNs 40883, 40886, 40890; Cheng et al., GCN 40906) with the Chandra X-ray Observatory through a Director’s Discretionary Time request (PI: Eyles-Ferris) using ACIS-S. Our observation started at 2025-09-05 23:26:41 UT, approximately 65 days after the initial Fermi trigger, and lasted 39.55 ks.
At the position of GRB 250702B, we detect the X-ray counterpart (Cheng et al., GCN 40906; Kennea et al., GCN 40919; O’Connor et al., GCN 41309) with a preliminary count rate of ~3.1e-4 ct/s. Assuming the same spectrum as derived from Swift/XRT observations, this corresponds to a flux ~6.7e-15 erg/cm^2/s. This is broadly consistent with the alpha ~ 1.9 decay slope measured in both the Swift/XRT light curve and previous Chandra observations (O’Connor et al., GCN 41309). Further analysis of these data is ongoing.
We thank Pat Slane and the Chandra X-ray Center team for approving and scheduling our DDT request.
GCN Circular 41309
Subject
GRB 250702B: Chandra X-ray Detection
Date
2025-08-09T23:30:50Z (2 months ago)
From
Brendan O'Connor at Carnegie Mellon University <boconno2@andrew.cmu.edu>
Via
Web form
B. O’Connor (CMU), D. Pasham (Eureka/George Washington), I. Andreoni (UNC), J. Hare (Catholic/GSFC), X. Hall (CMU), J. Carney (UNC), A. Palmese (CMU), M. Busmann (LMU), D. Gruen (LMU), report on behalf of a larger collaboration:
We observed the position of the ultra-long X-ray and gamma-ray transient GRB 250702B (GCN #40883, #40886, #40890), also known as EP250702a (GCN #40906), with the Chandra X-ray Observatory (CXO) through Director's Discretionary Time (PI: O'Connor). Observations were carried out with ACIS-S starting on 2025-08-09 at 05:49:28 UT, corresponding to ~38 d after the initial Fermi trigger, for a total of 27.7 ks.
We detect a clear X-ray source at the position of the infrared and radio counterparts of GRB 250702B (GCNs #40924, #41053). Adopting the best-fit spectrum from Swift/XRT (GCN #40919), we derive an unabsorbed 0.3-10 keV flux of ~3.3e-14 erg/cm^2/s. This is consistent with the extrapolation of the decay observed by Swift/XRT at earlier times (<10 days), and favors a powerlaw with temporal slope ~-1.9 as measured from the initial Fermi trigger time (GRB 250702D; GCN #40886).
Further analysis is underway.
We thank Pat Slane for approving our DDT request, and the entire staff of the Chandra X-ray Observatory for scheduling the observations.
GCN Circular 41215
Subject
GRB 250702B: SMA observations
Date
2025-08-01T22:24:26Z (2 months ago)
Edited On
2025-08-04T05:15:37Z (2 months ago)
From
lauren.rhodes@mcgill.ca
Edited By
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov>
Via
Web form
L. Rhodes (McGill), P. Atri (Astron), J.S. Bright (Oxford), F. Carotenuto (INAF, Romę), M. Gurwell (Harvard), G.K. Keating (Harvard) and N. Sarin (Cambridge) report:
We observed the position of GRB 250702B (GCN #40883, #40886, #40890) with the Submillimeter Array (SMA) at a central frequency 225.5GHz for 4.5hours beginning at 06:51UT on 31 July 2025. Vesta and MWC349A were used as the flux calibrator, while 3C84 was used to calibrate the bandpass response. 1743-038 and 1911-201 were used as interleaved complex gain calibrators.
The data was processed using the COMPASS pipeline (Keating et al, in prep). We do not detect any emission at the position of GRB 250702B (GCN #40924) with a 3sigma upper limit of 0.84mJy/beam.
We thank the staff at the SMA for carrying out these observations.
GCN Circular 41147
Subject
EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
Date
2025-07-24T17:27:21Z (3 months ago)
From
stephane.corbel@cea.fr
Via
Web form
Author: N. Grollimund, S. Corbel (Univ. Paris Cité & CEA Saclay), A. Coleiro, F. Cangemi (Univ. Paris Cité), J. Rodriguez (CEA Saclay) on behalf of a larger team.
We observed the field of EP250702a (GCN 40906) with the MeerKAT radio telescope (proposal ID MKT-24172; PI: Corbel) using the S-band receivers, at a central frequency of 3.06 GHz. We conducted our observations from 2025-07-21 23:34:37 UTC, with a total on-source time of 11 min. We used J1939-6342 for flux and bandpass calibration, and J1822-0938 for complex gain calibration.
We detect a point source with a flux density of 147 +/- 19 uJy at the position of EP250702a, with an RMS noise level of ~15 uJy/beam. Our observation, in combination with the detection of a ~100 uJy point source reported in GCN 40985, implies that the flux of EP250702a increased by ~50% at 3 GHz between 2025-07-04 and 2025-07-21.
Averaging the fitted positions from all of our S-band observations, we find a refined radio position for the source: R.A. = 18:58:45.549 +/- 0.01s, Dec. = -7:52:26.54 +/- 0.15’'. This position is consistent with the radio position reported by VLA in GCN 41053, as well as the NIR and X-ray counterparts (GCNs 40924, 40906).
Further observations are planned.
We thank the SARAO staff for rapidly scheduling these observations. The MeerKAT telescope is operated by the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation, an agency of the Department of Science and Innovation. This work has made use of the "MPIfR S-band receiver system" designed, constructed and maintained by funding of the MPI für Radioastronomie and the Max-Planck-Society.
GCN Circular 41145
Subject
EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
Date
2025-07-24T06:13:17Z (3 months ago)
From
Arvind Balasubramanian <arvind6895@gmail.com>
Via
Web form
A. Balasubramanian (IIA), L. Resmi (IIST), D. Eappachen (IIA), S K Jagan (IIST), V. Bhalerao (IITB), B. Zhang (HKU), G.C. Anupama (IIA), H Sun (NAO, CAS), D. K. Sahu (IIA), and W. Yuan (NAO, CAS) report:
We observed the field of the X-ray transient EP250702a/GRB250702 B,D,E (GCNs 40906, 40883, 40886, 40890, 40891) with upgraded Giant Metrewave Radio Telescope under the joint uGMRT ToO proposals 48_059 (PI: D. Eappachen) and 48_167 (PI: L. Resmi) on 12th July 2025 in band 5 (1.26 GHz) for a total of 4 hours starting from 19:30 UTC.
In our preliminary analysis, we detect a point source with a flux density of ~90 uJy at the position of EP250702a. We used 3C48 for the flux calibration and J1911+201 for complex gain and phase calibration. The CAPTURE-CASA6 pipeline was used for data calibration and imaging.
We thank the staff of the GMRT that made these observations possible. GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research.
GCN Circular 41122
Subject
EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
Date
2025-07-19T15:21:36Z (3 months ago)
Edited On
2025-07-21T16:10:23Z (3 months 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
H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Y. N. Ma, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM mission team.
SVOM/VT conducted two ToO follow-up observations of EP250702a (Cheng et al., GCNs 40906, 40917), which was likely associated with the long burst GRB250702B,D,E (Fermi GBM Team, GCNs 40883, 40886, 40890; DeLaunay et al., GCN 40903; Frederiks et al., GCN 40914; Wang et al., GCN 40923).
The first observation was made on July 3, 2025 in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously, between 10:54:08 and 15:10:00 (UTC), 32.0 to 36.3 hours after the EP/WXT trigger (Cheng et al., GCN 40906). The second one was made on July 5, 2025, between 08:56:18 and 15:41:13, 3.25 days to 3.53 days after the EP/WXT trigger (Cheng et al., GCN 40906).
The counterpart detected by VLT (Martin-Carrillo et al., GCN 40924; Levan et al., GCN 40961), MOSFIRE (Sharma et al., GCN 41044), HST (Levan et al., GCN 41096), MeerKAT (Bright et al., GCN 40985), VLA (Sfaradi et al., GCN 41053) and ALMA (Alexander et al., GCN 41059) was not detected in our images for both observations.
The 3 sigma upper limit magnitudes were estimated:
Mid-time | Exposure time | Band | upper limit (AB)
34.2 hours | 80*100 sec | VT_R | 23.6 mag
34.2 hours | 81*100 sec | VT_B | 23.8 mag
3.53 days | 81*100 sec | VT_R | 23.6 mag
3.53 days | 81*100 sec | VT_B | 23.8 mag
The Mid-time above is the relative time from the trigger time of EP/WXT (Cheng et al., GCN 40906).
The result is consistent with the optical upper limit from GOTO (Kumar et al., GCN 40908), MASTER (Lipunov et al., GCN 40912), Colibri (Becerra et al., GCN 40918), CAHA (Pérez-García et al., GCN 40929), WFST (Hua et al., GCN 40943), FTW (Busmann et al., GCN 40949), UVOT (Siegel et al., GCN 40952), SYSU (Li et al., GCN 40986) and GRANDMA(Akl et al., GCN 41016).
