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[vsnet-grb-info 38850] IPN triangulation of GRB 250620С (long/bright)
by GCN Circulars 22 Jun '25

22 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40809 SUBJECT: IPN triangulation of GRB 250620С (long/bright) DATE: 25/06/22 09:58:12 GMT FROM: Dmitry Svinkin at Ioffe Institute <dmitrysvinkin(a)gmail.com> D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi GBM team, and S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, A. Tohuvavohu, and J. DeLaunay on behalf of the Swift-BAT team, report: The bright long-duration GRB 250620C (Fermi-GBM detection: The Fermi GBM team, GCN 40794; Mukherjee, GCN 40799; SVOM-GRM detection: Wang et al., GCN 40807) was detected by Fermi (GBM trigger 772128434), Swift (BAT), Konus-Wind, and SVOM (GRM) at about 58030 s UT (16:07:10). The burst was outside the coded field of view of the BAT. We have triangulated it to a preliminary, 3 sigma error box whose area is 17.6 sq. deg, and its maximum dimension is 25.5 deg (the minimum one is 51.0 arcmin). The Sun distance was ~50 deg. This localization may be improved. The IPN localization is consistent with, but reduces the area of, the Fermi-GBM (GCN 40794) and BALROG (https://grb.mpe.mpg.de/grb/GRB250620672/?data_version=tte_v00) localizations. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB250620_T58026/IPN The HEALPix triangulation map is the multi-order HEALPix in units of probability density. The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/40809. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38849] GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
by GCN Circulars 22 Jun '25

22 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40808 SUBJECT: GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst DATE: 25/06/22 06:07:38 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Frédéric Piron (LUPM) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a short burst GRB 250621B (SVOM trigger reference: sb25062104) at 2025-06-21T09:13:47.100 UTC (T0), which is also detected by Fermi/GBM (TrigNum 772190032). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a narrow spike with a T90 of 0.11 +0.02/-0.03 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250621B.png The SVOM/GRM on-ground localization of this burst is (J2000): RA: 273.9 deg DEC: -24.8 deg Error: 2.9 deg (1sigma, statistical only) We caution that the calibration of SVOM/GRM is undergoing and this localization is subject to systematic errors. In addition, the position of this burst, as determined by GRM, is located at about 8 degrees from the SVOM optical axis, but ECLAIRs was not collecting data at the time of this burst. With this localization, the time-averaged spectrum from T0-0.3 to T0+0.2 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.05 +0.25/-0.27 and the cutoff energy, parameterized as Epeak, is 31 +/- 3 keV. The event fluence (10-1000 keV) in this time interval is (3.79 +/-0.15)E-07 erg/cm^2. We note that the localization of this burst is relatively close to the Galactic disk and compatible with the position of SGR 1806-20, as well as the hardness and duration all suggest a magnetar X-ray burst. 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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/40808. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38848] GRB 250620C: SVOM/GRM observation
by GCN Circulars 22 Jun '25

22 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40807 SUBJECT: GRB 250620C: SVOM/GRM observation DATE: 25/06/22 05:55:58 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Ulysse Jacob (LUPM) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a bright burst GRB 250620C (SVOM trigger reference: sb25062006) at 2025-06-20T16:07:10.100 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN#40794). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a narrow spike with a T90 of 30.1 +/-1.5 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250620C.png In addition, the position of this burst, as determined by Fermi/GBM (RA= 142.6, DEC= 55.0, GCN#40794), is located at about 161 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-1 to T0+40 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.22 +0.13/-0.12 and the cutoff energy, parameterized as Epeak, is 502 +74/-55 keV. The event fluence (10-1000 keV) in this time interval is (9.15 +0.26/-0.28)E-07 erg/cm^2. The localization of GRB 250620C in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/grb250620C_amati.png 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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/40807. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38847] GRB 250620A: SVOM/GRM observation of a short burst
by GCN Circulars 22 Jun '25

22 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40806 SUBJECT: GRB 250620A: SVOM/GRM observation of a short burst DATE: 25/06/22 05:55:18 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Ulysse Jacob (LUPM) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a bright burst GRB 250620A (SVOM trigger reference: sb25062002) at 2025-06-20T08:05:19 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN#40791) and Swift/BAT (James DeLaunay et al., GCN#40796). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a narrow spike with a T90 of 0.15 +/-0.05 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250620A.png In addition, the position of this burst, as determined by Fermi/GBM (RA= 46.2, DEC= 65.8, GCN#40791), is located at about 111 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-0.2 to T0 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.64 +0.25/-0.19 and the cutoff energy, parameterized as Epeak, is 1310 +1780/-780 keV. The event fluence (10-1000 keV) in this time interval is (8.36 +0.89/-0.87)E-07 erg/cm^2. The localization of GRB 250620A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/grb250620A_amati.png 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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/40806. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38846] GRB250620A: Fermi GBM Observation
by GCN Circulars 21 Jun '25

