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[vsnet-grb-info 43720] GRB 260903A: SVOM detection of a soft faint burst
by GCN Circulars 03 Sep '26

03 Sep '26

TITLE: GCN CIRCULAR NUMBER: 45499 SUBJECT: GRB 260903A: SVOM detection of a soft faint burst DATE: 26/09/03 13:18:42 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> GRB 260903A: SVOM detection of a soft faint burst M. Brunet, O. Godet, H. Yang (IRAP), R.-C. Chen (NJU), T. Xiao (GXU) report on behalf of the SVOM mission team: At 2026-09-03T12:37:20 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260903A (SVOM burst-id sb26090302). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 2 alerts. CRT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 7.70 in the [5-8] keV energy band over a time window of 20.40 seconds starting at 2026-09-03T12:36:59 UTC. The localization of the best alert is R.A., Dec. 25.614, 11.389 degrees: R.A. (J2000) = 1h42m27.28s Dec. (J2000) = 11d23m21.52s with a 90% confidence level (C.L.) radius of 10.20 arcmin (including systematic error of 2 arcmin added in quadrature). The SVOM/ECLAIRs light curve showed a broad structure with a duration of about 20 s. Due to the detection significance being below the slew threshold, no immediate slew was performed on this burst. No X-ray observation could be performed by SVOM/MXT for the time being. No optical observation could be performed by SVOM/VT for the time being. A SVOM ToO has been scheduled. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is R.-C. Chen: chrczxx(a)smail.nju.edu.cn. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/45499. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43719] EP260901a: SVOM/VT optical upper limits
by GCN Circulars 03 Sep '26

03 Sep '26

TITLE: GCN CIRCULAR NUMBER: 45498 SUBJECT: EP260901a: SVOM/VT optical upper limits DATE: 26/09/03 13:17:07 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, J. R. Xu, L. J. Chen, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM/VT performed a Target of Opportunity observation of EP260901a detected by EP/WXT (Liang et al., GCN 45487; Liang et al., GCN 45497). SVOM/VT began observing the field at 2026-09-02T13:45:25 UTC, 32.628 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. No credible candidate was detected in our stacked images within the error box provided by EP/WXT position (Liang et al., GCN 45487) down to 5-sigma upper limits of about 22.5 mag (AB) in both channels at the mid time of 33 hr post trigger, compared to the PanSTARRS catalogue. Our results are consistent with MASTER (Buckley et al., GCN 45492). The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/45498. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43718] EP260901a: EP-FXT follow-up observation
by GCN Circulars 02 Sep '26

02 Sep '26

TITLE: GCN CIRCULAR NUMBER: 45497 SUBJECT: EP260901a: EP-FXT follow-up observation DATE: 26/09/02 13:58:08 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. F. Liang, J. Y. Liu (PMO), X. Mao, Q. H. Lao, Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of EP260901a (Liang et al., GCN 45487; Buckley et al., GCN 45492) starting at 2026-09-01T22:26:36 (UTC), approximately 17 hours after the WXT detection. With an exposure time of 4 ks, no significant X-ray source was detected within the 2.4 arcmin radius of the EP-WXT position. The derived 0.5-10 keV upper limit is about 1.0e-13 erg cm^-2 s^-1. 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). Previous Circular View this GCN Circular online at https://gcn.nasa.gov/circulars/45497. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43717] Konus-Wind detection of GRB 260829A
by GCN Circulars 02 Sep '26

02 Sep '26

TITLE: GCN CIRCULAR NUMBER: 45496 SUBJECT: Konus-Wind detection of GRB 260829A DATE: 26/09/02 11:12:15 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia(a)mail.ioffe.ru> A. Ridnaia, D. Frederiks, A. Lysenko, V. Panteleeva, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 260829A (Fermi-GBM detection: Fermi GBM team, GCN 45464; Malacaria et al., GCN 45467; BALROG localization: Preis & Greiner, GCN 45465; GECAM-B detection: Zao et al., GCN 45470; IPN triangulation: Kozyrev et al., GCN 45476; AstroSat CZTI detection: Goyal et al., GCN 45485; SVOM-GRM detection: Luo et al., GCN 45495) triggered Konus-Wind at T0=22110.076 s UT (06:08:30.076). The burst light curve shows an initial weak emission episode starting at ~T0-21.3 s, followed by a brighter multi-peaked structure. The total burst duration is ~34.8 s. The emission is seen up to ~4 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260829_T22110/ As observed by Konus-Wind, the burst had the total fluence of 2.05(-0.09,+0.10)x10^-5 erg/cm2, and the 64-ms peak flux, measured from T0+2.208 s, of 8.44(-0.91,+0.92)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+16.640 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.94(-0.09,+0.09) and Ep = 330(-24,+28) keV (chi2 = 114/98 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.8 (chi2 = 114/97 dof). The spectrum near the maximum count rate (measured from T0+0.256 to T0+8.448 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.75(-0.08,+0.08) and Ep = 314(-17,+19) keV (chi2 = 122/88 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -3.0 (chi2 = 122/87 dof). All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/45496. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43716] GRB 260829A: SVOM/GRM observation
by GCN Circulars 02 Sep '26

