July 2025 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 39180] LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
by GCN Circulars 20 Jul '25

20 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41124 SUBJECT: LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate DATE: 25/07/20 03:09:16 GMT FROM: Sourav Das at IUCAA <sourav.das(a)iucaa.in> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: The trigger S250720j is no longer considered to be a candidate of interest. The significance arose from a coincidence with a Fermi GRB trigger. Further analysis by Fermi showed that the event was not a GRB [1]. [1] R. Hamburg, et al., GCN Circ. 41123 (https://gcn.nasa.gov/circulars/41123) View this GCN Circular online at https://gcn.nasa.gov/circulars/41124. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39179] Fermi Gamma-ray Burst Monitor trigger 774670514/250720094 is not a GRB
by GCN Circulars 20 Jul '25

20 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41123 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 774670514/250720094 is not a GRB DATE: 25/07/20 02:42:21 GMT FROM: rhamburg(a)usra.edu R. Hamburg (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 774670514/250720094 at 02:15:09.73 UT on 20 July 2025, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to local particles." View this GCN Circular online at https://gcn.nasa.gov/circulars/41123. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39178] EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
by GCN Circulars 19 Jul '25

19 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41122 SUBJECT: EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit DATE: 25/07/19 15:21:36 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, 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) report on behalf of the SVOM mission team. SVOM/VT conducted two ToO follow-up observations of EP250702a (Cheng et al., GCNs 40906, 40917), which was likely associated with the long burst GRB250702B,D,E (Fermi GBM Team, GCNs 40883, 40886, 40890; DeLaunay et al., GCN 40903; Frederiks et al., GCN 40914; Wang et al., GCN 40923). The first observation was made on July 3, 2025 in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously, between 10:54:08 and 15:10:00 (UTC), 32.0 to 36.3 hours after the EP/WXT trigger (Cheng et al., GCN 40906). The second one was made on July 5, 2025, between 08:56:18 and 15:41:13, 3.25 days to 3.53 days after the EP/WXT trigger (Cheng et al., GCN 40906). The counterpart detected by VLT (Martin-Carrillo et al., GCN 40924; Levan et al., GCN 40961), MOSFIRE (Sharma et al., GCN 41044), HST (Levan et al., GCN 41096), MeerKAT (Bright et al., GCN 40985), VLA (Sfaradi et al., GCN 41053) and ALMA (Alexander et al., GCN 41059) was not detected in our images for both observations. The 3 sigma upper limit magnitudes were estimated: Mid-time | Exposure time | Band | upper limit (AB) 34.2 hours | 80*100 sec | VT_R | 23.6 34.2 hours | 81*100 sec | VT_B | 23.8 3.53 days | 81*100 sec | VT_R | 23.6 3.53 days | 81*100 sec | VT_B | 23.8 The Mid-time above is the relative time from the trigger time of EP/WXT (Cheng et al., GCN 40906). The result is consistent with the optical upper limit from GOTO (Kumar et al., GCN 40908), MASTER (Lipunov et al., GCN 40912), Colibri (Becerra et al., GCN 40918), CAHA (Pérez-García et al., GCN 40929), WFST (Hua et al., GCN 40943), FTW (Busmann et al., GCN 40949), UVOT (Siegel et al., GCN 40952), SYSU (Li et al., GCN 40986) and GRANDMA(Akl et al., GCN 41016). 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/41122. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39177] GRB 250717B: COLIBRÍ optical upper limit
by GCN Circulars 18 Jul '25

