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

[vsnet-grb-info 39703] EP250831a: NOT optical observations and tentative afterglow candidate
by GCN Circulars 01 Sep '25

01 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41637 SUBJECT: EP250831a: NOT optical observations and tentative afterglow candidate DATE: 25/09/01 19:46:02 GMT FROM: Gregory Corcoran at University College Dublin <gregory.corcoran(a)ucdconnect.ie> S.Y. Fu (HUST), J. Sanchez-Sierras (Radboud), J. An, L.B. He, S.Q. Jiang, X. Liu, Z.P. Zhu, D. Xu (NAOC), J.P.U. Fynbo (DAWN/NBI), G. Corcoran (UCD), P. G. Jonker (Radboud), A. J. Levan (Radboud and Warwick), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), J. A. Quirola-Vasquez (Radboud), A. Henderson (NOT) report: We observed the field of EP250831a (Yang et al., GCN 41619) using the Nordic Optical Telescope (NOT) located in La Palma (Canary Islands, Spain). We obtained 6 x 300 s r-band and 9 x 200 s z-band images. Within the EP-FXT error circle (Yang et al., GCN 41625), a new optical source is marginally visible in the stacked r-band image, at coordinates R.A. (J2000) = 02:51:55.49 Dec. (J2000) = -36:11:14.9 with an uncertainty of ~ 0.5 arcsec. We measure an AB magnitude r ~ 23.8 mag at an epoch of 18.23 hr after the EP trigger, calibrated against the Legacy Survey DR10 and not corrected for Galactic extinction. This source is not detected in the stacked z-band image, with a limiting magnitude of z > 22.0 mag (AB). There is a source in the Legacy Survey about 1.7” SE of our candidate, with a tabulated magnitude r = 23.83. We caution about the low S/N of our detection so we only report this object as a tentative optical counterpart to EP250831a. Further observations are planned in order to secure a template imaging and assess fading. View this GCN Circular online at https://gcn.nasa.gov/circulars/41637. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39702] EP250827b: FTW Observations of AT 2025wkm
by GCN Circulars 01 Sep '25

01 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41636 SUBJECT: EP250827b: FTW Observations of AT 2025wkm DATE: 25/09/01 19:30:16 GMT FROM: xjh(a)andrew.cmu.edu Xander J. Hall (Carnegie Mellon U.), Malte Busmann (LMU), Daniel Gruen (LMU), Brendan O’Connor (Carnegie Mellon U.), Antonella Palmese (Carnegie Mellon U.), Mansi Kasliwal (Caltech), Tomas Ahumada (Caltech), and Gokul Srinivasaragavan (UMD) report: We observed the localization of the X-ray flare EP250827b and optical transient AT 2025wkm as reported by Schroeder et al. (GCN 41635), with the Three Channel Imager (3KK) at the Fraunhofer Telescope at Wendelstein Observatory (FTW) in the r, i, and J bands starting at 2025-08-31T02:01:59 UTC (3.82 days after the X-ray flare) for 24 x 180s. In the difference imaging with templates from PS1, we detect AT 2025wkm at r = 20.14 +/- 0.02 AB mag, The magnitudes are calibrated against the PS1 catalog and not corrected for Galactic extinction. Furthermore, we see no other candidates in the difference imaging to a limiting depth of r = 23.15, which supports the association of AT 2025wkn and EP250827b. Further analysis is underway. We thank Michael Schmidt from the Wendelstein Observatory staff for obtaining these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/41636. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39701] EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
by GCN Circulars 01 Sep '25

