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

[vsnet-grb-info 39396] LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
by GCN Circulars 13 Aug '25

13 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41336 SUBJECT: LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate DATE: 25/08/13 02:36:38 GMT FROM: neil.lu(a)ligo.org The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S250813k during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2025-08-13 02:12:00.444 UTC (GPS time: 1439086338.444). The candidate was found by the cWB [1], GstLAL [2], MBTA [3], MLy [4], PyCBC Live [5], and SPIIR [6] analysis pipelines. S250813k is an event of interest because its false alarm rate, as estimated by the online analysis, is 1.3e-10 Hz, or about one in 1e2 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250813k The classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), BNS (<1%), or NSBH (<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 (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,0, an initial localization generated by BAYESTAR [8], distributed via GCN and SCiMMA notices about 24 seconds after the candidate event time. * bayestar.multiorder.fits,1, 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,1. For the bayestar.multiorder.fits,1 sky map, the 90% credible region is well fit by an ellipse with an area of 21 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(09h01m, +73d31m, 5.03d, 1.32d, 107.20d) Marginalized over the whole sky, the a posteriori luminosity distance estimate is 932 +/- 209 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] 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 [3] Alléné et al. CQG 42, 105009 (2025) doi:10.1088/1361-6382/add234 [4] Skliris et al. PRD 110, 104034 (2024) doi:10.1103/PhysRevD.110.104034 [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.93.0240 View this GCN Circular online at https://gcn.nasa.gov/circulars/41336. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39395] GRB 250812A: EP-FXT counterpart detection
by GCN Circulars 13 Aug '25

13 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41335 SUBJECT: GRB 250812A: EP-FXT counterpart detection DATE: 25/08/13 01:33:04 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. Zhou (PMO, CAS), M.-H. Zhang and W.-D. Zhang (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of the SVOM/ECLAIRs-detected burst GRB 250812A (SVOM/sb25081201, Xin et al. GCN 41322) at 2025-08-12T04:21:33 (UTC), about 1.6 hour after the SVOM/ECLAIRs trigger, with an exposure time of 3578s. One uncatalogued source is detected within the ECLAIRs error circle, and the source is spatially consistent with the counterpart reported in optical and X-ray bands (He et al. GCN 41324, Sbarrato et al. GCN 41325, Xin et al. GCN 41326, Rakotondrainibe et al. GCN 41328, Freeberg et al. GCN 41331, Evans et al. GCN 41334). Preliminary analysis on this source are automatically conducted, and details are listed as follows. Source 1: EPF_J021113.9-430953 RA (J2000): 32.8080 Dec (J2000): -43.1644 Flux: 3.76 x 10^-12 erg/s/cm2 (observed, 0.5-10 kev) Flux_err: 2.31 x 10^-13 erg/s/cm2 (1 sigma) The position uncertainty of the source is about 10 arcsec in radius (90% C.L. statistical and systematic). 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/41335. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39394] GRB 250812A: Swift ToO observations
by GCN Circulars 12 Aug '25

12 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41334 SUBJECT: GRB 250812A: Swift ToO observations DATE: 25/08/12 23:14:45 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 ToO observation of the SVOM/ECLAIRs-detected event GRB 250812A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021856 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the SVOM/ECLAIRs event. 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/41334. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39393] GRB 250812A: Swift ToO observations
by GCN Circulars 12 Aug '25

12 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41334 SUBJECT: GRB 250812A: Swift ToO observations DATE: 25/08/12 23:14:45 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 ToO observation of the SVOM/ECLAIRs-detected event GRB 250812A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021856 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the SVOM/ECLAIRs event. 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/41334. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39392] GRB 250807B: Swift-BAT refined analysis
by GCN Circulars 12 Aug '25

12 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41333 SUBJECT: GRB 250807B: Swift-BAT refined analysis DATE: 25/08/12 19:39:29 GMT FROM: Mike Moss at NASA GSFC <mikejmoss3(a)gmail.com> S. D. Barthelmy (GSFC), R. Gupta (GSFC), N. J. Klingler (GSFC/UMBC/CRESSTII), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-60 to T+243 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250807B (trigger #1340561) (Klingler, et al., GCN Circ. 41268). The BAT ground-calculated position is RA, Dec = 15.611, -59.098 deg which is RA(J2000) = 01h 02m 26.7s Dec(J2000) = -59d 05' 52.2" with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 64%. The mask-weighted light curve displays a complex structure with several pulses. The T90 (15-350 keV) is 104.17 +- 29.17 sec (estimated error including systematics). The time-averaged spectrum from T-51.00 to T+85.16 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.72 +- 0.12. The fluence in the 15-150 keV band is 2.5 +- 0.2 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T-48.59 sec in the 15-150 keV band is 0.9 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1340561 View this GCN Circular online at https://gcn.nasa.gov/circulars/41333. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39391] EP 250812a: GOTO optical upper limit
by GCN Circulars 12 Aug '25