21 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40805 SUBJECT: GRB250620A: Fermi GBM Observation DATE: 25/06/21 23:52:54 GMT FROM: rhamburg(a)usra.edu R. Hamburg (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 08:05:18.94 UT on 20 June 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250620A (trigger 772099523/250620337) which was also detected by Swift/BAT-GUANO (DeLaunay et al. 2025, GCN 40796). The angle from the Fermi LAT boresight is 164 degrees. The GBM light curve two pulses with a duration (T90) of about 12 s (50-300 keV). The time-averaged spectrum from T0-0.3 to T0+10 s is best fit by a simple power law function with index -1.6 +/- 0.2. The event fluence (10-1000 keV) in this time interval is (1.1 +/- 1.3)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+3.8 s in the 10-1000 keV band is 9 +/- 2 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak = 2000 +/- 200 keV, alpha = -1.08 +/- 0.03 and beta = -2.44 +/- 0.09. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/40805. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38845] GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
by GCN Circulars 21 Jun '25

21 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40804 SUBJECT: GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation. DATE: 25/06/21 21:08:57 GMT FROM: Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, Messina, Italy <giovannicalapai(a)tiscali.it> Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, (Messina) Italy Member of: GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani. Report: We observed the field of GRB 250617B detected by Swift/BAT (Page et al. GCN 40760) with the 11 inches Schmidt-Cassegrain (Celestron 11) telescope F/D=6,3. The observations were started at 2025-06-17 23:10:55 UT (approximately 2.15 hours after burst) stacking a two consecutive sets of unfiltered CCD image. The observations were carried out with visibility disturbed by passing clouds. The OT was detected at the following position: RA (J2000.0) 22h 11m 35.21s +/- 0.02 Decl. (J2000.0) +32° 43' 57.6" +/- 1.1 The results of our photometry are: Observation Mid-Time T-T0 (hr) Exposure Filter Mag. S/N Mag. err. 2025-06-18 00:05:21 UT 3.06 90x60s CR 19.24 9.1 +/-0.17 2025-06-18 01:47:28 UT 4.76 88x60s CR 20.75 3.4 +/-0.30 Given the low S/N for the OT of second set, we cannot completely rule out it being due to background fluctuation. Along the span of our observations and within our uncertainties, the afterglow evolves in agreement with a power-law decay index of ~0.89. Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied. Our observations are consistent with other already reported Moskvitin et al. (GCN 40761); Jelinek et al. (GCN 40762); Kumar et al. (GCN 40768); Lipunov et al. (GCN 40769); Grossan et al. (GCN 40771); Ma et al. (GCN 40772); Williams et al. (GCN 40773); Schneider et al. (GCN 40774); Antier et al. (GCN 40775); Corcoran et al. (GCN 40776); Turpin et al. (GCN 40777); Siegel et al. (GCN 40778); Pankov et al. (GCN 40783); Gendreau-Distler et al. (GCN 40789). The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40804. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38844] Fermi GRB 250621A: Global MASTER-Net observations report
by GCN Circulars 21 Jun '25

21 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40803 SUBJECT: Fermi GRB 250621A: Global MASTER-Net observations report DATE: 25/06/21 02:30:51 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) started inspect of the Fermi GRB 250621A ( Fermi GBM team, GCN 40801) errorbox 79 sec after notice time and 111 sec after trigger time at 2025-06-21 01:16:46 UT, with upper limit up to 18.2 mag. The observations began at zenith distance = 77 deg. The sun altitude is -45.4 deg. The galactic latitude b = 10 deg., longitude l = 248 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2910652 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 122 | 2025-06-21 01:16:46 | MASTER-OAFA | (08h 35m 57.13s , -26d 43m 55.5s) | C | 20 | 17.4 | 161 | 2025-06-21 01:17:21 | MASTER-OAFA | (08h 46m 34.40s , -23d 40m 16.6s) | C | 30 | 17.8 | 202 | 2025-06-21 01:17:57 | MASTER-OAFA | (08h 46m 34.42s , -23d 40m 16.3s) | C | 40 | 17.9 | 253 | 2025-06-21 01:18:43 | MASTER-OAFA | (08h 46m 34.45s , -23d 40m 16.4s) | C | 50 | 18.0 | 315 | 2025-06-21 01:19:40 | MASTER-OAFA | (08h 46m 34.42s , -23d 40m 15.2s) | C | 60 | 17.9 | 386 | 2025-06-21 01:20:46 | MASTER-OAFA | (08h 46m 34.44s , -23d 40m 15.4s) | C | 70 | 18.2 | 472 | 2025-06-21 01:22:02 | MASTER-OAFA | (08h 46m 34.52s , -23d 40m 15.8s) | C | 90 | 18.2 | 573 | 2025-06-21 01:23:38 | MASTER-OAFA | (08h 46m 34.55s , -23d 40m 15.7s) | C | 100 | 18.2 | 702 | 2025-06-21 01:25:32 | MASTER-OAFA | (08h 39m 15.15s , -24d 49m 47.5s) | C | 130 | 18.1 | 848 | 2025-06-21 01:27:48 | MASTER-OAFA | (08h 39m 15.35s , -24d 49m 48.3s) | C | 150 | 17.9 | 1019 | 2025-06-21 01:30:24 | MASTER-OAFA | (08h 39m 15.58s , -24d 49m 49.7s) | C | 180 | 17.8 | 1205 | 2025-06-21 01:33:30 | MASTER-OAFA | (08h 39m 15.88s , -24d 49m 51.5s) | C | 180 | 17.6 | 1392 | 2025-06-21 01:36:36 | MASTER-OAFA | (08h 39m 16.16s , -24d 49m 53.1s) | C | 180 | 17.5 | 1578 | 2025-06-21 01:39:42 | MASTER-OAFA | (08h 39m 16.38s , -24d 49m 59.7s) | C | 180 | 17.2 | 1763 | 2025-06-21 01:42:48 | MASTER-OAFA | (08h 39m 16.61s , -24d 50m 07.5s) | C | 180 | 16.8 | 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/40803. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38843] GRB 250619B: Fermi GBM Observation
by GCN Circulars 21 Jun '25