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 41096
Subject
EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
Date
2025-07-15T12:48:10Z (3 months ago)
From
Andrew Levan at Radboud University <a.levan@astro.ru.nl>
Via
Web form
EP250702a / GRB 250702BD,D,E: Hubble Space Telescope Observations
A. J. Levan (Radboud and Warwick), A. Martin-Carrillo (UCD), P. G. Jonker (Radboud), D. B. Malesani (DAWN/NBI and Radboud Univ.), A. Saccardi (CEA/Irfu), P. O’Brien (Univ. of Leicester), R. A. J. Eyles-Ferris (Univ. of Leicester), A. de Ugarte Postigo (LAM), G. Corcoran (UCD), S. D. Vergani (LUX-Paris Obs.), N. R. Tanvir (U. Leicester), B. P. Gompertz (U. Birmingham) report for the Stargate collaboration:
We observed the location of EP250702a / GRB 250702B,D,E (Cheng et al., GCNs 40906, 40917; Fermi GBM Team, GCNs 40883, 40886, 40890; DeLaunay et al., GCN 40903; Frederiks et al., GCN 40914) with the Hubble Space Telescope on 15 July 2025. A total of 2196 s of observations were obtained using WFC3 and the F160W (broad-band H) filter.
At the location of the infrared counterpart (Martin-Carrillo et al., GCN 40924; Levan et al., GCN 40961) we clearly resolve a galaxy, whose nucleus is offset 0.7” from the transient location. The galaxy has an edge-on morphology, and either a disturbed disc or prominent dust lane. The transient lies on the stellar field of this galaxy, and the low probability of chance alignment (0.05%: Levan et al., GCN 40961) strongly implies that EP250702a / GRB 250702BDE is indeed an extragalactic transient. A weak excess of emission over the smooth disc is present at the transient location, but it appears likely the flux is now dominated by galaxy light.
If extragalactic in origin the very long duration of the outburst is extremely unusual. Only relativistic TDEs have been seen to have such long-lived emission in gamma-rays. However, the non-nuclear nature of the transient is not in keeping with the expected location of a supermassive black hole, although is consistent with the expectations for white-dwarf - intermediate mass black hole disruptions.
We thank Bill Januszewski, Joel Green, Claus Leitherer and Jennifer Lotz for their rapid work in approving and scheduling these observations.
GCN Circular 41095
Subject
GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
Date
2025-07-15T09:19:06Z (3 months ago)
From
Mathieu de Naurois at Laboratoire Leprince Ringuet, CNRS, Deputy Director of the H.E.S.S. Collaboration <denauroi@in2p3.fr>
Via
Web form
The H.E.S.S. array of imaging atmospheric Cherenkov telescopes conducted follow-up observations of the transient EP250702a, at the localization provided by the EP-WXT (Cheng et al., GCN 40906). H.E.S.S. observed this source position for a total of 6 hours over 4 consecutive nights, starting on 2025-07-04, under fairly good observing conditions. A preliminary off-site analysis shows no evidence for a significant signal in either the full dataset or the four nights individually, consistent with the non-detection reported by the LST-1 and MAGIC telescopes (Paneque et al., GCN 41067). Our upper limits are expected to be compatible with the H.E.S.S. sensitivity curves (e.g., Fig. 6 of https://doi.org/10.22323/1.236.0847), scaled to the observation duration.
The observations took place during the following times:
2025-07-04, 00:06 - 03:01 UTC
2025-07-05, 00:48 - 02:19 UTC
2025-07-06, 01:41 - 03:08 UTC
2025-07-07, 02:36 - 03:00 UTC
H.E.S.S. is an array of five imaging atmospheric Cherenkov telescopes that detects very-high-energy gamma rays (>100 GeV) and is located in the Khomas Highland in Namibia. It was constructed and is operated by researchers from Armenia, Australia, Austria, France, Germany, Ireland, Japan, the Netherlands, Poland, South Africa, Sweden, UK, and the host country, Namibia. For more details see https://hess.in2p3.fr/.
GCN Circular 41067
Subject
EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
Date
2025-07-11T17:01:56Z (3 months ago)
From
David Paneque at Max Planck Institute for Physics <dpaneque@mppmu.mpg.de>
Via
Web form
D. Paneque (MPP Munich), M. Teshima (MPP Munich), Arnau Aguasca-Cabot (UB, ICCUB, and IEEC-UB), Alessio Berti (MPP Munich), Sweta Menon (UNIROMA2 & INAF), Edna Ruiz-Velasco (LAPP Annecy), Monica Seglar-Arroyo (IFAE Barcelona) and Andrea Simongini (UNIROMA2 & INAF), on behalf of the CTAO-LST and MAGIC Collaborations report:
We observed the field of EP250702a / GRBs 250702B,D,E (GCN 40883, 40886, 40890, 40891, 40906). A total of 2.94 hours of observations were conducted with the MAGIC telescopes, beginning at 2025-07-04 01:25:53 UTC. The final 1.79 hours of this period were carried out jointly with LST-1.
A preliminary offline analysis of the LST-1 and MAGIC dataset shows no excess of gamma rays above 200 GeV in the field of EP250702a (GCN 40906). These results have been obtained using the LST analysis software, lst-chain (LST Collaboration, 2023 ApJ 956 80, v0.10.7), and the MAGIC analysis software MARS (Zanin et al. 2013, v 3.2.1). Observations were affected by reduced atmospheric transparency. A more in-depth analysis of this data set is ongoing.
Subsequent observations are planned after the moonbreak, subject to the nature of upcoming detections.
LST-1 is a prototype of the Large-Sized Telescope (LST) for the Cherenkov Telescope Array Observatory, and is located on the Canary island of La Palma, Spain. The telescope design is optimized for observation of gamma rays in the range from 20 GeV to 3 TeV.
MAGIC is a system of two 17m-diameter Imaging Atmospheric Cherenkov Telescopes located on the Canary island of La Palma, Spain, and designed to perform gamma-ray astronomy in the energy range from 50 GeV to greater than 50 TeV.
GCN Circular 41061
Subject
GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
Date
2025-07-10T21:08:34Z (3 months ago)
From
alexandra.tetarenko@uleth.ca
Via
Web form
A.J. Tetarenko (ULethbridge), J. Bright (Oxford), G. Bower (EAO/JCMT), S. Graves (EAO/JCMT):
The James Clerk Maxwell Telescope (JCMT) observed the position of GRB 250702B,D,E/EP250702A (GCNs 40906, 40883, 40885, 40886, 40890, 40891, ATels 17259, 17261) on 2025 July 08 between ~08:50 - 12:30 UTC for 3 scans totalling 0.55 hrs on-source and 2025 July 09 between ~08:15 - 09:20 UTC for 2 scans totalling 1.05 hrs on-source. The observations were made at a central frequency of 850 um (350 GHz) with the SCUBA-2 instrument. We do not detect a target source at the previously reported VLA radio position (RA: 18:58:45.565, Dec: -07:52:26.42; GCN 41053), yielding a 3-sigma upper limit of 6.3 mJy from stacking all of the data.
Extrapolating the previous radio detections with MeerKAT/VLA at 1.28/10 GHz of ~0.1/0.5 mJy (which imply a spectral index of ~1.3; GCN 41053), we would expect a clear detection at 350 GHz of ~50 mJy, suggesting a break in the spectrum between the cm and mm/sub-mm regions for this source. However, the recent ALMA detection at 97.5 GHz of ~2 mJy (GCN 41059), taken nearly simultaneously with our JCMT observations, implies a flatter spectral index of ~0.6. Therefore, a more accurate estimate of the expected 350 GHz flux density at the time of our JCMT observations would be ~4 mJy, consistent with our 3-sigma upper limit. Given these constraints, the source appears to likely have an inverted optically thick spectrum extending into the sub-mm bands.
We thank the JCMT staff for rapidly scheduling these observations. The JCMT is operated by the EAO on behalf of ASIAA and NARIT. Additional funds for the construction of SCUBA-2 were provided by the Canada Foundation for Innovation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
GCN Circular 41059
Subject
GRB 250702B,D,E / EP250702a: ALMA detection
Date
2025-07-10T18:59:43Z (3 months ago)
From
Kate D. Alexander at University of Arizona <katedenhamalexander@gmail.com>
Via
Web form
Kate D. Alexander (U of Arizona), James Miller-Jones (Curtin U), Adelle Goodwin, (Curtin U), Noah Franz (U of Arizona), Raffaella Margutti (UC Berkeley) Ryan Chornock (UC Berkeley), Dheeraj Pasham (Eureka Scientific/George Washington), Edo Berger (Harvard), Yvette Cendes (U of Oregon), and Collin Christy (U of Arizona) report on behalf of a larger collaboration:
We observed the location of the unusual transient GRB 250702B,D,E / EP250702a (GCNs 40906, 40883, 40885, 40886, 40890, 40891) with the Atacama Large Millimeter/submillimeter Array (ALMA) at multiple frequencies (program 2023.1.01731.T, PI: Miller-Jones). On 2025 July 9 02:09:03 UT, 6.97 days after the first detection with the Einstein Probe (GCN 40906) and 6.51 days after the first Fermi trigger (GCN 40883), we clearly detected the source at a mean frequency of 97.5 GHz with a preliminary flux density of ~2 mJy. Further ALMA observations are planned.
