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

[vsnet-grb-info 40564] GRB 251027A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
by GCN Circulars 27 Oct '25

27 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42480 SUBJECT: GRB 251027A: SVOM/COLIBRÍ (FM-GFT) optical upper limit DATE: 25/10/27 14:47:37 GMT FROM: J.-G. Ducoin at CPPM <ducoin(a)cppm.in2p3.fr> Damien Dornic (CPPM), William H. Lee (UNAM), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), Alan M. Watson (UNAM), Fredd Alvarez (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), Y. H.Cheng (YNU) and Y. F. Liang (PMO) : We imaged the field of the SVOM GRB 251027A (Cheng et al., GCN Circ. 42471) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2025-10-27T10:08:34 to 2025-10-27T10:47:17 UTC (from 31 to 69 minutes after the trigger) and obtained 32x60 seconds of exposure in the r and z filters. The data were reduced and coadded with the COLIBRÍ pipeline and analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction (Av>2). In the stacked image, we do not detect any new source at the ECLAIRs source position (Cheng et al., GCN Circ. 42471) down to the following 5-sigma limit: r > 23.57 z > 22.26 Further analysis is ongoing. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/42480. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40563] GRB 251017A: Mondy AZT-33IK and Koshka Zeiss-1000 optical observations
by GCN Circulars 27 Oct '25

27 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42479 SUBJECT: GRB 251017A: Mondy AZT-33IK and Koshka Zeiss-1000 optical observations DATE: 25/10/27 13:47:19 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. Volnova (IKI), E. Klunko (ISTP), A. Novichonok (Petrozavodsk State University, KIAM), I. Nikolenko (INASAN), A. Pozanenko (IKI), N. Pankov (HSE, IKI), report on behalf of IKI-GRB-FuN: We observed the optical counterpart (Perez-Garcia et al., 42323; Antier et al., 42325; Sasada et al., 42329; Lipunov et al., 42330; Fu et al., 42331; Mo et al., 42336; Adami et al., 42339; Xin et al., 42341; Izzo et al., 42350; Shilling et al., 42355; Akl et al., 42368; Midavaine et al., 42370; Volnova et al., 42477) of the Swift GRB 251017A (Gupta et al., GCN 42322) in the R-filter with 1.5-meter AZT-33IK telescope of Sayan Solar Observatory (Mondy) on Oct. 17,18,23, 2025, and in the Rb filter with 1-meter Zeiss-1000 telescope of the Koshka Observatory (INASAN) on Oct. 20, 2025. Preliminary photometry and observation details are the following: Date UT start t-T0 Exp. Filter OT Err. UL Site/Instrum (mid,days) (n*s) (3sigma) 2025-10-17 11:25:01 0.14333 20*120 R 20.41 0.07 21.8 Mondy/AZT-33IK 2025-10-17 12:49:15 0.19065 26*120 R 20.88 0.07 22.3 Mondy/AZT-33IK 2025-10-18 11:40:09 1.14891 35*120 R 21.79 0.13 22.5 Mondy/AZT-33IK 2025-10-20 16:36:07 3.37307 40*180 R n/d n/d 21.1 Koshka/Zeiss-1000 2025-10-23 13:18:38 6.22425 45*120 R n/d n/d 22.5 Mondy/AZT-33IK The photometry is based on several nearby PS1 stars (R-magnitudes Lupton's transformation) and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42479. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40562] GRB 251023B / EP251023b: Mondy optical upper limit
by GCN Circulars 27 Oct '25

27 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42478 SUBJECT: GRB 251023B / EP251023b: Mondy optical upper limit DATE: 25/10/27 13:44:29 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. Volnova (IKI), A. Pozanenko (IKI) , N. Pankov (HSE, IKI), E. Klunko (ISTP) report on behalf of IKI-GRB-FuN: We observed the field of the GRB 251023B / EP251023b (Kang et al., GCN Circ. 42392; Nakahira et al., GCN Circ. 42402; Wu et al., GCN Circ. 42415; Cheung et al., GCN Circ. 42407) in the R-filter with the AZT-33IK 1.5m telescope of the Sayan Solar Observatory (Mondy) starting Oct. 25, 2025, 17:50:36 UT, and taking several frames with 120 s exposures. The optical candidate reported by Mandarakas et al. (GCN Circ. 42404) is not detected in the stacked frame. Photometry and observational details are the following: Date UT start t-T0 Exp. Filter OT Err. UL (mid,days) (n*s) (3sigma) 2025-10-25 17:50:36 2.40386 40*120 R n/d n/d 22.7 The photometry is based on several nearby SDSS stars (R-magnitudes Lupton's transformation) and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42478. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40561] GRB 251017A: INASAN-Kislovodsk optical observations
by GCN Circulars 27 Oct '25

