GRB 260708A
GCN Circular 45296
Subject
GRB 260708A: cubesat Avion detection
Date
2026-08-06T08:47:21Z (2 days ago)
From
Andrey Bogomolov at Moscow State University <aabboogg@srd.sinp.msu.ru>
Via
email
From Andrey Bogomolov at Moscow State University <aabboogg@srd.sinp.msu.ru>
A. Bogomolov, V. Bogomolov, A. Iyudin, S. Svertilov, N. Vasiliev
on behalf of the MSU “Sozvezdie-270” team, report:
At 2026-07-08 ~10:11:16 UT the long-duration GRB 260708A (Fermi/GBM detection: GCN #45115, Fermi/LAT detection: GCN #45117, GCN #45145, IceCube observation: GCN #45120, GCN #45134, GCN #45171, GECAM-B detection: GCN #45126, Glowbug detection: GCN #45130) was detected by the DeCoR-1 and DeCoR-3 instruments on the cubesat Avion of the Moscow University project “Sozvezdie-270” [1].
Total amount of photons detected by Avion is 403 (energy band >40 keV), it corresponds to a fluence of ~1.8*10^(-6) erg/cm^2 in the range 40-500 keV.
LC in the energy range of 40-500 keV is a single episode, a maximum flux is ~2.6 phot/(cm^2*s) at ~10 s after the start of the burst.
А total duration (T90) of the burst is ~25 s.
The light curve obtained by Avion is available here:
https://swx.sinp.msu.ru/models/grb_cat/data/pictures/GRB260708A_LC_Avion.png
Parameters of GRB 260708A as well as other GRBs detected by Moscow University cubesats are listed at: https://swx.sinp.msu.ru/models/grb_cat/grb.php?lang=en
Avion is one of 5 cubesats of the Moscow University project “Sozvezdie-270” [1] launched on 2023 June 27. The payload of Avion is a set of scintillation gamma-ray detectors DeCoR [2], the energy range is >30 keV, the time resolution is 0.5s.
[1] Svertilov et al. 2023 https://link.springer.com/chapter/10.1007/978-3-031-50248-4_21
[2] Bogomolov et al. 2026 Cosmic Research 64, 262 https://link.springer.com/article/10.1134/S0010952526600071
GCN Circular 45295
Subject
SN 2026stf / GRB 260708A: ATLAS forced photometry
Date
2026-08-06T00:07:04Z (3 days ago)
From
Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf@iac.es>
Via
Web form
I. Pérez-Fournon (IAC and ULL), F. Poidevin (IAC and ULL), A. López-Oramas (IAC and ULL), D. Aguado (IAC and ULL), N. Abreu García (ULL), D. Cano-Morales (ULL), I. Correa-Plasencia (ULL), A.E. Hernández-Díaz (ULL), E. Lekaroz-Urriza (ULL), M. Magdalena-Rodríguez (ULL), M. Quintana-Ansaldo (ULL), D. Rodríguez-Fernández (ULL), and J. Uríbarri-Dermit (ULL)
We report results of ATLAS forced photometry of the type Ic-BL SN 2026stf at z = 0.055 (Corcoran et al., GCN 45283) which appears associated with the LONG GRB 260708A detected by Fermi-GBM, Fermi-LAT, GECAM, and Glowbug (Fermi-GBM Team, GCN 45115; Holzmann Airasca et al., GCN 45117; Malacaria, GCN 45124; Ren et al., GCN 45126; Cheung et al., GCN 45130) and EP/FXT (Li et al., GCN 45150). The optical counterpart (AT 2026stf, MASTER OT J150237.02-435307.7) was discovered by MASTER (Shilova et al., GCN 45123; and Zhirkov et al., TNS Astronomical Transient Report No. 313535), with other reported optical detections (Freeberg et al., GCN 45127, Shi et al., GCN 45140, Sheng et al. GCN 45147, Shi et al., GCN 45280, Corcoran et al., GCN 45283, and O'Neill et al., TNS photometry report).