We thank the ALMA staff for quickly scheduling these observations and for providing the quick-look reduction.
GCN Circular 41054
Subject
GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
Date
2025-07-09T22:26:57Z (3 months ago)
From
lauren.rhodes@mcgill.ca
Via
Web form
Pikky Atri (Astron), Lauren Rhodes (TSI/McGill), Rob Fender (Oxford), Andrew Hughes (Oxford),and Sara Motta (INAF-OAB) report on behalf of the XKAT Collaboration.
The MeerKAT radio telescope observed the position of GRB 250702B,D,E/EP250702A (GCNs 40906, 40883, 40885, 40886, 40890, 40891) as part of the XKAT program on 06-07-2025 starting at 18:53:41 UT for 15 minutes. The observation was made at a central frequency of 1.28GHz with a bandwidth of 856MHz. We detect a point source with a flux density of ~100uJy at the coordinates R.A.: 18:58:45.5, Dec: -07:52:28.2 with a positional uncertainty of ~1" (please note the slight offset in declination).
The proximity of EP250702a on the sky to the neutron star X-ray Swift J1858.6-0814 allowed us to check archival observations from MeerKAT of the new transient’s position. Using our most recent observation of the Swift J1858.6-0814 from 02-03-2020 (Rhodes et al 2020), we place a 3-sigma upper limit of 114uJy/beam at the position of the EP250702a.
Further observations are planned.
We thank the SARAO staff for rapidly scheduling these observations. The MeerKAT telescope is operated by the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation, an agency of the Department of Science and Innovation.
X-KAT is a large MeerKAT open-time programme to observe X-ray binaries in the radio band, performing weekly monitoring of bright, active systems, with capacity for higher cadence observations, and in coordination with large X-ray and optical monitoring programmes. For further information on this programme contact Rob Fender.
GCN Circular 41053
Subject
GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
Date
2025-07-09T18:15:39Z (3 months ago)
From
Itai Sfaradi at University of California, Berkeley <itai.sfaradi@mail.huji.ac.il>
Via
Web form
Authors: I. Sfaradi (UC Berkeley), Y. Yao (UC Berkeley), H. Sears (Rutgers), E. Wiston (UC Berkeley), R. Margutti (UC Berkeley), R. Chornock (UC Berkeley), K.D. Alexander (U of Arizona), T. Laskar (Utah), E. Hammerstein (UC Berkeley), W. Lu (UC Berkeley)
We report here a radio detection of GRB 250702B,D,E / EP250702a (GCNs 40906, 40883, 40885, 40886, 40890, 40891) with the Karl G. Jansky Very Large Array (VLA program 25A-109; PI: Yao). We conducted our observation from 2025-07-08 05:29:18 (UTC) to 2025-07-08 06:29:03 (UTC), 6.13 days after the first detection with the Einstein Probe (GCN 40906) and 5.7 days after the first Fermi trigger (GCN 40883). Calibration and imaging were performed in CASA using the VLA calibration pipeline, with 3C286 as a bandpass and flux density calibrator, and J1832-1035 as the complex gain calibrator.
Our observation in X-band, with a 3.9 GHz bandwidth centered around 10 GHz, results in a detection of a point source with a flux density of 0.49 +/- 0.05 mJy (including 10% systematic flux calibration uncertainties) at R.A.: 18:58:45.565 +/- 0.015s, Dec.: -07:52:26.42 +/- 0.35’’ (J2000), consistent within 1 sigma uncertainty with the NIR counterpart (GCN 40924) and the EP X-ray counterpart (GCN 40906). The in-band spectral slope of F_nu ~ nu^1.3 implies optically thick emission. Radio detection with the MeerKAT telescope of a 0.1 mJy point source at 3 GHz was previously reported in GCN 40985.
We plan to continue monitoring this source and encourage further multi-wavelength observations.
We thank the VLA and the NRAO staff for scheduling and performing this observation.
GCN Circular 41016
Subject
EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
Date
2025-07-07T19:18:12Z (3 months ago)
From
Dalya Akl at American Uni. SHJ <dalyaakl.d@gmail.com>
Via
Web form
D. Akl (AUS), K. Noysena, A. Manasanun (NARIT), M. Freeberg, R. Hellot (KNC), C. Andrade (UMN), W. Corradi (LNA), M. Pillas (Uliege), S. Antier (OCA/IJCLAB), N. Kochiashvili (AbAO), M. Lamoureux (UCLouvain), on behalf of GRANDMA:
We observed the field of EP250702a (GCN 40906; associated with GRBs 250702/B/D/E) with GRANDMA and Kilonova Catcher and did not detect any optical counterpart.
All our measurements can be downloaded from: https://skyportal-icare.ijclab.in2p3.fr/public/sources/EP250702a/
All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the Sloan filters were calibrated using the PanSTARRS DR1 catalog. Images obtained with the Johnson-Cousin filters were calibrated using the Gaia DR3 Synphot catalog.
We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023).
Our observations are consistent with previously reported measurements (refer to SkyPortal for a subset of GCN measurements we collected).
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 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/).
GCN Circular 41014
Subject
EP250702a/ GRB 250702B: NuSTAR X-ray Observations
Date
2025-07-07T17:46:46Z (3 months ago)
From
Brendan O'Connor at Carnegie Mellon University <boconno2@andrew.cmu.edu>
Via
Web form
Brendan O’Connor (CMU), Dheeraj Pasham (Eureka Scientific/George Washington), Igor Andreoni (UNC), Jeremy Hare (Catholic/GSFC) report on behalf of a larger collaboration:
We observed the X-ray transient EP250702a (GCN 40906), which is also associated with the multiple gamma-ray triggers designated as GRB 250702B/D/E (GCNs 40883, 40886, 40890, 40891, 40931, 40903, 40914, 40923), with the NuSTAR X-ray Telescope through a Target of Opportunity observation through GO program 11282 (PI: Pasham). The observation occurred between 2025-07-03 20:45:21 and 2025-07-04 09:15:00 UTC for an on-source exposure of ~21.5 ks, simultaneous with Swift/XRT observations (ObsID: 19906002).
The source is clearly detected at an average rate of ~0.4 cts/s. The 3-79 keV X-ray lightcurve shows short term variability throughout the full exposure in both FPMA and FPMB, but no flaring is observed. The source varies in count rate by a factor of 2-3 on timescales as short as a few ks. Compared to NuSTAR observations of GRB 221009A at a similar count rate (GCNs 32695, 32788), the source shows more significant variability, which we suggest disfavors an ultralong GRB origin, especially in conjunction with the July 1st onset reported by the Einstein Probe (GCN 40906).
The X-ray spectra are featureless and do not show any Fe lines or reflection features. This is consistent with the lack of features in the Swift/XRT spectra. The 3-79 keV spectrum (FPMA+FPMB) is well fit by an absorbed powerlaw with a photon index of Gamma~1.81+/-0.03, which is consistent with the initial Swift/XRT spectral index within errors (GCN 40919). The hydrogen column density was fixed to 1e22 cm^-2 as per the best-fit Swift/XRT spectra (see https://www.swift.ac.uk/LSXPS/transients/9377). The unabsorbed 3-79 keV flux (time-averaged) is (2.35+/-0.05)e-11 erg/cm^2/s during our observation.
We also performed a fit with an absorbed cutoff powerlaw and find a cutoff energy >60 keV. In this case, the best-fit photon index is Gamma~1.67+/-0.08. This has better agreement with the EP/FXT result, although the FXT observation was obtained at an earlier time (GCN 40917). The C-stat between both fits to the NuSTAR data was nearly identical and the cutoff powerlaw is not a statistically significant improvement. We suggest that the lack of Fe lines, and lack of cutoff in the powerlaw spectra (out to at least 60 keV), is atypical for an X-ray binary.
We performed a Lomb-Scargle analysis on the barycenter corrected X-ray data, and did not identify any periodic signals over the frequency range 1e-3 to 100 Hz, consistent with the EP/FXT report (GCN 40917). The periodogram becomes red noise dominated below 3e-3 Hz.
Further analysis is underway and additional NuSTAR and Swift observations are planned.
We thank the NuSTAR SOC, and in particular Karl Forster and Brian Grefenstette, for promptly implementing these observations.
GCN Circular 40986
Subject
GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
Date
2025-07-06T04:15:00Z (3 months ago)
From
lixia76@mail2.sysu.edu.cn
Via
Web form
Xia Li, Chun Chen, Zhong-nan Dong, Duo-le Cao, Wei-Sen Huang, Jin-Ji Li, Jia-Qi Lin, Pu Lin, Yan Yu, Hao-Nan Yang, Hao-Ran Zhang, Xiang-Tao Zeng, 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 GRBs 250702B,C,D,E / EP250702a (H. Q. Cheng et al., GCN 40906; Y. Kawakubo et al., GCN 40910; D. Frederiks et al., GCN 40914; H. Q. Cheng et al., GCN 40917; J. A. Kennea et al., GCN 40919; Chen-Wei Wang et al., GCN 40923; E. Neights et al., GCN 40931) using the Sun Yat-sen University 80cm infrared telescope with 58 x 20 s exposures in J band. The calculated position is RA. = 18:58:45.61, DEC =-07:52:26.9 J2000, from Swift/XRT observation (J. A. Kennea et al., GCN 40919). Our observations began at 2025-7-3 19:36:00 UTC (29.67 hours after the first Fermi trigger, GRB 250702B).
