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

[vsnet-grb-info 42977] GRB 260604A: Glowbug gamma-ray detection
by GCN Circulars 05 Jun '26

05 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44845 SUBJECT: GRB 260604A: Glowbug gamma-ray detection DATE: 26/06/05 22:03:48 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung(a)nrl.navy.mil> C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report: The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 260604A, which was also detected by Fermi/GBM (GCN 44812). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-06-04 02:24:24.648 with a duration of 4.1 s and a total significance of about 9.8 sigma. The light curve comprises a single peak. Note that data from ~T0-5s to +1s suffered from deadtime in various detectors. The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12. [1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108 Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/44845. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42976] GRB 260604C: LCO optical upper limit
by GCN Circulars 05 Jun '26

05 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44844 SUBJECT: GRB 260604C: LCO optical upper limit DATE: 26/06/05 21:22:48 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> A. Saccardi (CEA/Irfu), D. B. Malesani (DAWN/NBI and Radboud), S. Bisero (CEA/Irfu) report on behalf of the SVOM mission team: We observed the field of GRB 260604C (Fermi GBM Team, GCN 44822; Gotz et al., GCN 44823) with the LCO 1m telescope at South African Astronomical Observatory equipped with the Sinistro instrument. Our observation started on 2026-06-05 at 20:08:32 UT (about 1 day after the trigger) and we obtained 3x200 s exposures in the SDSS r filter. In the stacked image we do not detect the optical counterpart (Lipunov et al., GCN 44827; Konno et al., GCN 44828; Zhu et al., GCN 44832, Becerra et al., GCN 44834; Hellot et al., GCN 44835; Gompertz et al., GCN 44837; Gompertz et al., GCN 44843). We measure the following upper limit calibrated against the Pan-STARRS catalog, and not corrected for Galactic extinction: r > 21.8 AB (3-sigma, mid-time 0.997 days after the trigger). This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/44844. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42975] GRB 260604C: Liverpool Telescope optical detection
by GCN Circulars 05 Jun '26

05 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44843 SUBJECT: GRB 260604C: Liverpool Telescope optical detection DATE: 26/06/05 14:01:06 GMT FROM: Dimple at University of Birmingham <dimplepanchal96(a)gmail.com> B. P. Gompertz (U. Birmingham), D. B. Malesani (DAWN/NBI and Radboud) and Dimple (U. Birmingham) report on behalf of a larger collaboration: We conducted follow-up observations of GRB 260604C (Fermi Team, GCN Circ. 44822, Gotz et al., GCN Circ. 44823) with the IO:O camera on the 2m robotic Liverpool Telescope (LT). Observations began at 00:14:01 UT on 2026-06-05, ~3.92 hr after the burst, and consisted of 5 x 120 s exposures in each of the SDSS r, g, i and z filters. We detect the optical counterpart (Lipunov et al., GCN 44827; Konno et al., GCN 44828; Zhu et al., GCN 44832, Becerra et al., GCN 44834; Hellot et al., GCN 44835; Gompertz et al. 44837) in all the filters, and measure an AB magnitude of r = 18.60 ± 0.05. Magnitudes are calibrated against nearby Pan-STARRS stars and are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44843. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42974] The EP-WXT trigger 01709267001 is likely a flaring star
by GCN Circulars 05 Jun '26

05 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44842 SUBJECT: The EP-WXT trigger 01709267001 is likely a flaring star DATE: 26/06/05 12:57:39 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R.-Z. Li (YNAO), X. Tian (GXU), C.-L. Guo and C.-C. Jin (NAOC) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709267001 at the time of 2026-06-05T12:42:11, is likely a stellar flare associated with RX J1431.6+0047 (High Proper Motion Star). The estimated flux of the flare is around 1.8 x 10^(-10) erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 4.8 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/44842. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42973] EP260602d: EP-FXT follow-up observation
by GCN Circulars 05 Jun '26

