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

[vsnet-grb-info 39783] LIGO/Virgo/KAGRA S250904br: Updated Sky localization
by GCN Circulars 05 Sep '25

05 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41717 SUBJECT: LIGO/Virgo/KAGRA S250904br: Updated Sky localization DATE: 25/09/05 08:01:58 GMT FROM: Michael J. Williams at University of Portsmouth <michael.williams(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 S250904br (GCN Circular 41692). 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/S250904br For the Bilby.multiorder.fits,0 sky map, the 90% credible region is well fit by an ellipse with an area of 232 deg2 described by the following DS9 region (right ascension, declination, semi-major axis, semi-minor axis, position angle of the semi-minor axis): icrs; ellipse(15h39m, +13d59m, 21.87d, 3.41d, 70.39d) Marginalized over the whole sky, the a posteriori luminosity distance estimate is 2547 +/- 578 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/41717. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39782] The EP-WXT trigger 01709201259: a brightening of LMXB 1ES 1735-26.9
by GCN Circulars 05 Sep '25

05 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41716 SUBJECT: The EP-WXT trigger 01709201259: a brightening of LMXB 1ES 1735-26.9 DATE: 25/09/05 07:07:13 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R. D. Liang (NAOC), Y. Wang (PMO), Y.H.Cheng (SWIFAR,YNU), W. D. Zhang (NAOC) on behalf of the Einstein Probe (EP) team: We report on the detection of X-ray brightening of Low Mass X-ray Binary (LMXB) 1ES 1735-26.9 by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The burst triggered EP-WXT (ID: 01709201259) at the time of 2025-09-05T05:11:45 UTC. The WXT position of the source is R.A. = 264.569 deg, DEC = -26.997 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). The estimated flux in the 0.5-4 keV band is around 5 x 10^-10 erg/cm^2/s, which is an order of magnitude higher than the previous detection. A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. An X-ray source was detected at R.A. = 264.5679 deg, DEC = -26.9927 (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic), which is consistent with the position of known LMXB 1ES 1735-26.9. The estimated flux in the 0.5-10 keV band is around 2 x 10^-10 erg/cm^2/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/41716. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39781] GRB 250905A: KAIT optical upper limit
by GCN Circulars 05 Sep '25

05 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41715 SUBJECT: GRB 250905A: KAIT optical upper limit DATE: 25/09/05 04:51:12 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB) and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, observed the field of Swift GRB 250905A (Brivio et al., GCN 41714) starting at 03:14 UT, ~64 minutes after the burst. A set of 34x60s clear (roughly R) filter images were obtained under twilight condition. We do not detect any new optical counterpart candidate within the XRT error circles (Brivio et al., GCN 41714), down to an upper limit of about 20.0 (Vega) mag at a mid time of 94 minutes after the burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/41715. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39780] GRB 250905A: Swift detection of a burst
by GCN Circulars 05 Sep '25

05 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41714 SUBJECT: GRB 250905A: Swift detection of a burst DATE: 25/09/05 02:25:34 GMT FROM: David Palmer at LANL <palmer(a)lanl.gov> R. Brivio (INAF-OAB), S. Dichiara (PSU), D. M. Palmer (LANL), C. Salvaggio (INAF-OAB), T. Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 02:09:54 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250905A (trigger=1347265). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 233.047, +0.777 which is RA(J2000) = 15h 32m 11s Dec(J2000) = +00d 46' 39" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). Due to a telemetry gap, the BAT lightcurve is not immediately available. The XRT began observing the field at 02:12:11.4 UT, 136.6 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 233.00629, 0.79395 which is equivalent to: RA(J2000) = 15h 32m 01.51s Dec(J2000) = +00d 47' 38.2" with an uncertainty of 3.4 arcseconds (radius, 90% containment). This location is 158 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 5.50 x 10^20 cm^-2 (Willingale et al. 2013). UVOT took a finding chart exposure of 150 seconds with the White filter starting 140 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.054. Burst Advocate for this burst is R. Brivio (riccardo.brivio AT inaf.it). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) View this GCN Circular online at https://gcn.nasa.gov/circulars/41714. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39779] Swift GRB250905.09: Global MASTER-Net observations report
by GCN Circulars 05 Sep '25

05 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41713 SUBJECT: Swift GRB250905.09: Global MASTER-Net observations report DATE: 25/09/05 02:16:50 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB250905.09 (trigger No 1347265,15h 32m 11.28s , +00d 46m 37.2s, R=0.05) errorbox 18 sec after notice time and 87 sec after trigger time at 2025-09-05 02:11:22 UT, with upper limit up to 16.0 mag. The observations began at zenith distance = 78 deg. The sun altitude is -49.0 deg. The galactic latitude b = 43 deg., longitude l = 6 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2985121 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 97 | MASTER-OAFA | C | 20 | 16.0 | 124 | MASTER-OAFA | C | 20 | 15.9 | 155 | MASTER-OAFA | C | 30 | 16.0 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/41713. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39778] Swift GRB 250904A: Global MASTER-Net observations report
by GCN Circulars 04 Sep '25