Using the ATLAS forced-photometry server (Shingles et al. 2021, Transient Name Server AstroNote 2021-7), we find four detections of the fading afterglow in the ATLAS orange filter starting on MJD = 61230.82579, at about 1.40 days after the Fermi trigger, at an ATLAS orange magnitud of o = 18.567 +/- 0.106, and more detections close to the minimum of the light curve and in 10 more epochs that include the rebrightening in the SN Ic-BL phase. The last ATLAS non detection was on MJD = 61228.84782, about 0.58 days before the Fermi trigger.
The following table gives the ATLAS forced photometry since MJD = 61200. We note that according to the methods of the ATLAS forced photometry, if the flux is negative, then a magnitude is still quoted and denoted with a negative sign (see https://fallingstar-data.com/forcedphot/resultdesc/). Magnitudes are in the AB system and are not corrected for interstellar medium absorption. Fluxes are in uJy.
MJD. | mag | e_mag |flux |e_flux| filter| observation
----------------------------------------------------------------------------------------------
61203.257379 18.634 0.491 128.0 63 o 04a61203o0384o
61203.260575 -18.648 0.712 -126.0 90 o 04a61203o0391o
61203.285519 20.077 0.581 34.0 20 o 04a61203o0444o
61203.29178 20.792 1.566 18.0 27 o 04a61203o0457o
61206.11809 21.107 4.412 13.0 58 o 04a61206o0248o
61206.12176 -18.955 0.647 -95.0 62 o 04a61206o0256o
61206.127177 -19.91 1.685 -39.0 66 o 04a61206o0268o
61206.137231 -18.837 0.787 -106.0 83 o 04a61206o0290o
61208.003738 -21.432 0.984 -10.0 10 c 03a61208o0094c
61208.006902 21.842 1.825 7.0 12 c 03a61208o0101c
61208.03234 -22.219 2.429 -5.0 11 c 03a61208o0156c
61208.037748 -23.402 7.111 -2.0 11 c 03a61208o0168c
61215.101062 20.405 0.87 25.0 22 o 04a61215o0341o
61215.106041 -20.875 1.571 -16.0 26 o 04a61215o0352o
61215.109687 21.063 1.366 14.0 19 o 04a61215o0360o
61215.116029 20.644 1.086 20.0 22 o 04a61215o0374o
61215.125947 23.114 8.294 2.0 17 o 04a61215o0396o
61220.18041 20.739 2.089 18.0 38 o 04a61220o0405o
61220.212007 -19.219 0.46 -74.0 34 o 04a61220o0473o
61220.215569 -20.976 2.384 -15.0 35 o 04a61220o0480o
61220.244229 -20.8 2.407 -17.0 42 o 04a61220o0541o
61221.106872 -20.685 1.464 -19.0 28 o 04a61221o0347o
61221.110508 19.599 0.571 52.0 30 o 04a61221o0355o
61221.114247 19.799 0.677 44.0 30 o 04a61221o0363o
61221.119822 19.554 0.429 55.0 24 o 04a61221o0375o
61221.129752 20.192 1.137 30.0 35 o 04a61221o0394o
61224.134068 17.646 2.756 317.0 875 o 04a61224o0172o
61224.137394 17.479 1.786 370.0 661 o 04a61224o0179o
61224.143895 -18.04 2.122 -221.0 468 o 04a61224o0193o
61224.153723 14.528 0.353 5608.0 1982 o 04a61224o0214o
61224.850689 -22.279 2.743 -4.0 12 o 03a61225o0364o
61224.854295 20.341 0.58 26.0 15 o 03a61225o0372o
61224.860177 20.367 0.6 26.0 16 o 03a61225o0385o
61224.870545 -21.838 2.262 -7.0 15 o 03a61225o0408o
61225.953387 -23.99 15.857 -1.0 15 o 03a61226o0036o
61225.957069 21.685 1.891 8.0 14 o 03a61226o0044o
61225.962523 20.444 0.561 24.0 14 o 03a61226o0056o
61225.982975 20.19 0.653 30.0 20 o 03a61226o0100o
61227.828562 21.292 0.881 11.0 10 o 03a61228o0314o
