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

[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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[vsnet-grb-info 43218] GRB 260619A: SVOM/VT optical counterpart confirmation
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45003 SUBJECT: GRB 260619A: SVOM/VT optical counterpart confirmation DATE: 26/06/19 14:30:00 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Y. N. Ma, Z. H. Yao, J. R. Xu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA/Irfu), Kuan Liu (GXU), Zhiyong Liu (GZNU) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observations of GRB260619A triggered by SVOM/ECLAIRs (sb26061901, Goto et al., GCN 44985). The observation started at 2026-06-19T05:54:32 UTC, approximately 3.71 hours post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. The optical candidate (Ducoin et al., GCN 44999) was detected in both channels. The following measurements are in the AB magnitude and are not corrected for Galactic extinction: Mid time | Band | Exposure Time | Brightness 6.13 h VT_B 14*70 s 22.56 +/- 0.15 mag 6.14 h VT_R 13*70 s 22.63 +/- 0.18 mag 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/45003. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43217] GRB 260618B: SVOM/VT optical candidate
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45001 SUBJECT: GRB 260618B: SVOM/VT optical candidate DATE: 26/06/19 13:38:11 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, J. R. Xu, Y. N. Ma, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. T. Palmerio (CEA/Irfu) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observations for GRB 260618B detected by Fermi-LAT (Gupta et al., GCN 44983) and Fermi-GBM (the Fermi GBM team, GCN 44979). The observation started at 2026-06-19T01:44:32 UTC, i.e., 8.83 hours post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. An uncatalogued optical candidate was clearly detected in both channels compared with the Legacy Survey, with an angular separation of 8.7 arcminutes from the Fermi-LAT position (Gupta et al., GCN 44983). The position is at R.A., Dec. = 354.333559, -44.735518 degrees, equivalent to: R.A. (J2000) = 23:37:20.05 Dec. (J2000) = -44:44:07.87 with an uncertainty of 0.5 arcsec. The following measurements are in the AB magnitude and are not corrected for Galactic extinction: Mid time | Band | Exposure Time | Brightness 10.53 h VT_B 48*70 s 20.8 +/-0.1 mag 10.53 h VT_R 41*70 s 20.9 +/-0.1 mag 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/45001. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43216] Fermi-LAT Gamma-ray Observations of IceCube-260610A
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45002 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-260610A DATE: 26/06/19 14:05:43 GMT FROM: Leo Pfeiffer at University of Würzburg <pfeiffer.leo(a)gmail.com> L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg) and S. Garrappa (Weizmann Institute of Science) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC260610A neutrino event (GCN 44899) with all-sky survey data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 26-06-10 at 20:02:41.03 UTC (T0) with J2000 position RA = 309.20 (+2.04, -2.06) deg, Decl. = 37.22 (+0.96/-0.93) deg 90% PSF containment. Two cataloged >100 MeV gamma-ray source are located within the 90% IC260610A localization error, at a distance of roughly 0.77 and 1.45 deg (4FGL-DR4; The Fourth Fermi-LAT catalog Data Release 4, The Fermi-LAT collaboration 2023, arXiv:2307.12546). These are the objects: 4FGL J2035.0+3632 associated with PSR J2034+3632. Based on a preliminary analysis of the LAT data over the timescale of 1-day and 1-month, this object is not significantly detected at gamma-rays. 4FGL J2030.0+3641 associated with PSR J2030+3641. Based on a preliminary analysis of the LAT data over the timescale of 1-day, this object is not significantly detected at gamma-rays. On a 1-month integration timescale prior to T0, it is detected significantly but the flux is in agreement with the average flux of the source reported in 4FGL-DR4. We conclude that the source is not in high state. We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (> 100 MeV) within the IC260610A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC260610A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 2.7e-9 ph cm^-2 s^-1 for ~18-years (2008-08-04 / T0), <1.2e-08 (<2.6e-07) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. For this source the Fermi-LAT contact person is Leonard Pfeiffer (leonard.pfeiffer at uni-wuerzburg.de). The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/45002. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43215] GRB 260618B: SVOM/VT optical candidate
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 45000 SUBJECT: GRB 260618B: SVOM/VT optical candidate DATE: 26/06/19 13:04:05 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, J. R. Xu, Y. N. Ma, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. T. Palmerio (CEA/Irfu) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observations for GRB 260618B detected by Fermi-LAT (Gupta et al., GCN 44983) and Fermi-GBM (the Fermi GBM team, GCN 44979). The observation started at 2026-06-19T01:44:32 UTC, i.e., 8.83 hours post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. An uncatalogued optical candidate was clearly detected in both channels compared with the Legacy Survey, with an angular separation of 8.7 arcminutes from the Fermi-LAT position. The position is at R.A., Dec. = 240.862173, 50.563348 degrees, equivalent to: R.A. (J2000) = 16:03:26.92 Dec. (J2000) = +50:33:48.05 with an uncertainty of 0.5 arcsec. The following measurements are in the AB magnitude and are not corrected for Galactic extinction: Mid time | Band | Exposure Time | Brightness 10.53 h VT_B 48*70 s 20.8 +/-0.1 mag 10.53 h VT_R 41*70 s 20.9 +/-0.1 mag 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/45000. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43214] GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44999 SUBJECT: GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate DATE: 26/06/19 13:01:35 GMT FROM: J.