July 2026 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 43324] EP260707a: LCOGT Optical Upper Limit
by GCN Circulars 07 Jul '26

07 Jul '26

TITLE: GCN CIRCULAR NUMBER: 45110 SUBJECT: EP260707a: LCOGT Optical Upper Limit DATE: 26/07/07 21:12:22 GMT FROM: Robert Strausbaugh at Eastern Illinois University <rstrausbaugh(a)eiu.edu> R. Strausbaugh (Eastern Illinois University), A. Cucchiara (NASA) report on behalf of a larger collaboration: We observed the EP260707a field (Zhou et al., GCN 45107) with the LCOGT 1-meter Sinistro instrument at the South African Astronomical Observatory site, on July 7, from 20:02 to 20:35 UT (corresponding to 3.28 to 3.83 hours after the trigger time) with the SDSS r and i filters. We performed a series of 3x300s exposures in i-band and r-band. We do not detect an uncatalogued source in the FXT error region, consistent with other optical upper limits (Liu et al., GCN 45109). The following magnitudes are calculated using the PanSTARRS catalog as reference: r > 22.1 i > 21.6 These magnitudes are not corrected for galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/45110. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43323] EP260707a: TRT optical upper limit
by GCN Circulars 07 Jul '26

07 Jul '26

TITLE: GCN CIRCULAR NUMBER: 45109 SUBJECT: EP260707a: TRT optical upper limit DATE: 26/07/07 19:33:31 GMT FROM: liuxing(a)nao.cas.cn X. Liu (NAOC), K. Noysena, K. Chanchaiworawit, S. Tinyanont (NARIT), S.Y. Fu (HUST), S.Q. Jiang, J. An, L.B. He, Z.P. Zhu, D. Xu (NAOC) report: We observed the field of EP260707a detected by EP (Zhou et al., GCN 45107) using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at New South Wales, Australia (SBO). 4x300s frames in the R-band were obtained at a median time of 1.52 hr post-trigger. No uncatalogued optical transient is detected in the stacked image within the EP/FXT error circle (Zhou et al., GCN 45107), down to a 5-sigma limiting magnitude of R ~ 21.0 (Vega), calibrated with Pan-STARRS DR2 stars in the field converted using Lupton (2005) equations and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/45109. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43322] Fermi GBM trigger 805087514/260707142 (GRB 260707A) is not a GRB
by GCN Circulars 07 Jul '26

07 Jul '26

TITLE: GCN CIRCULAR NUMBER: 45108 SUBJECT: Fermi GBM trigger 805087514/260707142 (GRB 260707A) is not a GRB DATE: 26/07/07 19:31:42 GMT FROM: Suman Bala at USRA <sumanbala2210(a)gmail.com> S. Bala (USRA) reports report on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 805087514/260707142 at 03:25:09.33 UT on 07 July 2026, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to Terrestrial Gamma-ray Flash (TGF)." View this GCN Circular online at https://gcn.nasa.gov/circulars/45108. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43321] EP260707a: Einstein Probe detection of an X-ray transient
by GCN Circulars 07 Jul '26

07 Jul '26

TITLE: GCN CIRCULAR NUMBER: 45107 SUBJECT: EP260707a: Einstein Probe detection of an X-ray transient DATE: 26/07/07 18:30:09 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. Zhou, Y. F. Liang (PMO), K. R. Ni (CCNU), C.-K. Kan (HKU), H. Sun (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 EP260707a. The transient triggered EP-WXT (ID: 01709274241) at 2026-07-07T16:45:24 (UTC). The WXT position of the source is R.A. = 306.233 deg, DEC = -26.589 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 automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 306.1900 deg, DEC = -26.5853 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). Further information will be updated when the telemetry data is received. 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/45107. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43320] Nova AT2026oyp (ASASSN-26dt): Pre-outburst Swift UVOT observation
by GCN Circulars 07 Jul '26

07 Jul '26

TITLE: GCN CIRCULAR NUMBER: 45106 SUBJECT: Nova AT2026oyp (ASASSN-26dt): Pre-outburst Swift UVOT observation DATE: 26/07/07 17:06:06 GMT FROM: Paul Kuin at MSSL <npkuin(a)gmail.com> The LMC nova AT2026oyp (ASASSN-26dt) was observed by Swift UVOT in the UVW1 filter on 2017-11-14 in a 54. s exposure. That predated the eruption reported in ATEL #17878 (Chomiuk et al.) and the nova was reported to have peaked at g=10.5 mag on 2026 June 11. The quescent magnitude in the UVOT UVW1 filter was UVW1 = 19.56 +/- 0.26 (stat) +/- 0.03 (sys) (AB) mag consistent with the other reported quiescent values, at a position RA = 00h 50m 45.11s, Dec = -71d 38m 38.51s (J2000) with uncertainty = +/- 1.05" (90% confidence) marginally consistent with the reported position at RA=01:50:45.142, Dec= -71:38:36.96. View this GCN Circular online at https://gcn.nasa.gov/circulars/45106. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43319] GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
by GCN Circulars 07 Jul '26

