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[vsnet-grb-info 43572] IceCube-260807A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 10 Aug '26

10 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45353 SUBJECT: IceCube-260807A: Upper limits from a search for additional neutrino events in IceCube DATE: 26/08/11 04:52:36 GMT FROM: syan079(a)icecube.wisc.edu The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-260807A (https://gcn.nasa.gov/circulars/45307) in a time range of 1000 seconds centered on the alert event time (2026-08-07 05:56:21.723 UTC to 2026-08-07 06:13:01.723 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-260807A. We report a p-value of 1.00 in this time window. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, ranges from 1.4e-01 to 1.5e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-260807A in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 3e+02 GeV and 2e+05 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2026-08-06 06:04:41.723 UTC to 2026-08-08 06:04:41.723 UTC). In this case, we report a p-value of 0.45, consistent with no significant excess of track events. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, is 1.6e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-260807A in a 2 day time window. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu. [1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) View this GCN Circular online at https://gcn.nasa.gov/circulars/45353. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43571] GRB260808B: MAO/AZT-22 optical observations
by GCN Circulars 10 Aug '26

10 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45352 SUBJECT: GRB260808B: MAO/AZT-22 optical observations DATE: 26/08/11 04:48:45 GMT FROM: Yodgor Rajabov at UBAI <rajabov(a)astrin.uz> O. Burkhonov, Y. Rajabov, B.Abidkhanov, S. Ehgamberdiev, Y. Tillayev (UBAI), A. Shaymanov, T. Boyqobilov (Maidanak Observatory/UBAI), M. Coughlin (UMN), P. Hello (IJCLAB), S. Antier (IJCLAB), M. Pillas (IAP), and S. Karpov (FZU) report on behalf of UBAI team and GRANDMA collaboration. We observed the field of GRB 260808B detected by SVOM (Bouchet et al., GCN 45316) with the AZT-22 1.5m telescope of the Maidanak Observatory (MAO) starting on 2026-08-10 at 21:07:04 UT, i.e, ~2.2932 days after the SVOM/ECLAIRs trigger. In total we obtained 6x300 s exposures in the R-band using 4kx4k CCD SNUCAM camera (Im et al., 2010). We detect the optical counterpart reported by many teams (Turpin et al., GCN 45318; Li et al., GCN 45320; Adami et al., GCN 45323; Saccardi et al., GCN 45328; Schneider et al., GCN 45329; Bochenek et al., GCN 45330; Basa et. al., GCN 45341). Preliminary photometry is as follows: Date UTstart Exptime t-T0 Filter OT Err. UL SNR Site/Telescope (nxs) (mid, days) 2026-08-10 21:07:04 6x300 2.29327 R 21.51 0.05 23.10 18 MAO/AZT-22 All the data have been reduced by a single data processing pipeline, STDWeb (Karpov 2025). Images obtained in Johnson Cousins filters were calibrated using the Gaia DR3 Synphot catalog. Our measurements in Vega magnitude system and the data has not corrected for the Galactic extinction. Maidanak astronomical observatory (MAO) is an observational facility of the Ulugh Beg Astronomical Institute (UBAI), Uzbekistan Academy of Sciences (http://maidanak.uz/) 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/) Astrophysics Center for Multimessenger studies in Europe is supported Skyportal/ICARE (contact camille.douzet(a)ijclab.in2p3.fr, skyportal.io). View this GCN Circular online at https://gcn.nasa.gov/circulars/45352. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43570] GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
by GCN Circulars 10 Aug '26

10 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45351 SUBJECT: GRB 250607A: SVOM/ECLAIRs detection through offline targeted search DATE: 26/08/10 20:23:02 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> H. Yang, O. Godet, S. Guillot (IRAP), D. Turpin (CEA) report on behalf of the SVOM team: The SVOM/ECLAIRs telescope detected GRB 250607A, also detected by Fermi/GBM (GCN 40648) and SVOM/GRM (GCN 40651), starting at 2025-06-07T14:00:51 UTC (T0), through an offline targeted search with the event-by-event data downloaded via the X-band ground station. The burst was detected within several timescales and energy ranges. The best detection is obtained by the image trigger with a signal-to-noise ratio of 7.4 within 4-20 keV over a time window of 10 s starting at T0. This event was not detected onboard because it was too faint and near the edge of the field of view. The ECLAIRs lightcurve shows a multi-peaked structure lasting around 10 s, with most of the detected photons below 50 keV. The localization of the source is RA, Dec = 228.408, -19.894 degrees: RA (J2000) = 15h13m38s Dec (J2000) = -19d53m38s with a 90% C.L. radius of 10.8 arcmin (including systematic error of 2 arcmin added in quadrature). This localization is broadly consistent with that reported by Fermi/GBM (GCN 40648). The angular separation between the two positions is 15 degrees, which is compatible with the 10.15 degrees systematic uncertainty of the GBM localization. The time-averaged spectrum from T0 to T0+10 s in the 5-120 keV is well fitted by a power law with a photon index of 1.6+/-0.2 and a corresponding 4-120 keV fluence of (1.2+/-0.3)e-6 erg/cm^2. The spectral properties measured with SVOM/ECLAIRs are consistent with those reported by SVOM/GRM (GCN 40651). All quoted errors are at the 68% confidence level. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. ECLAIRs was developed jointly by APC, CEA, CNES, and IRAP. The SVOM/ECLAIRs point of contact for this event is : Hui Yang (hui.yang(a)cnrs.fr) View this GCN Circular online at https://gcn.nasa.gov/circulars/45351. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43569] GRB 260809A: J-band upper limit with WINTER
by GCN Circulars 10 Aug '26