We do not detect any optical counterpart (A. Kumar et al., GCN 40908; V.Lipunov et al., GCN 40912; Rosa L. Becerra et al., GCN 40918; I. Pérez-García et al., GCN 40929; Yan-Long Hua et al., GCN 40943; Malte Busmann et al., GCN 40949; M. H. Siegel, GCN 40952) at the position of the near-infrared afterglow (A. Martin-Carrillo et al., GCN 40924; A. J. Levan et al., GCN 40961), down to a 5-sigma depth of J~ 17.5 Vega magnitudes.
The SYSU 80cm infrared telescope is operated and managed by the Department of Astronomy, Sun Yat-sen University.
GCN Circular 40985
Subject
EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
Date
2025-07-05T23:18:15Z (3 months ago)
From
Joe Bright at U of Oxford <joe.bright@physics.ox.ac.uk>
Via
Web form
Authors: J. Bright (Oxford), F. Carotenuto (INAF, Rome), P. G. Jonker (Radboud), on behalf of a larger collaboration
We observed the field of EP250702a (GCN 40906; associated with GRBs 250702/B/D/E) with the MeerKAT radio telescope from 2025-07-04 17:37:32 UTC to 2025-07-04 18:39:55 UTC (with a total time on source of 44 minutes) using the S band receiver at a central frequency of 3.06 GHz. Analysing the SARAO Science Data Processor output continuum image we detect a source at the position of EP250702a with a flux density of around 100uJy/beam, with a typical image noise of around 8uJy/beam. Our detection is consistent with the upper limit reported by the Allen Telescope Array (GCN 40979).
Under the assumption of a source distance of 10 kpc we infer a radio luminosity of around 3.5e28 erg/s, consistent with X-ray binaries during the less luminous phases of their outburst cycles. The extragalactic/galactic nature of EP250702a is therefore not clarified by these observations.
Further observations will be conducted to check for variability.
We thank the SARAO staff for rapidly scheduling these observations. The MeerKAT telescope is operated by the South African Radio Astronomy Observatory, which is a facility of the National Research Foundation, an agency of the Department of Science and Innovation. This work has made use of the "MPIfR S-band receiver system" designed, constructed and maintained by funding of the MPI für Radioastronomie and the Max-Planck-Society.
GCN Circular 40983
Subject
EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
Date
2025-07-05T22:26:12Z (3 months ago)
From
akashjanaki98@gmail.com
Via
Web form
Akash Anumarlapudi (UNC Chapel Hill), David Kaplan (UWM), Igor Andreoni (UNC Chapel Hill), Dougal Dobie (U. Sydney/OzGrav), Tara Murphy (U. Sydney) on behalf of the VAST collaboration.
Fermi Gamma-ray Burst Monitor (GBM) reported the discovery of four possible long-durational GRBs, GRB 250702B,C,D,E, that might likely be coming from the same source (GCN #40891). Further X-ray observations by the Einstein Probe (EP; GCN #40906), MAXI (GCN #40910), Konus-WIND (GCN #40914), and SVOM (GCN #40923) resulted in the discovery of an X-ray counterpart. Data from the Wide-field X-ray Telescope (WXT) aboard EP revealed that the source was active in X-rays even a day before the Fermi GBM discovery. Follow-up observations from the Follow-up X-ray Telescope on EP (FXT, GCN #40906) constrained the position of the source to 20 arcseconds (90% confidence). No optical counterparts were reported down to i=22.0 (GCN #40918), but infrared observations have resulted in the discovery of a candidate counterpart (GCN #40924) with Ks~17.3 Vega, which is very red in color and rapidly fading (GCN #40961). Subsequent analysis of GBM data suggested that the burst GRB 250702C is likely not related to GRB 250702 B/D/E, but an unrelated short GRB (GCN #40931).
Here we report the archival radio observations of this source taken at the Australian SKA Pathfinder (ASKAP) observations as part of the Variable And Slow Transients Survey (VAST; Murphy et al. 2021) at 887.5 MHz.
The position of the source was observed for 13 epochs, roughly with a two-week cadence between March 2024 and December 2024. Each observation lasted approximately 12 minutes, reaching a sensitivity (noise level) of 250 uJy. The source was not detected in any of the single-epoch images. We stacked the individual exposures, which also resulted in a non-detection. The 1-sigma noise level at the location of the source is 75 uJy, and hence we place a limit on the persistent radio flux density (5-sigma) of the source to be < 375 uJy.
GCN Circular 40979
Subject
Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
Date
2025-07-05T16:16:46Z (3 months ago)
From
Itai Sfaradi at University of California, Berkeley <itai.sfaradi@mail.huji.ac.il>
Via
Web form
Authors: I. Sfaradi (UC Berkeley), R. Margutti (UC Berkeley), W. Farah (SETI Institute, UC Berkeley), S. Sheikh (SETI Institute, UC Berkeley), R. Chornock (UC Berkeley), V. Garcia Lopez (SETI Institute), J. Bright (Oxford), K. Alexander (University of Arizona), A. Siemion (Oxford, SETI Institute), A. Pollak (SETI Institute), Y. Yao (UC Berkeley), Nayana A.J. (UC Berkeley), H. Sears (Rutgers U)
We observed the field of the Einstein Probe source EP250702a (GCN 40906) with the Allen Telescope Array (ATA) on July 4, 2025, between 04:25:12 to 10:48:50 (UTC) about 2 days after first discovery. Our observation was carried out with four spectral windows centered around 1.5 and 3, 5, and 8 GHz, each with a bandwidth of 672 MHz. Calibration and imaging were performed using CASA with 3C286 as a bandpass and absolute flux scale calibrator, and 1822-096 as a complex gain calibrator.
No radio emission was detected at the position of EP250702a and we report here a flux density upper limit (3 sigma image RMS) of 1.1 mJy/beam in 5 GHz. For comparison, while the distance of this EP source is not known, we note that the level of emission in GRB 221009A was ~18 mJy at 5 GHz, ~2 days after discovery (Bright et al. 2023).
The Allen Telescope Array refurbishment program and its ongoing operations are being substantially funded through the Franklin Antonio Bequest. Additional contributions from Frank Levinson, Greg Papadopoulos, the Breakthrough Listen Initiative and other private donors have been instrumental in the renewal of the ATA. Breakthrough Listen is managed by the Breakthrough Initiatives, sponsored by the Breakthrough Prize Foundation. The Paul G. Allen Family Foundation provided major support for the design and construction of the ATA, alongside contributions from Nathan Myhrvold, Xilinx Corporation, Sun Microsystems, and other private donors. The ATA has also been supported by contributions from the US Naval Observatory and the US National Science Foundation.
GCN Circular 40961
Subject
GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
Date
2025-07-04T21:57:00Z (3 months ago)
From
Andrew Levan at Radboud University <a.levan@astro.ru.nl>
Via
Web form
A. J. Levan (Radboud & Warwick), A. Martin-Carrillo (UCD), B. Schneider (LAM), P. G. Jonker (Radboud), D. B. Malesani (DAWN/NBI and Radboud), B. P. Gompertz (Birmingham), G. Corcoran (UCD), M. De Pasquale (Univ. Messina) report on behalf of the Stargate collaboration:
We performed a second observation of the near-infrared source reported by Martin-Carrillo et al. (GCN 40924) likely associated with EP250702a (Cheng et al., GCNs 40906, 40917) and GRB 250702B,D,E detected by Fermi/GBM (Fermi GBM Team, GCNs 40883, 40886, 40890), Swift/BAT (via the GUANO system; DeLaunay et al., GCN 40903) and Konus/Wind (Frederiks et al., GCN 40914). We used the ESO VLT UT4 (Yepun) equipped with the HAWK-I near-infrared camera. We obtained 10-min exposures in each of the H and K bands, starting on 2025 July 4 at 03:16:28 UT (1.56 days after the first Fermi trigger, GRB 250702B).
Compared to our previous measurement (Martin-Carrillo et al., GCN 40924), the counterpart has faded by ~1.3 mag in the K band (and a consistent amount in H). Assuming a power-law decay, this gives a decay index ~1.7 (relative to the first Fermi trigger time).
The source is also extremely red, with an approximate colour of H-K ~ 2.5 (Vega). This is far from what is typically observed in transients and is not straightforward to explain even through dust extinction. The red color also easily explains the lack of optical detections (Siegel, GCN 40952; Busmann et al., GCN 40949; Hua et al., GCN 40943; Pérez-García et al., GCN 40929; Becerra et al., GCN 40918; Kumar et al., GCN 40908).
Our second epoch clearly reveals an extended source under the location of the near-infrared source. The true nature of this extended source is still not confirmed, although it appears morphologically to be a disc-like galaxy. On this assumption, based on the offset and approximate magnitude, we infer a chance probability of ~0.05%. If this is correct, it would suggest an extragalactic origin for GRBs 250702B,D,E / EP250702a.
