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

[vsnet-grb-info 42130] The EP-WXT trigger 01709258851: Las Cumbres upper limit
by GCN Circulars 15 Mar '26

15 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44009 SUBJECT: The EP-WXT trigger 01709258851: Las Cumbres upper limit DATE: 26/03/15 01:07:35 GMT FROM: Wenxiong Li at NAOC <liwenxiong1992(a)gmail.com> Wenxiong Li, Runduo Liang (NAOC), Iair Arcavi, Ido Keinan (TAU), David Sand (U of Arizona) We observed the position of the EP-WXT trigger 01709258851 with a Las Cumbres 1m telescope at Sutherland Observatory, South Africa, 50 mins after the Einstein Probe WXT trigger. We took 4x300s exposures in the broad optical w band. We didn’t detect any uncataloged source within the EP-WXT error circle down to a limiting r-band mag of 21.5 mag. View this GCN Circular online at https://gcn.nasa.gov/circulars/44009. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42129] GRB 260314A: GECAM-B observation of a burst
by GCN Circulars 15 Mar '26

15 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44008 SUBJECT: GRB 260314A: GECAM-B observation of a burst DATE: 26/03/15 01:04:49 GMT FROM: xueyuan zao <zaoxueyuan(a)gmail.com> Xue-Yuan Zao, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered on-ground by GRB 260314A, at 2026-03-14T00:58:53.100 UTC, which is also detected by Fermi/GBM (Fermi GBM team, GCN #43997). The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260314A.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/44008. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42128] Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
by GCN Circulars 14 Mar '26

14 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44007 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB DATE: 26/03/14 18:19:35 GMT FROM: Bagrat Mailyan at Florida Tech <mbagrat(a)gmail.com> B. Mailyan (Florida Tech) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 795185313/260314534 at 12:48:28.23 UT on 14 March 2026, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely accidental." View this GCN Circular online at https://gcn.nasa.gov/circulars/44007. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42127] GRB 260310A / AT2026fgk: SAO RAS optical observations
by GCN Circulars 14 Mar '26

14 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44006 SUBJECT: GRB 260310A / AT2026fgk: SAO RAS optical observations DATE: 26/03/14 15:46:52 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Spiridonova (SAO RAS), A. Pozanenko (IKI), N. Pankov (IKI), A. Volnova (IKI), report on behalf of GRB follow-up team and IKI-GRB-FuN. We observed the field of the AT2026fgk, potential counterpart of the GRB 260310A (Fermi GBM team, GCN 43951; Hamburg and Meegan, GCN 43975; Salunke et al., GCN 43958) with the Zeiss-1000 1m telescope of the SAO RAS equipped with the CCD photometer. We obtained series of 300 sec images in B, V, Rc, Ic filters on March 12/13 and 13/14. The observations carried out under a good weather conditions and typical seeing of 1".5--2".5. The candidate discovered by GOTO (O'Neill et al. 2026, TNS Discovery Report 294132) and observed by numerous observatories (Konno et al., GCN 43974; Hinds et al., GCN 43977; Lipunov et al., GCN 43978; Martin-Carrillo et al., GCN 43979; Moren Méndez et al., GCN 43980; de Ugarte Postigo et al., GCN 43984; Hsu et al., GCN 43986; Pursiainen et al., GCN 43990; Becerra et al., GCN 43991; Li et al., GCN 43993; Jayaraman et al., GCN 43994; Stein et al., GCN 43996; Martin-Carrillo et al., GCN 44000; Watson et al., GCN 44001; Lai et al., GCN 44002; Izzo, GCN 44003; Brivio et al., GCN 44004; Rhodes et al., GCN 44005) is clearly detected in our images with the following brightness. Date UT_start t_mid - T0, filter exp, mag +/- err days s 2026.03.12T23:27:00 2.80565 B 5*300 18.77 +/- 0.01 2026.03.12T23:09:50 2.79577 Rc 6*300 18.00 +/- 0.01 2026.03.13T23:56:42 3.82450 B 5*300 18.92 +/- 0.01 2026.03.13T23:45:30 3.81664 Rc 4*300 18.14 +/- 0.01 This preliminary photometry is based on the nearby stars from PanSTARRS catalogue. Magnitudes of standards converted to B, Rc with the Lupton 2005 equations. The magnitudes of the AT2026fgk are not corrected for Galactic and host extinction and may be contaminated by the host galaxy. We can not trace any colour evolution between the two epochs (2.8 and 3.8 days after GRB trigger). View this GCN Circular online at https://gcn.nasa.gov/circulars/44006. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42126] GRB 260310A/AT 2026fgk: radio detection at 15GHz
by GCN Circulars 14 Mar '26

