February 2026 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 41799] EP260209a: Einstein Probe detection of a fast X-ray transient
by GCN Circulars 11 Feb '26

11 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43693 SUBJECT: EP260209a: Einstein Probe detection of a fast X-ray transient DATE: 26/02/11 11:43:58 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.J. Zhang (THU), R. Shi (PMO), Z. H. Yang, Q. C. Zhao (IHEP), G. Y. Zhao (SYSU) and Z. X. Ling (NAOC) on behalf of the Einstein Probe (EP) team: We report on the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260209a. The EP-WXT observation started at 2026-02-09T13:44:06 (UTC). The WXT position of the source is R.A. = 159.683 deg, DEC = 28.312 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). The light curve exhibits a flare in the first 50 seconds of the WXT observation, with a 0.5--4 keV flux of approximately 7.4 × 10^-10 erg s^-1 cm^-2. The delayed report of the transient is due to its relatively low detection significance. We performed a follow-up observation with the Follow-up X-ray Telescope (FXT), starting at 2026-02-10T07:02:41 (UTC), about 17 hours after the detection. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 159.6834 deg, DEC = 28.3078 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic). The uncatalogued X-ray source has a 0.5--10 keV flux of 1.1 x 10^-13 erg s^-1 cm^-2, with a powerlaw index of 1.3 and a fixed galactic NH value (1.6 x 10^20 cm^-2). 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/43693. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41798] EP260210a: Optical upper limits with Kinder observations
by GCN Circulars 11 Feb '26

11 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43692 SUBJECT: EP260210a: Optical upper limits with Kinder observations DATE: 26/02/11 08:35:06 GMT FROM: Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941(a)gmail.com> A. Aryan, C.-S. Lin, T.-W. Chen (all NCU), A. K. H. Kong (NTHU), J. H. Gillanders, S. J. Smartt (both Oxford), Y. J. Yang (NYUAD), Y.-H. Lee, A. Sankar.K, M.-H. Lee, C.-H. Lai, Y.-C. Pan, C.-C. Ngeow, W.-J. Hou, H.-Y. Hsiao, H.-C. Lin, J.-K. Guo (all NCU), S. Yang, Z. N. Wang, L. L. Fan, G. H. Sun (all HNAS), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (both IfA, Hawaii) report: We observed the field of the fast X-ray transient EP260210a (Shi et al. GCN 43681) using the 40cm SLT and 1m LOT at the Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al. 2025, ApJ, 983, 86, doi:10.3847/1538-4357/adb428). The first SLT epoch of observations in r-band started at 13:57 UTC on 10th of February 2026 (MJD 61081.582), 3.57 hr after the EP-WXT trigger. We utilized the astroalign (Beroiz et al. 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al. 2022, ApJ, 935, 167) packages to align and stack the individual frames. We utilized the Python-based package AutoPhOT (Brennan & Fraser 2022, A&A, 667, A62) to perform template subtraction with the DESI Legacy Survey (Dey et al. 2019, AJ 157, 168) DR10 image (for r-band) and Pan-STARRS1 3Pi (Chambers et al. 2016, arXiv:1612.05560) archive image (for i-band) using the 'SFFT' (Hu et al. 2022, ApJ, 936, 157) algorithm. Moreover, we used AutoPhOT to perform PSF photometry. We do not detect any new or uncataloged sources within the 20" EP-FXT localization circle. The details of the observations and the measured 3-sigma upper limits (in the AB system) are as follows: Telescope | Filter | MJD (start)| t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass SLT | r | 61081.582 | 3.57 | 300 * 12 | >22.0 | 1".5 | 1.47 LOT | r | 61081.584 | 3.62 | 300 * 6 | >22.9 | 1".3 | 1.54 SLT | i | 61081.628 | 4.69 | 300 * 20 | >21.6 | 1".4 | 1.18 The non-detections in our observations are consistent with those reported by Kang et al. (GCN 43683), Fortin et al. (GCN 43684), and Li et al. (GCN 43687). The presented magnitude is calibrated using the field stars from the ATLAS-RefCat2 catalog from MAST (Tonry J. L. et al. 2018, ApJ, 867, 105) and is not corrected for the expected Galactic foreground extinction of A_r = 0.034 mag and A_i = 0.026 mag in the direction of the transient (Schlafly & Finkbeiner 2011). The methodology, details on the Lulin observatory telescopes, and a compilation of our optical follow-up campaign for FXTs discovered within the first year of operation of the Einstein-Probe mission are presented in Aryan et al. 2025, ApJS, 281, 20, doi:10.3847/1538-4365/adfc69. View this GCN Circular online at https://gcn.nasa.gov/circulars/43692. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41797] IPN triangulation of GRB 260207B (short/hard with EE)
by GCN Circulars 10 Feb '26