27 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42477 SUBJECT: GRB 251017A: INASAN-Kislovodsk optical observations DATE: 25/10/27 13:36:52 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. Volnova (IKI), A.N. Tarasenkov (INASAN), A. Pozanenko (IKI), N. Pankov (HSE) report on behalf of IKI GRB-FuN: We observed the field of the Swift GRB 251017A (Gupta et al., GCN 42322) with RC500 telescope of the INASAN-Kislovodsk observatory. We took several 120-seconds frames in the R-band starting Oct. 17, 2025, 15:09:15 (UT). In the stacked image the optical counterpart (Perez-Garcia et al., 42323; Antier et al., 42325; Sasada et al., 42329; Lipunov et al., 42330; Fu et al., 42331; Mo et al., 42336; Adami et al., 42339; Xin et al., 42341; Izzo et al., 42350; Shilling et al., 42355; Akl et al., 42368; Midavaine et al., 42370) is clearly detected. Preliminary photometry is the following: Date UT start t-T0 Exp. Filter OT Err. UL (mid,days) (n*s) (3sigma) 2025-10-17 15:09:15 0.34348 100*120 R 21.45 0.16 22.0 The photometry is based on several nearby PS1 stars (R-magnitudes Lupton's transformation) and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42477. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40560] GRB 251026A: Mondy optical upper limit
by GCN Circulars 27 Oct '25

27 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42476 SUBJECT: GRB 251026A: Mondy optical upper limit DATE: 25/10/27 13:34:08 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. Volnova (IKI), A. Pozanenko (IKI) , N. Pankov (HSE, IKI), E. Klunko (ISTP) report on behalf of IKI-GRB-FuN: We observed the field of GRB 251026A detected by SVOM/ECLAIRs (Cao et al., GCN 42454) in the R-filter with the AZT-33IK 1.5m telescope of the Sayan Solar Observatory (Mondy) starting Oct. 26, 2025, 20:15:58 (UT) taking several frames with 120 s exposures. Inside the error box of the SVOM/MXT (Cao et al., GCN 42454) we did not detect any new uncatalogued source. Photometry and observational details are the following: Date UT start t-T0 Exp. Filter OT Err. UL (mid,days) (n*s) (3sigma) 2025-10-26 20:15:58 0.51293 30*120 R n/d n/d 22.4 The photometry is based on several nearby PS1 stars (R-magnitudes Lupton's transformation) and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42476. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40559] GRB 251025B: Mondy optical observations
by GCN Circulars 27 Oct '25

27 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42475 SUBJECT: GRB 251025B: Mondy optical observations DATE: 25/10/27 13:31:43 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. Volnova (IKI), A. Pozanenko (IKI) , N. Pankov (HSE, IKI), E. Klunko (ISTP) report on behalf of IKI-GRB-FuN: We observed the field of the GRB 251025B (Hussein et al., GCN 42437) in the R-filter with the AZT-33IK 1.5m telescope of the Sayan Solar Observatory (Mondy) starting Oct. 26, 2025, 16:25:44 UT, and taking several frames with 120 s exposures. The optical counterpart (Wu et al., GCN 42438; Gress et al., GCN 42439; Wu et al., GCN 42440; Beardmore et al., GCN 42445; Mohan et al., GCN 42447; Hernández Funget al., GCN 42450; Pereyra et al., GCN 42452; Li et al., GCN 42453; Mo et al., GCN 42459; Rakotondrainibe et al., GCN 42460; Rajabov et al., 42466; Saccardi et al., 42472; Freeberg et al., 42474) is clearly detected in the stacked frame. Preliminary photometry is the following: Date UT start t-T0 Exp. Filter OT Err. UL (mid,days) (n*s) (3sigma) 2025-10-26 16:25:44 1.10532 60*120 R 20.50 0.05 23.1 The photometry is based on several nearby SDSS stars (R-magnitudes Lupton's transformation) and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42475. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40558] GRB 251025B: Kilonova-Catcher optical afterglow detection
by GCN Circulars 27 Oct '25