01 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41635 SUBJECT: EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm DATE: 25/09/01 19:20:45 GMT FROM: Tomas Ahumada at Caltech <tfahumada94(a)gmail.com> G. Schroeder (Cornell), T. Ahumada (Caltech), A. Y. Q. Ho (Cornell), M. Kasliwal (Caltech), L.Yan (Caltech), G. Srinivasaragavan (UMD), X. J. Hall (CMU), M. Coughlin (UMN), D. Y. Li (NAO, CAS), J. Yang (ZZU), X. Tian (GXU), K.R., Ni, (CCNU), H. L., Peng (NJNU), H. Y, Liu, Y. J., Song, H. Sun, Y. Liu, C.C.Jin, W. Yuan (NAO, CAS) on behalf of the Zwicky Transient Facility and Einstein Probe (EP) Partnership We report the contemporaneous detection of the X-ray flare EP250827b associated with the optical transient ZTF25abmpngy/AT 2025wkm (RA = 02:26:20.64, Dec = +37:29:59.90). This event was highlighted in the cross-matching of ZTF alerts with EP alerts, an experiment first announced in Ahumada et al (GCN 39791). ZTF25abmpngy/AT 2025wkm was first detected on 2025-08-27T09:38:04 UT, 3.27 hrs after the X-ray flare, and with an r-band apparent magnitude of r = 20.33 +/- 0.11 mag. We note the transient sits on top of a potential host galaxy with no archival spectroscopic redshift. EP250827b was first detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission at RA.= 36.581, DEC.= 37.499, with an uncertainty of 2.4 arcmin in radius (90% C.L. statistical and systematic). The X-ray detection is 14.7 arcseconds away from the optical position. The X-ray transient started at 2025-08-27T06:22:27 (UT), and lasted for more than 1000 seconds as seen from the WXT light curve. The X-ray spectrum can be fitted by an absorbed power law model, with the absorption fixed at the Galactic value of 5.4x10^20 cm^-2 , and a photon index of 2.2 (-0.7, +0.8). The average unabsorbed 0.5-4keV flux is 2.6 (-0.9, +1.3) x 10^-11 erg/s/cm2. In the follow-up WXT coverage approximately 5 hours later at the position, the source was no longer detected, indicating a fast decay in the soft X-ray band. We performed a follow-up target of opportunity observation with EP-FXT. The observation began at 2025-09-01T02:35:49 with an exposure time of 2995 seconds, about 5 days after the burst detected by EP-WXT. Within the WXT error circle, no X-ray source was detected at the optical position, setting a flux upper limit at 90% confidence level around 5 x 10^-14 erg/s/cm2. Based on the current temporal and spatial consistency, EP250827b is likely associated with AT2025wkn. However, due to the significant systematic uncertainty in the WXT position and the non-detection in the follow-up FXT observation, this association cannot be fully confirmed. We are pursuing and encouraging follow-up observations to classify the source and validate the X-ray and optical association. 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). Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Award #2407588 and a partnership including Caltech, USA; Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; University of Wisconsin at Milwaukee, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan; Operations are conducted by Caltech's Optical Observatory (COO) and Caltech/IPAC. View this GCN Circular online at https://gcn.nasa.gov/circulars/41635. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39700] EP250831a: EP-FXT follow-up observation
by GCN Circulars 01 Sep '25

01 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41625 SUBJECT: EP250831a: EP-FXT follow-up observation DATE: 25/09/01 07:35:09 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> J. Yang (ZZU), X. Tian (GXU), D. Y. Li, Y. Liu (NAO, CAS) report on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of EP250831a (GCN 41619) at 2025-08-31T15:30:41 (UTC), about 6 hours after the WXT detection, with an exposure time of 2.9 ks. The source was also followed by Swift-XRT (GCN 41624). FXT detected an uncatalogued source within the WXT error circle at R.A. = 42.9816, DEC = -36.1872 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). The FXT X-ray spectrum of this uncatalogued source can be fitted with an absorbed powerlaw with the absorption fixed at the Galactic value of 1.9x10^20 cm^-2, and a photon index of 2.3(+/-0.6). The derived unabsorbed 0.5-10 keV flux is approximately 8.15x10^-14 erg/s/cm2. The uncertainties are at the 90% confidence level for the above parameters. We noted that EP-FXT also detected the uncatalogued X-ray source outside the WXT error circle detected by Swift-XRT. 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/41625. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39699] GRB 250901A: SVOM detection of a burst
by GCN Circulars 01 Sep '25

01 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41634 SUBJECT: GRB 250901A: SVOM detection of a burst DATE: 25/09/01 19:02:28 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> F. Piron (LUPM), C. Guépin (LUPM), S. Schanne (CEA), T. Maiolino (LUPM), C.-W. Wang (IHEP), M. Moita (CEA), report on behalf of the SVOM mission team: At 2025-09-01T18:14:22 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 250901A (SVOM burst-id sb25090101). 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 9 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 10.49 in the [8-120] keV energy band over a time window of 20.48 seconds starting at 2025-09-01T18:14:17. The localization of the best alert is R.A., Dec. 356.0950, -15.6712 degrees (J2000) with a 90% confidence level (C.L.) radius of 7.61 arcmin (including systematic error of 2 arcmin added in quadrature). This burst was also detected by SVOM/GRM with a significance of 10. The SVOM/GRM light curve showed a single peak structure with a T90 duration of about 17 seconds. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250901A.png SVOM slewed to the burst. SVOM/MXT began observing the field at 2025-09-01T18:17:20 UTC, 178 seconds after T0. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec. 356.1835, -15.7952 degrees: R.A. (J2000) = 23h44m44.04s Dec. (J2000) = -15d47m42.73s with a 90% C.L. radius of 194 arcseconds (including systematic error). This location is 9.03 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. We notice that the source SWIFT J2344.7-1573 is located 3.9 arcmin from the MXT position and 5.4 arcmin from the ECLAIRs position. 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 Frédéric Piron: piron(a)in2p3.fr. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/41634. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39698] GRB 250831B: SVOM/GRM observation
by GCN Circulars 01 Sep '25

01 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41633 SUBJECT: GRB 250831B: SVOM/GRM observation DATE: 25/09/01 18:09:16 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: Olivier GODET (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 250831B (SVOM trigger reference: sb25083101) at 2025-08-31T06:09:22.000 UTC (T0). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a single pulse with a T90 of 9.5 +4.0/-3.0 s in the 15-5000 keV band. ECLAIRs was not collecting data at the time of this burst. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250831B.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/41633. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39697] GRB 250830C: Insight-HXMT detection
by GCN Circulars 01 Sep '25