61227.831716 22.195 2.425 5.0 12 o 03a61228o0321o
61227.837861 21.672 1.562 8.0 12 o 03a61228o0334o
61227.847773 0.0 21.251 -0.0 12 o 03a61228o0356o
61228.828314 20.573 0.548 21.0 12 o 03a61229o0313o
61228.831947 23.404 7.462 2.0 12 o 03a61229o0321o
61228.837418 -21.735 1.435 -7.0 10 o 03a61229o0333o
61228.847822 23.144 4.533 2.0 9 o 03a61229o0356o
61230.825786 18.567 0.106 136.0 14 o 03a61231o0303o
61230.829421 18.463 0.089 150.0 13 o 03a61231o0311o
61230.83483 18.536 0.1 140.0 14 o 03a61231o0323o
61230.847461 18.6 0.098 132.0 13 o 03a61231o0351o
61233.132315 19.314 0.21 68.0 14 o 04a61233o0234o
61233.152559 19.689 0.312 48.0 15 o 04a61233o0277o
61233.155718 19.645 0.277 50.0 14 o 04a61233o0284o
61233.168334 19.367 0.185 65.0 12 o 04a61233o0311o
61234.819699 19.127 0.166 81.0 14 o 03a61235o0253o
61234.822959 19.42 0.243 62.0 15 o 03a61235o0260o
61234.828055 19.497 0.231 58.0 13 o 03a61235o0271o
61234.840874 19.112 0.161 82.0 13 o 03a61235o0299o
61236.79229 18.959 0.239 95.0 23 o 03a61237o0226o
61236.795085 19.905 0.853 40.0 34 o 03a61237o0232o
61236.801591 19.14 0.382 80.0 31 o 03a61237o0245o
61236.811886 18.648 0.173 126.0 22 o 03a61237o0267o
61237.809594 19.061 0.123 86.0 11 o 03a61238o0262o
61237.812764 19.156 0.163 79.0 13 o 03a61238o0269o
61237.8201 19.148 0.147 80.0 12 o 03a61238o0285o
61237.830145 19.069 0.121 86.0 10 o 03a61238o0307o
61240.79296 19.048 0.147 87.0 13 o 03a61241o0092o
61240.796119 19.057 0.157 86.0 14 o 03a61241o0099o
61240.801526 18.923 0.138 98.0 14 o 03a61241o0111o
61240.835558 19.297 0.213 69.0 15 o 03a61241o0184o
61242.787705 18.836 0.173 106.0 18 o 03a61243o0213o
61242.793772 18.852 0.164 104.0 17 o 03a61243o0226o
61242.796932 18.821 0.185 108.0 20 o 03a61243o0233o
61242.807162 18.875 0.223 102.0 23 o 03a61243o0255o
61243.802909 18.507 0.214 144.0 31 o 03a61244o0135o
61243.851004 18.728 0.234 117.0 28 o 03a61244o0151o
61243.856046 18.883 0.273 102.0 28 o 03a61244o0162o
61243.868817 18.547 0.206 138.0 28 o 03a61244o0190o
61245.908433 19.092 0.268 84.0 22 o 03a61246o0447o
61245.929595 18.977 0.271 93.0 25 o 03a61246o0492o
61245.935043 19.026 0.263 89.0 23 o 03a61246o0504o
61245.959763 19.081 0.37 85.0 31 o 03a61246o0558o
61247.804195 19.022 0.28 89.0 25 o 03a61248o0239o
61247.807349 18.81 0.239 109.0 26 o 03a61248o0246o
61247.812913 18.911 0.292 99.0 29 o 03a61248o0258o
61247.823386 19.47 0.493 59.0 29 o 03a61248o0281o
61249.247796 19.688 0.712 48.0 34 o 01a61249o0018o
61249.251905 18.651 0.255 126.0 32 o 01a61249o0027o
61249.2583 18.647 0.246 126.0 31 o 01a61249o0041o
61249.274816 18.898 0.294 100.0 29 o 01a61249o0077o
61253.787954 18.938 0.185 96.0 18 o 03a61254o0205o
61253.791569 18.882 0.144 102.0 15 o 03a61254o0213o
61253.797995 18.984 0.164 92.0 15 o 03a61254o0227o
61253.807829 19.042 0.217 88.0 19 o 03a61254o0248o
61256.862169 -20.237 10.875 -29.0 317 o 03a61257o0091o
61256.871251 -16.142 1.031 -1268.0 1308 o 03a61257o0111o
This work is part of grant CEX2025-001609-S, awarded to the Instituto de Astrofísica de Canarias under the Severo Ochoa Centre of Excellence program and funded by MICIU/AEI/10.13039/501100011033.