10 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43691 SUBJECT: IPN triangulation of GRB 260207B (short/hard with EE) DATE: 26/02/10 20:33:53 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia(a)mail.ioffe.ru> A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the HEND/Mars Odyssey team, A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, 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 W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr, and A.S. Gardner on on behalf of the GRS-Odyssey GRB team, report: The short-duration GRB with extended emission GRB 260207B (Fermi-GBM detection: Fermi GBM team, GCN 43629; Sonawane & Bala, GCN 43634; GECAM-B observation: Zao et al., GCN 43644; AstroSat CZTI detection: Goyal et al., GCN 43680) was detected by Fermi (GBM trigger 792162735), Konus-Wind, GECAM-B, AstroSat (CZTI), and Mars-Odyssey (HEND) at about 47531 s UT (13:12:11). We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 283.695 (18h 54m 47s) +51.643 (+51d 38' 34") Corners: 284.134 (18h 56m 32s) +51.778 (+51d 46' 39") 283.959 (18h 55m 50s) +51.758 (+51d 45' 29") 283.258 (18h 53m 02s) +51.506 (+51d 30' 22") 283.432 (18h 53m 44s) +51.527 (+51d 31' 36") --------------------------------------------- The error box area is 67 sq. arcmin, and its maximum dimension is 36 arcmin (the minimum one is 2 arcmin). The Sun distance was 74 deg. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB260207_T47529/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/43691. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41796] GRB 260210C: Fermi GBM Final Real-time Localization
by GCN Circulars 10 Feb '26

10 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43690 SUBJECT: GRB 260210C: Fermi GBM Final Real-time Localization DATE: 26/02/10 20:00:13 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 19:49:42 UT on 10 Feb 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260210C (trigger 792445787.668744 / 260210826). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 338.7, Dec = 22.6 (J2000 degrees, equivalent to J2000 22h 34m, 22d 36'), with a statistical uncertainty of 7.5 degrees. The angle from the Fermi LAT boresight is 26.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260210826/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260210826/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260210826/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43690. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41795] GRB 260210A: Glowbug gamma-ray detection
by GCN Circulars 10 Feb '26

10 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43689 SUBJECT: GRB 260210A: Glowbug gamma-ray detection DATE: 26/02/10 19:04:18 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung(a)nrl.navy.mil> C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report: The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 260210A, which was also detected by AstroSat/CZTI, SVOM/GRM, and Konus-Wind (GCN 43686). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-02-10 11:27:33.624 with a duration of 27.6 s and a total significance of about 49 sigma. The Glowbug light curve comprises three main peaks at ~T0+4s, +16s, and +26s. The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12. [1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108 Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/43689. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41794] GRB 260210B: Fermi GBM Final Real-time Localization
by GCN Circulars 10 Feb '26

10 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43688 SUBJECT: GRB 260210B: Fermi GBM Final Real-time Localization DATE: 26/02/10 18:24:59 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 18:14:06 UT on 10 Feb 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260210B (trigger 792440051.126154 / 260210760). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 6.0, Dec = -48.3 (J2000 degrees, equivalent to J2000 00h 24m, -48d 17'), with a statistical uncertainty of 10.3 degrees. The angle from the Fermi LAT boresight is 22.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260210760/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260210760/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260210760/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43688. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41793] EP260210a: SVOM/VT optical upper limit
by GCN Circulars 10 Feb '26