10 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45350 SUBJECT: GRB 260809A: J-band upper limit with WINTER DATE: 26/08/10 17:58:29 GMT FROM: tanishk.mohan(a)iitb.ac.in Tanishk Mohan (IITB), Geoffrey Mo (Caltech/Carnegie), Viraj Karambelkar (Columbia), Benjamin Schneider (LAM), Tomas Ahumada (NOIRLab), Robert Stein (UMD), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the field of GRB 260809A (Brunet et al., GCN 45331; also see Sun et al., GCN 45344) in the near-infrared J band with the Palomar 1-m telescope, equipped with the 1.2-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024). Observations began at 2026-08-10T05:11:10.816 UTC in the J band (14.23 hr after the SVOM/ECLAIRs trigger), consisting of 15*120 sec exposures. The images were processed using the WINTER data reduction pipeline implemented with mirar (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565) We do not detect the optical counterpart (Li et al., GCN 45336; Adami et al., GCN 45338; Rajabov et al., GCN 45339; Izzo et al., GCN 45340; Basa et al., GCN 45342) in our stacked image. We obtain the following 5-sigma upper limit: J = 18.6 mag (AB). WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research. View this GCN Circular online at https://gcn.nasa.gov/circulars/45350. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43568] EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
by GCN Circulars 10 Aug '26

10 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45349 SUBJECT: EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07 DATE: 26/08/10 17:01:42 GMT FROM: Andrea Saccardi at CEA/Irfu <andrea.saccardi(a)cea.fr> A. Saccardi (CEA/Irfu), B. Schneider (LAM), G. Corcoran (UCD), F.-F. Song (YNAO, CAS), A. L. Thakur (INAF/IAPS), N. R. Tanvir (U. Leicester), K. E. Heintz (DTU), S. D. Vergani (LUX-Paris Obs.) report on behalf of the Stargate collaboration: We observed the optical counterpart (Adami et al., GCN 45324; Jiang et al., GCN 45325; Basa et al., GCN 45326) of EP260809a (Sun et al., GCN 45321; Sun et al., GCN 45332) using the ESO VLT UT3 (Melipal) equipped with the X-shooter spectrograph. From the acquisition images (3x60s) we find a magnitude of the optical transient of r = 22.44+/-0.04 at 6.95 hr post-burst. Our spectra cover the wavelength range 3000-20000 AA, and consist of 4 exposures of 1200 s each. The observation start time was 07:46 UT on 2026 Aug 9 (7.12 hr after the EP/WXT trigger). We detect afterglow continuum in each arm, with a strong absorption trough around 4950 AA. Interpreting this as Lyman-alpha absorption at z = 3.07, we also detect weak metal lines of Si II, O I, C II, Al II, Fe II, Mg II, along with a series of H_2 Lyman-Werner band lines at the same redshift. From a preliminary analysis we determine a column density of neutral hydrogen to be log10(N(HI))=22.4+/-0.3. We also detect an intervening system at z = 1.43. We acknowledge the excellent support from the observing staff in Paranal, in particular Luca Sbordone, Israel Blanchard and Jonathan Smoker. The analysis of this spectrum was carried out with the help of the zHunter tool (https://doi.org/10.5281/zenodo.15189495) View this GCN Circular online at https://gcn.nasa.gov/circulars/45349. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43567] GRB 260806A: Glowbug gamma-ray detection
by GCN Circulars 10 Aug '26

10 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45348 SUBJECT: GRB 260806A: Glowbug gamma-ray detection DATE: 26/08/10 16:16:28 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung(a)nrl.navy.mil> 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 260806A, also detected by CALET (trigger 1470036404). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-08-06 07:27:00.088 with a duration of 51.2 s and a total significance of about 46 sigma. The light curve comprises two multi-peaked emission structures from T0 to T0+26.6s and T0+40.5s to T0+51.2s. 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/45348. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43566] GRB 260808A: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 10 Aug '26

