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

[vsnet-grb-info 38802] GRB 250617B: SAO RAS optical observations
by GCN Circulars 17 Jun '25

17 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40761 SUBJECT: GRB 250617B: SAO RAS optical observations DATE: 25/06/17 22:54:57 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin, O. Spiridonova, Yu. Sotnikova (SAO RAS), A. Ghosh, S. Razzaque (CAPP, University of Johannesburg) We observed the field of the GRB 250617B (Page et al., GCN 40760) with SAO RAS 1-m telescope Zeiss-1000 equipped with CCD-photometer. We obtained series of 60, 120 and 300 sec. exposures in Rc band and also one BVIc series. Observations started on 21:28:06 UT, since 26 minutes after the trigger. The OT (Page et al., GCN 40760) is clearly visible in individual images with the brightness of R = 18.31 +/- 0.04 (t_mid - T0 = 0.5444 hours) and R = 18.66 +/- 0.04 (t_mid - T0 = 0.7635 hours). This preliminary photometry is calibrated against R2 magnitudes of following nearby USNO-B1 stars and not corrected for the Galaxy extinction. R.A. Dec. (2000) R2 22:11:38.4 +32:43:48.4 14.880 22:11:19.9 +32:44:17.5 15.280 22:11:41.0 +32:40:41.2 15.070 22:11:45.2 +32:42:19.8 14.690 Observations are ongoing. View this GCN Circular online at https://gcn.nasa.gov/circulars/40761. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38801] GRB 250617B: Swift detection of a burst with an optical counterpart
by GCN Circulars 17 Jun '25

17 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40760 SUBJECT: GRB 250617B: Swift detection of a burst with an optical counterpart DATE: 25/06/17 21:24:27 GMT FROM: David Palmer at LANL <palmer(a)lanl.gov> K. L. Page (U Leicester), R. Gupta (NASA GSFC), A. Y. Lien (U Tampa), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. H. Siegel (PSU) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 21:01:50.11 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250617B (trigger=1325580). Swift did not slew immediately to the burst. The BAT on-board calculated location is RA, Dec 332.902, +32.727 which is RA(J2000) = 22h 11m 37s Dec(J2000) = +32d 43' 38" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The currently available BAT light curve showed a complex structure with a duration of at least 10 sec. However, the light curve data from ~T+8 s to ~T+100 s is unavailable in the immediate data downlink. The peak count rate was ~900 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 21:15:03.4 UT, 793.4 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 332.89735, 32.73270 which is equivalent to: RA(J2000) = 22h 11m 35.36s Dec(J2000) = +32d 43' 57.7" with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 24 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 in excess of the Galactic value (9.66 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 5.7 (+4.15/-3.46) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 796 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 22:11:35.25 = 332.89686 DEC(J2000) = +32:43:56.9 = 32.73247 with a 90%-confidence error radius of about 0.62 arc sec. This position is 1.9 arc sec. from the center of the XRT error circle. The estimated magnitude is 18.17 with a 1-sigma error of about 0.15. No correction has been made for the expected extinction corresponding to E(B-V) of 0.087. Burst Advocate for this burst is K. L. Page (klp5 AT leicester.ac.uk). 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/40760. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38800] GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
by GCN Circulars 17 Jun '25

17 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40759 SUBJECT: GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit DATE: 25/06/17 16:55:47 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 imaged the field of GRB 250615A detected by Swift/BAT (Dichiara et al. GCN 40736), with the 11 inches Schmidt-Cassegrain (Celestron 11) telescope F/D=6,3. The observations were started at 2025-06-15 23:21:59 UT (approximately 56 minutes after burst) stacking a set of unfiltered CCD image. We co-added 180 exposures of 60 sec each. Start T0+ End T0+ CR lim 0.94 hour 4.33 hour 19.6 We did not found any optical uncatalogued object within the Swift error circle. Magnitudes were estimated with the PanSTARRS cat. and are not corrected for galactic dust extinction. Our upper limit is consistent with other observations reported by Kuin et al. (GCN 40747), Becerra et al. (GCN 40748), Magnani et al. (GCN 40749). The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40759. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38799] GRB 250617A: Fermi GBM Final Real-time Localization
by GCN Circulars 17 Jun '25