21 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40802 SUBJECT: GRB 250619B: Fermi GBM Observation DATE: 25/06/21 01:38:07 GMT FROM: Jacob Smith at Fermi-GBM Team <jrs0118(a)uah.edu> Jacob Smith (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: At 23:36:17.17 UT on 19 June 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250619B (trigger 772068982/250619984). which was also detected by Swift/BAT-GUANO (J. DeLaunay et al. 2025, GCN 40795). The Fermi GBM on-ground location is consistent with the Swift/BAT-GUANO position. The angle from the Fermi LAT boresight is 48 degrees. The GBM light curve consists of a double emission episode with a duration (T90) of about 29 s (50-300 keV). The time-averaged spectrum from T0-1 to T0+28.7 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.1 +/- 0.2 and the cutoff energy, parameterized as Epeak, is 67 +/- 9 keV. A Band function fits the spectrum equally well with Epeak = 57 +/- 13 keV, alpha = -1 +/- 0.4 and beta = -2.5 +/- 0.4. The event fluence (10-1000 keV) in this time interval is (1.4 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.32 s in the 10-1000 keV band is 2.2 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/ View this GCN Circular online at https://gcn.nasa.gov/circulars/40802. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38842] GRB 250621A: Fermi GBM Final Real-time Localization
by GCN Circulars 21 Jun '25

21 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40801 SUBJECT: GRB 250621A: Fermi GBM Final Real-time Localization DATE: 25/06/21 01:25:28 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 01:14:55 UT on 21 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250621A (trigger 772161300.203902 / 250621052). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 129.7, Dec = -25.1 (J2000 degrees, equivalent to J2000 08h 38m, -25d 06'), with a statistical uncertainty of 1.9 degrees. The angle from the Fermi LAT boresight is 50.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250621052/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250621052/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250621052/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40801. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38841] GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
by GCN Circulars 21 Jun '25

21 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40800 SUBJECT: GRB 250620B: Swift/BAT-GUANO localization skymap of a burst DATE: 25/06/21 00:30:05 GMT FROM: Samuele Ronchini at PSU <sjs8171(a)psu.edu> Samuele Ronchini (PSU), James DeLaunay (PSU), Aaron Tohuvavohu (Caltech), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC), Maia Williams (PSU) report: Swift/BAT did not localize GRB 250620B onboard (T0: 2025-06-20T13:22:56.94 UTC, Fermi/GBM GCN 40792) The Fermi 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). 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. The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), performed on the temporal window [T0-20 s, T0+20 s], detects the burst with a sqrt(TS) of 13.83 in a 4.096 s analysis time bin, starting at T0 - 1.024 s. Using the NITRATES analysis, parameter estimation was performed to obtain the localization of this burst in the form of a HEALPIX Multi-Order Coverage (MOC) skymap. This localization accounts for both statistical and systematic errors. More details in the creation and calibration of these maps will soon be published (DeLaunay et al. 2025. in prep) The 90% credible area is 8,562 deg2 and the 50% credible area is 2,685 deg2. The integrated probability inside the coded field of view is 8%. The NITRATES skymap is consistent with the Fermi localization reported in the final position notice (GCN 40792). The combined Fermi/GBM+NITRATES 90% credible area is 158 deg2 and the 50% credible area is 51 deg2. A plot of the probability skymap can be viewed here: [skymap_plot](https://guano.swift.psu.edu/trigger_report?id=772118612/#:~:te… The probability skymap and joint skymap files can be downloaded from the links here [skymap_fits_file](https://guano.swift.psu.edu/files/772118612/0_n_PROBMAP) [joint_skymap_fits_file](https://guano.swift.psu.edu/files/772118612/0_n_JOI… Instructions on how to read and manipulate this map can be found here: https://guano.swift.psu.edu/documentation More details about this burst can be found on the trigger report page here: https://guano.swift.psu.edu/trigger_report?id=772118612 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/40800. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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