- vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 43209] EP260618a: OHP/T193 optical observations
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44994 SUBJECT: EP260618a: OHP/T193 optical observations DATE: 26/06/19 11:05:46 GMT FROM: Christophe Adami at LAM <christophe.adami(a)lam.fr> P. Amram (LAM/Pytheas/AMU), C. Adami (LAM/Pytheas/AMU), D. Russeil (LAM/Pytheas/AMU) report on behalf of a larger collaboration: We observed the field of EP260618a (Yang et al., GCN44978; see also Fermi GBM Team , GCN44973 and Jiang et al., GCN44991) using the T193cm telescope at Observatoire de Haute-Provence (France) with the MISTRAL spectro-imager. We obtained 2x10 minutes of exposure in the r-band starting at 2026-06-18T21:12:40 UT (12.63 hr after the Yang et al. trigger). In the stacked images, the optical counterpart detected by Becerra et al. (GCN44988) and Malesani et al. (GCN44990) is visible with preliminary magnitude of: r = 21.86 +/- 0.09 mag in good agreement with their measurements. The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the STDWeb/STDPipe tools (Karpov 2025), is in the AB system, and is not corrected for Galactic extinction. We acknowledge the excellent support from Observatoire de Haute-Provence and in particular Stephane Favard. We acknowledge the excellent support of J. Schmitt and J.C. Brunel in the recent MISTRAL upgrade. View this GCN Circular online at https://gcn.nasa.gov/circulars/44994. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43208] GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44993 SUBJECT: GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection DATE: 26/06/19 10:18:21 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Divyanshu Janghel, Debalina kar, Pankaj Pawar, Dhruv Jain and Kuntal Misra (ARIES) report: We observed the field of GRB 260610B/AT 2026owq discovered by Fermi (The Fermi GBM team, GCN 44901; Godwin and Meegan; GCN 44931; Yu et al., GCN 44944)) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2026-06-15 at 16:53:40 UT, i.e., ~ 4.71 days after the Fermi trigger (GCN 44901). We have taken multiple frames with an exposure time of 300 s in the R and I filter. We stacked the images after the alignment. We detect a optical afterglow in our stacked image. We obtain the following preliminary magnitude in the stacked image: Date Mid_UT T_start-T0 (days) Filter Exp time (s) Magnitude ================================================================= 2026-06-15 17:24:09.406 ~4.73 R 300s*12 20.88 +/-0.05 The optical detection of the burst is consistent with 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; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959; Moskvitin et al., GCN 44963; Pankov et al., GCN 44977; Gassert et al., GCN 44981. The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the Gaia DR3 Synphot catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/44993. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43207] GRB 260619A: Kilonova-Catcher optical upper limit
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44992 SUBJECT: GRB 260619A: Kilonova-Catcher optical upper limit DATE: 26/06/19 09:54:36 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> R. Hellot (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 260619A detected by SVOM/ECLAIRs (Goto et al., GCN 44985) with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with a CDK17 telescope located at AITP San Pedro Chile Observatory and operated by R. Hellot. Our observations started at TGRB+4.0 hours and were taken with the sdssr filter. In our stacked frames, subtracted from the PanSTARRS DR2 template image, we do not detect any optical uncatalogued source inside the SVOM/ECLAIRs error box. We report our follow-up results in the table below: | Tmid-TGRB (hr)| Exp (s) | Filter | Magnitude | Instrument | | ------------ | ------------ |------------ |------------ |------------ | | 4.29 | 12 x 300s | r (AB) | 20.3 (5 sigma) | AITP | All the data have been 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. 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/) View this GCN Circular online at https://gcn.nasa.gov/circulars/44992. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43206] EP260618a: EP-FXT follow-up observation
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44991 SUBJECT: EP260618a: EP-FXT follow-up observation DATE: 26/06/19 09:13:11 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> S. Q. Jiang (NAO, CAS), J. Yang (ZZU), H. Sun (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of the X-ray transient EP260618a (Yang et al., GCN 44978), which is possibly associated with GRB 260618A (Fermi GBM team, GCN 44973). The observation started at 2026-06-18T18:09:47 (UTC), about 9.58 hours after the initial WXT detection, with an exposure time of 3 ks. An uncatalogued source was detected within the WXT error circle at R.A. = 276.6799, DEC = 23.8439 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). The FXT spectrum can be fitted with an absorbed powerlaw with a hydrogen column density fixed at the Galactic value of 1.32 x 10^21 cm^-2 and a photon index of 2.09 +/- 0.13. The derived unabsorbed 0.5-10 keV flux is 1.28 (+0.13, -0.10) x 10^-12 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. The position of the uncatalogued X-ray source is consistent with the optical counterpart (Becerra et al., GCN 44988; Malesani et al., GCN 44990). Further EP-FXT follow-up observations will be arranged. Launched on 2024 January 9, Einstein Probe is a space-based X-ray observatory designed to monitor the dynamic X-ray sky and perform rapid follow-up observations of newly discovered transients (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/44991. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43205] EP260618a: LCO optical counterpart confirmation
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44990 SUBJECT: EP260618a: LCO optical counterpart confirmation DATE: 26/06/19 08:41:05 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> D. B. Malesani (DAWN/NBI and Radboud), J. A. Quirola-Vasquez (Radboud), J. Sanchez-Sierras (Radboud), G. Corcoran (UCD), A. J. Levan (Radboud and Warwick), A. Martin-Carrillo (UCD), P. G. Jonker (Radboud), J. Chacon (PUC), report on behalf of a larger collaboration: We observed the field of the fast X-ray transient EP260618a (Yang et al., GCN 44978), possibly the afterglow of GRB 260618A (Fermi GBM team, GCN 44973), using an LCO 1m telescope located at the Teide Observatory (Spain) equipped with the SINISTRO instrument. We obtained 6x300 s exposures in the SDSS-r filter starting on 2026-06-18 at 21:56:12 UT (13.56 hr after the trigger). The object reported by Becerra et al. (GCN 44988) is detected in the stack of our images, with a magnitude of r = 21.93 +/- 0.16 (AB), calibrated against the Pan-STARRS catalogue and not corrected for Galactic extinction. We note that our magnitude indicates little or no fading compared to the COLIBRÍ observation, which was carried out about 6.5 hr later (Becerra et al., GCN 44988). Further follow-up is encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/44990. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43204] GRB 260617A: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44989 SUBJECT: GRB 260617A: CALET Gamma-Ray Burst Monitor detection DATE: 26/06/19 08:20:00 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> S. Torii (Waseda U), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (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 260617A at 21:36:43.92 UTC on 17 June 2026 (trigger #1465767277; https://cgbm.calet.jp/cgbm_trigger/flight/1465767277/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 (The Fermi GBM team et al., GCN #44969; Godwin et al., GCN #44972), Konus-Wind and Mars-Odyssey (IPN triangulation: Kozyrev et al., GCN #44982). The burst signal was seen by HXM1 and SGM. The burst light curve shows a short pulse from T-0.25 s to T-0.15 s. The T90 and T50 durations measured with the SGM data are 0.09 +/- 0.02 s and 0.05 +/- 0.01 s in the 40-1000 keV band, respectively. The ground-processed light curve is available at: https://cgbm.calet.jp/cgbm_trigger/ground/1465767277/ 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/44989. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43203] EP260618a: COLIBRÍ optical counterpart candidate
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44988 SUBJECT: EP260618a: COLIBRÍ optical counterpart candidate DATE: 26/06/19 05:09:23 GMT FROM: Rosa Leticia Becerra Godínez at Instituto de Astronomía, UNAM <rbecerra(a)astro.unam.mx> Rosa L. Becerra (UNAM), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), and Alan M. Watson (UNAM) report: We imaged the field of the EP260618a (Yang et al., GCN Circ. 44978), possibly associated with GRB 260618A (Fermi GBM team GCN Circ. 44973), using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-06-19 03:44 to 04:55 UTC (from 19.15 to 20.34 hours after the trigger) and obtained 55 minutes of simultaneous exposure in the r and z filters. The data were reduced and coadded with the ASU COLIBRÍ pipeline The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction, which is particularly significant in this direction (A_r = 1.1 mag; Schlafly & Finkbeiner 2011) due to the proximity of the field to the Galactic plane. We detect an uncatalogued source, absent in Pan-STARRS template images and and located within the WXT error region (Yang et al., GCN Circ. 44978) at: RA(J2000) = 18:26:43.13 = 276.6797 degrees, Dec(J2000) = +23:50:37.8 = 23.8438 degrees, with an uncertainty of 0.5 arcsec. The preliminary magnitudes derived for this source are: r = 21.90 +/- 0.04, z = 21.49 +/- 0.08. We therefore suggest that this source is the optical counterpart of EP260618a. Further observations and analysis are ongoing. We thank the staff of the Observatorio Astronómico Nacional at Sierra de San Pedro Mártir, as well as the technical and engineering teams at CEA, CPPM, IRAP, LAM, OHP, OSU Pytheas, and UNAM. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/44988. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43202] GRB 260616A: NuSTAR detection of prompt emission