02 Sep '26

TITLE: GCN CIRCULAR NUMBER: 45495 SUBJECT: GRB 260829A: SVOM/GRM observation DATE: 26/09/02 10:51:42 GMT FROM: Xinghao Luo at IHEP <2952704891(a)qq.com> SVOM/GRM team: Xing-Hao Luo, Yue Wang, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Stéphane Schanne (CEA) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 260829A at 2026-08-29T06:08:29.000 (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #45464) and GECAM-B (Xue-Yuan Zao et. al., GCN #45470). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of muplti-pulses with a T90 of 28 +3/-5 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn/gcn/2026/svgrb260829A.png In addition, the position of this burst, as determined by Fermi/GBM (RA = 242.3, Dec = -34.6, with a statistical uncertainty of 1.0 degrees, GCN #45464), is located at about 134 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-25 to T0+13 s is best fitted by a power law function. The power law index is -2.11 +0.07/-0.08. The event fluence (10-1000 keV) in this time interval is (6.197 +0.467/−0.406)E-05 erg/cm^2. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Xing-Hao Luo (IHEP) (luoxh(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/45495. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43715] GRB 260818A: ATCA detection of a candidate radio counterpart
by GCN Circulars 01 Sep '26

01 Sep '26

TITLE: GCN CIRCULAR NUMBER: 45494 SUBJECT: GRB 260818A: ATCA detection of a candidate radio counterpart DATE: 26/09/02 03:38:38 GMT FROM: Tao An at USTC <antao(a)shao.ac.cn> Tao An (USTC), Ailing Wang (YNAO, CAS) report on behalf of a large collaboration: We observed the field of GRB 260818A (Yin et al., GCN 45391; EP-FXT X-ray afterglow: GCN 45400, 45434) with the Australia Telescope Compact Array (ATCA), starting at 2026-08-30 10:48:49 UTC (12.4 days after the SVOM/ECLAIRs trigger). Data were obtained simultaneously at central frequencies of 6.53 GHz and 10.36 GHz. The 1-sigma image rms noise levels are 9.5 uJy/beam at 6.53 GHz and 7.5 uJy/beam at 10.36 GHz. A radio source is detected both frequencies at a significance >~ 7 sigma at R.A. (J2000) = 23:20:25.422, Dec. (J2000) = −32:05:49.60, consistent with the fading X-ray afterglow EPF_J232025.8-320549 (Plasse et al., GCN 45434). A detailed analysis is underway. Further ATCA observations are being considered to test for radio variability and to confirm the association with the high-energy transient. We thank the CSIRO Space and Astronomy staff, in particular Jamie Stevens, for supporting these observations. The Australia Telescope Compact Array is part of the Australia Telescope National Facility which is funded by the Australian Government for operation as a National Facility managed by CSIRO. View this GCN Circular online at https://gcn.nasa.gov/circulars/45494. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43714] EP260830a: EP-FXT follow-up observation
by GCN Circulars 01 Sep '26

01 Sep '26

TITLE: GCN CIRCULAR NUMBER: 45493 SUBJECT: EP260830a: EP-FXT follow-up observation DATE: 26/09/02 02:14:40 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> X. Mao, Q. H. Lao (NAO, CAS), Y. F. Liang, J. Y. Liu (PMO), Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of EP260830a (Mao et al., GCN 45280; Segura et al., GCN 45481) starting at 2026-09-01T17:56:36 (UTC), approximately 50 hours after the WXT detection. With an exposure time of 5 ks, no significant X-ray source was detected within the 2.4 arcmin radius of the EP-WXT position. The derived 0.5-10 keV upper limit is about 8.8e-14 erg cm^-2 s^-1. 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/45493. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43713] EP260901a: Global MASTER-Net observations report
by GCN Circulars 01 Sep '26