This work made use of the Astro-COLIBRI platform (P. Reichherzer et al. 2021, ApJS, 256, 5).
GCN Circular 45283
Subject
GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
Date
2026-08-04T08:19:29Z (5 days ago)
From
Gregory Corcoran at University College Dublin <gregory.corcoran@ucdconnect.ie>
Via
Web form
G. Corcoran (UCD), A. Martin-Carrillo (UCD), D. B. Malesani (DAWN/NBI and Radboud), L. P. Xin (NAOC) report on behalf of the Stargate collaboration:
We observed the counterpart of GRB 260708A detected by Fermi-GBM, Fermi-LAT, Glowbug and GECAM (Fermi-GBM Team, GCN 45115; Holzmann Airasca et al., GCN 45117; Malacaria, GCN 45124; Ren et al., GCN 45126; Cheung et al., GCN 45130), AT 2026stf (Shilova et al., GCN 45123; Freeberg et al., GCN 45127; Shi et al., GCN 45140, Sheng et al., GCN 45147; Li et al., GCN 45150) with a possible emerging supernova (Shi et al., GCN 45280) using the FORS2 spectrograph with the 300V grism and the GG435 order blocker on the ESO VLT UT1 (Antu). Observations started at 23:13:36 UT on 2026-08-02 (~25.5 days after the GRB trigger). Our spectra cover the wavelength range ~4560-8690 AA and consist of 4 exposures of 600 s each.
In an R-band acquisition image we measure a magnitude of R=19.12+/-0.09 (AB) calibrated using nearby stars in the SkyMapper catalog and not corrected for Galactic extinction. We note that this is likely contaminated with host light as the candidate host has an r-band magnitude of r=20.06+/-0.02 from the DECam Local Volume Exploration Survey (DELVE, Drlica-Wagner et al. 2021, doi:10.3847/1538-4365/ac079d).
In a stack of the quicklook spectra provided on the ESO archive, we identify clear narrow emission features from the candidate host galaxy consistent with a redshift of z = 0.055. In addition, using SNID-SAGE (Stoppa et al. 2026, doi:10.1093/mnras/stag1066) we identify clear supernova features consistent with a broad-lined type Ic (Ic-BL) supernova post peak at a consistent redshift. A comparison figure of our spectrum (blue line) to a template Ic-BL SN is available at the following link: https://shorturl.at/rzxgB
We acknowledge the excellent support from the observing staff in Paranal, in particular Elisa Rita Garro and Edouard Gonzalez.
GCN Circular 45280
Subject
GRB 260708A: LCO further optical observations show supernova features
Date
2026-08-04T02:02:22Z (5 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
Y.Y. Shi (GXU), C. Wu, L.P. Xin (NAOC), A. Saccardi, D. Turpin (CEA/Irfu), Y.X. Guan, S.J. Yin (GXU) report on behalf of the SVOM mission team:
We have continued monitoring the optical counterpart (Shilova et al., GCN 45123; Freeberg et al., GCN 45127; Sheng et al., GCN 45147) of the Fermi long GRB 260708A (Fermi/GBM Team, GCN 45115; Fermi-LAT, Holzmann Airasca et al., GCN 45117), using SINISTRO instruments mounted on 1-m telescopes of the LCO global network.