10 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43687 SUBJECT: EP260210a: SVOM/VT optical upper limit DATE: 26/02/10 17:33:25 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, Y. N. Ma, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM/VT performed a Target of Opportunity observation of EP260210a detected by Einstein Probe (Shi et al., GCN 43681). The observation started at 2026-02-10T10:56:57 UTC, 34.52 minutes after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. No uncatalogued sources are detected in single or stacked images within the error box of EP-FXT (Shi et al., GCN 43681), which is compatible with the earlier upper limits from SVOM/C-GFT (Kang et al., GCN 43683) and COLIBRÍ (Fortin et al, GCN 43684). The 3 sigma limit magnitudes are derived as below: Mid time | Band | Exposure Time | 3 sigma limit magnitude 2.316 hour VT_B 42*50 sec > 23.2 mag 1.535 hour VT_R 39*50 sec > 22.9 mag Our photometry was not corrected for Galactic extinction. 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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/43687. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41792] GRB 260210A: AstroSat CZTI detection
by GCN Circulars 10 Feb '26

10 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43686 SUBJECT: GRB 260210A: AstroSat CZTI detection DATE: 26/02/10 17:17:11 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> A. Arya (IITB), A. Goyal (IITB), M. Tembhurnikar (IUCAA), S. Salunke (IUCAA), Harsha K. H. (IUCAA), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long GRB 260210A which was also detected by SVOM/GRM (via GCN notices), and KONUS-Wind (via IPN notices). The source was clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-02-10 11:27:38.52 UTC. The measured peak count rate associated with the burst is 292 (+76, -33) counts/s above the background in the combined data of all quadrants, with a total of 3215 (+487, -705) counts. The local mean background count rate was 1390 (+5, -5) counts/s. We measure a T90 of 34 (+2, -9) s from the cumulative Veto light curve. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/43686. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41791] GRB 260208C: AstroSat CZTI detection
by GCN Circulars 10 Feb '26

10 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43685 SUBJECT: GRB 260208C: AstroSat CZTI detection DATE: 26/02/10 17:14:45 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> M. Tembhurnikar (IUCAA), Harsha K. H. (IUCAA), S. Salunke (IUCAA), A. Arya (IITB), A. Goyal (IITB), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long GRB 260208C which was also detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 43646) and SVOM/GRM (Yue Wang, GCN Circ. 43679). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-02-08 15:12:17.5 UTC. The measured peak count rate associated with the burst is 99 (+40, -11) counts/s above the background in the combined data of all quadrants, with a total of 577 (+174, -169) counts. The local mean background count rate was 283 (+3, -4) counts/s. Using cumulative rates, we measure a T90 of 13 (+1, -8) s. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/43685. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41790] EP260210a: COLIBRÍ optical upper limit
by GCN Circulars 10 Feb '26

10 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43684 SUBJECT: EP260210a: COLIBRÍ optical upper limit DATE: 26/02/10 14:47:40 GMT FROM: F. Fortin at IRAP <ffortin.sci.edu(a)gmail.com> Francis Fortin (IRAP), Edilberto Aguilar-Ruiz (UNAM), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the EP260210a (Shi et al., GCN Circ. 43681) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-02-10 11:13:20 to 13:11:12 UTC (from 0.83 to 2.80 hours after the trigger) and obtained 85 minutes of simultaneous exposure in the r and z filters. The data were reduced and coadded with the COLIBRÍ pipeline and analysed 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. In the stacked image, we do not detect any new source at the FXT source position (Shi et al., GCN Circ. 43681) down to the following 5-sigma limit: r > 23.59 z > 22.15 Our upper limits are compatible with the earlier upper limits of Kang et al. (GCN Circ. 43683). 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/43684. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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