01 Sep '26

TITLE: GCN CIRCULAR NUMBER: 45492 SUBJECT: EP260901a: Global MASTER-Net observations report DATE: 26/09/01 21:45:38 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> D.Buckley (SAAO), 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 (Lomonosov MSU) A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) A.Sosnovskij (CrAO RAS) A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory) L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) R.Rebolo (The Instituto de Astrofisica de Canarias) O.Gress, N.Budnev(ISU) M. Segura, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA) MASTER-SAAO robotic telescope [1] located in South Africa (South African Astronomical Observatory) was pointed to the EP260901a ( EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> et al., GCN 45487) errorbox 23673 sec after notice time and 53037 sec after trigger time at 2026-09-01 19:51:42 UT, with upper limit up to 17.8 mag. The observations began at zenith distance = 38 deg. The sun altitude is -45.1 deg. The galactic latitude b = 9 deg., longitude l = 6 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3497756 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 53068 | 2026-09-01 19:51:42 | MASTER-SAAO | (17h 20m 52.36s , -19d 19m 12.5s) | C | 60 | 17.4 | 53162 | 2026-09-01 19:53:16 | MASTER-SAAO | (17h 20m 57.98s , -19d 20m 07.5s) | C | 60 | 17.6 | 53256 | 2026-09-01 19:54:51 | MASTER-SAAO | (17h 20m 52.19s , -19d 21m 03.2s) | C | 60 | 17.6 | 53350 | 2026-09-01 19:56:24 | MASTER-SAAO | (17h 20m 57.58s , -19d 20m 49.1s) | C | 60 | 17.7 | 53454 | 2026-09-01 19:58:08 | MASTER-SAAO | (17h 20m 54.81s , -19d 19m 14.3s) | C | 60 | 17.7 | 53973 | 2026-09-01 20:06:47 | MASTER-SAAO | (17h 20m 51.34s , -19d 19m 37.7s) | C | 60 | 17.8 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/45492. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43712] IceCube-260827A: No transient candidates from the Zwicky Transient Facility
by GCN Circulars 01 Sep '26

01 Sep '26

TITLE: GCN CIRCULAR NUMBER: 45491 SUBJECT: IceCube-260827A: No transient candidates from the Zwicky Transient Facility DATE: 26/09/01 15:42:00 GMT FROM: Cristobal Zilleruelo Cañas at DESY <cristobal.zilleruelo.canas(a)desy.de> Cristobal Zilleruelo Cañas (DESY), Jannis Necker (Leiden University), Akshay Eranhalodi (DESY), Robert Stein (JSI), and Anna Franckowiak (Ruhr University Bochum) report, On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: As part of the ZTF neutrino follow up program (Stein et al. 2023), we observed the localization region of the neutrino event IceCube-260827A (Velazquez et. al, GCN 45455) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We started observations in the g- and r-band beginning at 2026-08-28 11:45 UTC, approximately 20.2 hours after event time. We covered 89.8% (0.8 sq deg) of the reported localization region. This estimate accounts for chip gaps. Each exposure was 300s with a typical depth of 21.0 mag. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019, Stein et al. 2021) was used to search the alerts database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019) . No candidate counterparts were detected. ZTF and GROWTH are worldwide collaborations comprising Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan; OKC, Sweden; DZA, Germany. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done by AMPEL (Nordin et al. 2019). Alert filtering is performed with the nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf ). View this GCN Circular online at https://gcn.nasa.gov/circulars/45491. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43711] GRB 260831B / sb26083106: SVOM/GWAC-F60A/B confirmation of optical vairation of nova V* GK Per
by GCN Circulars 01 Sep '26

01 Sep '26

TITLE: GCN CIRCULAR NUMBER: 45490 SUBJECT: GRB 260831B / sb26083106: SVOM/GWAC-F60A/B confirmation of optical vairation of nova V* GK Per DATE: 26/09/01 15:29:59 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> S.J. Yin ,Y.X. Guan (GXU), C. Wu, L.P. Xin, X.H. Han, P.P. Zhang, J.L. Wang (NAOC), report on behalf of the SVOM follow-up team: We observed the field of sb26083106 triggerd by SVOM (Godet et al., GCN 45477) with the GWAC-F60A/B at Xinglong Observatory, China. We started observing at 2026-08-31T18:37:43.39 UTC with a set of 50 images in R-band, 1.5 min after the trigger. We do not detect credible uncataloged candidates within ECLAIRs' error box, which is consistent with the reports from LCO (Guan et al., GCN 45482) and SVOM/VT (Li et al., GCN 45489). The following upper limit magnitude are derived R>18.6 mag (5-sigma at mid-time of 6.3 minutes after trigger), calibrated against USNO-B1.0 catalog, and not corrected for Galactic extinction. We also measure the classical nova V* GK Per ,which shows an amplitude variation cosistent with that reported by SVOM/VT (Li et al., GCN 45489). Two 60-cm GWAC-F60(A/B) are operated by Guangxi University and NAOC, CAS, at Xinglong Observatory, China. The field of view is 19*19 arcmin. View this GCN Circular online at https://gcn.nasa.gov/circulars/45490. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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