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[vsnet-grb-info 43228] EP260618a: JinShan optical observations
by GCN Circulars 20 Jun '26

20 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45012 SUBJECT: EP260618a: JinShan optical observations DATE: 26/06/20 06:12:59 GMT FROM: L. B. He at NAOC <helb(a)bao.ac.cn> L.B. He, S.Q. Jiang, J. An, X. Liu, Z.P. Zhu, D. Xu (NAOC), S.Y. Fu, A.D. Zhu, L. Lei (HUST), J.Z. Liu (XAO) report: We observed the field of EP260618a detected by EP/WXT (Yang et al., GCN 44978; Jiang et al., GCN 44991), possibly associated with GRB 260618A (Fermi GBM Team, GCN 44973) using the JinShan 100C telescope located at Altay, Xinjiang, China. The previously reported optical counterpart (Becerra et al., GCN 44988; Malesani et al., GCN 44990; Amram et al., GCN 44994) is detected in our stacked images with a brightness of r ~ 21.4 mag at a median time of 1.429 days since the EP trigger, i.e. 1.504 days since the Fermi GBM trigger, calibrated with Pan-STARRS DR2 stars in the field and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/45012. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43227] The EP-WXT trigger 01709271197 is likely a flaring star
by GCN Circulars 20 Jun '26

20 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45013 SUBJECT: The EP-WXT trigger 01709271197 is likely a flaring star DATE: 26/06/20 06:51:55 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.H. Jiang (NJU), Q.Y. WU, W. D. Zhang (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709271197 at the time of 2026-06-20T05:24:06, is likely a stellar flare associated with 2MASS J18430597-4058047. The estimated flux of the flare is around 1.0 x 10 ^(-10) erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 4.1 x 10^(31) erg/s. 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/45013. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43226] GRB 260616B/EP260616a: SVOM/GRM detection of a burst
by GCN Circulars 20 Jun '26

20 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45011 SUBJECT: GRB 260616B/EP260616a: SVOM/GRM detection of a burst DATE: 26/06/20 04:00:46 GMT FROM: yzh807926(a)163.com SVOM/GRM team: Zheng-Hang Yu, Chen-Wei Wang, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Ulysse Jacob (LUPM), Olivier GODET, Jean-Luc Atteia (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a burst GRB 260616B/EP260616a (SVOM trigger reference: sb26061603) at 2026-06-16T07:05:16.900 UTC (T0), which is also detected by Fermi/GBM (C. Malacaria et al., GCN #44953). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a main episode with two peaks a T90 of 13.30 +0.8/-0.4 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb2606016B.png In addition, the position of this burst, as determined by EP/WXT (RA= 256.059 deg, DEC= -32.305 deg, ERR=2.2 arcmin, GCN#44956), is located at about 67 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view, and ECLAIRs was totally blocked by the Earth. Nevertheless, ECLAIRs detected this burst clearly over the 4-120 keV via atmospheric reflection. With this localization, the time-averaged spectrum from T0-2 to T0+14 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.11 +/-0.04 and the cutoff energy, parameterized as Epeak, is 622 +80/-66 keV. The event fluence (10-1000 keV) in this time interval is (2.29 +/-0.06)E-05 erg/cm^2. The 1s peak spectrum, measured from T0+9.8 to T0+10.8 s, if fitted by a power law function with an exponential high-energy cutoff, the power law index is -0.90 +0.05/-0.06 and the cutoff energy, parameterized as Epeak, is 472 +52/-44 keV. The flux (10-1000 keV) in this time interval is (4.85 +/-0.17)E-06 erg/cm^2/s. The localization of GRB 260616B in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260616B_amati.png The localization of GRB 260616B in the 'Yonetoku' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260616B_yonetoku.png 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: Zheng-Hang Yu(IHEP)(zhyu(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/45011. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43225] GRB 260618B: Fermi GBM Observation
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45010 SUBJECT: GRB 260618B: Fermi GBM Observation DATE: 26/06/19 17:39:30 GMT FROM: Peter Veres at University of Alabama in Huntsville <veresp(a)gmail.com> P. Veres (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 16:55:04.71 UT on 18 June 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260618B (trigger 803494509/260618705), which was also detected by Fermi/LAT (Gupta et al., GCN 44983) and SVOM/VT (Li et al., GCN 45001). The Fermi GBM on-ground location is consistent with the LAT and the SVOM/VT position. The angle from the Fermi LAT boresight is 16 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 20 s (50-300 keV). The time-averaged spectrum from T0 to T0+10 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.42 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 1030 +/- 20 keV. The event fluence (10-1000 keV) in this time interval is (9.4 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.96 s in the 10-1000 keV band is 4.3 +/- 0.2 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak= 1000 +/- 20 keV, alpha = -0.41 +/- 0.02 and beta = -3.2 +/- 0.2. 