10 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45347 SUBJECT: GRB 260808A: CALET Gamma-Ray Burst Monitor detection DATE: 26/08/10 13:51:56 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> M. L. Cherry (LSU), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The CALET Gamma-ray Burst Monitor (CGBM) detected GRB 260808A at 02:51:52.41 UTC on 8 August 2026 (trigger #1470192693; https://cgbm.calet.jp/cgbm_trigger/flight/1470192693/index.html) No real-time CGBM GCN notice was distributed about this trigger because the real-time communication from the ISS was off (loss of signal). This event was also reported by Fermi GBM (Fermi GBM Team, GCN #45313; Preis and Greiner, GCN #45315) and NuSTAR (Waratkar et al., GCN #45327). The burst signal was seen by all CGBM detectors. The burst light curve shows a multi-peaked structure starting at T-10.6 s and ending at T+4.4 s. The T90 and T50 durations measured with the SGM data are 13.4 +/- 0.9 s and 7.1 +/- 0.6 s in the 40-1000 keV band, respectively. The ground-processed light curve is available at: https://cgbm.calet.jp/cgbm_trigger/ground/1470192693/ The CALET data used in this analysis were provided by the Waseda CALET Operation Center located at Waseda University. View this GCN Circular online at https://gcn.nasa.gov/circulars/45347. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43565] GRB 260805C: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 10 Aug '26

10 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45346 SUBJECT: GRB 260805C: CALET Gamma-Ray Burst Monitor detection DATE: 26/08/10 13:48:32 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> N. Cannady (GSFC), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The CALET Gamma-ray Burst Monitor (CGBM) detected GRB 260805C at 07:27:40.04 UTC on 5 August 2026 (trigger #1469950046; https://cgbm.calet.jp/cgbm_trigger/flight/1469950046/index.html) No real-time CGBM GCN notice was distributed about this trigger because the real-time communication from the ISS was off (loss of signal). This event was also reported by Glowbug (Cheung et al., GCN #45292). The burst signal was seen by all CGBM detectors. The burst light curve shows a single pulse starting at T-0.6 s and ending at T+8.0 s. The T90 and T50 durations measured with the SGM data are 7.6 +/- 0.5 s and 4.4 +/- 0.5 s in the 40-1000 keV band, respectively. The ground-processed light curve is available at: https://cgbm.calet.jp/cgbm_trigger/ground/1469950046/ The CALET data used in this analysis were provided by the Waseda CALET Operation Center located at Waseda University. View this GCN Circular online at https://gcn.nasa.gov/circulars/45346. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43564] GRB 260804A: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 10 Aug '26

10 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45345 SUBJECT: GRB 260804A: CALET Gamma-Ray Burst Monitor detection DATE: 26/08/10 13:46:23 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> T. Tamura (Kanagawa U), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu (Kanagawa U), N. Cannady (GSFC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The CALET Gamma-ray Burst Monitor (CGBM) detected GRB 260804A at 03:07:25.16 UTC on 4 August 2026 (trigger #1469848033; https://cgbm.calet.jp/cgbm_trigger/flight/1469848033/index.html) No real-time CGBM GCN notice was distributed about this trigger because the real-time communication from the ISS was off (loss of signal). This event was also reported by Fermi GBM (Fermi GBM team, GCN #45281; and Glowbug (Cheung et al., GCN #45288). The burst signal was seen by all CGBM detectors. The burst light curve shows a multi-peaked structure starting at T-18.7 s, peaking at T+2.4 s, and ending at T+3.3 s. The T90 and T50 durations measured with the SGM data are 20.3 +/- 1.0 s and 8.5 +/- 1.1 s in the 40-1000 keV band, respectively. The ground-processed light curve is available at: https://cgbm.calet.jp/cgbm_trigger/ground/1469848033/ The CALET data used in this analysis were provided by the Waseda CALET Operation Center located at Waseda University. View this GCN Circular online at https://gcn.nasa.gov/circulars/45345. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43563] GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
by GCN Circulars 10 Aug '26

10 Aug '26

TITLE: GCN CIRCULAR NUMBER: 45344 SUBJECT: GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation DATE: 26/08/10 12:12:39 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> X. X. Sun(NAO, CAS), Q. J. Huang (PMO, CAS), K. J. Zhang(YNU), J. P. Chen (SYSU), Z. X. Ling(NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of GRB 260809A detected by SVOM/ECLAIRs (Brunet et al., GCN 45331). The observation started at 2026-08-09 17:30:29 (UTC), about 2.55 hr after the SVOM trigger, with a total exposure time of around 3 ks. On-ground analysis of the FXT data found a source EPF_J234751.2+210212 at R.A. = 356.9632, deg and Dec. = 21.0368 deg (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). The source position is consistent with the optical counterpart (Li et al., GCN 45336; Adami et al., GCN 45338; Rajabov et al., GCN 45339; Izzo et al., GCN 45340; Basa et al. 45342). The observed flux is approximately 4.5 × 10^-12 erg s^-1 cm^-2 in the 0.5-10 keV energy band. 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). View this GCN Circular online at https://gcn.nasa.gov/circulars/45344. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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