We acknowledge excellent support from the observing staff in Paranal, in particular Susana Cerda-Hernandez, Thomas Szeifert, Marco Berton and Robert Klement
GCN Circular 40952
Subject
GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
Date
2025-07-04T14:09:07Z (3 months ago)
From
Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>
Via
Web form
M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the Einstein Probe (GCN Circ. 40906) location of the source that showed repeated outbursts detected by Fermi/GBM (GCN Circ. 40883, 40885, 40886, 40890, 40891) and Swift/BAT-GUANO (GCN #40903) 82 ks after the initial EP detection. No optical afterglow consistent with the XRT position (Kennea et al., GCN Circ. 40919) is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) using the initial EP detection as T_0 are:
Filter T_start(s) T_stop(s) Exp(s) Mag
b 82576 99156 235 >19.83
uvm2 99570 99822 247 >19.33
u 82491 104859 302 >19.73
v 82985 99566 115 >18.44
uvw1 82327 104787 628 >19.93
uvw2 82661 99481 663 >20.12
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.27 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 40949
Subject
GRB 250702B / EP2050702a: FTW optical and NIR observations
Date
2025-07-04T13:59:08Z (3 months ago)
From
Malte Busmann at Ludwig-Maximilians-Universität München <m.busmann@physik.lmu.de>
Via
Web form
Malte Busmann (LMU), Xander J. Hall (Carnegie Mellon U.), Brendan O’Connor (Carnegie Mellon U.), Daniel Gruen (LMU), Julian Sommer (LMU), and Antonella Palmese (Carnegie Mellon U.) report:
We observed the location of GRB 250702B / EP250702a (Fermi GBM Team, GCNs 40883, 40886, 40890; Neights et al., GCNs 40891, 40931; DeLaunay et al., GCN 40903; Cheng et al., GCNs 40906, 40917; Kawakubo et al, GCN 40910; Frederiks et al., GCN 40914; Wang et al., GCN GCN 40923) with the Three Channel Imager (3KK) at the Fraunhofer Telescope at Wendelstein Observatory (FTW) in the r, i and J band simultaneously for 40 x 180 s starting at 2025-07-03T21:52:47 UT.
We do not detect the source seen by Martin-Carrillo et al. (GCN 40924) or any other new source in the Swift/XRT localization (Kennea at al., GCN 40919) to 3 sigma limiting magnitudes of
r > 23.6 AB mag
i > 22.7 AB mag
J > 21.7 AB mag.
Compared to the K-band magnitude reported by Martin-Carrilo et al. (GCN 40924) this implies an extremely red color of the source, which implies a dusty environment, as also supported by the hydrogen column density inferred from the Swift/XRT observations (Kennea at al., GCN 40919). This is consistent with previous observations by Lipunov et al. (GCNs 40904, 40905, 40912), Kumar et al. (GCN 40908), Becerra et al. (GCN 40918), and Pérez-García et al. (GCN 40929).
The r and i band magnitudes are calibrated against the PS1 catalog and the J band is calibrated with the 2MASS Catalog. The magnitudes are not corrected for Galactic extinction.
We thank Silona Wilke from the Wendelstein Observatory staff for obtaining these observations.
GCN Circular 40943
Subject
EP250702a: WFST optical observations
Date
2025-07-04T10:42:26Z (3 months ago)
From
ylhua@pmo.ac.cn
Via
Web form
Yan-Long Hua, Jin-Jun Geng, Xue-Feng Wu, Hui Sun, Ye Li, Zhi-Ping Jin, Tian-Rui Sun, Yi-Fang Liang, Ding-Fang Hu, Yuan-Tai Yang, Ji-An Jiang report on behalf of the WFST team:
Following the detection of EP250702a by Einstein Probe (Cheng et al., GCN 40906, 40917), Fermi/GBM (Fermi GBM Team, GCNs 40883, 40885, 40886, 40890), Swift/BAT (via the GUANO system; DeLaunay et al., GCN 40903), and Konus/Wind (Frederiks et al., GCN 40914), all likely originating from the same astrophysical source (Neights et al., GCN 40891), the VLT (A. Martin-Carrillo et al., GCN 40924) identified a bright source that is absent in archival H- and K-band images from VISTA/VHS and UKIDSS.
We performed follow-up observations using the Wide Field Survey Telescope (WFST Collaboration; arXiv:2306.07590) at the Lenghu Astronomical Observation Base in Qinghai Province, China. Observations in the r-band began at 2025-07-03T17:26:10 UTC, approximately 28.29 hours after the trigger. The limiting magnitude of the stacked image reaches 22.19 (AB), and no unknown transient sources were detected in the region corresponding to the VLT observation.
We thank the WFST staff for supporting these observations.
GCN Circular 40931
Subject
Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
Date
2025-07-04T03:47:31Z (3 months ago)
From
eliza.neights@gmail.com
Via
Web form
E. Neights (GWU, NASA GSFC), O.J. Roberts (USRA, NASA MSFC), E. Burns (LSU), P. Veres (UAH), E. Bissaldi (Politecnico and INFN Bari) report on behalf of the Fermi-GBM Team:
On July 2, 2025, Fermi-GBM triggered four times on gamma-ray emission emanating from a similar localization of the sky (GCNs 40883, 40885, 40886, 40890, 40891), over an interval of 11.5 ks, believed likely to be from the same source. Konus-Wind observations (GCN 40914) provide further support that these triggers may be related to a similar origin, but with a combined duration of >15 ks. A combined GBM skymap was found to be spatially consistent with Swift-BAT GUANO detections of 250702D, C and E (GCN 40903). Emission from 250702E was found to be spatially and temporally coincident with Einstein Probe Transient, EP250702a (GCN 40906, 40917). While it is currently named with the phenomenological GRB convention, the physical origin is still uncertain.
Upon further investigation, the pulse which caused the GBM trigger labeled 250702C was from an unrelated short GRB. That is, emission from the short burst and the ultra-long 250702B are contemporaneous, but arise from inconsistent locations.
In light of this, spectral analysis was conducted for the three triggers of GRB 250702B, matched to their previous designations below. We observe photons in the BGO up to 1 MeV, with the majority of the photons occurring in the 50-300 keV range. The spectral analyses of these events are summarized below, which are fit about equally well with power law and Band function models:
GRB Name | Trigger Time/T0 (UT) | Interval (s) | Power Law Index | Fluence (erg/cm2)
250702E | 16:21:33.07 | T0-6.1 - T0+147.5 | -1.38 +/- 0.01 | (2.74 +/- 0.05)E-05
250702B | 13:56:05.77 | T0-30.7 - T0+26.6 | -1.34 +/- 0.01 | (1.24 +/- 0.03)E-05
250702D | 13:09:02.03 | T0-95.2 - T0+12.3 | -1.29 +/- 0.02 | (1.04 +/- 0.05)E-05
GRB Name | Trigger Time/T0 (UT) | Interval (s) | Band Alpha | Band Beta | Band Peak Energy (keV) | Fluence (erg/cm2)
250702E | 16:21:33.07 | T0-6.1 - T0+147.5 | -0.81 +/- 0.05 | -5.1 +/- 22.7 | 610 +/- 60 | (3.4 +/- 0.1)E-05
250702B | 13:56:05.77 | T0-30.7 - T0+26.6 | -0.8 +/- 0.1 | -1.52 +/- 0.04 | 400 +/- 200 | (1.38 +/- 0.05)E-05
250702D | 13:09:02.03 | T0-95.2 - T0+12.3 | -0.2 +/- 0.3 | -1.7 +/- 0.1 | 400 +/- 100 | (1.48 +/- 0.09)E-05
GCN Circular 40929
Subject
GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
Date
2025-07-04T02:24:14Z (3 months ago)
From
I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg@iaa.es>
Via
Web form
I. Pérez-García, A. J. Castro-Tirado, M. D. Caballero-García, S. Guziy, R. Sánchez-Ramírez, S.-Y. Wu (IAA-CSIC Granada), G. García-Segura (Instituto de Astronomía de la UNAM, Ensenada), M. Gritsevich (Univ. of Helsinki), Y.-D. Hu (Guanxi Univ.), S. Góngora-García and J.-F.Agüí-Fernández (CAHA), on behalf of a larger collaboration, report:
We observed the location of EP250702a (Cheng et al., GCN 40906, 40917), associated with the four high-energy events GRB 250702B,C,D,E, all detected by Fermi/GBM (Fermi GBM Team, GCN 40883, 40885, 40886, 40890), Swift/BAT (GUANO system; DeLaunay et al., GCN 40903) and Konus/Wind (Frederiks et al., GCN 40914), with all these events likely originating from the same astrophysical source (Neights et al., GCN 40891).
Using the 2.2m CAHA telescope in Spain (equipped with CAFOS), we obtained 60s exposures in the z-band, starting on 2025 July 3 at 23.99 UT (i.e. 34.1 hr after the first Fermi trigger, GRB 250702B). At the location of the UVOT-enhanced position provided by Swift/XRT (Kennea et al., GCN 40919) and the VLT nIR source reported by Martin-Carrillo et al. (GCN 40924), we do not detect an optical source on the co-added z-band (1980s total exposure time) down to z = 21.4 (3-sigma limiting magnitude), using the Pan-STARRS1 DR2 (Magnier et al. 2025) catalogue as reference.