05 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44841 SUBJECT: EP260602d: EP-FXT follow-up observation DATE: 26/06/05 12:47:27 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> J.Y. Cao, Z. X. Li, G. L. Huang, (IHEP, CAS), J. W. Hu, Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team: The X-ray transient EP260602d was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Cao et al., GCN 44796) at 2026-06-02T21:13:25 (UTC). Follow-up observation by the Follow-up X-ray Telescope (FXT) on board EP was performed at 2026-06-04T04:27:19(UTC), ~31 hours after the WXT detection. The exposure time of the observation is around 4 ks. The on-ground analysis of the FXT data found a source within the error circle of WXT at R.A. = 267.9681 deg, DEC = 18.1658 deg (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic) which have no historical X-ray source within 10 arcsec. The average FXT 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 6.7×10^20 cm^-2, and a photon index of 0.8 (-0.3, +0.4). The derived average unabsorbed 0.5-10 keV flux is 3.2 (-1.2, +1.8) ×10^(-14) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. Since this source is below the RASS upper limit and shows no significant fading, we cannot identify it as the counterpart of EP260602d at present. The optical and infrared follow-up observations were performed by A. Aryan et al. (GCN 44813) and Tanishk Mohan et al. (GCN 44830) without detection. 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/44841. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42972] EP260602c: EP-FXT follow-up observation
by GCN Circulars 05 Jun '26

05 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44840 SUBJECT: EP260602c: EP-FXT follow-up observation DATE: 26/06/05 11:56:50 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> EP260602c: EP-FXT follow-up observation J.Y. Cao, Z. X. Li, G. L. Huang, (IHEP, CAS), J. W. Hu, Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team: The X-ray transient EP260602c was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Cao et al., GCN 44792) at 2026-06-02T09:06:44 (UTC). Follow-up observation by the Follow-up X-ray Telescope (FXT) on board EP was performed at 2026-06-03T18:37:43(UTC), ~33 hours after the WXT detection. The exposure time of the observation is around 4 ks. The on-ground analysis of the FX-A data found three sources within the error circle of WXT. Source 1 is at R.A. = 134.8551 deg, DEC = -75.673 deg (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). This position is 12 arcsec from a known X-ray source 1eRASS J085924.9-754010 with the historical flux of 1.8 ×10^(-14) erg/s/cm^2 in 0.3-2.3 keV band. The average FXT 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 8×10^20 cm^-2, and a photon index of 1.9 (-1.2, +1.2). The observed 0.5-10.0 keV flux is 9.1 (+/-2.9) ×10^(-14) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. Source 2 is at R.A. = 134.5839 deg, DEC = -75.7147 deg (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). This position is 5 arcsec from a known X-ray source 1eRASS J085820.6-754257 with the historical flux of 2.0 ×10^(-14) erg/s/cm^2 in 0.3-2.3 keV band. The average FXT 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 8×10^20 cm^-2, and a photon index of 0.13 (-0.68, +0.61). The observed 0.5-10.0 keV flux is 5.1 (+/-2.0) ×10^(-14) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. Source 3 is at R.A. = 134.5079 deg, DEC = -75.6493 deg (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic) which have no historical X-ray source within 10 arcsec. The average FXT 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 8×10^20 cm^-2, and a photon index of 3.1 (-1.3, +1.7). The observed 0.5-10.0 keV flux is 3.51 (+/-1.6) ×10^(-14) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. Since none of them is significantly above the eRASS1 upper limit or shows fading trends, we cannot identify the counterpart of EP260602c at present. 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/44840. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42971] GRB 260601B / EP260601a: AstroSat CZTI detection
by GCN Circulars 05 Jun '26

05 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44839 SUBJECT: GRB 260601B / EP260601a: AstroSat CZTI detection DATE: 26/06/05 11:44:11 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> A. Arya (IITB), A. Goyal (IITB), Harsha K. H. (IUCAA), S. Salunke (IUCAA), M. Tembhurnikar (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 260601B, associated with EP260601a, which was also detected by Einstein Probe / WXT (Yang et. al., GCN Circ. 44766), GECAM-C (Yu et al., GCN Circ. 44767), NuSTAR (Waratkar et. al. , GCN Circ. 44771), CALET (Sugita et. al., GCN Circ. 44773), and Insight HXMT (Wang et. al., GCN Circ. 44785). 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 2026-06-01 19:12:50.54 UTC. AstroSat was departing the South Atlantic Anomaly (SAA) region and hence the background rates were higher. The measured peak count rate associated with the burst is 498 (+39, -46) counts/s above the background in the combined data of three quadrants (out of four), with a total of 12100 (+491, -799) counts. The local mean background count rate was 278 (+4, -4) counts/s. Using cumulative rates, we measure a T90 of 54 (+2, -2) s. The source was also 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 2026-06-01 19:12:50.66 UTC. The measured peak count rate associated with the burst is 1468 (+92, -129) counts/s above the background in the combined data of four quadrants, with a total of 29202 (+2008, -3307) counts. The local mean background count rate was 1805 (+20, -8) counts/s. We measure a T90 of 51 (+1, -2) 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/ET20260601T191246/ET20260601T1… 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/44839. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42970] GRB 260527A/EP260527a: 6 GHz VLA observations
by GCN Circulars 05 Jun '26

