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

[vsnet-grb-info 39296] GRB 250805A: Swift-XRT refined Analysis
by GCN Circulars 05 Aug '25

05 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41240 SUBJECT: GRB 250805A: Swift-XRT refined Analysis DATE: 25/08/05 16:15:28 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> K.L. Page (U. Leicester), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-OAR), S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), A.P. Beardmore (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 6.1 ks of XRT data for GRB 250805A, from 3.5 ks to 27.4 ks after the trigger. The data are entirely in Photon Counting (PC) mode. The light curve can be modelled with a power-law decay with a decay index of alpha=0.89 (+/-0.08). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.63 (+/-0.14). The best-fitting absorption column is 1.4 (+/-0.5) x 10^21 cm^-2, in excess of the Galactic value of 8.4 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.4 x 10^-11 (5.1 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.4 (+/-0.5) x 10^21 cm^-2 Galactic foreground: 8.4 x 10^20 cm^-2 Excess significance: 2.0 sigma Photon index: 1.63 (+/-0.14) If the light curve continues to decay with a power-law decay index of 0.89, the count rate at T+24 hours will be 0.042 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.8 x 10^-12 (2.1 x 10^-12) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01339848. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41240. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39295] GRB 250804B: Swift-XRT observations
by GCN Circulars 05 Aug '25

05 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41239 SUBJECT: GRB 250804B: Swift-XRT observations DATE: 25/08/05 14:17:29 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 IPN-detected burst GRB 250804B in a series of observations tiled on the sky. The total exposure time is 3.3 ks, distributed over 3 tiles; the maximum exposure at a single sky location in the tiling was 2.2 ks. The data were collected between T0+79.5 ks and T0+92.2 ks, and are entirely in Photon Counting (PC) mode. Three uncatalogued X-ray sources have been detected, however none of them is above the RASS limit or shows definitive signs of fading. Therefore, at the present time we cannot identify which, if any, is the afterglow. Details of these sources are given below: Source 5: RA (J2000.0): 40.9795 = 02:43:55.09 Dec (J2000.0): -46.5917 = -46:35:30.2 Error: 6.8 arcsec (radius, 90% conf.) Count-rate: (6.1 [+3.1, -2.3])e-3 ct s^-1 Distance: 1117 arcsec from IPN position. Flux: (1.60 [+0.81, -0.62])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 6: RA (J2000.0): 40.8694 = 02:43:28.64 Dec (J2000.0): -46.4818 = -46:28:54.4 Error: 7.1 arcsec (radius, 90% conf.) Count-rate: (9.6 [+4.0, -3.2])e-3 ct s^-1 Distance: 1217 arcsec from IPN position. Flux: (1.78 [+0.75, -0.59])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) Source 7: RA (J2000.0): 40.5489 = 02:42:11.74 Dec (J2000.0): -46.5143 = -46:30:51.5 Error: 8.8 arcsec (radius, 90% conf.) Count-rate: (8.8 [+4.8, -3.6])e-3 ct s^-1 Distance: 924 arcsec from IPN position. Flux: (3.0 [+1.6, -1.2])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV) Four catalogued sources were also detected. The results of the XRT-team automatic analysis of the tiled XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/xrt_products/TILED_GRB00138. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41239. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39294] GRB 250805A: Enhanced Swift-XRT position
by GCN Circulars 05 Aug '25

05 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41238 SUBJECT: GRB 250805A: Enhanced Swift-XRT position DATE: 25/08/05 12:52:44 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team. Using 912 s of XRT Photon Counting mode data and 3 UVOT images for GRB 250805A, 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 = 24.21207, -81.40174 which is equivalent to: RA (J2000): 01h 36m 50.90s Dec (J2000): -81d 24' 06.3" with an uncertainty of 2.4 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/41238. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39293] GRB 250804C: AstroSat CZTI detection of a long burst
by GCN Circulars 05 Aug '25

05 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41237 SUBJECT: GRB 250804C: AstroSat CZTI detection of a long burst DATE: 25/08/05 12:31:17 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar(a)iitb.ac.in> M. Tembhurnikar (IUCAA), G. Waratkar (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-duration GRB 250804C which was also detected by Fermi GBM (Trigger Num. 776041355). The source was clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-08-04 23:02:29.76 UTC. The measured peak count rate associated with the burst is 376 (+68, -57) counts/s above the background in the combined data of all quadrants, with a total of 1452 (+225, -237) counts. The local mean background count rate was 1338 (+8, -9) counts/s. We measure a T90 of 5.7 (+0.7, -1.2) s from the cumulative Veto light curve. The source was also faintly detected in the CZT detectors in the 20-200 keV energy range. 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/41237. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39292] GRB 250805A: TRT optical upper limits
by GCN Circulars 05 Aug '25