We thank the staff at CAHA for their excellent support.
GCN Circular 40924
Subject
GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
Date
2025-07-03T18:17:16Z (3 months ago)
Edited On
2025-07-05T16:17:13Z (3 months ago)
From
Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo@ucd.ie>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani@nbi.ku.dk>
Via
Web form
A. Martin-Carrillo (UCD), A. J. Levan (Radboud), B. Schneider (LAM), J. An (NAOC), D. Xu (NAOC), S. Campana (INAF-OAB), G. Corcoran (UCD), P. G. Jonker (Radboud), D. B. Malesani (DAWN/NBI and Radboud) report on behalf of the Stargate collaboration:
We observed the location of EP250702a (Cheng et al., GCNs 40906, 40917) likely associated with GRB 250702B,C,D,E detected by Fermi/GBM (Fermi GBM Team, GCNs 40883, 40885, 40886, 40890), Swift/BAT (via the GUANO system; DeLaunay et al., GCN 40903) and Konus/Wind (Frederiks et al., GCN 40914), all likely originating from the same astrophysical source (Neights et al., GCN 40891). We used the ESO VLT UT4 (Yepun) equipped with the HAWK-I near-infrared camera. We obtained two 20 min exposures in each of the H and K bands, starting on 2025 July 3 at 07:03:03 UT (17.1 hr after the first Fermi trigger, GRB 250702B).
At the location of the UVOT-enhanced (2" radius) coordinates provided by Swift/XRT (Kennea et al., GCN 40919) we identify a bright source not visible in archival H and K images from VISTA/VHS and UKIDSS at the following coordinates (J2000):
RA (J2000) = 18:58:45.57
Dec (J2000) = -07:52:26.2
with an uncertainty of ~0.5" in each axis. The source has a magnitude of K ~ 17.3 (Vega), calibrated against 2MASS stars.
We note that, while the source is dominated by point-like emission, it appears to be extended along the E-W direction. As this is a crowded field, this could be just the result of source confusion. Alternatively, if the extension is real, it could be related to nebulosity around a Galactic source, or be a distant host galaxy which would imply an extragalactic origin for GRBs 250702B,C,D,E / EP250702a.
Further observations are planned and encouraged to reveal the nature of this unusual gamma-ray burster.
We acknowledge excellent support from the observing staff in Paranal, in particular Marco Berton, Robert Klement, Susana Cerda-Hernandez, Thomas Rivinius, and Thomas Szeifert.
GCN Circular 40923
Subject
GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
Date
2025-07-03T16:44:09Z (3 months 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: Alexis Coleiro (APC)
Report on behalf of the SVOM team:
On July 2, 2025, SVOM/GRM detected a hard X-ray activity using event-by-event data downloaded via the X-band ground station. This activity is consistent with detections reported by Fermi/GBM (Fermi GBM Team, GCN #40883, #40885, #40886, #40890, #40891), Swift/BAT (James DeLaunay et al., GCN #40903), and Konus-Wind (D. Frederiks et al., GCN #40914). These transient events may be associated with the soft X-ray transient EP250702a (GCN #40906), also detected by MAXI/GSC (GCN #40910).
At the time of the hard X-ray triggers, the refined position reported by EP/WXT (R.A. = 284.6911 deg, DEC = -7.8715 deg J2000, GCN#40906) was approximately 48 degrees from the SVOM optical axis, which is just outside the ECLAIRs field of view. GRD 02 and GRD 03 provided continuous coverage of this transient activity (with incident angle of 30 and 48 degrees, respectively) from the very beginning to about 2025-07-02T15:20:00, except passing the SAA and Earth’s shadow.
The SVOM/GRM light curve of GRB 250702D can be found here:
https://www.bursthub.cn//admin/static/svgrb250702D.png
We note that the report here is very preliminary, refined analysis is still ongoing.
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)
GCN Circular 40919
Subject
GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
Date
2025-07-03T15:14:48Z (3 months ago)
From
Jamie Kennea at Penn State <jak51@psu.edu>
Via
Web form
J. A. Kennea, M. H. Siegel (PSU), P. A. Evans, K. L. Page (Leicester) and B. O'Connor (CMU) report on behalf of the Swift Team:
Swift began an TOO observation of the Einstein Probe (GCN #40906) of this source that showed repeated outbursts detected by Fermi/GBM (GCN #40883, #40885, #40886, #40890, #40891) and Swift/BAT-GUANO (GCN #40903) on July 3, 2025 at 01:34UT. We detect a bright uncatalogued X-ray point source at the following localization: RA/Dec(J2000) = 284.69006, -7.87413 which is equivalent to:
RA(J2000) = 18h 58m 45.61s,
Dec(J2000) = -07d 52' 26.9'',
with an estimated error uncertainty of 2.0 arc-seconds radius (90% confidence). This position is not coincident with any UVOT detected source. The X-ray flux during the Swift TOO observation is highly variable, showing a rapid fading behavior during the first orbit of data, suggesting the tail end of a flare, with the average rate over the orbit of 1.5 +/- 0.1 c/s. Following orbits the source has count rate between of 0.4-0.5 c/s.
The spectrum is well fit by an absorbed power law with N_H = 1.1 +/- 0.2 x 10^22 cm^-2, and a photon index of 1.65 +/- 0.20. The average flux of the source is 4.5 +/- 0.4 10^-11 erg/s/cm^2 (0.3-10 keV) observed, and 6.8 (+0.9/-0.6) x 10^-11 erg/s/cm^2 (0.3 - 10 keV) corrected for absorption.
Further Swift observations of this object are planned. Follow-up observations to classify the source are highly encouraged.
GCN Circular 40918
Subject
GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
Date
2025-07-03T15:12:02Z (3 months ago)
From
Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra@roma2.infn.it>
Via
Web form
Rosa L. Becerra (U Roma), Damien Dornic (CPPM), Margarita Pereyra (UNAM), Jean-Luc Atteia (IRAP), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Fredd Alvarez (UNAM), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Nathaniel R. Butler (ASU), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM):
We imaged the field of the likely ULGRB detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 40883, 40885, 40886, 40890, 40891) specifically at the position of EP250702a (Cheng et al., GCN Circ. 40906) using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2025-07-03 08:19 to 09:45 UTC, from 29.4 to 30.9 hours after the EP/WXT trigger (Cheng et al., GCN Circ. 40906) and obtained 64 minutes of exposure in the i filter.
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.
In the stacked image and after performing image subtraction, we do not detect any new source at the EP/FXT source position (Cheng et al., GCN Circ. 40906) down to the following 3-sigma limit:
i > 22.0
This upper limit is consistent with the one reported by GOTO (Kumar et al. GCN Circ. 40908)
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 40917
Subject
EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
Date
2025-07-03T15:05:29Z (3 months ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
H. Q. Cheng (NAO, CAS), Y. J. Zhang (THU), G. Y. Zhao (SYSU), C. Zhou (HUST), Y. H. Cheng (SWIFAR, YNU), Y. L. Wang (NAO, CAS; ICE, CSIC-IEEC), F. Coti Zelati, A. Marino, N. Rea (ICE, CSIC-IEEC), J. W. Hu, H. Sun, Z. X. Ling, W. Yuan (NAO, CAS) on behalf of the Einstein Probe (EP) team:
Following the detection of GRB 250702B, C, D, E by Fermi/GBM (GCN 40883, 40885, 40886, 40890, 40891) and its likely X-ray counterpart EP250702a detected by Einstein Probe (EP, GCN 40906, ATel #17261), MAXI (GCN 40910) and Konus-Wind (GCN 40914), we performed a follow-up observation on EP250702a with the Follow-up X-ray Telescope (FXT) onboard EP. The observation began at 2025-07-03T02:44:11, with an exposure of about 3875 s.
Our on-ground analysis showed that an X-ray source is detected at R.A.= 284.6895 deg, Dec= -7.8738 deg, with an uncertainty of 10 arcsecond (90% C.L. systematic and statistical), which is within the error circle of the EP-WXT position of EP250702a. Considering the possibility of the source being a Galactic object and given the improved source localization, we also designate the source EP J185845.5-075225. The FXT spectrum can be fitted with an absorped power law model, yielding a column density of (7.9+/-0.6)e21 cm^-2, a photon index of 1.57+/-0.07, and an unabsorbed 0.5-10 keV flux of (5.52+/-0.21)e-11 erg/s/cm^2. We also performed preliminary timing analysis using the FXT data collected so far, and no significant periodic or quasi-periodic signals were detected.
EP-FXT will continue to monitor this source in the next days. The contact transient advocates of this source are Huaqing Cheng (hqcheng@nao.cas.cn) and Yi-Jia Zhang (zhangyij21@mails.tsinghua.edu.cn). Please contact them for coordination of multi-wavelength follow-up observations.