05 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44838 SUBJECT: GRB 260527A/EP260527a: 6 GHz VLA observations DATE: 26/06/05 10:05:25 GMT FROM: muskan.yadav(a)students.uniroma2.eu M. Yadav, R. Ricci, E. Troja (U Rome) report: We observed the field of EP260527a (Yang et al., GCN 44718), likely associated with the short GRB 260527A (Svinkin et al., GCN 44722, Yu et al., GCN 44724; Kawakubo et al., GCN 44726, Wang et al., GCN 44735, Svinkin et al., GCN 44744, Cheung et al., GCN 44757) with Very Large Array in C-band at the centre frequency of 6 GHz with a bandwidth of 4 GHz in two epochs on May 29th 2026 (2.01 days after the trigger) and June 4th 2026 (8.05 days after the trigger). Data were calibrated and imaged using standard procedures in CASA (6.6.6.18). 1331+305 (3C286) was used for flux density and bandpass calibration and J1224+0330 was used for complex gain calibration. The radio source reported by Schroeder et al. (GCN 44740) is detected in our first epoch at a consistent position and flux level, and is seen to fade below detection threshold in our second epoch, yielding a preliminary 3-sigma upper limit of ~30 uJy/beam. We therefore confirm this source as the radio counterpart of EP260527a. We thank the VLA staff for executing the observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/44838. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42969] GRB 260604C: GOTO detections of the optical afterglow
by GCN Circulars 05 Jun '26

05 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44837 SUBJECT: GRB 260604C: GOTO detections of the optical afterglow DATE: 26/06/05 09:47:43 GMT FROM: Ben Gompertz at U of Birmingham <b.gompertz(a)bham.ac.uk> B. P. Gompertz, S. Moran, D. O’Neill, A. Kumar, G. Ramsay, R. Starling, K. Ackley, M. Dyer, J. Lyman, K. Ulaczyk, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, B. Godson, T. Killestein and M. Pursiainen, on behalf of the GOTO collaboration: We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to GRB 260604C, discovered by Fermi/GBM and SVOM (Fermi GBM Team, GCN 44822; Gotz et al., GCN 44823). Observations were taken in the GOTO-L filter (400 - 700nm) with 4x90s exposures. Images were processed immediately after acquisition using the GOTO pipeline. The optical counterpart (Lipunov et al., GCN 44827; Konno et al., GCN 44828; Zhu et al., GCN 44832, Becerra et al., GCN 44834; Hellot et al., GCN 44835) was detected in three epochs: | mid-time(UT) | t-t0(hr) | ABmag | | 2026-06-04 23:46:15 | 3.46 | 18.45 ± 0.04 | | 2026-06-05 00:54:05 | 4.59 | 18.70 ± 0.08 | | 2026-06-05 02:00:28 | 5.70 | 19.06 ± 0.12 | Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester, the University of Birmingham and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/44837. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42968] GRB 260604C: Correction to GCN 44828
by GCN Circulars 05 Jun '26

05 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44836 SUBJECT: GRB 260604C: Correction to GCN 44828 DATE: 26/06/05 08:46:15 GMT FROM: Ruslan Konno at Weizmann Institute of Science <ruslankonno(a)gmail.com> R. Konno (WIS), S. Garrappa (WIS), E. A. Zimmerman (WIS), A. Horowicz (WIS), E. O. Ofek (WIS), S. Ben-Ami (WIS), D. Polishook (WIS), O. Yaron (WIS), S. Fainer (WIS), A. Krassilchtchikov (WIS), Y. M. Shani (WIS), E. Segre (WIS), A. Gal-Yam (WIS), and S. Spitzer (WIS) report on behalf of the LAST Collaboration. This is a correction to the GCN Circular "GRB 260604C: LAST detection of optical counterpart candidate" (GCN 44828). The photometry within the circular was erroneously listed in the reverse order. The correct photometry is | Tmid-T0 (h) | Mag (AB) | | ------------ | ------------ | | 0.33 | 16.42 +/- 0.02 | | 0.45 | 16.63 +/- 0.02 | | 0.57 | 16.85 +/- 0.02 | | 0.75 | 17.12 +/- 0.02 | A correction of the archival circular has been requested, apologies for any confusion. View this GCN Circular online at https://gcn.nasa.gov/circulars/44836. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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