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[vsnet-grb-info 43110] GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44955 SUBJECT: GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations DATE: 26/06/16 15:30:51 GMT FROM: James Gillanders at University of Oxford <jhgillanders.astro(a)gmail.com> J. H. Gillanders (Oxford), M. Huber, K. C. Chambers (IfA, Univ. Hawaii), S. J. Smartt, K. W. Smith (Oxford/QUB), S. Srivastav (Oxford), M. Nicholl, D. Young (QUB), T.-W. Chen (NCU, Taiwan), A. S. B. Schultz, T. de Boer, J. Fairlamb, G. Paek, C. C. Lin, T. Lowe, E. Magnier, P. Minguez, I. A. Smith, R. J. Wainscoat (IfA, Univ. Hawaii). We have been observing AT 2026owq (O’Neill et al., GCNs 44903, 44914; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; 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), the optical counterpart to GRB 260610B (detected by Fermi/GBM; GCN 44901) with a nightly cadence in grizy using the Pan-STARRS telescope system (Chambers et al., 2016) since MJD 61202.4. The Pan-STARRS system consists of two 1.8m telescope units located at the summit of Haleakala on the Hawaiian island of Maui, employing an SDSS-like filter system denoted as grizy. Our observations consist of 200 second exposures, and have been processed with the standard Pan-STARRS pipeline. After astrometric and photometric calibration, reference images were subtracted from the target images (Magnier et al., 2020a; Magnier et al., 2020b; Waters et al., 2020). Our most recent photometry indicates that the lightcurve evolution of AT 2026owq is no longer fading; instead, the transient appears to be flattening, or re-brightening, across all of griz. Full photometry is presented below. Note that these photometric measurements have not been corrected for Galactic extinction. MJD | Filter | Mag (AB) 61205.271 | g | 21.7+/-0.2 61205.273 | r | 21.2+/-0.1 61205.276 | i | 20.9+/-0.1 61205.278 | z | 20.7+/-0.2 61206.276 | g | 21.8+/-0.3 61206.270 | r | 21.3+/-0.2 61206.268 | i | 20.7+/-0.2 61206.265 | z | 20.6+/-0.2 At the redshift of AT 2026owq (z=0.473; O’Neill et al., GCN 44914), observer-frame i approximately corresponds to rest-frame g. Thus, the absolute magnitude of AT 2026owq on MJD 61206.3, in rest-frame g, is approximately -21.4. Given that, at MJD 61206.3, the transient is only ~2.9 rest-frame days post-explosion, this excess is too bright to be powered by the emergence of a typical GRB-supernova signal. Further follow-up is scheduled with Pan-STARRS to determine its nature. View this GCN Circular online at https://gcn.nasa.gov/circulars/44955. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43109] The EP-WXT trigger 01709270148 is likely a flaring star
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44954 SUBJECT: The EP-WXT trigger 01709270148 is likely a flaring star DATE: 26/06/16 14:44:19 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> T. Y. Liu, D. Y. Li (NAO, CAS), J. H. Wu (GZHU), Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709270148 at the time of 2026-06-16T14:22:03, is likely a stellar flare associated with LP 820-19. The estimated flux of the flare is around 1.2 x 10 ^(-10) erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 8.6 x 10^(30) 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/44954. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43108] GRB 260616B: Fermi GBM Detection