27 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42474 SUBJECT: GRB 251025B: Kilonova-Catcher optical afterglow detection DATE: 25/10/27 12:53:57 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> M. Freeberg, R. Hellot (KNC), D. Turpin (CEA-Saclay/Irfu), C. Andrade(UMN), S. Antier (OCA/IJCLab), M. Coughlin (UMN), S. Karpov (FZU), P. Hello (IJCLAB), M. Pillas (IAP) on behalf of the GRANDMA/Kilonova-Catcher collaboration: We observed the field of GRB 251025B detected by SVOM (Hussein et al., GCN 42437) with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with a TEC160FL and a 0.43m Dall-Kirkham telescopes operated by M. Freeberg and a CDK17 telescope located at AITP San Pedro Chile Observatory operated by R. Hellot. Our observations started at TGRB+5.7hr and were taken with BRc and sdss ri filters. In our stacked frames, subtracted from the PanSTARRS DR2 template image, we detect the optical counterpart reported by SVOM/C-GFT (Wu et al., GCN 42438), MASTER (Gress et al., GCN 42439), SVOM/VT (Wu et al., GCN 42440), Swift/XRT (Beardmore et al., GCN 42445), GROWTH (Mohan et al., GCN 42447), IAC80 (Hernández Fung et al., GCN 42450), SVOM/COLIBRÍ (FM-GFT) (Pereyra et al., GCN 42452), WINTER (Mo et al., GCN 42459), OHP/T193 (Rakotondrainibe et al., GCN 42460), the MAO/AZT-22 (Rabajov et al., GCN 42466) and VLT/MUSE (Saccardi et al., GCN 42472). We report part of our follow-up results in the table below: +---------------+-----------+-----------+----------------+---------------+ | Tmid-TGRB (hr)| Exp (s) | Filter | Magnitude | Instrument | +===============+===========+===========+================+===============+ | 6.28 | 20 x 180s | B (Vega) | 20.58 +/- 0.16 | 0.43/DK | | 12.46 | 12 x 300s | r (AB) | 19.93 +/- 0.10 | CDK17 AITP | | 13.37 | 40 x 180s | r (AB) | 20.37 +/- 0.13 | TEC160FL | +---------------+-----------+-----------+----------------+---------------+ All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the sloan filters were calibrated using the PanSTARRS DR1 catalog. 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/42474. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40557] Konus-Wind detection of GRB 251016A (short/hard)
by GCN Circulars 27 Oct '25

27 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42473 SUBJECT: Konus-Wind detection of GRB 251016A (short/hard) DATE: 25/10/27 12:47:24 GMT FROM: Valentina Panteleeva at Ioffe Institute <panteleevav228(a)gmail.com> V. Panteleeva, D. Frederiks, A. Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The short-duration GRB 251016A (SVOM/ECLAIRs detection: Basa et al., GCN 42308; Brunet et al., GCN 42374; Fermi-GBM detection: The Fermi GBM team, GCN 42309; Smith and Meegan, GCN 42365; Glowbug detection: Woolf et al., GCN 42313; CALET-GBM detection: Kawakubo et al., GCN 42321; AstroSat-CZTI detection: Arya et al., GCN 42327; Insight-HXMT/HE detection: Zao et al., GCN 42359) triggered Konus-Wind at T0=53956.564 s UT (14:59:16.564). The burst light curve shows a single pulse which starts at ~T0-0.2 s and has a total duration of ~0.5 s. The emission is seen up to ~3 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB251016_T53956/ As observed by Konus-Wind, the burst had the total fluence of 6.32(-0.91,+1.04)x10^-6 erg/cm2, and the 16-ms peak flux, measured from T0+0.018 s, of 2.46(-0.52,+0.58)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+0.256 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.44(-0.20,+0.35), the high energy photon index beta = -2.14(-0.72,+0.34), the peak energy Ep = 825(-282,+293) keV (chi2 = 30/25 dof). All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/42473. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40556] GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003
by GCN Circulars 27 Oct '25