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 40914
Subject
GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
Date
2025-07-03T12:51:12Z (3 months ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
Via
email
D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin,
A. Tsvetkova, M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:
On July 2, 2025, Konus-Wind (KW) detected, in the waiting mode,
a hard X-ray activity, consistent in time with GRBs 250702B, C, D, E,
reported by Fermi-GBM team (GCN 40883, 40885, 40886, 40890, 40891),
localized by Swift/BAT-GUANO (GCN 40903),
associated with the X-ray transient EP250702a (GCN 40906),
and detected by MAXI/GSC (GCN 40910).
KW observed multiple overlapped emission episodes
in in the time interval from ~12:40 to ~16:50 UT.
The emission is clearly visible in all three KW waiting mode
energy bands (20-75, 75-300, 300-1250 keV).
From our preliminary background estimates,
the total duration of the event is >~15.5 ks.
The Konus-Wind light curve is available at
http://www.ioffe.ru/LEA/GRBs/GRB250702BCDE/
In the 20-1250 keV range, the time-integrated spectrum of the emission is best described
by a simple power law (PL) function with the PL photon index of (-1.3 ± 0.06).
The total observed fluence in this energy band is (5.95 ± 0.32)x10^-4 erg/cm^2
and the 2.944 s peak energy flux is (5.33 ± 0.29)x10^-7 erg/cm^2/s.
All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.
GCN Circular 40912
Subject
EP250702a: Global MASTER-Net observations report
Date
2025-07-03T11:09:30Z (3 months ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko,
G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A.Sosnovskij (CrAO),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP250702a ( EP Team et al., GCN 40906) errorbox 1 days 2370 sec after trigger time at 2025-07-03 03:33:14 UT, with upper limit up to 17.4 mag. The observations began at zenith distance = 29 deg. The sun altitude is -73.4 deg.
The galactic latitude b = -6 deg., longitude l = 27 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2923840
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
88860 | 2025-07-03 03:33:14 | MASTER-OAFA | (18h 57m 22.01s , -08d 01m 07.7s) | C | 180 | 17.4 |
89047 | 2025-07-03 03:36:20 | MASTER-OAFA | (18h 57m 21.64s , -08d 01m 10.1s) | C | 180 | 17.3 |
89233 | 2025-07-03 03:39:27 | MASTER-OAFA | (18h 57m 21.26s , -08d 01m 13.3s) | C | 180 | 17.4 |
89419 | 2025-07-03 03:42:32 | MASTER-OAFA | (18h 57m 20.88s , -08d 01m 16.3s) | C | 180 | 17.3 |
104587 | 2025-07-03 07:56:21 | MASTER-OAFA | (18h 58m 32.22s , -07d 41m 30.2s) | C | 60 | 17.4 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 40910
Subject
GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
Date
2025-07-03T09:47:38Z (3 months ago)
Edited On
2025-07-16T13:56:17Z (3 months ago)
From
Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp>
Via
Web form
Y. Kawakubo, M. Serino (AGU), H. Negoro, M. Nakajima, , K. Takagi, H. Takahashi,
K. Tatano, H. Nishio (Nihon U.), T. Mihara, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN),
T. Sakamoto, S. Sugita, H. Hiramatsu, Y. Kondo, A. Yoshida (AGU),
Y. Tsuboi, H. Sugai, N. Nagashima (Chuo U.),
M. Shidatsu, Y. Niida, C. Kang, T. Nakamoto (Ehime U.),
I. Takahashi, Y. Yatsu (Science Tokyo),
S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA),
Y. Ueda, K. Fujiwara (Kyoto U.),
M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.),
K. Yamaoka (Nagoya U.),
M. Sugizaki (Kanazawa U.),
W. Iwakiri (Chiba U.),
T. Kawamuro (Osaka U.),
S. Yamada (Tohoku U)
We report on the MAXI/GSC detection of an X-ray transient source on July 2, 2025 (MJD 60858) associated with GRB 250702B,C,D,E/EP250702a.
The source was clearly detected at three scan transits from 2025-07-02T12:59 UT
to 2025-07-02T16:15.
Assuming that the source flux was constant over the three transits, we obtain the
source position at (284.462 deg, -7.936 deg) = (18 57 50, -07 56 09) (J2000)
with a statistical 90% C.L. elliptical error region
with long and short radii of 0.34 deg and 0.24 deg, respectively.
The roll angle of the long axis from the north direction is 54.0 deg counterclockwise.
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the three scans was 54 +- 11 mCrab.
The time and the source position determined by the MAXI observations are consistent
with GRB 250702B, C, D, E, observed by Fermi-GBM (GCN 40883, 40885, 40886, 40890, 40891),
the source localization skymap provided by Swift/BAT-GUANO (GCN 40903)
and EP250702a observed by the Einstein Probe/WXT, FXT (GCN 40906).
Follow-up observations are encouraged.
GCN Circular 40908
Subject
EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
Date
2025-07-03T07:38:27Z (3 months ago)
From
Amit Kumar at Royal Holloway - UoL/ U of Warwick, UK <amitkundu515@gmail.com>
Via
Web form
A. Kumar, B. P. Gompertz, G. Ramsay, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, D. O'Neill, B. Godson, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, and J. Casares report on behalf of the GOTO collaboration:
We report on observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to GRB 250702B, C, D and E (Fermi GBM Team, GCNs 40883, 40885, 40886, 40890 and 40891). Targeted observations were performed between 2025-07-02 23:16:56 UT and 2025-07-03 02:52:31 UT (between 20.39 and 23.98 hours after trigger). Each observation 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 of the same pointings. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogues. Human vetting was carried out in real time on any candidates that passed the above checks.
We identify no candidate optical counterparts within the EP/FXT (Cheng et al. 40906) 90% localisation region with typical 3-sigma limits ranging between L > 19.85 to L > 20.35 (AB). The deepest of these was taken at a mid-time of 2025-07-03 02:06:10 UT (23.21 hours after trigger).
Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction.
(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 40906
Subject
EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
Date
2025-07-03T04:20:00Z (3 months ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
H. Q. Cheng (NAO, CAS), G. Y. Zhao (SYSU), C. Zhou (HUST), Y. H. Cheng (SWIFAR, YNU), Y. J. Zhang (THU), J. W. Hu, H. Sun and Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team:
We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP250702a. The source was first detected in an observation starting at 2025-07-02T02:53:44 (UTC), and was continuously detected in subsequent observations spanning from 2025-07-02T05:57:06 to 2025-07-02T22:32:44. The WXT position of the source is R.A. = 284.700 deg, DEC = -7.869 deg (J2000) with an uncertainty of 2.4 arcmin in radius (90% C.L. statistical and systematic). The source reached a peak flux in the observation starting at 2025-07-02T16:10:11 with an exposure of 827s, the epoch of which is generally consistent with the burst time of GRB 250702E (GCN 40890). Considering that EP250702a is spatially and temporally coincident with the GRB 250702B,C,D,E detected by Fermi /GBM (GCN 40883, 40885, 40886, 40890, 40891), we suggest that EP250702a is likely the X-ray source associated with GRB 250702B,C,D,E. The WXT position is also consistent with the source localization skymap provided by the Swift/BAT-GUANO (GCN 40903).
Stacking of the WXT data taken prior to the WXT detection indicated that the source has already emerged on July 1st, 2025. The WXT spectrum of the peak flux epoch can be fitted with an absorbed power-law model (with the column density fixed at the Galactic absorption value of 5e21 cm^-2), yielding a photon index of 0.2+/-0.1 and an unabsorbed 0.5-4 keV flux of (5.5+/-0.7)e-10 ergs/s/cm^2.
A follow-up observation with the Follow-up X-ray Telescope (FXT) onboard EP was performed but the telemetry data is still not available yet. The FXT onboard source detection algorithm gives an improved source position at R.A. = 284.6911 deg, DEC = -7.8715 deg (J2000) with an uncertainty of 20 arcsecond in radius (90% C.L. statistical and systematic). More information will be updated when the telemetry data is received.
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 40905
Subject
Fermi GRB 250702E: Global MASTER-Net observations report
Date
2025-07-03T02:15:35Z (3 months ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko,
G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A.Sosnovskij (CrAO),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 250702E ( Fermi GBM team, GCN 40890) errorbox 28126 sec after notice time and 28161 sec after trigger time at 2025-07-03 00:10:54 UT, with upper limit up to 18.6 mag. The observations began at zenith distance = 28 deg. The sun altitude is -68.5 deg.
The galactic latitude b = -12 deg., longitude l = 19 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2923298
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
28191 | 2025-07-03 00:10:54 | MASTER-SAAO | (18h 58m 11.78s , -10d 24m 39.1s) | C | 60 | 18.2 |
28289 | 2025-07-03 00:12:31 | MASTER-SAAO | (19h 06m 18.96s , -10d 26m 55.8s) | C | 60 | 18.6 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 40904
Subject
Fermi GRB 250702B: Global MASTER-Net observations report
Date
2025-07-03T02:15:23Z (3 months ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko,
G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A.Sosnovskij (CrAO),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 250702B ( Fermi GBM team, GCN 40883) errorbox 36852 sec after notice time and 36888 sec after trigger time at 2025-07-03 00:10:54 UT, with upper limit up to 18.6 mag. The observations began at zenith distance = 28 deg. The sun altitude is -68.5 deg.