17 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40758 SUBJECT: GRB 250617A: Fermi GBM Final Real-time Localization DATE: 25/06/17 16:19:51 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 16:09:13 UT on 17 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250617A (trigger 771869358.345712 / 250617673). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 354.8, Dec = 35.4 (J2000 degrees, equivalent to J2000 23h 39m, 35d 23'), with a statistical uncertainty of 2.6 degrees. The angle from the Fermi LAT boresight is 51.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250617673/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250617673/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250617673/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40758. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38798] IPN triangulation of GRB 250612C (short/hard)
by GCN Circulars 17 Jun '25

17 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40757 SUBJECT: IPN triangulation of GRB 250612C (short/hard) DATE: 25/06/17 16:02:15 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> 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 Y. Zhang, C. Wang, S. Xiong, J. Wei, and B. Cordier on behalf of the SVOM-GRM team, report: The bright, short-duration GRB 250612C (Fermi-GBM detection: The Fermi GBM team, GCN 40704; Neights and Meegan, GCN 40713; BALROG localization: Preis and Greiner, GCN 40706; SVOM-GRM detection: Wang et al., GCN 40708; GRID detection: Yang et al., GCN 40732; Konus-Wind detection: Frederiks et al., GCN 40746) was detected by Fermi (GBM trigger 771432801), SVOM (GRM), Konus-Wind, and GRID at about 53596 s UT (14:53:16). We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: ------------------------------- RA(2000), deg Dec(2000), deg ------------------------------- Center: 115.493 18.574 Corners: 116.886 22.070 116.633 22.036 113.718 15.372 113.864 15.182 -------------------------------- The error box area is 5.5 sq. deg, and its maximum dimension is 7 deg (the minimum one is 14.7 arcmin). The Sun distance was 33 deg. This localization may be improved. The IPN localization is consistent with, but reduces the area of, the Fermi-GBM (GCN 40704) and BALROG (GCN 40706) localizations. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB250612_T53591/IPN/ The HEALPix triangulation map is the multi-order HEALPix in units of probability density. View this GCN Circular online at https://gcn.nasa.gov/circulars/40757. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38797] EP#01709178975: Swift-XRT counterpart detection
by GCN Circulars 17 Jun '25

17 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40756 SUBJECT: EP#01709178975: Swift-XRT counterpart detection DATE: 25/06/17 15:41:32 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 EP#01709178975, collecting 594 s of Photon Counting (PC) mode data between T0+2.1 ks and T0+2.8 ks after the trigger. A candidate counterpart has been found. The details of this source are: Source 1 (SWIFT J154403.9-331113): ================================== RA (J2000.0): 236.0166 = 15h 44m 03.98s Dec (J2000.0): -33.1871 = -33d 11' 13.6" Error: 3.6 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 52 arcsec from the Einstein Probe/WXT position. Mean rate: 1.079 +/- 0.065 ct s^-1 Mean flux: (3.14 +/- 0.19)e-11 erg cm^-2 s^-1 Peak rate: 1.49 +/- 0.24 ct s^-1 Peak flux: (4.32 +/- 0.70)e-11 erg cm^-2 s^-1 ECF: 2.91e-11 erg cm^-2 ct^-1, assuming NH=1.85e+21 cm^-2, gamma=2.42; determined from a spectral fit. This matches a catalogued X-ray source XMMSL3 J154404.2-331108 in the XMM-NEWTON/XMMSLEWCLN catalogue. Details: Separation: 3.0" from the XRT source Cat Rate: 5.9e-01 +/- 2.8e-01 ct s^-1 Cat Flux: 4.6e-12 +/- 2.2e-12 erg cm^-2 s^-1 (0.3-10 keV) so the source is 5.2-sigma above the catalogued flux. There is no evidence for fading. A SIMBAD object `CD-32 11039B' is 3.3" away. There is 1 2MASS object within the source's 3-sigma error radius. We have detected a total of 2 sources. These have been automatically classified as follows: * 0 likely counterparts * 1 candidate counterpart * 1 uncatalogued X-ray source * 0 known X-ray sources Uncatalogued X-ray sources -------------------------- Source 2 (SWIFT J154417.0-331013): ================================== RA (J2000.0): 236.0710 = 15h 44m 17.04s Dec (J2000.0): -33.1705 = -33d 10' 13.8" Error: 10.3 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 2.5 arcmin from the Einstein Probe/WXT position. Mean rate: 0.0122 [+0.0068, -0.0053] ct s^-1 Mean flux: (1.56 [+0.87, -0.67])e-11 erg cm^-2 s^-1 Peak rate: 0.0122 [+0.0068, -0.0053] ct s^-1 Peak flux: (1.56 [+0.87, -0.67])e-11 erg cm^-2 s^-1 ECF: 1.28e-09 erg cm^-2 ct^-1, assuming NH=3.49e+23 cm^-2, gamma=9.92; determined from a spectral fit. XMM UL: 1.8e-12 erg cm^-2 s^-1, (0.3-10 keV) so the source is 1.8-sigma above this 3-sigma upper limit. There is no evidence for fading. A SIMBAD object `UCAC4 285-083088' is 1.7" away. There are 10 2MASS objects within the source's 3-sigma error radius. 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. This circular is an officicial product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40756. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38796] EP-WXT trigger 01709178975: GOTO optical upper limit
by GCN Circulars 17 Jun '25