05 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41236 SUBJECT: GRB 250805A: TRT optical upper limits DATE: 25/08/05 08:56:31 GMT FROM: liuxing(a)nao.cas.cn X. Liu (NAOC), K. Noysena, K. Chanchaiworawit, S. Tinyanont (NARIT), L.B. He, Z.P. Zhu, S.Q. Jiang, J. An, D. Xu (NAOC), S.Y. Fu (HUST) report on behalf of a large collaboration: We observed the field of GRB 250805A (Ambrosi et al, GCN 41233), using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Cerro Tololo Inter-American Observatory, Chile. Observations started at 06:27:50.5 UTC on 2025-08-05, i.e., ~ 0.3 hr after the Swift/BAT trigger, and 10 x 200 s frames were obtained in the Sloan r- and i- bands. No new optical source is detected in the co-added r- and i-band images within the Swift/XRT error circle (Kennea et al, GCN 41234). The limiting magnitudes are as follow: | Tmid(s) | band | upper limit(3sigma) | | :-----: | :--: | :-----------------: | | 2746.99 | i | 20.7 | | 3545.62 | r | 20.8 | The magnitudes are calibrated against Legacy Survey DR10 and are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/41236. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39291] IceCube-250804A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 05 Aug '25

05 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41235 SUBJECT: IceCube-250804A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 25/08/05 07:56:02 GMT FROM: A. Zegarelli at Ruhr University Bochum <azegarelli(a)icecube.wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 2025-08-04 20:16:26.65 UT IceCube detected a track-like event with a moderate probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_Bronze alert stream. The average astrophysical neutrino purity for Bronze alerts is 30%. This alert has an estimated false alarm rate of 2.2075 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/141198_19914656.amon) more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 2025-08-04 Time: 20:16:26.65 UT RA: 79.50 (+0.51, -0.52 deg 90% PSF containment) J2000 Dec: 16.65 (+0.49, -0.45 deg 90% PSF containment) J2000 We encourage follow-up by ground and space-based instruments to help identify a possible astrophysical source for the candidate neutrino. No known gamma-ray sources listed in the Fermi 4FGL-DR4 or 3FHL catalogs are located within the 90% uncertainty region of the event. 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 View this GCN Circular online at https://gcn.nasa.gov/circulars/41235. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39290] GRB 250805A: Swift-XRT observations
by GCN Circulars 05 Aug '25

05 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41234 SUBJECT: GRB 250805A: Swift-XRT observations DATE: 25/08/05 07:51:10 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.A. Kennea (PSU), G. Cusumano (INAF-IASF PA) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: The XRT began observing the field of GRB 250805A at 07:08:01.8 UT, 3532.9 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 24.20214, -81.40161 which is equivalent to: RA(J2000) = 01h 36m 48.51s Dec(J2000) = -81d 24' 05.8" with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 30 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. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (8.44 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.6 (+3.34/-2.82) x 10^21 cm^-2 (90% confidence). View this GCN Circular online at https://gcn.nasa.gov/circulars/41234. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39289] GRB 250805A: Swift detection of a burst
by GCN Circulars 05 Aug '25

05 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41233 SUBJECT: GRB 250805A: Swift detection of a burst DATE: 25/08/05 06:26:15 GMT FROM: Elena Ambrosi at INAF-IASF <elena.ambrosi(a)inaf.it> E. Ambrosi (INAF-IASFPA), S. Dichiara (PSU), R. Gupta (NASA GSFC), K. L. Page (U Leicester) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 06:09:08 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250805A (trigger=1339848). The BAT on-board calculated location is RA, Dec 24.153, -81.406 which is RA(J2000) = 01h 36m 37s Dec(J2000) = -81d 24' 22" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 30 sec. The peak count rate was ~1800 counts/sec (15-350 keV), at ~0 sec after the trigger. Due to an observing constraint, Swift will not slew until ~ 57 minutes. There will be no XRT or UVOT data until this time. Burst Advocate for this burst is E. Ambrosi (elena.ambrosi 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/41233. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39288] Swift GRB250805.26: Global MASTER-Net observations report
by GCN Circulars 05 Aug '25

05 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41232 SUBJECT: Swift GRB250805.26: Global MASTER-Net observations report DATE: 25/08/05 06:16:56 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 GRB250805.26 (trigger No 1339848,01h 36m 36.72s , -81d 24m 21.6s, R=0.05) errorbox 18 sec after notice time and 44 sec after trigger time at 2025-08-05 06:09:52 UT, with upper limit up to 17.9 mag. The observations began at zenith distance = 53 deg. The sun altitude is -65.4 deg. The galactic latitude b = -36 deg., longitude l = 301 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2960226 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 49 | MASTER-OAFA | C | 10 | 17.6 | 65 | MASTER-OAFA | C | 10 | 17.6 | 87 | MASTER-OAFA | C | 20 | 17.9 | 113 | MASTER-OAFA | C | 20 | 17.9 | 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/41232. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39287] GRB 250804B: Tiled Swift observations
by GCN Circulars 05 Aug '25

05 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41231 SUBJECT: GRB 250804B: Tiled Swift observations DATE: 25/08/05 02:51:01 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a series of observations, tiled on the sky, of the IPN GRB 250804B. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/xrt_products/TILED_GRB00138 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. The probability of finding serendipitous sources, unrelated to the IPN event is high: any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41231. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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