The galactic latitude b = -7 deg., longitude l = 27 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2923151
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
36919 | 2025-07-03 00:10:54 | MASTER-SAAO | (18h 58m 11.78s , -10d 24m 39.1s) | C | 60 | 18.2 |
37016 | 2025-07-03 00:12:31 | MASTER-SAAO | (19h 06m 18.96s , -10d 26m 55.8s) | C | 60 | 18.6 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 40903
Subject
GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
Date
2025-07-03T01:29:21Z (3 months ago)
From
Jimmy DeLaunay at Penn State <delauj2@gmail.com>
Via
Web form
James DeLaunay (PSU), Samuele Ronchini (PSU), Aaron Tohuvavohu (Caltech), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC), Maia Williams (PSU) report:
Fermi/GBM triggered on four possible GRBs with similar localizations (GCN 40891) that may all have a common origin. Three of these bursts (GRB 250702D GCN 40886, GRB 250702C GCN 40885, GRB 250702E GCN 40890) have been detected in Swift/BAT-GUANO data.
GRB 250702D (T0: 2025-07-02T13:09:02.03 UTC, Fermi/GBM trig 773154547) was detected by the NITRATES analysis (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169) with a sqrt(TS) of 14.6 in a 8.192 s analysis time bin, starting at T0 - 6.144 s.
The localization resulted in a 90% credible area of 5,318 deg2, a 50% credible area of 1,192 deg2, and an integrated probability of 5% inside the coded field of view.
GRB 250702C (T0: 2025-07-02T14:49:31.91 UTC, Fermi/GBM trig 773160576) was detected by the NITRATES analysis with a sqrt(TS) of 7.5 in a 16.384 s analysis time bin, starting at T0 - 4.096 s.
The localization resulted in a 90% credible area of 13,685 deg2, a 50% credible area of 4,087 deg2, and an integrated probability of 7% inside the coded field of view.
GRB 250702E (T0: 2025-07-02T16:21:33.07 UTC, Fermi/GBM trig 773166098) was detected by the NITRATES analysis with a sqrt(TS) of 12.3 in a 8.192 s analysis time bin, starting at T0 - 4.096 s.
The localization resulted in a 90% credible area of 8,604 deg2, a 50% credible area of 2,099 deg2, and an integrated probability of 3% inside the coded field of view.
The localizations of all three bursts are consistent with the combined GBM skymap (GCN 40891). When the three NITRATES localizations are combined with the combined GBM skymap there is a slight improvement, with a 90% credible region of 142 deg2 centered at,
RA, Dec = 285.820, -4.182 deg
More details about these bursts and their skymaps can be found here:
GRB 250702D https://guano.swift.psu.edu/trigger_report?id=773154577
GRB 250702C https://guano.swift.psu.edu/trigger_report?id=773160607
GRB 250702E https://guano.swift.psu.edu/trigger_report?id=773166128
The combined NITRATES and Fermi GBM skymap localization can be found here:
https://zenodo.org/records/15795079
Additionally, imaging was performed to search for persistent emission while the source was in the coded field of view from ~13:28 to 13:48 UTC and from ~17:50 to 18:06 UTC, but nothing significant was found.
GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches.
A live reporting of Swift/BAT event data recovered by GUANO can be found at:
https://www.swift.psu.edu/guano/
GCN Circular 40897
Subject
Fermi GRB 250702C: Global MASTER-Net observations report
Date
2025-07-02T22:15:26Z (3 months ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko,
G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A.Sosnovskij (CrAO),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 250702C ( Fermi GBM team, GCN 40885) errorbox 23400 sec after notice time and 23443 sec after trigger time at 2025-07-02 21:20:15 UT, with upper limit up to 18.3 mag. The observations began at zenith distance = 34 deg. The sun altitude is -69.7 deg.
The galactic latitude b = 11 deg., longitude l = 29 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2923228
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
940 | 2025-07-02 15:04:42 | MASTER- | (18h 24m 35.12s , +11d 59m 59.4s) | C | 60 | 17.4 | Coadd
23474 | 2025-07-02 21:20:15 | MASTER-SAAO | (17h 52m 31.98s , +01d 13m 24.2s) | C | 60 | 18.3 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 40891
Subject
Fermi GBM Triggers 250702B, C, D and E are likely from the same source
Date
2025-07-02T19:04:27Z (3 months ago)
Edited On
2025-07-02T19:10:12Z (3 months ago)
From
eliza.neights@gmail.com
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov>
Via
Web form
E. Neights (GWU, NASA GSFC), O.J. Roberts (USRA, NASA MSFC), E. Burns (LSU), P. Veres (UAH) report on behalf of the Fermi-GBM Team:
At 13:09:02.03 UT, Fermi GBM triggered on GRB 250702D and was initially localized to an RA and Dec of 292.9 and 3.6 (19h, 31m, +03,33’; J2000), with an error of 14.7 deg. The light curve shows several peaks occurring over ~60 seconds.
Since then, an additional three bursts have triggered GBM with similar lightcurve characteristics and localizations. The trigger times and localizations are summarized as follows:
GRB Name MET (s) Time (UT) RA (deg) Dec (deg) Err (deg)
250702E 773166098 16:21:33.07 286.8 -17.7 11.6 (GCN 40890)
250702C 773160576 14:49:31.91 270.3 1.4 12.7 (GCN 40885)
250702B 773157370 13:56:05.77 286.0 -8.7 7.8 (GCN 40883)
250702D 773154547 13:09:02.03 292.9 3.6 14.7 (GCN 40886)
Despite the similar position lying close to or on the galactic plane, we observe photons in the BGO up to 1 MeV, with the majority of the photons occurring in the 50-300 keV range, which suggest the source may not be a typical galactic source and might be an ultra-long GRB or another source class. If a GRB origin is confirmed, it is 11.5 ks long, making it one of the longest ultra-long GRBs detected.
The combined GBM skymap can be found here: https://zenodo.org/records/15793558. The skymaps are all associated with each other with confidence between 89.2 and 98.5%.
There were no joint-GW detections during these triggered times.
We strongly suggest follow-up of the region to determine the nature of the source over multiple wavelengths.
GCN Circular 40890
Subject
GRB 250702E: Fermi GBM Final Real-time Localization
Date
2025-07-02T16:32:10Z (3 months ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
The Fermi GBM team reports the detection of a likely LONG GRB
At 16:21:33 UT on 2 Jul 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250702E (trigger 773166098.071902 / 250702682).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 286.8, Dec = -17.7 (J2000 degrees, equivalent to J2000 19h 07m, -17d 41'), with a statistical uncertainty of 11.6 degrees.
The angle from the Fermi LAT boresight is 106.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250702682/quicklook/glg_skymap_all_bn250702682.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250702682/quicklook/glg_healpix_all_bn250702682.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250702682/quicklook/glg_lc_medres34_bn250702682.gif
GCN Circular 40886
Subject
GRB 250702D: Fermi GBM Final Localization Correction
Date
2025-07-02T15:19:41Z (3 months ago)
From
eliza.neights@gmail.com
Via
Web form
The Fermi GBM team reports the detection of a likely LONG GRB
"At 13:09:02.03 UT on 02 July 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250702D (trigger 773154547/250702548).
This trigger was initially classified as Below horizon by the flight software,
but is in fact a GRB.
The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 292.86, Dec = 3.55 (J2000 degrees, equivalent to J2000 19h 31m, +3d 32'),
with a statistical uncertainty of 14.69 degrees.
The angle from the Fermi LAT boresight is 92 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250702548/quicklook/glg_skymap_all_bn250702548.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250702548/quicklook/glg_healpix_all_bn250702548.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250702548/quicklook/glg_lc_medres34_bn250702548.gif"
GCN Circular 40885
Subject
GRB 250702C: Fermi GBM Final Real-time Localization
Date
2025-07-02T14:59:49Z (3 months ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
The Fermi GBM team reports the detection of a likely LONG GRB
At 14:49:31 UT on 2 Jul 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250702C (trigger 773160576.914616 / 250702618).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 270.3, Dec = 1.4 (J2000 degrees, equivalent to J2000 18h 01m, 1d 23'), with a statistical uncertainty of 12.7 degrees.
The angle from the Fermi LAT boresight is 68.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250702618/quicklook/glg_skymap_all_bn250702618.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250702618/quicklook/glg_healpix_all_bn250702618.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250702618/quicklook/glg_lc_medres34_bn250702618.gif
GCN Circular 40883
Subject
GRB 250702B: Fermi GBM Final Real-time Localization
Date
2025-07-02T14:06:41Z (3 months ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
The Fermi GBM team reports the detection of a likely LONG GRB
At 13:56:05 UT on 2 Jul 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250702B (trigger 773157370.765606 / 250702581).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 286.0, Dec = -8.7 (J2000 degrees, equivalent to J2000 19h 03m, -8d 41'), with a statistical uncertainty of 7.8 degrees.
The angle from the Fermi LAT boresight is 90.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250702581/quicklook/glg_skymap_all_bn250702581.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250702581/quicklook/glg_healpix_all_bn250702581.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250702581/quicklook/glg_lc_medres34_bn250702581.gif