We observed the optical counterpart in imaging using the g, r, i bands from 2026-07-11 (3.56 days after the trigger) to 2026-08-02 (25.03 days after the trigger).
The optical counterpart shows a color change toward blue. It was measured to have a brightness of g=19.56+/-0.02 mag at 3.56 days post-trigger and g=18.88+/-0.02 mag at 11.48 days respectively, which show a rebrightening of the counterpart with a rise time of ~11.5 days post-trigger. Photometry was calibrated against the UCAC4 catalog, without template subtraction and not corrected for Galactic extinction.
We suggest that it is likely the supernova associated with the burst. Multi-band photometric and spectroscopic observations are encouraged.
This project is funded by the SVOM collaboration.
GCN Circular 45150
Subject
GRB 260708A: slowly decaying X-ray emission observed by EP/FXT
Date
2026-07-14T02:48:42Z (a month ago)
From
Rui-Zhi Li at Yunnan Observatories, CAS <liruizhi@ynao.ac.cn>
Via
Web form
R.-Z. Li (YNAO, CAS), J. Mao (YNAO, CAS), S. Antier (IJCLAB), M. Pillas (IAP), D. Turpin (CEA/Irfu), O. Pyshna (Caltech) report on behalf of a larger collaboration:
We report two EP/FXT Target of Opportunity (ToO) observations of the Fermi long GRB 260708A (Fermi/GBM Team, GCN 45115; Fermi/LAT, Holzmann Airasca et al., GCN 45117; GECAM-B, Ren et al., GCN 45126; Glowbug, Cheung et al., GCN 45130).
The first EP/FXT follow-up observation started at 2026-07-11T01:06:38 (UTC), approximately 2.62 days after the Fermi/GBM trigger, with a total exposure time of 2.7 ks.
EP/FXT detected an uncatalogued X-ray source at the following coordinates (J2000):
R.A., Decl. = 225.6537, -43.8844
with a localization uncertainty of 10 arcsec radius (90% confidence level, including both statistical and systematic uncertainties). The X-ray position is consistent with that of AT 2026stf reported by MASTER (Shilova et al., GCN 45123).
The average 0.5-10 keV EP/FXT spectrum can be fitted by an absorbed power law with a Galactic hydrogen column density of (0.36 +/- 0.12) x 10^22 cm^-2 and a photon index of 2.25 +/- 0.32. The derived average unabsorbed 0.5-10 keV flux is (1.31 +/- 0.13) x 10^-12 erg cm^-2 s^-1.
The second EP/FXT follow-up observation started at 2026-07-13T12:09:39 (UTC), approximately 5.08 days after the Fermi/GBM trigger, with a total exposure time of 6 ks. On-ground analysis of the EP/FXT data again detected an uncatalogued X-ray source consistent with the source detected in the first observation. The average 0.5-10 keV EP/FXT spectrum can be fitted by an absorbed power law with a Galactic hydrogen column density of (0.40 +/- 0.5) x 10^22 cm^-2 and a photon index of 2.36 +/- 0.38. The derived average unabsorbed 0.5-10 keV flux is (5.46 +/- 0.68) x 10^-13 erg cm^-2 s^-1.
The temporal decay index of X-ray emission between the two observations is 1.32 +/- 0.24. Given the slow temporal evolution observed in both the optical band (Shilova et al., GCN 45123; Freeberg et al., GCN 45127; Shi et al., GCN 45140; Sheng et al., GCN 45147) and the X-ray band, optical spectroscopy is strongly encouraged to determine the classification of the source.
All quoted uncertainties correspond to the 1-sigma confidence level.