14 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44005 SUBJECT: GRB 260310A/AT 2026fgk: radio detection at 15GHz DATE: 26/03/14 15:23:56 GMT FROM: Lauren Rhodes at McGill <lauren.rhodes(a)mcgill.ca> Lauren Rhodes (McGill), Andrew Hughes, Rob Fender (Oxford), Joe Bright (Oxford/Breakthrough Listen), Dave Green, Dave Titterington (Cambridge) report: We observed the position of GRB 260310A/AT 2026fgk (Fermi GBM Team, GCN 43951; Konno et al., GCN 43974; Hinds et al., AstroNote 2026-65; O’Neill et al. 2026, TNS Discovery Report 294132) with the Arcminute Microkelvin Imager Large-Array (AMI-LA) at 15.2 GHz beginning at 2026 March 13 23:20:06 for a total of 8 hours. The flux standard 3c286 was used to calibrate the bandpass response and flux scale of the AMI-LA and J1435+7605 was used as an interleaved complex gain calibrator. We detect an unresolved source with coordinates consistent with those of GRB 260310A/AT 2026fgk. We measure a peak flux density of 9.8 +/- 0.5 mJy/beam. Given the high flux density of the source, we cross checked with the VLASS survey and find no preexisting radio emission at the afterglow coordinates down to a 3sigma upper limit of around 0.5mJy/beam. We thank the staff at the Mullard Radio Astronomy Observatory for carrying out these observations and operating the AMI-LA. View this GCN Circular online at https://gcn.nasa.gov/circulars/44005. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42125] GRB 260310A / AT2026fgk: TNG NIR detection
by GCN Circulars 14 Mar '26

14 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44004 SUBJECT: GRB 260310A / AT2026fgk: TNG NIR detection DATE: 26/03/14 14:48:10 GMT FROM: Riccardo Brivio at INAF-OAB <riccardo.brivio(a)inaf.it> R. Brivio (INAF-OAB), D. Malesani (DAWN/NBI and Radboud), L. Izzo (INAF-OACn and DARK/NBI), P. D’Avanzo (INAF-OAB), V. D’Elia (ASI-SSDC), A. Melandri (INAF-OAR), A. Rossi (INAF-OAS), M. de Pasquale (Univ. Messina), Aldo Fiorenzano (INAF-TNG), Carmen Padilla (INAF-TNG) report on behalf of the CIBO collaboration: We observed the likely counterpart of GRB 260310A, detected by Fermi/GBM (Fermi GBM team, GCN 43951; Hamburg & Meagan, GCNC 43975) and AstroSat CZTI (Salunke et al., GCN 43958) with the Italian 3.6m TNG telescope equipped with the near-infrared camera NICS. A series of images was obtained with the J and H filters starting on 2026 March 14 at 05:11:46 UT (i.e. 96.2 hours after the burst), and lasted 40 minutes for each filter. The optical/NIR counterpart, also reported as AT2026fgk (Konno et al., GCN 43974; Hinds et al., GCN 43977; Lipunov et al., GCN 43978; Martin-Carrillo et al., GCN 43979; Moreno Méndez et al., GCN 43980; de Ugarte Postigo et al., GCN 43984; Hsu et al., GCN 43986; Pursiainen et al., GCN 43990; Becerra et al., GCN 43991; Li et al., GCN 43993; Stein et al, GCN 43996; Martin-Carrillo et al., GCN 44000; Watson et al., GCN 44001; Lai et al., GCN 44002; L. Izzo, GCN 44003) is detected in the co-added images with the following magnitudes: J = 17.0 +/- 0.1 (Vega, calibrated against the 2MASS catalogue), at a mid-time of 96.5 hr after the trigger; H = 15.9 +/- 0.1 (Vega, calibrated against the 2MASS catalogue), at a mid-time of 97.1 hr after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/44004. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42124] GRB 260310A / AT2026fgk: OASDG optical observations
by GCN Circulars 14 Mar '26