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/" View this GCN Circular online at https://gcn.nasa.gov/circulars/45010. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43224] IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45009 SUBJECT: IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube DATE: 26/06/19 16:38:39 GMT FROM: Yuhua Yao at IceCube/UW-Madison <yyao255(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-Cascade 260618A (https://gcn.gsfc.nasa.gov/notices_amon_icecube_cascade/142737_24549075.amon) in a time range of 1000 seconds centered on the alert event time (2026-06-18 05:19:19.175 UTC to 2026-06-18 05:35:59.175 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-Cascade 260618A. 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-Cascade 260618A 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 2e+02 GeV and 8e+04 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2026-06-17 05:27:39.175 UTC to 2026-06-19 05:27:39.175 UTC). In this case, we report a p-value of 0.48, 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, ranges from 1.6e-01 to 1.8e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-Cascade 260618A 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/45009. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43223] GRB 260619A: TRT optical counterpart confirmation
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45008 SUBJECT: GRB 260619A: TRT optical counterpart confirmation DATE: 26/06/19 16:30:48 GMT FROM: L. B. He at NAOC <helb(a)bao.ac.cn> L.B. He (NAOC), K. Noysena, K. Chanchaiworawit, S. Tinyanont (NARIT), S.Y. Fu (HUST), J. An, X. Liu, Z.P. Zhu, S.Q. Jiang, D. Xu (NAOC) report: We observed the field of GRB 260619A detected by SVOM/ECLAIRs (Goto et al., GCN 44985) using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Cerro Tololo Inter-American Observatory, Chile (CTO). The previously reported optical counterpart (Ducoin et al., GCN 44999; Li et al., GCN 45003) is detected in our stacked images with a brightness of r~21.4 at a median time of 3.95 hrs post-trigger, calibrated with Pan-STARRS DR2 stars in the field and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/45008. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43222] GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45007 SUBJECT: GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection DATE: 26/06/19 15:24:48 GMT FROM: marion.pillas(a)ligo.org A. Simon (TShNU of Kyiv), M. Mašek (FZU), N. Kochiashvili (AbAO), M. Pillas (IAP), D. Akl (NYUAD), R. Hanna (IJCLAB), P. Putsathan (KKU), Y. Rajabov (UBAI), S. Antier (IJCLAB), P. Hello (IJCLAB), M. Coughlin (UNM), S. Karpov (FZU), C. Douzet (IJCLAB), D. Rusanova (TShNU of Kyiv), V. Shynkarova (TShNU of Kyiv), A. Korosko (TShNU of Kyiv), O. Burkhonov (UBAI), S. Ehgamberdiev (UBAI), Y. Tillayev (UBAI), P. Put (NARIT), K. Noysena (NARIT), M. Tanasan (CMU/NARIT), D. Turpin (CEA-Saclay/Irfu), M. Freeberg (KNC), C. Limonta (OCA), A. Dupin (OCA), Q. André (OCA), M. Molham (NRIAG), E. Elhosseiny (NRIAG), A. Takey (NRIAG), T. Kvernadze (AbAO) on behalf of on GRANDMA collaboration: We continued our observations of the field of the Fermi Long GRB 260610B (Fermi GBM team, GCN 44901). The additional observations started on June 2026, 16 up to now. We still detect the optical afterglow using TTT-200cm, T150 at Abastumani Observatory, UBAI-AZT-22 at Madainak Observatory, AZT-8 at Lisnyky Observatory, KAO-1.88m at Kottamia Astronomical Observatory. We detect a re-brightening, which is consistent with other measurements reported in GCN 44955, GCN 44958, GCN 44959, GCN 44963, GCN 44993, 44999, 45003, 45004. 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/2026owq. 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. 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 (kilonovacatcher.in2p3.fr). Astrophysics Center for Multimessenger studies in Europe is supported Skyportal/ICARE (contact camille.douzet(a)ijclab.in2p3.fr, skyportal.io). The TTT Observing Time Rights (DTO) used were provided by Light Bridges, SL. View this GCN Circular online at https://gcn.nasa.gov/circulars/45007. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43221] GRB 260604B: 239Alferov CubeSat detection
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45006 SUBJECT: GRB 260604B: 239Alferov CubeSat detection DATE: 26/06/19 14:51:29 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> GRB 260604B: 239Alferov CubeSat detection D. Svinkin (Ioffe), D. Frederiks (Ioffe), D. Kapshtan (Geoscan), M. Orlov (Geoscan), V. Bazunova (Geoscan), E. Shchepin (Geoscan), E. Meltsov (Geoscan), K. Starikov (Geoscan, SPbSU), A. Khogoev (Geoscan), A. Razdobarin (SPbAU), and D. Dolmatov (SPbSU), on behalf of the 239Alferov team, report: The long-duration GRB 260604B (Fermi-GBM detection: The Fermi GBM team, GCN 44818; SVOM-GRM detection: Zhang et al., GCN 44850) was detected by 239Alferov 3U CubeSat at about 31555 s (08:45:55) UT. The burst was also detected by Konus-Wind in the waiting mode. The burst light curve, as measured by 239Alferov detector, shows a multi-peaked structure with a duration of ~8 s. The emission is seen up to ~500 keV. The light curve recorded by 239Alferov is available at: http://www.ioffe.ru/LEA/239Alferov/260604B/ 239Alferov GRB detections are listed at: http://www.ioffe.ru/LEA/239Alferov/ 239Alferov is an educational 3U CubeSat mission at SSO combining amateur radio and space research objectives. The gamma-ray detector onboard 239Alferov contains a 64x72x15 mm NaI(Tl) scintillator read out by a SiPM array and covers the energy range from ~20 keV to ~1000 keV. Currently, the instrument records count rates in five energy bands: ~20-50 keV, ~50-100 keV, ~100-500 keV, 500-1000 keV, and > 1000 keV, with 0.5 s temporal resolution. The ground segment of the mission utilizes the SONIKS open ground station network. View this GCN Circular online at https://gcn.nasa.gov/circulars/45006. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43220] GRB 260604A: 239Alferov CubeSat detection
