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

[vsnet-grb-info 38911] LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
by GCN Circulars 29 Jun '25

29 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40867 SUBJECT: LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate DATE: 25/06/29 06:56:02 GMT FROM: 林峻哲Lin, Chun-Che <lupin(a)phys.ncku.edu.tw> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S250629ae during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2025-06-29 05:50:36.925 UTC (GPS time: 1435211454.925). The candidate was found by the cWB [1], cWB BBH [2], GstLAL [3], MBTA [4], and PyCBC Live [5] analysis pipelines. S250629ae is an event of interest because its false alarm rate, as estimated by the online analysis, is 3.2e-08 Hz, or about one in 11 months. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250629ae The classification of the GW signal, in order of descending probability, is BBH (98%), Terrestrial (2%), NSBH (<1%), or BNS (<1%). Assuming the candidate is astrophysical in origin, the probability that at least one of the compact objects is consistent with a neutron star mass (HasNS) is <1%. [6] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [6] Both HasNS and HasRemnant consider the support of several neutron star equations of state for maximum neutron star mass. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. The source chirp mass falls with highest probability in the bin (22.0, 44.0) solar masses, assuming the candidate is astrophysical in origin. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [7], distributed via GCN and SCiMMA notices about 40 seconds after the candidate event time. * bayestar.multiorder.fits,2, an initial localization generated by BAYESTAR [7], distributed via GCN and SCiMMA notices about 5 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,2. For the bayestar.multiorder.fits,2 sky map, the 90% credible region is 3184 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 4550 +/- 1295 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Klimenko et al. PRD 93, 042004 (2016) doi:10.1103/PhysRevD.93.042004 [2] T. Mishra et al. PRD 105, 083018 (2022) doi:10.1103/PhysRevD.105.083018 [3] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. PRD 109, 042008 (2024) doi:10.1103/PhysRevD.109.042008 [4] Alléné et al. CQG 42, 105009 (2025) doi:10.1088/1361-6382/add234 [5] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a [6] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [7] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/40867. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38910] LIGO/Virgo/KAGRA S250628am: Updated Sky localization
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40866 SUBJECT: LIGO/Virgo/KAGRA S250628am: Updated Sky localization DATE: 25/06/28 21:09:56 GMT FROM: Aditya Vijaykumar <aditya.vijaykumar(a)ligo.org> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S250628am (GCN Circular 40863). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN and SCiMMA notices, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S250628am For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 287 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 902 +/- 223 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. PRD 108, 123040 (2023) doi:10.1103/PhysRevD.108.123040 View this GCN Circular online at https://gcn.nasa.gov/circulars/40866. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38909] GRB 250628A: REM optical/NIR upper limits
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40865 SUBJECT: GRB 250628A: REM optical/NIR upper limits DATE: 25/06/28 20:02:00 GMT FROM: Matteo Ferro at INAF-OAB <matteo.ferro(a)inaf.it> R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of GRB 250628A detected by Swift/BAT (Ferro et al., GCN 40853) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, and H bands, started on 2025 June 28 at 06:17:20 UT (i.e. 5.4 hr after the burst), and lasted for about 1 hour. From preliminary inspection, we do not detect any possible counterpart within the Swift/XRT error region (Evans et al., GCN 40854) down to the following 3sigma limits: r > 20.1 (AB; calibrated against the SkyMapper catalogue), at a mid-time of 5.9 hr after the trigger; H > 14.8 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 5.4 hr after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/40865. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38908] GRB 250628C: Fermi GBM Final Real-time Localization