14 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44003 SUBJECT: GRB 260310A / AT2026fgk: OASDG optical observations DATE: 26/03/14 09:12:46 GMT FROM: luca.izzo(a)inaf.it L. Izzo (INAF-OACn and DARK/NBI) reports: We observed the likely counterpart of GRB 261013A (Fermi GBM team, GCN #43951; Hamburg et al., GCN #43975) using the 0.5-m T1 telescope of the Osservatorio Astronomico S. Di Giacomo, located in Agerola, Italy. Our observations started on 2026 March 14 at 00:04 UT, 3.797 days after the GRB trigger. We acquired a series of 8 × 300 s images in the Rc and Ic filters. The optical counterpart, also reported as AT2026fgk (Konno et al., GCN #43974; Hinds et al., GCN #43977; Lipunov et al., GCN #43978; Martin-Carrillo et al., GCN #43979; Moreno Méndez et al., GCN #43980; de Ugarte Postigo et al., GCN #43984; Hsu et al., GCN #43986; Pursiainen et al., GCN #43990; Becerra et al., GCN #43991; Martin-Carrillo et al., GCN #44000; Watson et al., GCN #44001; Lai et al., GCN #44002) is clearly detected in the individual frames. In the Rc-band stacked image, we measure a preliminary magnitude of Rc = 18.21 +/- 0.07 mag (AB), calibrated against nearby stars from the Pan-STARRS catalog and appropriately transformed to Rc magnitudes. The measured magnitude may still be affected by contamination from the bright host galaxy, but further analysis is ongoing. View this GCN Circular online at https://gcn.nasa.gov/circulars/44003. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42123] GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
by GCN Circulars 14 Mar '26

14 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44002 SUBJECT: GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations DATE: 26/03/14 08:19:29 GMT FROM: Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941(a)gmail.com> C.-H. Lai, A. Aryan, Y.-H. Lee, 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), A. Sankar.K, M.-H. Lee, 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 performed multiband optical observations of the field of the GRB 260310A (Fermi GBM team, GCN 43951, Hamburg et al., GCN 43975) using the 1m LOT at the Lulin observatory, as part of the Kinder collaboration (Chen et al. 2025, ApJ, 983, 86, doi:10.3847/1538-4357/adb428). The first LOT epoch of observations in g-band started at 13:45 UTC on 13th of March 2026 (MJD 61092.577), 3.37 days after the Fermi GBM detection. The reported optical counterpart, AT 2026fgk (Konno et al., GCN 43974; Hinds et al., GCN 43977; Lipunov et al., GCN 43978; Martin-Carrillo et al., GCN 43979; Moreno Méndez et al., GCN 43980; Ugarte Postigo et al., GCN 43984; Hsu et al., GCN 43986; Pursiainen et al., GCN 43990; Becerra et al., GCN 43991; Martin-Carrillo et al., GCN 44000; Watson et al., GCN 44001), is clearly visible in each individual frame. The GRB also had X-ray (Salunke et al., GCN 43958; Jayaraman et al., GCN 43994) and NIR (Li et al., GCN 43993; Stein et al., GCN 43996) detections. We utilized the Python-based package AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform template subtractions with the Pan-STARRS1 3Pi archive images (Chambers et al. 2016 arXiv:1612.05560) using the 'SFFT' (Hu et al. 2022, ApJ, 936, 157) algorithm. Moreover, we further used AutoPhOT to perform PSF photometry. The details of the observations and the measured photometry (in the AB system) are as follows: Telescope | Filter | MJD (start) | t-t0 (d) | Exposure (s) | Magnitude | avg.Seeing | Airmass LOT | g | 61112.573 | 3.367 | 300 * 1 | 18.72 +/- 0.02 | 1".94 | 2.35 LOT | r | 61112.576 | 3.371 | 300 * 1 | 18.42 +/- 0.02 | 1".70 | 2.32 LOT | i | 61112.581 | 3.374 | 300 * 1 | 18.26 +/- 0.02 | 1".77 | 2.28 LOT | z | 61112.584 | 3.378 | 300 * 1 | 17.96 +/- 0.05 | 1".90 | 2.25 In multiband photometry, the optical counterpart appears red. The presented magnitudes are calibrated using the field stars from the ATLAS-refcat2 catalog from MAST (Tonry J. L. et al. 2018, ApJ, 867, 105). In the direction of the transient, these magnitudes are not corrected for the expected Galactic foreground extinctions of 0.09, 0.06, 0.04, and 0.03 mags (Schlafly & Finkbeiner 2011) for the g, r, i, and z bands, respectively. The details on the Lulin observatory telescopes and the follow-up methodology for such transients 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/44002. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42122] GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
by GCN Circulars 14 Mar '26