18 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41121 SUBJECT: GRB 250717B: COLIBRÍ optical upper limit DATE: 25/07/18 21:30:53 GMT FROM: Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra(a)roma2.infn.it> Enrique Moreno Méndez (UNAM), Francis Fortin (IRAP), Rosa L. Becerra (U Roma), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Fredd Alvarez (UNAM), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM): We imaged the field of the Fermi/GBM GRB 250717B (Fermi GBM Team et al., GCN Circ. 41107) at the Swift/BAT-GUANO localization (Ronchini et al., GCN Circ. 41110) using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2025-07-18 09:16 to 11:31 UTC (from 19.5 to 21.8 hours after the trigger) and obtained 101 minutes of exposure in the i filter. The data were reduced and coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1, 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 Swift/BAT-GUANO error region (Ronchini et al., GCN Circ. 41110), including the XRT candidate position (Dichiara et al., GCN Circ. 41119) down to the following 5-sigma limit: i > 21.8 We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. 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/41121. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39176] LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
by GCN Circulars 18 Jul '25

18 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41120 SUBJECT: LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO DATE: 25/07/18 19:06:21 GMT FROM: Maia Williams at PSU <mjw6837(a)psu.edu> Maia Williams (PSU), Samuele Ronchini (PSU), Gayathri Raman, James DeLaunay (PSU), Tyler Parsotan (NASA GSFC), Jamie A. Kennea (PSU), Aaron Tohuvavohu (Caltech) report: Swift/BAT was observing 73.58% of the GW localization probability ([bayestar.multiorder.fits](https://gracedb.ligo.org/api/superevents/S250711q…) at merger time. A fraction 58.56% of the GW localization posterior is contained inside the BAT coded FoV. The LVK notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; [Tohuvavohu et al. 2020, ApJ, 900, 1](https://iopscience.iop.org/article/10.3847/1538-4357/aba94f)) Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground. Using the NITRATES analysis ([DeLaunay + Tohuvavohu 2022, ApJ, 941, 169](https://iopscience.iop.org/article/10.3847/1538-4357/ac9d38)) we searched for emission on 8 timescales from 0.128s to 16.384s in the interval [-20,+20] seconds around the merger time. We find no evidence for a signal, and derive the following upper limits. We quote the 5-sigma flux upper limits in the 15-350 keV band, weighted over the GW localization, for four spectral templates (soft, normal, and hard GRB-like templates described in [arXiv:1612.02395], and spectral shape from GRB170817A [arXiv:1710.05446]) and for four time bins. In units of 10^-7 erg/s/cm^2: |time_bin (s) |soft |normal|hard |GRB170817 |-|-|-|-|-| |0.256 |3.27 |2.72 |2.52 |2.89 |1.024 |1.67 |1.39 |1.29 |1.48 |4.096 |0.90 |0.75 |0.70 |0.80 |16.384 |0.57 |0.47 |0.44 |0.50 The upper limits as function of sky position are plotted here, alongside the GW localization: https://zenodo.org/records/16106142 The solid and dashed lines indicate the 90% and 50% GW contour levels, respectively. The corresponding fits file is also included. GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches. A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/ View this GCN Circular online at https://gcn.nasa.gov/circulars/41120. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39175] GRB 250717B: Swift-XRT observations
by GCN Circulars 18 Jul '25

18 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41119 SUBJECT: GRB 250717B: Swift-XRT observations DATE: 25/07/18 16:03:37 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> S. Dichiara (PSU), J.A. Kennea (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), S. Campana (INAF-OAB), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), D.N. Burrows (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Fermi/GBM-detected burst GRB 250717B, collecting 2.8 ks of Photon Counting (PC) mode data between T0+27.9 ks and T0+34.0 ks. One uncatalogued X-ray source has been detected within the estimated BAT-GUANO error region (3 arcmin), it is below the RASS limit and shows no definitive signs of fading. Therefore, at the present time we cannot confirm this as the afterglow. Details of this source are given below: Source 1: RA (J2000.0): 44.1037 = 02:56:24.88 Dec (J2000.0): +26.3758 = +26:22:32.8 Error: 8.9 arcsec (radius, 90% conf.) Count-rate: (1.90 [+1.27, -0.91])e-3 ct s^-1 Distance: 47 arcsec from BAT-GUANO position. The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/ToO_GRBs/00021846. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41119. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39174] GRB 250717B: Swift-XRT observations
by GCN Circulars 18 Jul '25

