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

[vsnet-grb-info 40134] GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
by GCN Circulars 02 Oct '25

02 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42064 SUBJECT: GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory DATE: 25/10/02 22:16:27 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> L. Juliá-Maroto, J. Basurto Merino, P.G. Berdayes, A. Caballero-Almagro, A. Cerón, M. Contreras, F. Díaz-Segado, T. Ferrer-Laviña, B. Gandolfi, V. Ghiraldo, J. Hernández Fung, E. Lekaroz-Urriza, M. Manzano García, E. Mejía-Martínez, J. Prieto Polo, M. Pulido-Torres, M. Quintana-Ansaldo, A. Schenone-Zanuzzi, A. Selezneva, T. Tundidor Rodríguez, E. Urquijo-Rodríguez (all ULL), M. Abdul-Masih (IAC and ULL), and I. Pérez-Fournon (IAC and ULL). We report on a Las Cumbres Observatory (LCO) 40-cm telescope early observation of the Gamma-Ray Burst GRB 251002A, detected by SVOM/ECLAIRs(Saccardi et al., GCN circ. 42060). We observed the field of GRB 251002A with the LCO 40-cm telescope (a Planewave Delta Rho 350 telescope equipped with a CMOS QHY600 camera) located at the LCO node at Sutherland Observatory (South Africa). The observation, a single exposure of 300 sec in the SDSS g filter, started on 2025-10-02 at 20:39:46 UT, about 24.9 minutes after the SVOM trigger. The optical counterpart detected by SVOM/VT (Palmerio et al., GCN circ. 42061), LCO 1-m (Turpin et al., GCN circ. 42062), and FRAM-ORM (Jelinek et al., GCN circ. 42063) is clearly detected in our image with a magnitude of g = 18.13 +/- 0.09, calibrated against PanSTARRS-1 DR2 and not corrected for galactic extinction. Based on observations made with the Las Cumbres Observatory’s education network telescopes that were upgraded through generous support from the Gordon and Betty Moore Foundation (program IAC2025B-010). These observations are part of a course in Astrophysical Techniques of the Master in Astrophysics of the Astrophysics Department of the University of La Laguna in collaboration with the Instituto de Astrofísica de Canarias (La Laguna, Tenerife, Canary Islands, Spain). View this GCN Circular online at https://gcn.nasa.gov/circulars/42064. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40133] GRB 251002A: FRAM-ORM afterglow detection
by GCN Circulars 02 Oct '25

02 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42063 SUBJECT: GRB 251002A: FRAM-ORM afterglow detection DATE: 25/10/02 21:58:23 GMT FROM: Martin Jelinek at Astro.Inst-AVCR,Ondrejov <martin.jelinek(a)asu.cas.cz> Martin Jelinek and Jan Strobl (ASU CAS Ondrejov, CZ), Sergey Karpov, Martin Masek, Petr Janecek, Jakub Jurysek, Jan Ebr, Ronan Cunniffe, Petr Travnicek and Michael Prouza (Institute of Physics, Prague, CZ) report: The 25cm robotic telescope FRAM-ORM at La Palma (Spain) reacted to the alert of GRB251002A (Saccardi et al. GCN 42060), obtaining a series of unfiltered images starting at 20:25:24 UT, i.e. ~10.5min post trigger. We clearly detect the optical transient reported by Palmerio et al. (GCN 42061) and Turpin et al. (GCN 42062). At the combination of 9 x 60 s images (Tmid=T0+23.5min) we measure the optical afterglow with the brightness r = 17.8 +/- 0.2 (AB) as calibrated against Atlas-REFCAT (Tonry et al. 2018, ApJ, 867, 105). View this GCN Circular online at https://gcn.nasa.gov/circulars/42063. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40132] GRB 251002A: LCO optical observation
by GCN Circulars 02 Oct '25