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44953 SUBJECT: GRB 260616B: Fermi GBM Detection DATE: 26/06/16 14:20:47 GMT FROM: Christian Malacaria at INAF-OAR <cmalacaria.astro(a)gmail.com> C. Malacaria (INAF-OAR) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 07:05:16.39 UT on 16 June 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260616B (trigger 803286321/260616295). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 257.49, Dec = -32.62 (J2000 degrees, equivalent to J2000 17h 9m, -32d 37'), with a statistical uncertainty of 1.70 degrees. (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a core-plus-tail model, with 90% of GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg systematic error [Connaughton et al. 2015, ApJS, 216, 32]). The angle from the Fermi LAT boresight is 76 degrees. The GBM light curve consists of two main pulses with a duration (T90) of about 13.8 s (50-300 keV). The time-averaged spectrum from T0+0.002 to T0+14.464 s is best fit by a Band function with Epeak = 240 +/- 10 keV, alpha = -0.63 +/- 0.04, and beta = -2.09 +/- 0.06. The event fluence (10-1000 keV) in this time interval is (2.03 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+10 s in the 10-1000 keV band is 21.3 +/- 0.4 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/" View this GCN Circular online at https://gcn.nasa.gov/circulars/44953. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43107] GRB 260604C: GRANDMA late observations with CFHT/MegaCam
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44952 SUBJECT: GRB 260604C: GRANDMA late observations with CFHT/MegaCam DATE: 26/06/16 13:14:53 GMT FROM: antier(a)ijclab.in2p3.fr Q. Bais (KNC), A. Bruna (KNC), L. Laumain (KNC), A. Delaplace (KNC), S. Antier (IJCLAB), M. Pillas (IAP), P. Hello (IJCLAB), M. Coughlin (UMN), L. Desrivieres (KNC) on behalf of GRANDMA and CM2 classroom of St Remy Lès Chevreuse: We conducted further follow-up observations of GRB 260604C (Fermi Team, GCN Circ. 44822, Gotz et al., GCN Circ. 44823) with the Canada-France-Hawaii Telescope/MegaPrime/MegaCam on 2026-06-10. We further detected the source and confirmed that the rebrightening episode ended on 2026-06-10. We posted some of our data in the public site group of the public ACME service Skyportal/ICARE https://skyportal-icare.ijclab.in2p3.fr/source/GCN-260604_202037. To access, one simply needs to create an account using your ORCID id. These measurements are aligned with all our previous GRANDMA measurements. We thanks the CFHT team for observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. We also acknowledge funding from the European Union’s Horizon Europe Research and Innovation Programme under Grant Agreement No 101131928 (ACME project). 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). View this GCN Circular online at https://gcn.nasa.gov/circulars/44952. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43106] GRB 260616B: BALROG localization (Fermi Trigger 803286321 / GRB 260616295)
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44951 SUBJECT: GRB 260616B: BALROG localization (Fermi Trigger 803286321 / GRB 260616295) DATE: 26/06/16 09:17:04 GMT FROM: Jochen Greiner at MPE <jcgrog(a)mpe.mpg.de> T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report: The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 803286321 at 07:05:16 on 16 June 2026 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60). The best-fit position is: RA(2000.0) = 255.8 deg Decl.(2000.0) = -32.1 deg The 1 sigma statistical error radius is 1.5 deg. We estimate an additional systematic error of 1 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB260616295/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB260616295/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB260616295/json View this GCN Circular online at https://gcn.nasa.gov/circulars/44951. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43105] The EP-WXT trigger 01709269893 is likely a flaring star
by GCN Circulars 15 Jun '26