17 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40755 SUBJECT: EP-WXT trigger 01709178975: GOTO optical upper limit DATE: 25/06/17 13:03:29 GMT FROM: Shane Moran at University of Leicester <smk48(a)leicester.ac.uk> S. Moran, M. Kennedy, A. Kumar, D. O'Neill, G. Ramsay, B. P. Gompertz, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, B. Godson, 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: The Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) performed the targeted observations of the field of EP-WXT trigger 01709178975 (Chen, et al., 40754) on 2025-06-17 from 11:35:33 to 11:47:07 UT (respectively from 13.46 mins to 25.03 mins after the trigger). The observation was taken by GOTO-South and consisted of 4x90s 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 within the EP-WXT localisation uncertainty region, down to a 5-sigma limiting magnitude of L > 20.7 in the initial image. We also did not see any evident variability of the CD-32 11039 in the GOTO L-band. 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/40755. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38795] The EP-WXT trigger 01709178975 is likely a flaring star
by GCN Circulars 17 Jun '25

17 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40754 SUBJECT: The EP-WXT trigger 01709178975 is likely a flaring star DATE: 25/06/17 11:56:18 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> X. L. Chen (YNU), H. Z. Wu (HUST), Y. P. Zhou (NJU), Y. Q. Zhao (USTC, PRIC), J. W. Hu, Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709178975 at the time of 2025-06-17T11:22:06, is likely a stellar flare associated with CD-32 11039. The estimated flux of the flare is around 1e-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 2.9e32 erg/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/40754. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38794] The EP-WXT trigger 01709178975 is likely a flaring star
by GCN Circulars 17 Jun '25

17 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40754 SUBJECT: The EP-WXT trigger 01709178975 is likely a flaring star DATE: 25/06/17 11:56:18 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> X. L. Chen (YNU), H. Z. Wu (HUST), Y. P. Zhou (NJU), Y. Q. Zhao (USTC, PRIC), J. W. Hu, Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709178975 at the time of 2025-06-17T11:22:06, is likely a stellar flare associated with CD-32 11039. The estimated flux of the flare is around 1e-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 2.9e32 erg/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/40754. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38793] Konus-Wind detection of GRB 250615A / EP250615a
by GCN Circulars 17 Jun '25

17 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40753 SUBJECT: Konus-Wind detection of GRB 250615A / EP250615a DATE: 25/06/17 11:35:08 GMT FROM: Dmitry Frederiks at Ioffe Institute <fred(a)mail.ioffe.ru> D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 250615A (Swift detection: Dichiara et al., GCN 40736; AstroSat CZTI detection: Tembhurnikar et al., GCN 40752), coincident with the X-ray transient EP250615a (Yang et al., GCN 40743), triggered Konus-Wind (KW) at T0=80722.429 s UT (22:25:22.429). The burst light curve shows a multi-peaked emission pulse which starts at ~T0-5 s and has a total duration of ~50 s. The emission is seen up to ~4 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250615_T80722/ As observed by Konus-Wind, the burst had a fluence of (3.57 ± 0.50)x10^-5 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 5.248 s, of (5.32 ± 0.53)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+49.408 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.96 (-0.09,+0.11), the high energy photon index beta = -2.41 (-1.15,+0.35), the peak energy Ep = 908 (-187,+218) keV, chi2 = 84/97 dof. The spectrum near the peak count rate(measured from T0 to T0+8.448 s) is best fit in the 20 keV - 15 MeV range by a GRB (Band) function with the following model parameters: the low-energy photon index alpha = -0.92 (-0.09,+0.09), the high energy photon index beta = -2.62 (-7.38,+0.41), the peak energy Ep = 1290 (-234,+320) keV, chi2 = 89/93 dof. All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/40753. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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