02 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42062 SUBJECT: GRB 251002A: LCO optical observation DATE: 25/10/02 21:05:15 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> D. Turpin (CEA/Irfu), A. Saccardi (CEA/Irfu), D. Gotz (CEA/Irfu), B. Cordier (CEA/Irfu), L. P. Xin (NAOC), C. Wu (NAOC), report on behalf of the SVOM mission team: We observed the field of GRB 251002A (Saccardi et al. GCN 42060) with the LCO 1m telescope at South African Astronomical Observatory equipped with the Sinistro instrument. Our observation started at 2025-10-02T20:34:02.740 about 19 min after the SVOM/ECLAIRs T0 time. We obtained 3x200 s exposures in the SDSS r filter. The optical counterpart reported by Palmerio et al. (GCN 42061) is clearly detected in our first image subtracted to the Pan-STARRS DR2 catalog image. We measure the following magnitude: r = 17.55 +/- 0.03 (AB), at a mid-time of 20.8 min after the trigger. Further observations are planned. This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/42062. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40131] GRB 251002A: SVOM/VT optical observation
by GCN Circulars 02 Oct '25

02 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42061 SUBJECT: GRB 251002A: SVOM/VT optical observation DATE: 25/10/02 20:58:44 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> J. T. Palmerio (CEA/Irfu), H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu report on behalf of the SVOM/VT team: After the trigger by SVOM/ECLAIRs at 2025-10-02T20:14:54 UTC (T0), SVOM performed an automatic slew on the burst location (Saccardi et al., GCN 42060). SVOM/VT began observing the field at 2025-10-02T20:19:44, 289.75 seconds after T0, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. From a preliminary analysis of the 1-bit subimage and source list downloaded via VHF network, at least one credible candidate is identified, the details of which are presented below. VT_ID 36: This candidate was flagged as un uncatalogued source. The position of this candidate is R.A., Dec. 13.9082, -5.5671 degrees, corresponding to: R.A. (J2000) = 0h55m38.0s Dec. (J2000) = -5d34m01.5s with an uncertainty of 1 arcsec. This location is within the R90 uncertainty region of the SVOM/MXT onboard localization. The source was detected in both VT_R and VT_B. The candidate's magnitudes are: | date-obs (UTC) | mid-time | exposure | band | mag(AB) | | -------------------- | ----------- | --------- | ----- | ------------- | | 2025-10-02T20:19:44 | 6.50 min | 4*50 sec | VT_B | 16.81 ± 0.01 | | 2025-10-02T20:19:44 | 6.50 min | 4*50 sec | VT_R | 16.24 ± 0.01 | Magnitudes were not corrected for dust extinction. Given the VT color of the counterpart, it might be a low redshift gamma-ray burst. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. The SVOM/VT point of contact for this burst is Jesse Palmerio: jesse.palmerio(a)cea.fr. View this GCN Circular online at https://gcn.nasa.gov/circulars/42061. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40130] GRB 251002A: SVOM detection of a burst
by GCN Circulars 02 Oct '25

02 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42060 SUBJECT: GRB 251002A: SVOM detection of a burst DATE: 25/10/02 20:43:05 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> A. Saccardi (CEA/Irfu), D. Gotz (CEA/Irfu), S. Schanne (CEA/Irfu), M. G. Bernardini (INAF & LUPM), N. Dagoneau (CEA/Irfu), P. Maggi (ObAS), report on behalf of the SVOM mission team: At 2025-10-02T20:14:54 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 251002A (SVOM burst-id sb25100211). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 15 alerts. CRT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 22.39 in the [8-120] keV energy band over a time window of 10.20 seconds starting at 2025-10-02T20:14:49. The SVOM/ECLAIRs light curve showed a multiple peak structure with a T90 duration of 11.7 (+2.6/-1.5) s. The localization of the best alert is R.A., Dec. 13.9059, -5.5440 degrees (J2000) with a 90% confidence level (C.L.) radius of 3.98 arcmin (including systematic error of 2 arcmin added in quadrature). This burst also triggered SVOM/GRM at 2025-10-02T20:14:52 with an SNR of 10.40. SVOM slewed to the burst. SVOM/MXT began observing the field at 2025-10-02T20:17:42 UTC, 168 seconds after T0. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec. 13.9179, -5.5679 degrees: R.A. (J2000) = 0h55m40s Dec. (J2000) = -5d34m04s with a 90% C.L. radius of 81 arcseconds. This location is 1.60 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received. VT began observing the field after the slew. The analysis of the data will be published in a future circular. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is Andrea Saccardi: andrea.saccardi(a)cea.fr. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/42060. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40129] Fermi trigger No 781128896: Global MASTER-Net observations report
by GCN Circulars 02 Oct '25