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 45147
Subject
GRB 260708A: GRANDMA Optical Observations
Date
2026-07-13T14:05:35Z (a month ago)
Edited On
2026-07-13T16:05:46Z (a month ago)
From
Xinyue Sheng at Queens University Belfast <xysheng.astro@gmail.com>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Xinyue Sheng at Queens University Belfast <xysheng.astro@gmail.com>
Via
Web form
X. Sheng (QUB), D. Turpin (CEA/Irfu), O. Pyshna (Caltech), R. Strausbaugh (EIU), A. Iskandarova (ShAO), S. Rahimli (Sumgayit State Uni), V. Morozov (KU Leuven), S. Antier (IJCLAB), A. Simon (TShNU of Kyiv), L. Wyrzykowski (Uni. Warsaw/NCBJ), J. Hambsch (VVS, GEOS, BAV), M. Freeberg (KNC), R. Hellot (KNC), A. Klotz (IRAP), E. Jehin (ULiège), M. Ferrais (ULiège), Rui-Zhi (YNAO), J. Mao (YNAO) on behalf of on GRANDMA collaboration:
We observed the field of the Fermi Long GRB 260708A (Fermi GBM team, GCN 45115; Fermi/LAT, Holzmann Airasca et al., GCN45117,; GECAM-B, Ren et al., GCN45126; Glowbug, Cheung et al., GCN 45130). The observations started at 14:30:42 UTC on the 9 of July 2026, 1.18 days post the Fermi Trigger.
We detected the optical afterglow candidate, reported by MASTER (Shilova et al, GCN 45123), in several epochs, using the 60cm telescope at les Makes Observatory, the LCO 0.4m telescope at the SAA Observatory, the TRAPPIST-South telescope at la SIlla Observatory, and Kilonova Catcher. However, we observed after template subtraction a softer decay than usual for the GRBs.
A subset of the photometry corrected for Galactic extinction is reported in the public ACME service Skyportal/ICARE https://skyportal-icare.ijclab.in2p3.fr/source/GRB-260708A. To access, one simply needs to create an account using your ORCID id.
The data were 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-Cousins filters were calibrated using the Gaia DR3 Synphot catalog.
Our results are consistent across GRANDMA but not totally with LCO (GCN 45140). Further template taken at later time are needed.
The observations are performed under the P7 campaign of GRANDMA to monitor SVOM alerts and LSST alerts from explosive fast transients filtered by BOOM/Babamul and FINK.
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 45140
Subject
GRB 260708A: LCO optical observations
Date
2026-07-12T05:22:33Z (a month ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
Y.Y. Shi (GXU), C. Wu, L.P. Xin (NAOC), A. Saccardi, D. Turpin(CEA/Irfu) report on behalf of the SVOM mission team:
We observed the field of the GRB 260708A detected by Fermi/GBM(Fermi GBM team, GCN 45115; GCN 45124) and Fermi/LAT (Holzmann Airasca et al., GCN 45117) with the LCO 1m telescope at Cerro Tololo Inter-American Observatory equipped with the Sinistro instrument.
Our observation started on 2026-07-11 at 23:37:53 UT (about 3.56 day after the trigger) and we obtained 3x200 s exposures in the SDSS g, r and i filters.
The optical counterpart (Shilova et al., GCN 45123; Freeberg et al., GCN 45127) is clearly detected in our images. We measure the following magnitudes calibrated against the UCAC4 catalog, and not corrected for Galactic extinction:
g = 19.56 +/- 0.02 AB (mid-time 3.56 day after the trigger);
r = 19.21 +/- 0.02 AB (mid-time 3.60 day after the trigger);
i = 19.17 +/- 0.03 AB (mid-time 3.59 day after the trigger).
It appears to be fading compared with the results reported by Shilova et al. (GCN 45123) and Freeberg et al.(GCN 45127).
This project is funded by the SVOM collaboration.
GCN Circular 45130
Subject
GRB 260708A: Glowbug gamma-ray detection
Date
2026-07-10T11:25:29Z (a month ago)
From
C.C. Cheung at Naval Research Lab <Teddy.Cheung@nrl.navy.mil>
Via
Web form
C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report:
The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 260708A, which was also detected by Fermi/GBM (GCN 45115, 45124), Fermi/LAT (GCN 45117), and GECAM-B (GCN 45126), and has a proposed optical counterpart (GCN 45123, 45127).