27 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42472 SUBJECT: GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003 DATE: 25/10/27 11:30:46 GMT FROM: Andrea Saccardi at CEA/Irfu <andrea.saccardi(a)cea.fr> A. Saccardi (CEA/Irfu), L. Izzo (INAF/OACn & DARK/NBI), P. Schady (University of Bath), D. B. Malesani (DAWN/NBI and Radboud), J. An (NAOC), A. A. Chrimes (ESA/ESTEC & Radboud Univ.), G. Corcoran (UCD), A. Martin-Carrillo (UCD), B. Schneider (LAM), N. R. Tanvir (U. Leicester), S. D. Vergani (LUX-Paris Obs.), report on behalf of the Stargate collaboration: We observed the field of the SVOM/ECLAIRs GRB 251025B (Hussein et al., GCN 42437), using the ESO VLT UT4 (Yepun) equipped with the MUSE spectrograph. Our observation started at 03:27:23 UT on 2025 October 27 (1.54 days after the GRB trigger), and consisted of 4 exposures of 700 s each. The optical counterpart (Wu et al., GCN 42438; Gress et al., GCN 42439; Wu et al., GCN 42440; Mohan et al., GCN 42447; Hernández Fung et al., GCN 42450; Pereyra et al., GCN 42452; Li et al., GCN 42453; Mo et al., GCN 42459; Rakotondrainibe et al., GCN 42460; Rajabov et al., GCN 42466) is well detected in the wavelength-stacked “white light” image. The afterglow has a synthetic magnitude Rc = 21.22 +/- 0.04 (AB). Our spectra cover the wavelength range 4750 - 9330 AA. In a preliminary reduction, we detect a continuum over the entire covered wavelength range. From the detection of several absorption features that we identify as due to Al II, Al III, Fe II, Mg II, and Mg I, we infer a common redshift of z = 2.003 for the GRB. Additionally, we note the presence of an intervening absorber at z = 0.73 with Mg II (and likely Mg I) absorption lines. As first noted by Pereyra et al. (GCN 42452), an archival object is visible in the Legacy Survey underlying the optical afterglow (g = 24.02 +/- 0.15; r = 23.32 +/- 0.21; z = 22.18 +/- 0.16). If this is the GRB host, at z = 2.0 it would have an absolute magnitude of M(2000 Å) ~ -21.6 AB. We acknowledge expert support from the observing staff in Paranal. The analysis of this spectrum was carried out with the help of the zHunter tool (https://doi.org/10.5281/zenodo.15189495) View this GCN Circular online at https://gcn.nasa.gov/circulars/42472. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40555] GRB 251027A: SVOM detection of a faint burst
by GCN Circulars 27 Oct '25

27 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42471 SUBJECT: GRB 251027A: SVOM detection of a faint burst DATE: 25/10/27 10:41:32 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Y. H.Cheng (YNU), Y. F. Liang (PMO), O. Godet, S. Guillot (IRAP), S. Schanne (CEA), L. Zhang (IHEP) At 2025-10-27T09:38:17 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 251027A (SVOM burst-id sb25102702). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was only detected by the Count-Rate Trigger (CRT), which produced a sequence of 1 alert. CRT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 8.33 in the [5-20] keV energy band over a time window of 20.40 seconds starting at 2025-10-27T09:37:56. The localization of the best alert is R.A., Dec. 95.1860, 11.6869 degrees: R.A. (J2000) = 6h20m44.64s Dec. (J2000) = 11d41m12.73s with a 90% confidence level (C.L.) radius of 9.46 arcmin (including systematic error of 2 arcmin added in quadrature). The GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb251027A.png Due to the ECLAIRs detection significance being below the slew threshold, no immediate slew was performed on this burst. But follow-up observations with SVOM/MXT and SVOM/VT have been requested. 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 Yehao Cheng: yhcheng(a)mail.ynu.edu.cn. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/42471. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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