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40864 SUBJECT: GRB 250628C: Fermi GBM Final Real-time Localization DATE: 25/06/28 19:25:46 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 19:15:16 UT on 28 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250628C (trigger 772830921.339792 / 250628802). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 169.9, Dec = -6.9 (J2000 degrees, equivalent to J2000 11h 19m, -6d 54'), with a statistical uncertainty of 3.7 degrees. The angle from the Fermi LAT boresight is 11.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250628802/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250628802/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250628802/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40864. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38907] LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40863 SUBJECT: LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate DATE: 25/06/28 19:08:45 GMT FROM: F. Llamas <francisco.llamas(a)ligo.org> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S250628am during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2025-06-28 18:23:19.785 UTC (GPS time: 1435170217.785). The candidate was found by the cWB [1], cWB BBH [2], GstLAL [3], MBTA [4], PyCBC Live [5], and SPIIR [6] analysis pipelines. S250628am is an event of interest because its false alarm rate, as estimated by the online analysis, is 1.7e-14 Hz, or about one in 1e6 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250628am The classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), NSBH (<1%), or BNS (<1%). Assuming the candidate is astrophysical in origin, the probability that at least one of the compact objects is consistent with a neutron star mass (HasNS) is <1%. [7] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [7] Both HasNS and HasRemnant consider the support of several neutron star equations of state for maximum neutron star mass. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. The source chirp mass falls with highest probability in the bin (5.5, 11.0) solar masses, assuming the candidate is astrophysical in origin. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [8], distributed via GCN and SCiMMA notices about 32 seconds after the candidate event time. * bayestar.multiorder.fits,2, an initial localization generated by BAYESTAR [8], distributed via GCN and SCiMMA notices about 5 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,2. For the bayestar.multiorder.fits,2 sky map, the 90% credible region is 427 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1112 +/- 273 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Klimenko et al. PRD 93, 042004 (2016) doi:10.1103/PhysRevD.93.042004 [2] T. Mishra et al. PRD 105, 083018 (2022) doi:10.1103/PhysRevD.105.083018 [3] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. PRD 109, 042008 (2024) doi:10.1103/PhysRevD.109.042008 [4] Alléné et al. CQG 42, 105009 (2025) doi:10.1088/1361-6382/add234 [5] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a [6] Chu et al. PRD 105, 024023 (2022) doi:10.1103/PhysRevD.105.024023 [7] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [8] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/40863. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38906] GRB 250628B: SVOM detection of a long burst
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40862 SUBJECT: GRB 250628B: SVOM detection of a long burst DATE: 25/06/28 17:30:16 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> D. Dornic, J-G. Ducoin, J-L. Atteia, O. Godet, C. Plasse, report on behalf of the SVOM mission team: At 2025-06-28T16:29:30 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 250628B (SVOM burst-id sb25062804). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was only detected by the Image Trigger (IMT), which produced a sequence of 1 alert. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 6.90 in the [5-20] keV energy band over a time window of 20.48 seconds starting at 2025-06-28T16:29:10. The localization of the best alert is R.A., Dec. 333.1563, -45.5663 degrees: R.A. (J2000) = 22h12m37.51s Dec. (J2000) = -45d33m58.52s with a 90% confidence level (C.L.) radius of 11.33 arcmin (including systematic error of 2 arcmin added in quadrature). The SVOM/ECLAIRs light curve showed a single/multiple broad/narrow peak structure with a T90 duration of about 33.51s (-3.02 +4.13). Due to the detection significance being below the slew threshold, no immediate slew was performed on this burst. A SVOM ToO has been programmed for follow-up. No X-ray observation could be performed by SVOM/MXT for the time being.No optical observation could be performed by SVOM/VT for the time being. 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. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is Dornic Damien: dornic(a)cppm.in2p3.fr. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/40862. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38905] Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40861 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB DATE: 25/06/28 16:15:00 GMT FROM: Jacob Smith at Fermi-GBM Team <jrs0118(a)uah.edu> Jacob Smith (UAH) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 772811638/250628579 at 13:53:53.18 UT on 28 June 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/40861. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38904] GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40860 SUBJECT: GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position DATE: 25/06/28 14:57:40 GMT FROM: J. An <jiean0813(a)foxmail.com> J. An (NAOC), B. Schneider (LAM), L. Izzo (INAF/OAC), R. Brivio (INAF/OABr), G. Corcoran (UCD), A. de Ugarte Postigo (LAM), B. P. Gompertz (Birmingham), A. J. Levan (Radboud and Warwick), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), report on behalf of a larger collaboration: We observed the optical afterglow of GRB 250625A detected by Fermi/GBM (Godwin et al., GCN 40833) and Swift/BAT (Ferro et al., GCN 40825) using the ESO VLT UT3 (Melipal) equipped with the X-shooter spectrograph. Our spectra cover the wavelength range 3000-21000 AA, and consist of 4 exposures of 1200 s each. The observation mid time was 2025 Jun 27.128 UT (34.98 hr after the GRB). The slit was aligned to cover the optical afterglow (Moskvitin et al., GCN 40828; Xin et al., GCN 40830; Zhu et al., GCN 40834; Fortin et al., GCN 40837; Adami et al., GCN 40838; Brosio et al., GCN 40839; de Ugarte Postigo et al., GCN 40486). In a preliminary reduction of the spectra, we detect no obvious continuum nor any emission lines across the entire covered wavelength range. This could simply indicate that the emission lines of the actual (faint) GRB host galaxy are below our detection sensitivity, or, alternatively, would be consistent with an association with the nearby galaxy at z = 0.655 reported by de Ugarte Postigo et al. (GCN 40486). We acknowledge excellent support from the ESO observing staff in Paranal, in particular Célia Desgrange, Rodrigo Palominos, and Boris Häußler. We also thank Liping Xin (NAOC) and the SVOM/VT team for sharing accurate coordinates of the afterglow (see also GCN 40830). View this GCN Circular online at https://gcn.nasa.gov/circulars/40860. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38903] GRB 250628A: VLT/X-shooter upper limits
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40859 SUBJECT: GRB 250628A: VLT/X-shooter upper limits DATE: 25/06/28 14:12:36 GMT FROM: Riccardo Brivio at INAF-OAB <riccardo.brivio(a)inaf.it> R. Brivio (INAF-OABr), A. Martin-Carrillo (UCD), G. Corcoran (UCD), L. Izzo (INAF/OAC), A. Rossi (INAF/OAS), D. B. Malesani (DAWN/NBI and Radboud), N. R. Tanvir (Leicester) report on behalf of the Stargate collaboration: We observed the field of GRB 250628A detected by Swift/BAT (Ferro et al., GCN 40853) using the ESO VLT UT3 (Melipal) equipped with the X-shooter acquisition camera. A short sequence of imaging was secured in the r (3x30 s), g (3x40 s), and z (3x60 s) bands. No afterglow is detected within the Swift/XRT enhanced error region (Evans et al., GCN 40854). From preliminary analysis, we measure the following 3sigma upper limits, calibrated against nearby stars from the Legacy Survey (DR9): g > 23.7 (AB) on Jun 28 at 08:51:48 UT (7.93 hr after the GRB trigger), r > 23.6 (AB) on Jun 28 at 08:45:04 UT (7.82 hr after the GRB trigger), z > 22.8 (AB) on Jun 28 at 08:48:21 UT (7.87 hr after the GRB trigger). We note the detection of significant excess absorption in the X-ray spectrum (Evans, GCN 40857; https://www.swift.ac.uk/xrt_spectra/01328546/). This argues against a high-redshift origin for GRB 250628A and likely indicates some dust extinction. We acknowledge excellent support from the ESO observing staff in Paranal, in particular Boris Häußler. View this GCN Circular online at https://gcn.nasa.gov/circulars/40859. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38902] GRB 250628A: Swift/UVOT Upper Limits
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40858 SUBJECT: GRB 250628A: Swift/UVOT Upper Limits DATE: 25/06/28 12:44:42 GMT FROM: Paul Kuin at MSSL <npkuin(a)gmail.com> Paul Kuin (MSSL/UCL) and M Ferro (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250628A 130 s after the BAT trigger (Ferro et al., GCN Circ. 40853). No optical afterglow consistent with the enhanced XRT position (Evans et al. GCN Circ. 40854) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 130 280 147 >20.8 u_FC 342 591 246 >19.3 white 130 641 167 >20.8 v 671 691 19 >17.8 b 597 617 19 >18.5 u 342 591 246 >19.3 w1 720 740 19 >18.2 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.023 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/40858. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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