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[vsnet-grb-info 43027] Konus-Wind detection of GRB 260601A
by GCN Circulars 10 Jun '26

10 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44894 SUBJECT: Konus-Wind detection of GRB 260601A DATE: 26/06/10 13:16:20 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia(a)mail.ioffe.ru> A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The short-duration GRB 260601A (Fermi-GBM detection: Fermi GBM team, GCN 44755, Holzmann Airasca et al., GCN 44760; Glowbug detection: Cheung et al., GCN 44763; GECAM-B detection: Wang et al., GCN 44778; SVOM-GRM detection: Wang et al., GCN 44793; CALET-GBM detection: Yamaoka et al., GCN 44817; IPN triangulation: Svinkin et al., GCN 44893) triggered Konus-Wind at T0=39609.166 s UT (11:00:09.166). The burst light curve shows a multipeaked structure which starts at ~T0 and has a total duration of ~0.2 s. The emission is seen up to ~2 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260601_T39609/ As observed by Konus-Wind, the burst had the total fluence of 3.05(-0.27,+0.29)x10^-6 erg/cm2, and the 16-ms peak flux, measured from T0+0.078 s, of 4.04(-0.53,+0.55)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+0.192 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 = -0.44(-0.13,+0.14) and Ep = 780(-91,+107) keV (chi2 = 36/39 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.6 (chi2 = 36/38 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/44894. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43026] IPN triangulation of GRB 260601A (short/hard)
by GCN Circulars 10 Jun '26

10 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44893 SUBJECT: IPN triangulation of GRB 260601A (short/hard) DATE: 26/06/10 13:06:10 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi-GBM team, Zheng-Hang Yu, Chen-Wei Wang, Shao-Lin Xiong, Chao Zheng, Cheng-Kui Li (IHEP) on behalf of GECAM team, C. Wang (IHEP), S. Xiong (IHEP), S. Zhang (IHEP), J. Wei (NAOC), B. Cordier (CEA) on behalf of the SVOM-GRM team, K. Yamaoka (Nagoya U), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, 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), on behalf of the CALET collaboration, report: The short-duration GRB 260601A (Fermi-GBM detection: The Fermi GBM team, GCN 44755; Holzmann Airasca, GCN 44760; Glowbug detection: Cheung et al., GCN 44763; GECAM-B detection: Y. Wang et al., GCN 44778; SVOM-GRM detection: Y. Wang et al., GCN 44793; CALET-GBM detection: Yamaoka et al., GCN 44817) was detected by Fermi (GBM trigger 802004417), CALET (GBM trigger 1464346716), Konus-Wind, Glowbug, SVOM (GRM), and GECAM-B at about 39612 s UT (11:00:12). We have triangulated it to the 3 sigma localization region whose area is 2.8 sq. deg, and its maximum dimension is 73 deg (the minimum one is 2.7 arcmin). A triangulation map and HEALPix FITS files are posted at http://www.ioffe.ru/LEA/GRBs/GRB260601_T39609/IPN/ The HEALPix triangulation map is the multi-order HEALPix in units of probability density. The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/44893. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43025] GRB 260610b: Fermi GBM Final Real-time Localization
by GCN Circulars 10 Jun '26

10 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44892 SUBJECT: GRB 260610b: Fermi GBM Final Real-time Localization DATE: 26/06/10 10:19:57 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 10:07:46 UT on 10 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260610b (trigger 802778871.805202 / 260610422). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 354.7, Dec = 8.4 (J2000 degrees, equivalent to J2000 23h 38m, 8d 24'), with a statistical uncertainty of 10.5 degrees. The angle from the Fermi LAT boresight is 102.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260610422/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260610422/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260610422/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44892. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43024] GRB 260610b: Fermi GBM Final Real-time Localization
by GCN Circulars 10 Jun '26

10 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44891 SUBJECT: GRB 260610b: Fermi GBM Final Real-time Localization DATE: 26/06/10 10:18:35 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 10:07:46 UT on 10 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260610b (trigger 802778871.805202 / 260610422). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 354.7, Dec = 8.4 (J2000 degrees, equivalent to J2000 23h 38m, 8d 24'), with a statistical uncertainty of 10.5 degrees. The angle from the Fermi LAT boresight is 102.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260610422/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260610422/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260610422/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44891. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43023] GRB 260610a: COLIBRÍ optical upper limits
by GCN Circulars 10 Jun '26

10 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44890 SUBJECT: GRB 260610a: COLIBRÍ optical upper limits DATE: 26/06/10 10:12:50 GMT FROM: Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo(a)gmail.com> Antonio de Ugarte Postigo (LAM), Diego López-Cámara (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (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), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) report: We imaged the field of EP260610a (Wu et al., GCN Circ. 44889) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-06-10 08:23:40 to 09:56:22 UTC (from 3.78 to 5.32 hours after the trigger) and obtained 69 minutes of simultaneous exposure in the r and z filters. The data were reduced and coadded and analysed 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. In the stacked image, we do not detect any new source at the FXT source position (Wu et al., GCN Circ. 44889) down to the following 5-sigma limits: r > 24.0 mag z > 22.6 mag 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/44890. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43022] EP260610a: Einstein Probe detection of a fast X-ray transient
by GCN Circulars 10 Jun '26