01 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41632 SUBJECT: GRB 250830C: Insight-HXMT detection DATE: 25/09/01 18:07:08 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> Chen-Wei Wang, Shao-Lin Xiong, and Chao Zheng report on behalf of the Insight-HXMT team: At 2025-08-30T14:51:55.100 (T0), Insight-HXMT/HE detected the burst GRB 250830C, which is also detected by GECAM-B (Wang et al., GCN #41630). The Insight-HXMT/HE light curve mainly consists of multi-pulses with a T90 of 12.6 +8.2/-3.6 s. The 1s peak rate, measured from T0+26.300 s, is 2735 cnts/sec. The total counts from this burst is 10641 counts. The HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb250830C.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/41632. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39696] EP250901a: Mephisto optical upper limits
by GCN Circulars 01 Sep '25

01 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41631 SUBJECT: EP250901a: Mephisto optical upper limits DATE: 25/09/01 18:00:45 GMT FROM: liuxk(a)ynu.edu.cn Xiangkun Liu, Chenxu Liu, Guowang Du, Xufeng Zhu, Shuai Xie, Xiaowei Liu (all SWIFAR, YNU), and Chao Wu (EP team) report on behalf of the Mephisto Team: The field of EP250901a, detected by EP-WXT (ID: 00109201113, triggered at 2025-09-01T12:05:03 UTC) and subsequently followed up by EP-FXT (GCN 41627), was observed with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. Simultaneous uvgr band photometric observations were conducted starting from 13:30:37 2025-09-01 UT (~1.5 hr after the trigger) and 6 frames with 45s exposure times were taken. No new optical counterpart was detected (consistent with the upper limits reported by Global MASTER-Net, GCN 41629) in the stacked images of uvgr bands. The preliminary photometry and 3 sigma upper limits are listed below. Start_Time(UT) | Band | Exp(s) | LimMag (AB) --------------------|------|--------|------------ 2025-09-01T13:30:37 | u | 45*6 | >21.68 2025-09-01T13:30:37 | v | 45*6 | >21.77 2025-09-01T13:37:13 | g | 45*6 | >22.17 2025-09-01T13:37:13 | r | 45*6 | >22.31 ------------------------------------------------------------------------------------------------- Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. It provides real-time, high-quality colors of stellar objects. The on-site telescope assemblage and commissioning were carried out in September 2022. The first light in all three channels was achieved on 2023 December 21. ------------------------------------------------------------------------------------------------- View this GCN Circular online at https://gcn.nasa.gov/circulars/41631. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39695] GRB 250830C: GECAM-B detection
by GCN Circulars 01 Sep '25

01 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41630 SUBJECT: GRB 250830C: GECAM-B detection DATE: 25/09/01 17:50:03 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by a bright long burst GRB 250830C at 2025-08-30T14:51:55.100 UTC (denoted as T0). According to the GECAM-B light curves in about 40-6000 keV, this burst mainly consists of a precursor followed by multiple pulses main emission with a duration (T90) of 23.6 +12.0/-8.4 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecamgrb250830C.png GECAM-B localized this burst to the following position (J2000): Ra: 240.1 deg Dec: 40.5 deg Err: 1.1 deg (1-sigma, statistical only) The time-averaged spectrum from T0-2 s to T0+40 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.06 +0.23/-0.24 and the cutoff energy, parameterized as Epeak, is 255 +121/-46 keV. The event fluence (10-1000 keV) in this time interval is (2.41 +/-0.36)E-05 erg/cm^2. The 'Amati' relation diagram of GRB 250830C is shown at: https://www.bursthub.cn//admin/static/grb250830C_amati.png Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/41630. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39694] EP250901a: Global MASTER-Net observations report
by GCN Circulars 01 Sep '25

01 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41629 SUBJECT: EP250901a: Global MASTER-Net observations report DATE: 25/09/01 17:18:37 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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the EP250901a ( EP Team et al., GCN 41627) errorbox 11710 sec after notice time and 17745 sec after trigger time at 2025-09-01 17:00:48 UT, with upper limit up to 17.5 mag. Observations started at twilight. The observations began at zenith distance = 53 deg. The sun altitude is -9.0 deg. The galactic latitude b = 16 deg., longitude l = 46 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2981475 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 17775 | 2025-09-01 17:00:48 | MASTER-SAAO | (18h 08m 55.12s , +18d 41m 44.3s) | C | 60 | 16.8 | 17776 | 2025-09-01 17:00:48 | MASTER-SAAO | (18h 10m 43.80s , +18d 26m 21.7s) | C | 60 | 15.2 | 18076 | 2025-09-01 17:05:48 | MASTER-SAAO | (18h 09m 00.19s , +18d 41m 53.8s) | C | 60 | 17.1 | 18076 | 2025-09-01 17:05:48 | MASTER-SAAO | (18h 10m 48.74s , +18d 26m 31.7s) | C | 60 | 16.3 | 18369 | 2025-09-01 17:10:42 | MASTER-SAAO | (18h 10m 47.53s , +18d 26m 45.9s) | C | 60 | 16.7 | 18369 | 2025-09-01 17:10:42 | MASTER-SAAO | (18h 08m 58.87s , +18d 42m 08.5s) | C | 60 | 17.5 | 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/41629. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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