12 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41332 SUBJECT: EP 250812a: GOTO optical upper limit DATE: 25/08/12 17:59:49 GMT FROM: kendall.ackley(a)warwick.ac.uk K. Ackley, A. Kumar, D. O'Neill, G. Ramsay, B.Godson, B. P. Gompertz, R. Starling, M. J. Dyer, J. Lyman, K. Ulaczyk, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, and J. Casares report on behalf of the GOTO collaboration: We report on observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022; Dyer et al. 2024) in response to EP250812a (Zhang et al. GCN 41327). Three targeted observations were performed by GOTO-South beginning at 14:58:30UT and continuing up to 17:23:59UT on 2025-08-12, corresponding to 1.84 hours, 3.03 hours, and 4.18 hours after trigger. Each observation consisted of 4x90 s exposures in the GOTO L-band (400-700 nm). We serendipitously observed the field by GOTO-South at 9.5 hours prior to the trigger time at 03:39:10UT on 2025-08-12, where each observation consisted of 4x45s exposures in the GOTO L-band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations of the same pointings. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogues. We do not identify any candidate optical counterparts at the location of the Swift-XRT afterglow candidate (Evans et al. GCN 41330) or within the EP/WXT localisation uncertainty region after the trigger time, down to a 3-sigma limiting magnitude for the three sets of observations of L >18.9 (AB), L >19.4 (AB), L >19.8 (AB). The observation at 9.5 hours prior to the trigger shows no source to a 3-sigma limit of L >18.1 mag (AB). Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction. GOTO (https://goto-observatory.org/) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/41332. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39390] GRB 250812A: Kilonova-Catcher optical afterglow detection
by GCN Circulars 12 Aug '25

12 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41331 SUBJECT: GRB 250812A: Kilonova-Catcher optical afterglow detection DATE: 25/08/12 17:32:39 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> M. Freeberg (KNC), D. Turpin (CEA-Saclay/Irfu), C. Andrade(UMN), M. Pillas (ULiege), M. Molham (NRIAG), M. Mašek (Institute of Physics, Prague, FZU, CZ), S. Antier (OCA/IJCLAB) on behalf of the GRANDMA/Kilonova-Catcher collaboration: We observed the field of GRB 250812A (Xin et al., GCN 41322) detected by SVOM/ECLAIRs with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with the iTelescope T72 telescope operated by M. Freeberg. Our observations started at T0+1.8hr. In our stacked frames, subtracted from the Legacy Survey DR10 template image, we detect an uncatalogued optical source at a position consistent with the TRT (He et al., GCN 41324), SVOM/VT (Xin et al., GCN 41326) and SVOM/COLIBRÍ (FM-GFT) (Rakotondrainibe et al., GCN 41328) optical afterglow candidate as well as the Swift/XRT (Sbarrato et al., GCN41325) x-ray afterglow candidate . We report our follow-up results in the table below: +---------------+-----------+-----------+----------------+------------+ | Tmid-TGRB (hr)| Exp (s) | Filter | Magnitude | Instrument | +===============+===========+===========+================+============+ | 2.3 | 10 x 300s | Rc (Vega) | 18.60 +/- 0.06 | iT72 | | 12.4 | 20 x 180s | Rc (Vega) | 19.12 +/- 0.11 | iT72 | +---------------+-----------+-----------+----------------+------------+ Our observations clearly show a fading behavior as also shown by the TRT and SVOM/VT observations (He et al., GCN 41324; Xin et al., GCN 41326). Thus we also suggest this source to be the afterglow of GRB 250812A. All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the Johnson-cousins filters were calibrated using the GAIA DR3 synphot catalog. We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023). GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/) View this GCN Circular online at https://gcn.nasa.gov/circulars/41331. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39389] EP250812a: Swift-XRT counterpart detection
by GCN Circulars 12 Aug '25

