GRB 250702C, GRB 250702E, GRB 250702B, GRB 250702D, EP250702a
GCN Circular 40883
Subject
GRB 250702B: Fermi GBM Final Real-time Localization
Date
2025-07-02T14:06:41Z (2 days 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
GCN Circular 40885
Subject
GRB 250702C: Fermi GBM Final Real-time Localization
Date
2025-07-02T14:59:49Z (2 days 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 40886
Subject
GRB 250702D: Fermi GBM Final Localization Correction
Date
2025-07-02T15:19:41Z (2 days 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 40890
Subject
GRB 250702E: Fermi GBM Final Real-time Localization
Date
2025-07-02T16:32:10Z (2 days 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 40891
Subject
Fermi GBM Triggers 250702B, C, D and E are likely from the same source
Date
2025-07-02T19:04:27Z (2 days ago)
Edited On
2025-07-02T19:10:12Z (2 days 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 40897
Subject
Fermi GRB 250702C: Global MASTER-Net observations report
Date
2025-07-02T22:15:26Z (2 days 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 40903
Subject
GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
Date
2025-07-03T01:29:21Z (2 days 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 40904
Subject
Fermi GRB 250702B: Global MASTER-Net observations report
Date
2025-07-03T02:15:23Z (2 days 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 40905
Subject
Fermi GRB 250702E: Global MASTER-Net observations report
Date
2025-07-03T02:15:35Z (2 days 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 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 (2 days 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 40908
Subject
EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
Date
2025-07-03T07:38:27Z (a day 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 40910
Subject
MAXI/GSC detection of an X-ray activity from a transient associated with GRB 250702B,C,D,E and EP250702a
Date
2025-07-03T09:47:38Z (a day ago)
From
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 40912
Subject
EP250702a: Global MASTER-Net observations report
Date
2025-07-03T11:09:30Z (a day 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 40914
Subject
GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
Date
2025-07-03T12:51:12Z (a day 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 40917
Subject
EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
Date
2025-07-03T15:05:29Z (a day 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 40918
Subject
GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
Date
2025-07-03T15:12:02Z (a day 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 40919
Subject
GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
Date
2025-07-03T15:14:48Z (a day 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 40923
Subject
GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
Date
2025-07-03T16:44:09Z (a day 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 40924
Subject
GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
Date
2025-07-03T18:17:16Z (a day ago)
From
Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo@ucd.ie>
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 de 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 40929
Subject
GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
Date
2025-07-04T02:24:14Z (16 hours 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 40931
Subject
Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
Date
2025-07-04T03:47:31Z (15 hours 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 40943
Subject
EP250702a: WFST optical observations
Date
2025-07-04T10:42:26Z (8 hours 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 40949
Subject
GRB 250702B / EP2050702a: FTW optical and NIR observations
Date
2025-07-04T13:59:08Z (4 hours 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 40952
Subject
GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
Date
2025-07-04T14:09:07Z (4 hours 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).