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45005 SUBJECT: GRB 260604A: 239Alferov CubeSat detection DATE: 26/06/19 14:48:42 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> D. Svinkin (Ioffe), D. Frederiks (Ioffe), D. Kapshtan (Geoscan), M. Orlov (Geoscan), V. Bazunova (Geoscan), E. Shchepin (Geoscan), E. Meltsov (Geoscan), K. Starikov (Geoscan, SPbSU), A. Khogoev (Geoscan), A. Razdobarin (SPbAU), and D. Dolmatov (SPbSU), on behalf of the 239Alferov team, report: The long-duration GRB 260604A (Fermi-GBM detection: The Fermi GBM team, GCN 44812; Glowbug detection: Cheung et al., GCN 44845; SVOM-GRM detection: Yu et al., GCN 44863) was detected by 239Alferov 3U CubeSat at about 8668 s (02:24:28) UT. The burst was also detected by Konus-Wind in the waiting mode. The burst light curve, as measured by 239Alferov detector, shows a single pulse with a duration of ~5 s. The emission is seen up to ~500 keV. The light curve recorded by 239Alferov is available at: http://www.ioffe.ru/LEA/239Alferov/260604A/ 239Alferov GRB detections are listed at: http://www.ioffe.ru/LEA/239Alferov/ 239Alferov is an educational 3U CubeSat mission at SSO combining amateur radio and space research objectives. The gamma-ray detector onboard 239Alferov contains a 64x72x15 mm NaI(Tl) scintillator read out by a SiPM array and covers the energy range from ~20 keV to ~1000 keV. Currently, the instrument records count rates in five energy bands: ~20-50 keV, ~50-100 keV, ~100-500 keV, 500-1000 keV, and > 1000 keV, with 0.5 s temporal resolution. The ground segment of the mission utilizes the SONIKS open ground station network. View this GCN Circular online at https://gcn.nasa.gov/circulars/45005. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43219] GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45004 SUBJECT: GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening DATE: 26/06/19 14:42:59 GMT FROM: Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo(a)ucd.ie> G. Corcoran (UCD), A. Martin-Carrillo (UCD), L. Izzo (INAF/OAC and DARK/NBI), J. An (NAOC), D. B. Malesani (DAWN/NBI and Radboud), B. P. Gompertz (Birmingham), A. J. Levan (Radboud and Warwick), A. de Ugarte Postigo (LAM), report on behalf of the Stargate collaboration: We performed spectroscopic observations of GRB 260610B discovered by Fermi (Fermi GBM team, GCN 44901; Godwin & Meegan GCN 44931) and SVOM (Yu et al., GCN 44944), whose optical afterglow has recently experienced an optical rebrightening (O’Neill et al., GCNs 44903, 44914; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCNs 44910, 44955; Akl et al., GCNs 44911, 44930; Moskvitin et al., GCNs 44918, 44929; Jackson-Horne et al., GCN 44919; Izzo et al., GCN 44920; Li et al., GCN 44921; Bochenek et al., GCNs 44927, 44932; Pankov et al., GCN 44946; Angulo et al., GCN 44958; Moskvitin et al., GCN 44963; Pankov et al., GCN 44977; Gassert et al., GCN 44981; Gupta et al., GCN 44993). We used the ESO Very Large Telescope (VLT) UT1 (Antu) equipped with the FORS2 spectrograph with the 300V grism, covering the wavelength range 4400-8650 AA. The observation consisted of 4 exposures of 600 s each. The observation started at 00:41:19 UT on June 17 2026 (6.04 days after the GRB). In our acquisition image, we measured an AB magnitude r ~ 20 (calibrated against Pan-STARRS, not corrected for Galactic extinction). Based on the reported light curve, this seems to indicate that our observation occurred during the peak of this late flaring episode. The spectrum of the optical counterpart reveals a power-law continuum across the entire covered range suggesting that the observed recent activity is likely caused by late jet activity. Faint undulations are seen overimposed to the continuum, at a flux level consistent with the emergence of an early, still faint SN, but further observations will be required to conclude about its presence. Additionally, through the detection of the Ca II doublet in absorption and [O II] doublet in emission, we confirm the redshift reported by O’Neill et al. (GCN 44914), measuring z = 0.474. Further spectroscopic observations of the source are planned to monitor the possible emergence of the supernova. We acknowledge excellent support from the ESO observing staff in Paranal, in particular Martina Baratella and Leo Rivas, for rapidly executing these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/45004. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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