10 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44889 SUBJECT: EP260610a: Einstein Probe detection of a fast X-ray transient DATE: 26/06/10 06:22:59 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H.Z. Wu, (HUST, CAS),C. L. Guo, H. Y. Ren, Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260610a. The transient triggered EP-WXT (ID: 01709268833) at 2026-06-10 04:37:09(UTC). The WXT position of the source is R.A. = 306.104 deg, DEC = -25.926 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed at 2026-06-10T04:49:21(UTC). Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 306.1055 deg, DEC = -25.9057 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). 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/44889. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43021] GRB 260609A: Fermi GBM Final Localization
by GCN Circulars 09 Jun '26

09 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44888 SUBJECT: GRB 260609A: Fermi GBM Final Localization DATE: 26/06/09 21:40:53 GMT FROM: eliza.neights(a)gmail.com The Fermi GBM team reports the detection of a likely LONG GRB "At 20:05:42.61 UT on 09 June 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260609A (trigger 802728347/260609837). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 42.43, Dec = -7.99 (J2000 degrees, equivalent to J2000 2h 49m, -7d 59'), with a statistical uncertainty of 8.05 degrees. The angle from the Fermi LAT boresight is 86 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260609837/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260609837/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260609837/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/44888. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43020] Konus-Wind detection of GRB 260604C
by GCN Circulars 09 Jun '26

09 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44887 SUBJECT: Konus-Wind detection of GRB 260604C DATE: 26/06/09 16:52:29 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia(a)mail.ioffe.ru> A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 260604C (Fermi-GBM detection: Fermi GBM team, GCN 44822, Neights et al., GCN 44831; SVOM-ECLAIRs detection: Gotz et al., GCN 44823, Brunet et al., GCN 44883; GECAM-B detection: Luo et al., GCN 44854; AstroSat-CZTI detection: Arya et al., GCN 44885) triggered Konus-Wind at T0=73128.568 s UT (20:18:48.568). The burst light curve shows a single pulse which starts at ~T0-3.2 s and has a duration of ~8.5 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/GRB260604_T73128/ As observed by Konus-Wind, the burst had the total fluence of 3.60(-0.26,+0.26)x10^-5 erg/cm2, and the 64-ms peak flux, measured from T0+3.056 s, of 2.25(-0.18,+0.18)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+12.032 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.92(-0.05,+0.06), the high energy photon index beta = -2.33(-0.19,+0.13), the peak energy Ep = 421(-37,+40) keV (chi2 = 82/89 dof). The spectrum near the maximum count rate (measured from T0+0.256 to T0+3.840 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.73(-0.06,+0.06), the high energy photon index beta = -2.07(-0.07,+0.06), the peak energy Ep = 374(-32,+35) keV (chi2 = 60/71 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/44887. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43019] GRB 260608A: Fermi GRB Observation
by GCN Circulars 09 Jun '26

09 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44886 SUBJECT: GRB 260608A: Fermi GRB Observation DATE: 26/06/09 16:34:28 GMT FROM: Padraig McDermott at University College Dublin <padraig.mcdermott(a)ucdconnect.ie> Padraig Mc Dermott (UCD) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 11:35:31.06 UT on 08 June 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260608A (trigger 802611336/260608483). which was also detected by SVOM ECLAIRs (M.Brunet et al. 2026, GCN 44870, GCN 44882). The Fermi GBM on-ground location is consistent with the SVOM ECLAIRs position. The angle from the Fermi LAT boresight is 31 degrees. The GBM light curve consists of a main emission followed by a smaller peak with a duration (T90) of about 50 s (50-300 keV). The time-averaged spectrum from T0-6.7 to T0+43.6 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.35 +/- 0.02 and the cutoff energy, parameterized as Epeak, is 93 +/- 3 keV. The event fluence (10-1000 keV) in this time interval is (2.83 +/- 0.11)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.83 s in the 10-1000 keV band is 2.1 +/- 0.2 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/44886. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43018] GRB 260604C: AstroSat CZTI detection
by GCN Circulars 09 Jun '26

09 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44885 SUBJECT: GRB 260604C: AstroSat CZTI detection DATE: 26/06/09 13:26:28 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> A. Arya (IITB), A. Goyal (IITB), Harsha K. H. (IUCAA), S. Salunke (IUCAA), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long GRB 260604C which was also detected by Fermi/GBM (Fermi GBM team, GCN Circ. 44822) and SVOM/ECLAIRs (D. Gotz et.al., GCN Circ. 44823). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2026-06-04 20:18:49 UTC. The measured peak count rate associated with the burst is 1274 (+126, -136) counts/s above the background in the combined data of all quadrants, with a total of 1904 (+116, -105) counts. The local mean background count rate was 282 (+4, -7) counts/s. Using cumulative rates, we measure a T90 of 2.7 (+0.5, -0.2) s. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2026-06-04 20:18:48 UTC. The measured peak count rate associated with the burst is 3712 (+112, -126) counts/s above the background in the combined data of all quadrants, with a total of 8150 (+207, -252) counts. The local mean background count rate was 1332 (+7, -6) counts/s. We measure a T90 of 3.3 (+0.2, -0.1) s from the cumulative Veto light curve. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI data products like interactive and downloadable light curves for this GRB can be found at: https://astrosat.iucaa.in/cift/cift_products/ET20260604T201844/ET20260604T2… CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/44885. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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