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-07-08 10:11:15.952 with a duration of 12.3 s and a total significance of about 7.7 sigma. The emission seen by Glowbug corresponds to the brightest portion of the GBM and GECAM-B light curves.
The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS.
Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12.
[1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959
[2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O
[3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108
Distribution Statement A: Approved for public release. Distribution is unlimited.
GCN Circular 45127
Subject
GRB 260708A: Kilonova-Catcher optical afterglow detection
Date
2026-07-09T17:01:32Z (a month ago)
From
Damien Turpin at CEA-Saclay <dturpin-astro@hotmail.com>
Via
Web form
M. Freeberg (KNC), D. Turpin (CEA-Saclay/Irfu), C. Andrade(UMN), S. Antier (IJCLab), M. Coughlin (UMN),S. Karpov (FZU), P. Hello (IJCLAB), M. Pillas (IAP) on behalf of the GRANDMA/Kilonova-Catcher collaboration:
We observed the field of GRB 260708A detected by Fermi/GBM (Fermi GBM team, GCN 45115; GCN 45124) and Fermi/LAT (Holzmann Airasca et al., GCN 45117) with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with a iTtelescope T30 located at Siding Spring Observatory operated by M. Freeberg. Our observations started at TGRB+1.17 days and were taken with the Johnson/Cousins R filter.
In our stacked frames, we clearly detect the optical counterpart reported by MASTER (Shilova et al., GCN 45123).
We report part of our follow-up results in the table below :
| Tmid-TGRB (days) | Exp (s) | Filter | Magnitude | Instrument |
|---|---|---|---|---|
| 1.18 | 3 x 300s | R (Vega) | 18.93 +/- 0.14 | iT30 |
Given the significant fading behavior compared to the previous MASTER epoch, we considered this optical candidate is the optical afterglow of the energetic burst GRB 260708A. Further observations are ongoing.
All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the Johnson-cousins 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).
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 45126
Subject
GRB 260708A: GECAM-B observation of a burst
Date
2026-07-09T16:35:09Z (a month ago)
From
renyz16607@163.com
Via
Web form
Yang-Zhao Ren, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team:
GECAM-B was triggered in-flight by GRB 260708A, at 2026-07-08T10:11:17.650 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #45115), and Fermi/LAT (Fermi LAT team, GCN #45117).
According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 46.5 +5.0/-6.5 s.
The GECAM-B light curve can be found here:
https://www.bursthub.cn//admin/static/gecambgrb260708A.png
Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS).
GCN Circular 45124
Subject
GRB 260708A: Fermi-GBM observation
Date
2026-07-09T15:29:24Z (a month ago)
From
Christian Malacaria at INAF-OAR <cmalacaria.astro@gmail.com>
Via
Web form
C. Malacaria (INAF-OAR) reports on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 10:11:16.89 UT on 08 July 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260708A (trigger 805198281/260708424). The Final real-time localization was reported in GCN 45115. Fermi-LAT also detected GRB 260708A (GCN 45117).
The GBM light curve displays a sharp peak with a duration (T90) of about 62 s (50-300 keV). The time-averaged spectrum from T0+0.5 to T0+49.7 s is best fit by a power law function with a power law index of -1.86 +/- 0.01 .