07 Jul '26

TITLE: GCN CIRCULAR NUMBER: 45105 SUBJECT: GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B DATE: 26/07/07 15:52:15 GMT FROM: James Freeburn at University of North Carolina at Chapel Hill <jamesfreeburn54(a)gmail.com> James Freeburn (UNC), Tomás Ahumada (NOIRLab), Jillian Rastinejad (UMD), Gokul Srinivasaragavan (UMD/Northwestern), Huei Sears (Rutgers), Anirudh Salgundi (UNC), report on behalf of a larger collaboration: We observed the field of GRB 260705A (SVOM burst-id sb26070502) detected by SVOM (Saccardi et al., GCN 45079) and Fermi (Hamburg et al., GCN 45080) using the SOAR and Gemini-South telescopes. We obtained 8 x 300 s of i-band imaging with SOAR using the Goodman High Throughput Spectrograph (SOAR2026A-018; PI: Andreoni) in imaging mode with the Red camera at a mid-time of 2026-07-07 10:19 UT, corresponding to ~45 hrs after the trigger. We performed SOAR data reduction with a custom pipeline using pre-reduced images from the Goodman pipeline (Torres et al. 2018). We obtained 4 x 120 s of r-band imaging at three different pointings using GMOS on Gemini-South (PI: Srinivasaragavan) at a mid-time of 2026-07-07 09:35 UT and performed image reduction with DRAGONS (Labrie et al. 2019). For both images, we performed image subtraction using SFFT (Hu et al. 2022) against DECam Legacy Survey images. The GMOS image covers ~77% of the SVOM localization (Saccardi et al., GCN 45079), while the resampled Goodman image covers ~65% of the localization. We detect a candidate optical counterpart at: R.A. (J2000) = 03:53:12.49 (58.30204 d) +/- 0.5’’ Dec. (J2000) = -31:39:08.61 (-31.65239 d) +/- 0.5’’ with AB magnitudes, calibrated with SkyMapper DR4 (Onken et al., 2024), of: r = 21.48 +/- 0.08 i = 21.44 +/- 0.04 These magnitudes have not been corrected for Galactic extinction of A_V = 0.028 mag. The brightness of this source is consistent with the upper limits found by LCO (Shi et al., GCN 45084), though these observations were taken ~30 hours prior. This candidate optical counterpart is embedded in a catalogued source, WISEA J035312.50-313908. WISEA J035312.50-313908.7 has no reported proper motion in Gaia DR3 (Gaia Collaboration 2022) and is classified as a ‘high-confidence galaxy’ in DES DR2 (Abbott et al. 2021), therefore we conclude the source is a galaxy. WISEA J035312.50-313908.7 has a photometric redshift of z = 0.178 +/- 0.009 from Legacy Survey DR10 (Duncan et al. 2022). The candidate optical counterpart is consistent with a nuclear origin with an offset of ~0.4” from the host center. We disfavor this counterpart as an AGN given the WISE color of W1-W2 = -0.05 (Cutri et al. 2013) and the absence of an AGN match in the Milliquas catalog (Flesch et al. 2023). We note that GRB 260705B, detected by Fermi (GCN 45081), has a localization consistent with GRB 260705A and was detected ~ 11 hr (~ 40,000 s) after. If these bursts are connected to the same source, this suggests a possible identification as an ultra-long GRB. The extended gamma-ray duration and nuclear location are also reminiscent of jetted TDEs (e.g., Swift J1644+57, Bloom et al. 2011; Swift J2058+05, Cenko et al. 2012; Swift J1112-82, Brown et al. 2015). Further observations are planned to assess the variability of this source. We thank the staff at Gemini-South and SOAR for their assistance with the observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/45105. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43318] GRB 260705C: Glowbug gamma-ray detection of a short burst
by GCN Circulars 07 Jul '26

07 Jul '26

TITLE: GCN CIRCULAR NUMBER: 45104 SUBJECT: GRB 260705C: Glowbug gamma-ray detection of a short burst DATE: 26/07/07 15:25:19 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 260705C, which was also detected by Fermi/GBM (GCN 45082). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-07-05 13:58:57.840 with a duration of 0.26 s and a total significance of about 19.5 sigma. The light curve comprises a single peak. 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/45104. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43317] GRB 260706A: SVOM/ECLAIRs refined analysis
by GCN Circulars 07 Jul '26