02 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42059 SUBJECT: Fermi trigger No 781128896: Global MASTER-Net observations report DATE: 25/10/02 20:30:48 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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB251002.84 (trigger No 781128896,01h 12m 38.40s , -05d 24m 00.0s, R=5.51) errorbox 259 sec after notice time and 291 sec after trigger time at 2025-10-02 20:19:42 UT, with upper limit up to 18.4 mag. The observations began at zenith distance = 50 deg. The sun altitude is -49.8 deg. The galactic latitude b = -67 deg., longitude l = 138 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3005496 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 322 | 2025-10-02 20:19:42 | MASTER-Kislovodsk | (00h 53m 34.79s , -05d 12m 04.9s) | P- | 60 | 17.4 | 402 | 2025-10-02 20:19:42 | MASTER-Kislovodsk | (00h 53m 34.79s , -05d 12m 04.8s) | P- | 220 | 18.4 | Coadd 322 | 2025-10-02 20:19:42 | MASTER-Kislovodsk | (00h 53m 50.27s , -05d 35m 28.4s) | P| | 60 | 18.0 | 395 | 2025-10-02 20:20:50 | MASTER-Kislovodsk | (00h 53m 34.79s , -05d 12m 08.8s) | P- | 70 | 18.1 | 395 | 2025-10-02 20:20:50 | MASTER-Kislovodsk | (00h 53m 50.31s , -05d 35m 30.7s) | P| | 70 | 18.0 | 483 | 2025-10-02 20:22:09 | MASTER-Kislovodsk | (00h 53m 34.83s , -05d 12m 10.6s) | P- | 90 | 18.1 | 483 | 2025-10-02 20:22:09 | MASTER-Kislovodsk | (00h 53m 50.43s , -05d 35m 32.0s) | P| | 90 | 18.1 | 592 | 2025-10-02 20:23:47 | MASTER-Kislovodsk | (00h 53m 34.96s , -05d 12m 12.3s) | P- | 110 | 18.4 | 592 | 2025-10-02 20:23:47 | MASTER-Kislovodsk | (00h 53m 50.58s , -05d 35m 34.4s) | P| | 110 | 18.1 | The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/42059. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40128] GRB 251001B: Swift-BAT refined analysis
by GCN Circulars 02 Oct '25

02 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42058 SUBJECT: GRB 251001B: Swift-BAT refined analysis DATE: 25/10/02 20:10:01 GMT FROM: Mike Moss at NASA GSFC <mikejmoss3(a)gmail.com> H. A. Krimm (NSF), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), R. Gupta (GSFC), 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+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 251001B (trigger #1400467) (Beardmore, et al., GCN Circ. 42039). The BAT ground-calculated position is RA, Dec = 42.668, -22.990 deg which is RA(J2000) = 02h 50m 40.2s Dec(J2000) = -22d 59' 23.9" with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 91%. The mask-weighted light curve shows a single FRED pulse from ~T0-5 s to ~T0+20 s. Statistically significant emission is found to occur out to ~T0+90 s. The T90 (15-350 keV) is 75.33 +- 46.90 sec (estimated error including systematics). The time-averaged spectrum from T-9.98 to T+91.72 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.49 +- 0.14. The fluence in the 15-150 keV band is 1.1 +- 0.1 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+2.29 sec in the 15-150 keV band is 0.8 +- 0.1 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/1400467 View this GCN Circular online at https://gcn.nasa.gov/circulars/42058. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40127] GRB 251001A: SVOM/GRM observation
by GCN Circulars 02 Oct '25