-G. Ducoin at CPPM <ducoin(a)cppm.in2p3.fr> Jean-Grégoire Ducoin (CPPM), Rosa L. Becerra (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), 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), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), Alan M. Watson (UNAM), Hatsune Goto (RIKEN), Jun Yang (ZZU), Kuan Liu (GXU), Zhiyong Liu (GZNU) report: We imaged the field of the SVOM GRB 260619A (Goto et al., GCN Circ. 44985) using the DDRAGO two-channel wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-06-19 09:49:05 to 11:11:49 UTC (from 7.62 to 9.01 hours after the trigger) and obtained 61 minutes of simultaneous exposure in the r and z filters. The data were reduced, coadded and analysed with the COLIBRÍ ASU pipeline and cross-analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. We detect an uncatalogued source (revealed by image subtraction using Legacy Survey) consistent with the ECLAIRs 11.33 arcmin error circle (Goto et al., GCN Circ. 44985) at: RA(J2000) = 23:56:24.46 = 359.10192 degrees Dec(J2000) = -15:27:41.0 = -15.46140 degrees with an uncertainty of 0.5 arcsec. The preliminary unsubtracted magnitude derived for that source is: r = 22.13 +/- 0.05 z = 21.91 +/- 0.14 The lack of clear evidence for variability, prevents a firm confirmation that this source is the optical afterglow of GRB 260619A. 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/44999. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43213] Konus-Wind detection of GRB 260617A
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44998 SUBJECT: Konus-Wind detection of GRB 260617A DATE: 26/06/19 12:29:15 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 260617A (Fermi-GBM detection: Fermi GBM team, GCN 44969; Godwin & Meegan, GCN 44972; IPN triangulation: Kozyrev et al., GCN 44982; CALET-GBM detection: Torii et al., GCN 44989) triggered Konus-Wind at T0=77808.934 s UT (21:36:48.934). The burst light curve shows a multi-peaked pulse, which starts at ~T0-64 ms and has a total duration of ~150 ms. 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/GRB260617_T77808/ As observed by Konus-Wind, the burst had the total fluence of 1.28(-0.16,+0.19)x10^-6 erg/cm2, and the 16-ms peak flux, measured from T0-0.060 s, of 1.73(-0.36,+0.38)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). Since the brightest peak of the burst light curve was detected before the trigger, the spectral analysis was performed using the KW 3-channel light curve data. Modelling the KW 3-channel time-integrated spectrum (measured from T0-0.064 s to T0+0.084 s) by a power law with exponential cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep), yields alpha = -0.26(-0.32,+0.40) and Ep = 537(-85,+129) keV. 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/44998. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43212] GRB 260616B: AstroSat CZTI detection
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44997 SUBJECT: GRB 260616B: AstroSat CZTI detection DATE: 26/06/19 12:22:02 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 (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 260616B which was also detected by Fermi/GBM (Fermi GBM team, GCN Circ. 44953), EP-WXT (D. Y. Li et. al., GCN Circ. 44956), CALET (Y. Asaoka et. al., GCN Circ. 44966), Konus-Wind (A. Ridnaia et. al., GCN Circ. 44968). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-06-16 07:05:27.69. The measured peak count rate associated with the burst is 543 (+46, -48) counts/s above the background in the combined data of all quadrants, with a total of 2787 (+162, -177) counts. The local mean background count rate was 277 (+2, -3) counts/s. We measure a T90 of 13 (+2, -1) s from the cumulative CZT light curve. The source was clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-06-16 07:05:27.10. The measured peak count rate associated with the burst is 1249 (+80, -86) counts/s above the background in the combined data of all quadrants, with a total of 5848 (+333, -346) counts. The local mean background count rate was 1225 (+5, -6) counts/s. We measure a T90 of 13 (+3, -1) s from the cumulative Veto light curve. CZTI data products like interactive and downloadable light curves for this GRB can be found at: https://astrosat.iucaa.in/cift/cift_products/ET20260616T070516/ET20260616T0… 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/44997. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43211] GRB 260616A: AstroSat CZTI detection
by GCN Circulars 19 Jun '26

19 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44996 SUBJECT: GRB 260616A: AstroSat CZTI detection DATE: 26/06/19 11:50:15 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> S.Salunke(IUCAA), Utkarsh Pathak(IITB), A. Goyal (IITB), A. Arya (IITB), Harsha K. H. (IUCAA), G. Waratkar (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 ML pipeline (Abraham et al., 2021, MNRAS, 504, 3084) and the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long, bright GRB 260616A which was also detected by Fermi/GBM (Fermi GBM team, GCN Circ. 44948), Fermi/LAT (S. Lopez et al., GCN Circ. 44960), GECAM-B (Hao-Xuan Guo et al., GCN Circ. 44964), Konus-Wind (A. Ridnaia et al., GCN Circ. 44967), Insight HXMT (Chen-Wei Wang et al., GCN Circ. 44980), NuSTAR(G. Waratkar et al., 44987). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-06-16 03:22:46.024. The measured peak count rate associated with the burst is 241 (+20, -9) counts/s above the background in the combined data of three quadrants (out of four), with a total of 16061 (+515, -588) counts. The local mean background count rate was 203 (+1, -2) counts/s. We measure a T90 of 113 (+5, -5) s from the cumulative CZT light curve. The source was clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-06-16 03:22:44.598. The measured peak count rate associated with the burst is 724 (+35, -35) counts/s above the background in the combined data of all quadrants, with a total of 45925.00 (+1118, -1178) counts. The local mean background count rate was 1290 (+2, -3) counts/s. We measure a T90 of 112 (+3, -4) s from the cumulative Veto light curve. In the preliminary analysis, we find 2989 Compton events associated with this event. CZTI data products like interactive and downloadable light curves for this GRB can be found at:https://astrosat.iucaa.in/cift/cift_products/ET20260616T032154/ET20260616T032154_details.html 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/44996. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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