18 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41119 SUBJECT: GRB 250717B: Swift-XRT observations DATE: 25/07/18 16:03:37 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> S. Dichiara (PSU), J.A. Kennea (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), S. Campana (INAF-OAB), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), D.N. Burrows (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Fermi/GBM-detected burst GRB 250717B, collecting 2.8 ks of Photon Counting (PC) mode data between T0+27.9 ks and T0+34.0 ks. One uncatalogued X-ray source has been detected within the estimated BAT-GUANO error region (3 arcmin), it is below the RASS limit and shows no definitive signs of fading. Therefore, at the present time we cannot confirm this as the afterglow. Details of this source are given below: Source 1: RA (J2000.0): 44.1037 = 02:56:24.88 Dec (J2000.0): +26.3758 = +26:22:32.8 Error: 8.9 arcsec (radius, 90% conf.) Count-rate: (1.90 [+1.27, -0.91])e-3 ct s^-1 Distance: 47 arcsec from BAT-GUANO position. The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/ToO_GRBs/00021846. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41119. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39173] GRB 250718B: Fermi GBM Final Localization Correction
by GCN Circulars 18 Jul '25

18 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41118 SUBJECT: GRB 250718B: Fermi GBM Final Localization Correction DATE: 25/07/18 09:55:46 GMT FROM: Marianna Dafčíková at Masaryk University <500025(a)mail.muni.cz> The Fermi GBM team reports the detection of a likely SHORT GRB "At 07:05:40.09 UT on 18 July 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250718B (trigger 774515145/250718296) which was initially named GRB 250718A (GCN 41117). The updated on-ground calculated location, using the Fermi GBM trigger data, is RA = 213.5, Dec = 1.7 (J2000 degrees, equivalent to J2000 14h 14m, 01d 40'), with a statistical uncertainty of 11.2 degrees. The angle from the Fermi LAT boresight is 87 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250718296/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250718296/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250718296/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/41118. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39172] GRB 250718A: Fermi GBM Final Real-time Localization
by GCN Circulars 18 Jul '25

18 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41117 SUBJECT: GRB 250718A: Fermi GBM Final Real-time Localization DATE: 25/07/18 07:16:14 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 SHORT GRB At 07:05:40 UT on 18 Jul 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250718A (trigger 774515145.094648 / 250718296). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 233.0, Dec = -26.0 (J2000 degrees, equivalent to J2000 15h 31m, -26d 00'), with a statistical uncertainty of 20.3 degrees. The angle from the Fermi LAT boresight is 119.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250718296/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250718296/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250718296/… View this GCN Circular online at https://gcn.nasa.gov/circulars/41117. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39171] Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
by GCN Circulars 18 Jul '25

18 Jul '25

TITLE: GCN CIRCULAR NUMBER: 41116 SUBJECT: Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits DATE: 25/07/18 05:24:16 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Enrique Moreno Méndez (UNAM), Francis Fortin (IRAP), Camila Angulo (UNAM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Fredd Alvarez (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Leonardo García García (UNAM), Noémie Globus (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Kin Ocelotl López (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM): We imaged the field of Swift Trigger 1334535 (Siegel et al, GCN Circ. 41115), possibly GRB 250718A, using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2025-07-18 03:52 to 04:30 UTC (from 3:38 to 4:16 hours after the trigger at 00:14 UTC) and obtained 32 minutes of exposure in the i filter. The data were reduced and coadded with the COLIBRÍ pipeline and analysed 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. In the stacked image, after subtracting the a template image from Legacy Survey DR10 (Dey et al. 2019), we do not detect any new source in the BAT uncertainty region (Siegel et al, GCN Circ. 41115) down to the following 5-sigma limit: i > 22.7 Our results are compatible with the earlier upper limit reported by Lipunov et al. (GCN Circ. 41114). We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. 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/41116. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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