02 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42057 SUBJECT: GRB 251001A: SVOM/GRM observation DATE: 25/10/02 14:35:15 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang. Wen-Jun Tan, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Frédéric Piron (LUPM), Olivier GODET (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a burst GRB 251001A (SVOM trigger reference: sb25100101) at 2025-10-01T02:40:58.000 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN#42034) and Insight-HXMT (Wang et al., GCN#42056). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multi-pulses with a T90 of 7.2 +1.8/-0.4 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb251001A.png In addition, the position of this burst, as determined by Fermi/GBM (RA= 224.4, DEC= -56.2, GCN#42034), is located at about 101 degrees from the SVOM optical axis, which is outside the field of view of ECLAIRs. Nevertheless, ECLAIRs detected the GRB through the shield above 50 keV. With this localization, the time-averaged spectrum from T0-2 to T0+7 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.73 +0.41/-0.32 and the cutoff energy, parameterized as Epeak, is 51 +/-7 keV. The event fluence (10-1000 keV) in this time interval is (7.92 +0.94/-0.92)E-06 erg/cm^2. The localization of GRB 251001A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb251001A_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/42057. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40126] GRB 251001A: Insight-HXMT detection
by GCN Circulars 02 Oct '25

02 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42056 SUBJECT: GRB 251001A: Insight-HXMT detection DATE: 25/10/02 14:27:57 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> Chen-Wei Wang, Zheng-Hang Yu, Cheng-Kui Li, Shao-Lin Xiong, and Chao Zheng report on behalf of the Insight-HXMT team: At 2025-10-01T02:40:57.600 (T0), Insight-HXMT/HE was trigger by the burst GRB 251001A, which is also detected by Fermi/GBM (Fermi GBM Team, GCN#42034). The Insight-HXMT/HE light curve mainly consists of multi-pulses with a T90 of 8.2 +/-1.6 s. The 1s peak rate, measured from T0+5.300 s, is 759 cnts/sec. The total counts from this burst is 2439 counts. The HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb251001A.png All measurements above are made with the CsI detectors operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://www.hxmt.org. View this GCN Circular online at https://gcn.nasa.gov/circulars/42056. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40125] GRB 251001B: Swift/UVOT Detection
by GCN Circulars 02 Oct '25

02 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42055 SUBJECT: GRB 251001B: Swift/UVOT Detection DATE: 25/10/02 12:12:59 GMT FROM: Alice Breeveld at MSSL-UCL <a.breeveld(a)ucl.ac.uk> A.A. Breeveld (UCL-MSSL), S.P.R. Shilling (Lancaster U.) and A.P. Beardmore (U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251001B 119 s after the BAT trigger (Beardmore et al., GCN Circ. 42039). A source consistent with the enhanced XRT position (Beardmore et al., GCN Circ. 42045) and also with the optical counterpart seen by Gompertz et al. (GCN Circ. 42040), An et al. (GCN Circ. 2041), Strausbaugh and Cucchiara (GCN Circ. 42043) and de Ugarte Postigo et al. (GCN Circ. 42050) is detected in the initial UVOT exposures. Preliminary detections using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposures and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 119 269 147 18.76 +/- 0.06 u_FC 331 581 246 18.86 +/- 0.15 white 611 630 10 19.0 +/- 0.25 white 861 1010 147 19.6 +/- 0.2 b 587 779 39 > 19.0 v 661 681 20 > 17.4 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.023 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42055. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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