12 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41330 SUBJECT: EP250812a: Swift-XRT counterpart detection DATE: 25/08/12 17:22:44 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P.A. Evans (U. Leicester), J.A. Kennea (PSU), E. Ambrosi (INAF-IASFPA) , A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB), D.N. Burrows (PSU), S. Campana (INAF-OAB), M. Capalbi (INAF-OAR), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), M. Ferro (INAF-OAB), A. Melandri (INAF-OAR), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M. Perri (SSDC & INAF-OAR), C. Salvaggio (INAF-OAB), T. Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), M.A. Williams (PSU) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Einstein Probe/WXT-detected source EP250812a, collecting 1.7 ks of Photon Counting (PC) mode data between T0+1.5 ks and T0+3.4 ks after the trigger. A likely counterpart has been found. The position is consistent with the uncatalogued X-ray source detected by EP-FXT (Zhang et al., GCN 41327). The details of this source are: Source 1 (SWIFT J020358.1-091907): ================================== RA (J2000.0): 30.9921 = 02h 03m 58.10s Dec (J2000.0): -9.3187 = -09d 19' 07.3" Error: 3.7 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 67 arcsec from the Einstein Probe/WXT position. Mean rate: 0.1069 +/- 0.0091 ct s^-1 Mean flux: (4.00 +/- 0.34)e-12 erg cm^-2 s^-1 Peak rate: 0.203 +/- 0.046 ct s^-1 Peak flux: (7.6 +/- 1.7)e-12 erg cm^-2 s^-1 ECF: 3.75e-11 erg cm^-2 ct^-1 assuming NH=4.71e+20 cm^-2, gamma=1.83 determined from a spectral fit. LSXPS UL: 1.5e-03 ct/sec, (0.3-10 keV) so the source is 4.4-sigma above this 3-sigma upper limit. The source may be fading, at the 2.6-sigma level. We have detected a total of 3 sources. These have been automatically classified as follows: * 1 likely counterpart * 0 candidate counterparts * 0 uncatalogued X-ray sources * 2 known X-ray sources Known X-ray sources ------------------- Source 2 (SWIFT J020340.7-092134): ================================== RA (J2000.0): 30.9196 = 02h 03m 40.70s Dec (J2000.0): -9.3596 = -09d 21' 34.6" Error: 5.8 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 4.8 arcmin from the Einstein Probe/WXT position. Mean rate: (8.5 [+3.0, -2.5])e-3 ct s^-1 Mean flux: (2.42 [+0.87, -0.71])e-13 erg cm^-2 s^-1 Peak rate: (8.5 [+3.0, -2.5])e-3 ct s^-1 Peak flux: (2.42 [+0.87, -0.71])e-13 erg cm^-2 s^-1 ECF: 2.86e-11 erg cm^-2 ct^-1 assuming NH=4.16e+20 cm^-2, gamma=2.23 determined from a spectral fit. This matches a catalogued X-ray source LSXPS J020340.7-092134 in the LSXPS catalogue. Details: Separation: 1.0" from the XRT source Cat Rate: 4.6e-03 +/- 8.6e-04 ct s^-1 Cat Flux: 1.3e-13 +/- 2.5e-14 erg cm^-2 s^-1 (0.3-10 keV) so the source is 1.3-sigma above the catalogued flux. There is no evidence for fading. A SIMBAD object `[VV2006] J020341.0-092134' is 3.4" away. Source 4 (SWIFT J020404.7-091504): ================================== RA (J2000.0): 31.0199 = 02h 04m 04.78s Dec (J2000.0): -9.2513 = -09d 15' 04.7" Error: 5.8 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 4.0 arcmin from the Einstein Probe/WXT position. Mean rate: (6.6 [+2.8, -2.2])e-3 ct s^-1 Mean flux: (2.14 [+0.92, -0.72])e-13 erg cm^-2 s^-1 Peak rate: (6.6 [+2.8, -2.2])e-3 ct s^-1 Peak flux: (2.14 [+0.92, -0.72])e-13 erg cm^-2 s^-1 ECF: 3.25e-11 erg cm^-2 ct^-1 assuming NH=2.48e+20 cm^-2, gamma=1.94 determined from a spectral fit. This matches a catalogued X-ray source LSXPS J020405.1-091509 in the LSXPS catalogue. Details: Separation: 7.3" from the XRT source Cat Rate: 5.6e-03 +/- 1.5e-03 ct s^-1 Cat Flux: 1.8e-13 +/- 4.9e-14 erg cm^-2 s^-1 (0.3-10 keV) so the source is 0.3-sigma above the catalogued flux. There is no evidence for fading. All fluxes are 0.3-10 keV, observed. For all flux conversions and comparisons with catalogues and upper limits from other missions, we assumed a power-law spectrum with NH=3x10^20 cm^-2 and photon index (Gamma)=1.7 unless otherwise stated. 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/EP/EP_FIELD00058. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41330. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39388] Fermi Gamma-ray Burst Monitor trigger 776705265/250812644 is not a GRB
by GCN Circulars 12 Aug '25

12 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41329 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 776705265/250812644 is not a GRB DATE: 25/08/12 15:49:37 GMT FROM: oindabimukherjee(a)gmail.com O. Mukherjee (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 776705265/250812644 at 15:27:40.88 UT on 12 August 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/41329. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39387] GRB 250807A: Swift-BAT refined analysis
by GCN Circulars 12 Aug '25

12 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41318 SUBJECT: GRB 250807A: Swift-BAT refined analysis DATE: 25/08/11 14:04:39 GMT FROM: Mike Moss at NASA GSFC <mikejmoss3(a)gmail.com> R. Gupta (GSFC), S. D. Barthelmy (GSFC), N. J. Klingler (GSFC/UMBC/CRESSTII), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-240 to T+520 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250807A (trigger #1340514) (Klingler, et al., GCN Circ. 41262). The BAT ground-calculated position is RA, Dec = 51.435, -47.882 deg which is RA(J2000) = 03h 25m 44.4s Dec(J2000) = -47d 52' 54.4" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 72%. The mask-weighted light curve displays a complex structure with several pulses. T90 (15-350 keV) is 75.46 +- 2.19 sec (estimated error including systematics). The time-averaged spectrum from T-20.35 to T+119.49 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.32 +- 0.03. The fluence in the 15-150 keV band is 2.5 +- 0.0 x 10^-05 erg/cm2. The 1-sec peak photon flux measured from T+33.82 sec in the 15-150 keV band is 16.7 +- 0.5 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1340514 View this GCN Circular online at https://gcn.nasa.gov/circulars/41318. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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