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44987 SUBJECT: GRB 260616A: NuSTAR detection of prompt emission DATE: 26/06/19 03:34:34 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> G. Waratkar (Caltech) and B. Grefenstette (Caltech) report on behalf of the NuSTAR Search for INteresting Gamma-ray Signals (SINGS) working group: The NuSTAR SINGS working group reports the detection of prompt emission from the long-duration GRB 260616A in both the NuSTAR CsI anti-coincidence shields. Details of the search algorithm will be described in a future paper. The NuSTAR SINGS algorithm, triggered at 2026-06-16T03:21:25.62 UTC, shows a detection of GRB 260616A, also detected by Fermi-GBM (Fermi GBM Team, GCN 44948), GECAM-B (Guo et al., GCN 44964), Konus-Wind (Ridnaia et al., GCN 44967), and Insight-HXMT (Wang et al., GCN 44980). The NuSTAR CsI shield data are recorded at 1 Hz. We detect a burst lasting for about 100-s. The peak count rate is ~1500-cps with a baseline rate of ~1000-cps during this time period. We do not see any evidence in the signal above 100 keV in the CZT detectors. The Fermi-LAT localization (Lopez et al., GCN 44960) at RA = 93.53, Dec = -32.07 implies an offset from the NuSTAR boresight of 133-deg (i.e. from the backside) and an offset from the geocenter of 86-deg. Lightcurves and analysis for this GRB can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/260616A Information on NuSTAR SINGS can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/ NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington. View this GCN Circular online at https://gcn.nasa.gov/circulars/44987. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43201] GRB 260614B: NuSTAR detection of prompt emission
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44986 SUBJECT: GRB 260614B: NuSTAR detection of prompt emission DATE: 26/06/19 03:32:52 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> G. Waratkar (Caltech) and B. Grefenstette (Caltech) report on behalf of the NuSTAR Search for INteresting Gamma-ray Signals (SINGS) working group: The NuSTAR SINGS working group reports the detection of prompt emission from the long-duration GRB 260614B in both the NuSTAR CsI anti-coincidence shields. Details of the search algorithm will be described in a future paper. The NuSTAR SINGS algorithm, triggered at 2026-06-14T13:49:47.0 UTC, shows a detection of GRB 260614B, also detected by Fermi-GBM (Fermi GBM Team, GCN 44937), SVOM (Godet et al., GCN 44938), and GECAM-B (Luo et al., GCN 44945). The NuSTAR CsI shield data are recorded at 1 Hz. We detect a burst lasting for about 20-s, consistent with the Fermi and GECAM-B lightcurve. The peak count rate is ~1500-cps with a baseline rate of ~1000-cps during this time period. We do not see any evidence in the signal above 100 keV in the CZT detectors. The SVOM/VT counterpart (Palmerio et al., GCN 44939) at RA = 353.90883, Dec = -54.11628 implies an offset from the NuSTAR boresight of 99-deg (i.e. from the side) and an offset from the geocenter of 125-deg. Lightcurves and analysis for this GRB can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/260614B Information on NuSTAR SINGS can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/ NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington. View this GCN Circular online at https://gcn.nasa.gov/circulars/44986. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43200] GRB 260619A: SVOM possible detection of a faint burst
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44985 SUBJECT: GRB 260619A: SVOM possible detection of a faint burst DATE: 26/06/19 03:10:53 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Hatsune Goto (RIKEN), Jun Yang (ZZU), Kuan Liu (GXU), Zhiyong Liu (GZNU) report on behalf of the SVOM mission team: At 2026-06-19T02:12:40 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260619A (SVOM burst-id sb26061901). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was only detected by the Image Trigger (IMT), which produced a sequence of 1 alert. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 6.90 in the [8-50] keV energy band over a time window of 40.96 seconds starting at 2026-06-19T02:11:59. The localization of the best alert is R.A., Dec. 359.0538, -15.3917 degrees: R.A. (J2000) = 23h56m12.91s Dec. (J2000) = -15d23m30.15s with a 90% confidence level (C.L.) radius of 11.33 arcmin (including systematic error of 2 arcmin added in quadrature). There’re 3 High Proper Motion Stars in the ECLAIRs error box: LP 764-29 GR* 276 BD-16 6388 These sources may cause this trigger. Due to the detection significance being below the slew threshold, no immediate slew was performed on this burst. 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 Kuan Liu: liuk(a)st.gxu.edu.cn. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/44985. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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