15 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44950 SUBJECT: The EP-WXT trigger 01709269893 is likely a flaring star DATE: 26/06/16 04:16:36 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> D. Y. Li, T. Y. Liu (NAO, CAS), J. H. Wu (GZHU), Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709269893 at the time of 2026-06-16T03:28:01, is likely a stellar flare associated with UCAC3 45-262017. The estimated flux of the flare is around 8.0 x 10^(-11) erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 1.2 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/44950. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43104] GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140)
by GCN Circulars 15 Jun '26

15 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44949 SUBJECT: GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140) DATE: 26/06/16 03:56:27 GMT FROM: Jochen Greiner at MPE <jcgrog(a)mpe.mpg.de> T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report: The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 803272919 at 03:21:54 on 16 June 2026 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60). The best-fit position is: RA(2000.0) = 94.4 deg Decl.(2000.0) = -32.1 deg The 1 sigma statistical error radius is 1.7 deg. We estimate an additional systematic error of 1 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB260616140/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB260616140/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB260616140/json View this GCN Circular online at https://gcn.nasa.gov/circulars/44949. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43103] GRB 260616A: Fermi GBM Final Real-time Localization
by GCN Circulars 15 Jun '26

15 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44948 SUBJECT: GRB 260616A: Fermi GBM Final Real-time Localization DATE: 26/06/16 03:34:02 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 03:21:54 UT on 16 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260616A (trigger 803272919.330008 / 260616140). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 95.0, Dec = -31.9 (J2000 degrees, equivalent to J2000 06h 19m, -31d 53'), with a statistical uncertainty of 1.4 degrees. The angle from the Fermi LAT boresight is 111.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260616140/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260616140/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260616140/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44948. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43102] GRB 260614B: SVOM/ECLAIRs refined analysis
by GCN Circulars 15 Jun '26

15 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44947 SUBJECT: GRB 260614B: SVOM/ECLAIRs refined analysis DATE: 26/06/15 21:03:45 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Brunet, O. Godet, S. Guillot (IRAP), M. Pillas (IAP) report on behalf of the SVOM/ECLAIRs team Using the event-by-event data downloaded through the X-band ground station, we report further analysis of SVOM/ECLAIRs observations of GRB 260614B (SVOM burst-id sb26061401 – GCN 44938, trigger time T0 = 2026-06-14T13:49:55 UTC), which was also detected by Fermi/GBM (GCN 44937, 44942) and GECAM-B (GCN 44945). The burst that triggered ECLAIRs onboard shows a multiple peak lightcurve. The burst duration is T90 = 88 +18/-9 s in the 4-120 keV energy band. The time-averaged spectrum before the slew from T0-4 s to T0+37 s in the 5-120 keV energy range is best fitted by a powerlaw model with a photon index of -1.04 +/- 0.03. With this model, the 4-120 keV fluence is (5.4 +/- 0.1)e-6 erg/cm^2 and the 4-120 keV photon flux is 2.50 +0.04/-0.06 ph/cm^2/s. All the quoted errors are at the 68% confidence level. 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. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. The SVOM/ECLAIRs point of contact for this burst is: Marius Brunet (IRAP) (marius.brunet at utoulouse.fr). View this GCN Circular online at https://gcn.nasa.gov/circulars/44947. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43101] GRB 260610B: Terskol optical observations
by GCN Circulars 15 Jun '26

15 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44946 SUBJECT: GRB 260610B: Terskol optical observations DATE: 26/06/15 08:46:27 GMT FROM: Nicolai Pankov at IKI <colinsergesen(a)gmail.com> N. Pankov (IKI), A. Salakhotdinova (INASAN), A. Shein (INASAN), E. Postnikova (INASAN), A. Pozanenko (IKI), A. Moskvitin (SAO RAS), A. Volnova (IKI) report on behalf of IKI-GRB-FuN: We observed the field of GRB 260610B (The Fermi GBM team, GCN 44891; GCN 44901) with the Zeiss-2000 2-meter telescope of the Terskol Observatory on epochs 2026-06-11 and 2026-06-12. The R-band observations were carried out using the CCD-photometer. In the first epoch we acquired a series of 3x120+12x120 sec images, while in the latter epoch 9x120 sec images were obtained. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek & Perley, GCN 44932) is clearly detected in our co-add images. The observational properties and preliminary photometry are provided further: Date UTstart t-T0 Exp. Filter Mag Err UL (mid,d) (n*s) (3-sigma) 2026-06-11 21:33:51 1.48481 3x120+12x90 R 19.81 0.06 22.4 2026-06-12 19:46:19 2.40802 9x120 R 20.70 0.13 22.3 The photometry is based on nearby SDSS stars (R-magnitudes obtained via Lupton 2005 transformation equations; Moskvitin et al., GCN 44918) and not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44946. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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