14 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44001 SUBJECT: GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations DATE: 26/03/14 06:20:02 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Alan M. Watson (UNAM), Damien Dornic (CPPM), Rosa L. Becerra (UNAM), Antonio de Ugarte Postigo (LAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (NYUAD), Camila Angulo (UNAM), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), 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), and Benjamin Schneider (LAM) report: We again imaged the field of AT 2026fgk (Lipunov et al., GCN Circ. 43954; Konno et al., GCN Circ. 43975; Hinds et al., GCN Circ. 43977; Lipunov et al., GCN Circ. 43978, Martin-Carrillo et al., GCN Circ. 43079; Moren Méndez et al., GCN Circ 43980; de Ugarte Postiga et al., GCN Circ. 43984; Hsu et al., GCN Circ. 43986; Pursiainen et al., GCN Circ. 43990; Becerra et al., GCN Circ 43991; Li et al., GCn Circ. 43993; Stein et al., GCN Circ 43996; Martin-Carrillo et al., GCn Circ. 44000), a possible counterpart of the Fermi GBM GRB 260310A (Fermi GBM Team, GCN Circ. 43951; Humburg & Meegan, GCN Circ. 43975) and also detected by AstroSat CZTI (Salunke et al., GCN Circ. 43958), using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-03-14 02:46 to 05:07 UTC (from 93.82 to 96.17 hours after the GRB trigger) and obtained 15, 14, and 28 minutes, respectively, of exposure in the g, r, and z filters. The data were reduced, coadded, calibrated, and analysed with the ASU pipeline. 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 images, we continue to detect AT 2026fgk with a preliminary PSF magnitude of: r = 18.47 +/- 0.01 Compared to the magnitudes in our first epoch reported in Moreno Méndez et al. (GCN Circ. 43980), we estimate a temporal decay index of about -1.2, consistent with the normal decay observed in GRBs. Moreover, from the optical/IR magnitudes from our first epoch and the photometry reported with WINTER (Stein et al., GCN Circ. 43996) between T+71.5 and T+72.5 hours, we estimate a spectral index beta of about -1.1 also supporting a synchrotron spectrum and a likely origin in a GRB afterglow. We thank the staff of the Observatorio Astronómico Nacional at Sierra de San Pedro Mártir, as well as the technical and engineering teams at CEA, CPPM, IRAP, LAM, OHP, OSU Pytheas, and UNAM. 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/44001. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42121] GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
by GCN Circulars 14 Mar '26

14 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44000 SUBJECT: GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay DATE: 26/03/14 04:43:17 GMT FROM: Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo(a)ucd.ie> A. Martin-Carrillo, E. Aasen, L. Brown, D. Colfer, M. Collins, J. Costello, C. Harris, R. Odunuga, H. O'Leary Jeffers, C. O'Malley, J. Parimkayala, J. Roca Garcia-Valino, R. Roddy, D. Scott, A. Valdivia y Alvarado Carvajal (UCD), A. Fernandez-Martin (CAHA), J. F. Agui Fernandez (CAHA), report on behalf of a larger collaboration: We observed the position of AT2026fgk, the likely counterpart to GRB 260310A (Fermi GBM team, GCN 43951; Salunke et al., GCN 43958; Konno et al., GCN 43974; Hinds et al., GCN 43977; Lipunov et al., GCN 43978; Martin-Carrillo et al., GCN 43979; Méndez et al., GCN 43980; de Ugarte Postigo et al., GCN 43984; Hsu et al., GCN 43986; Malesani et al., GCN 43990; Becerra et al., GCN 43991, Li et al., GCN 43993; Stein et al., GCN 43996; discovered by GOTO; O'Neill et al. 2026, TNS Discovery Report 294132) using the CAHA 1.23m telescope equipped with the DLR-MkIII CCD camera. A series of 3 x 150s exposures were taken in the BVRI bands starting at 2026-03-13T23:59:00 (~3.793 days after the Fermi trigger). The candidate is still well detected in the individual images with a preliminary AB magnitude of R = 18.3 +/- 0.1. Our photometry was calibrated using nearby stars from the Pan-STARRS catalogue and is neither corrected for Galactic extinction nor the host galaxy contribution. Comparing this new epoch with our previously reported R-band magnitude (Martin-Carrillo et al., GCN 43979) we infer a shallow decay with a power-law index of ~0.3, significantly shallower than the decay observed (~0.7) since the initial report by Konno et al., GCN 43974. These observations were made during the UCD Academy observing run at Calar Alto Observatory (Almeria, Spain) as part of the final year undergraduate projects of the University College Dublin BSc (Hons) in Physics with Astronomy and Space Science. View this GCN Circular online at https://gcn.nasa.gov/circulars/44000. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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