The event fluence (10-1000 keV) in this time interval is (2.14 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.5 s in the 10-1000 keV band is 19.6 +/- 0.5 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN Circular 45123
Subject
Fermi LAT GRB 260708A: MASTER OT J150237.02-435307.7 optical counterpart detection
Date
2026-07-09T10:23:14Z (a month ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
M.Shilova, K.Zhirkov, V.Lipunov, A.Kuznetsov, P.Balanutsa, G.Antipov, I.Panchenko, N.Tiurina, Ya.Kechin, E.Gorbovskoy, V.Senik, A.Chasovnikov, V.Topolev,D.Vlasenko,A.Sankovich, I.Gorbunov, V.Fedorova, A.Telnova (Lomonosov MSU),
F.Podesta, M.J. Segura, C.Francile, R.Podesta, E. Gonzalez (OAFA, SJNU),
D.Buckley (SAAO),
A.Sosnovskij (CrAO RAS),
N.Budnev, O.Gress (ISU),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich (Blagoveschensk Educational StateUniversity)
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez,J.Martinez,A.R.Corella,
J.Tanori, L. Villalobos, L.H.Rodriguez (INAOE, Guillermo Haro AstrophysicsObservatory)
MASTER-OAFA and MASTER-SAAO robotic telescopes of MASTER Global Robotic
Net [1-4] was pointed to the Fermi LAT GRB 260708A
(Holzmann Airasca et al. GCN 45117, trigger 2026-07-08 10:11:16.89 UT, RA, Dec = 225.61, -44.07 +-0.27 (J2000))
at 2026-07-08 22:40:00 UT (Lipunov et al. 45119).
There is optical counterpart of GRB 260708A
MASTER OT J150237.02-435307.7 https://www.wis-tns.org/object/2026stf
discovered by MASTER auto-detection system [1-4] at 2026-07-08 22:42:34.272UT with unfiltere m~17.6m.
The typical light curve points to GRB source.
spectral observations is required.
[1] Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L
[2] Lipunov et al. 2022, Universe, Vol. 8(5), id.271
[3] Lipunov et a. 2019, ARep, vol.63, 293
[4] Lipunov et al. 2023, Astronomical Robotic Networks and Operative Multichanel
Astrophysics,Lomonosov MSU PRESS, 591pp.
http://www.pereplet.ru/lipunov/625.html#625
GCN Circular 45117
Subject
GRB 260708A: Fermi-LAT detection
Date
2026-07-08T17:20:47Z (a month ago)
From
A. Holzmann Airasca at University of Trento and INFN Bari <a.holzmannairasca@unitn.it>
Via
Web form
A. Holzmann Airasca (UniTrento and INFN Bari), D. Depalo (Politecnico and INFN Bari) and P. Loizzo (UniTrento and INFN Bari) report on behalf of the Fermi-LAT collaboration:
At 10:11:16.89 UT on July 8th, 2026, Fermi-LAT detected high-energy emission from GRB 260708A, which was also detected by Fermi-GBM (trigger 805198281/260708424, GCN #45115).
The best LAT on-ground location is found to be
RA, Dec = 225.61, -44.07 (J2000)
with an error radius of 0.27 deg (90 % containment, statistical error only).
This was 43 deg from the LAT boresight at the time of the trigger.
The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally correlated with the trigger with high significance.
The photon flux above 100 MeV in the time interval 0 - 400 s after the GBM trigger is (1.9 ± 0.4)E-5 ph/cm2/s. The estimated photon index above 100 MeV is -2.5 ± 0.3. The highest energy photon has an energy of 2.1 GeV and occurs at 65.8 s after trigger time.
The Fermi-LAT point of contact for this burst is Pierpaolo Loizzo (pierpaolo.loizzo@ba.infn.it).
The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
GCN Circular 45115
Subject
GRB 260708A: Fermi-GBM detection
Date
2026-07-08T14:17:47Z (a month ago)
From
Christian Malacaria at INAF-OAR <cmalacaria.astro@gmail.com>
Via
Web form
The Fermi GBM team reports the detection of a likely LONG GRB
"At 10:11:16.89 UT on 08 July 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260708A (trigger 805198281/260708424).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 227.4, Dec = -44.5 (J2000 degrees, equivalent to J2000 15h 09m, -44d 30'), with a statistical uncertainty of 1.6 degrees.
The angle from the Fermi LAT boresight is 43 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260708424/quicklook/glg_skymap_all_bn260708424.png
The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260708424/quicklook/glg_healpix_all_bn260708424.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260708424/quicklook/glg_lc_medres34_bn260708424.gif"