04 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41712 SUBJECT: Swift GRB 250904A: Global MASTER-Net observations report DATE: 25/09/04 23:11:08 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Tavrida robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the Swift GRB 250904A ( C. Salvaggio et al., GCN 41704) errorbox 19454 sec after notice time and 19494 sec after trigger time at 2025-09-04 23:01:57 UT, with upper limit up to 15.5 mag. The observations began at zenith distance = 81 deg. The sun altitude is -35.9 deg. The galactic latitude b = -14 deg., longitude l = 201 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2984839 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 19585 | MASTER-Tavrida | C | 180 | 15.5 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/41712. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39777] GRB 250904A: Enhanced Swift-XRT position
by GCN Circulars 04 Sep '25

04 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41711 SUBJECT: GRB 250904A: Enhanced Swift-XRT position DATE: 25/09/04 19:57:22 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team. Using 343 s of XRT Photon Counting mode data and 1 UVOT images for GRB 250904A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 84.38044, +3.58445 which is equivalent to: RA (J2000): 05h 37m 31.31s Dec (J2000): +03d 35' 04.0" with an uncertainty of 2.5 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41711. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39776] IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 04 Sep '25

04 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41710 SUBJECT: IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube DATE: 25/09/04 19:32:11 GMT FROM: Yuhua Yao at IceCube/UW-Madison <yyao255(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-Cascade 250903A (https://gcn.gsfc.nasa.gov/notices_amon_icecube_cascade/141309_814805.amon) in a time range of 1000 seconds centered on the alert event time (2025-09-03 17:21:14.210 UTC to 2025-09-03 17:37:54.210 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-Cascade 250903A.We report a p-value of 1.00 in this time window. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-Cascade 250903A ranges from 1.3e-01 to 1.6e+00 GeV cm^-2 in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 3e+02 GeV and 7e+05 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2025-09-02 17:29:34.210 UTC to 2025-09-04 17:29:34.210 UTC). In this case, we report a p-value of 0.83, consistent with no significant excess of track events. The IceCube sensitivity to neutrino point sources with an E^-2.5 spectrum (E^2 dN/dE at 1 TeV) within the locations spanned by the 90% spatial containment region of IceCube-Cascade 250903A ranges from 1.5e-01 to 1.6e+00 GeV cm^-2 in a 2 day time window. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu. [1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) View this GCN Circular online at https://gcn.nasa.gov/circulars/41710. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39775] GRB 250904A: TRT optical counterpart detection
by GCN Circulars 04 Sep '25

04 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41709 SUBJECT: GRB 250904A: TRT optical counterpart detection DATE: 25/09/04 18:36:01 GMT FROM: syfu(a)nao.cas.cn S.Y. Fu (HUST), K. Noysena, K. Chanchaiworawit, S. Tinyanont (NARIT), L.B. He, X. Liu, Z.P. Zhu, S.Q. Jiang, J. An, D. Xu (NAOC) report on behalf of a large collaboration: We observed the field of GRB 250904A (Salvaggio et al., GCN 41704), using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at New South Wales, Australia (SBO). Observations started at 17:49:41.450 UTC on 2025-09-04, i.e., ~ 12.6 min after the Swift/BAT trigger and a series of frames in the R band were obtained. An uncatalogued source is detected in our stacked image within the enhanced Swift/XRT error circle (Evans et al., GCN 41706) with magnitude of R = 20.1 +/- 0.2 (AB) at 18.97 min post-trigger, calibrated with Pan-STARRS1 DR2 catalog converted using Lupton (2005) equations and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/41709. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39774] EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
by GCN Circulars 04 Sep '25

04 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41708 SUBJECT: EP250827a and EP250827b: Upper limit from Fermi-GBM Observations DATE: 25/09/04 18:18:09 GMT FROM: mariaedvige.ravasio(a)ru.nl M. E. Ravasio and P.G. Jonker (Radboud Univ.) on behalf of the Einstein Probe Team and E. Burns (LSU), C. M. Hui (NASA MSFC) and R. Hamburg (USRA) on behalf of the Fermi-GBM Team, report: Fermi-GBM had full spatial coverage of the transients EP250827a (Hua et al., GCN 41553, Ni et al., GCN 41573) and EP250827b (Schroeder et al., GCN 41635) detected by EP-WXT. There was no Fermi-GBM onboard trigger around both EP trigger times (T0=2025-08-27T07:39:01 UTC for EP250827a, and T0=2025-08-27T06:22:27 UTC for EP250827b). The GBM targeted search [1], the most sensitive, coherent search for GRB-like signals, was run in the time interval [T0-50; T0+500] s, seeking signals between 64 ms and 32.768 s in duration. No signal consistent with the EP transients, both temporally and spatially, is identified, as confirmed also by visual inspection of the data. Assuming a “soft” spectral template (Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7), and a duration of 8.192 s, we derive a flux upper limit of 3.5e-08 erg/cm2/s for EP250827a, and a flux upper limit of 3.0e-08 erg/cm2/s for EP250827b, in the energy band 10-1000 keV. [1] Goldstein et al. 2019 arXiv:1903.12597 View this GCN Circular online at https://gcn.nasa.gov/circulars/41708. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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