07 Jul '26

TITLE: GCN CIRCULAR NUMBER: 45103 SUBJECT: GRB 260706A: SVOM/ECLAIRs refined analysis DATE: 26/07/07 15:08:36 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Authors: S. Guillot, M. Brunet, J. Alaux (IRAP), F. Daigne, 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 260706A (SVOM Burst id sb26070606, GCN #45089) with trigger time T0 = 2026-07-06T16:12:23 UTC, which was also detected by Fermi/GBM (GCN #45088). The burst that triggered ECLAIRs onboard shows a multiple peak lightcurve, and the burst duration is T90 = 23.41 +0.64/-0.89 s in the 4-120 keV energy band. The time-averaged spectrum from T0 to T0+24 s in the 5-120 keV energy range is best fitted by a cut-off powerlaw model with alpha = -1.4 +/- 0.1 and Epeak = 38.1 +/- 6.4 keV. With this model, the 4-120 keV fluence is (3.5 +/- 0.3)e-6 erg/cm^2 and the 4-120 keV photon flux is 5.9 +/- 0.3 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: Sebastien Guillot (IRAP) (sebastien.guillot at utoulouse.fr) View this GCN Circular online at https://gcn.nasa.gov/circulars/45103. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43316] GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
by GCN Circulars 07 Jul '26

07 Jul '26

TITLE: GCN CIRCULAR NUMBER: 45102 SUBJECT: GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate DATE: 26/07/07 13:16:54 GMT FROM: F. Magnani at Aix-Marseille Université, CPPM/CNRS <francesco.magnani.work(a)gmail.com> GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate Noémie Globus (UNAM), Francesco Magnani (CPPM), Camila Angulo (UNAM), Jean-Grégoire Ducoin (CPPM), Nathaniel R. Butler (ASU), Stéphane Basa (UAR Pytheas), Jean-Luc Atteia (IRAP), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García-García (UNAM), Ramandeep Gill (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), Alan M. Watson (UNAM), W.J Xie (NAOC), Y. H. Cheng (YNU), C. Plasse (HKU), report: We imaged the field of the SVOM GRB 260704A (W.J Xie et al., GCN Circ. 45072) using the DDRAGO two-channel wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-07-05 07:25:02 to 11:20:12 UTC (from 27.7 to 31.7 hours after the trigger) and obtained 104 minutes of simultaneous exposure in the r and z filters. The data were reduced, coadded, and analyzed with the ASU 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. We tentatively detected a faint, uncatalogued source consistent with both the SVOM/MXT error circle (W.J. Xie et al., GCN Circ. 45072) and the EP/FXT error circle (Y.-H. I. Yin et al., GCN Circ. 45078) at: RA (J2000) = 21:14:51.52 = 318.71468 deg, Dec (J2000) = -25:30:29.4 = -25.50816 deg, with an estimated astrometric uncertainty of 0.5 arcsec. The preliminary unsubtracted magnitude derived for that source was: r = 23.54 ± 0.22 z = 22.70 ± 0.27 We reobserved from 2026-07-06 07:18:26 to 09:47:39 UTC (from 51.62 to 54.11 hours after the trigger) and obtained 111 minutes of simultaneous exposure in the r and z filters. Compared to our previous observations, the source has faded. The preliminary unsubtracted magnitude is: r = 24.08 ± 0.23 mag, z = 23.19 ± 0.28 mag. The detection of the source in two independent optical bands, together with its fading between the two observing epochs, makes it a possible candidate for the optical counterpart of the GRB. 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/45102. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43315] GRB 260706A: SVOM/GRM observation
by GCN Circulars 07 Jul '26

07 Jul '26

TITLE: GCN CIRCULAR NUMBER: 45101 SUBJECT: GRB 260706A: SVOM/GRM observation DATE: 26/07/07 12:40:33 GMT FROM: Yue Wang <m18509381757(a)163.com> SVOM/GRM team: Yue Wang, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Sebastien Guillot (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 260706A at 2026-07-06T16:12:22.000 (T0), which is also detected by SVOM/ECLAIRs (J. Alaux et. al., GCN #45089) and Fermi/GBM (Fermi GBM team, GCN #45088, #45093). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multiple peaks with a T90 of 31 +12/-8 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260706A.png In addition, the position of this burst, as determined by SVOM/ECLAIRs (RA = 33.8323 deg, Dec = -49.1375 deg, Error = 3.17 arcmin, GCN #45089), is used for the spectral analysis. With this localization, the time-averaged spectrum from T0-3.0 to T0+30.0 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.47 +0.16/-0.15 and the cutoff energy, parameterized as Epeak, is 53.98 +5.09/-4.96 keV. The event fluence (10-1000 keV) in this time interval is (3.96 +0.21/-0.19)E-06 erg/cm^2. The localization of GRB 260706A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260706A_amati.png The localization of GRB 260706A in the 'Yonetoku' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260706A_yonetoku.png 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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Yue Wang (IHEP) (yuewang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/45101. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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