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[vsnet-grb-info 41594] The EP-WXT trigger 01709251871 is likely a flaring star
by GCN Circulars 22 Jan '26

22 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43495 SUBJECT: The EP-WXT trigger 01709251871 is likely a flaring star DATE: 26/01/22 01:53:51 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R.D. Liang (NAOC), Z. X. Li, G. L. Huang, C. Wang (IHEP) and Y. Liu (NAOC) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709251871 at the time of 2026-01-22T00:00:14, is likely a stellar flare associated with [M81] I-308. The estimated flux of the flare is around 1x10^-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 8.5x10^31 erg/s. 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/43495. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41593] The EP-WXT trigger 01709251871 is likely a flaring star
by GCN Circulars 22 Jan '26

22 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43495 SUBJECT: The EP-WXT trigger 01709251871 is likely a flaring star DATE: 26/01/22 01:53:51 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R.D. Liang (NAOC), Z. X. Li, G. L. Huang, C. Wang (IHEP) and Y. Liu (NAOC) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709251871 at the time of 2026-01-22T00:00:14, is likely a stellar flare associated with [M81] I-308. The estimated flux of the flare is around 1x10^-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 8.5x10^31 erg/s. 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/43495. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41592] Fermi GRB 260120C: Global MASTER-Net observations report
by GCN Circulars 22 Jan '26

22 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43494 SUBJECT: Fermi GRB 260120C: Global MASTER-Net observations report DATE: 26/01/22 00:30:53 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 [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 260120C ( Fermi GBM team, GCN 43482) errorbox 1 days 3994 sec after notice time and 1 days 4027 sec after trigger time at 2026-01-22 00:14:13 UT, with upper limit up to 16.8 mag. The observations began at zenith distance = 81 deg. The sun altitude is -47.2 deg. The galactic latitude b = 20 deg., longitude l = 26 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3110218 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 44777 | 2026-01-21 11:32:53 | MASTER- | (17h 17m 02.82s , +06d 50m 25.2s) | C | 60 | 18.4 | 44777 | 2026-01-21 11:32:53 | MASTER- | (17h 18m 05.82s , +06d 16m 01.2s) | C | 60 | 18.4 | 44847 | 2026-01-21 11:34:03 | MASTER- | (17h 25m 13.44s , +06d 50m 33.0s) | C | 60 | 18.3 | 44847 | 2026-01-21 11:34:03 | MASTER- | (17h 26m 16.06s , +06d 16m 06.1s) | C | 60 | 18.2 | 45387 | 2026-01-21 11:43:03 | MASTER- | (17h 18m 07.00s , +06d 16m 05.5s) | C | 60 | 18.6 | 45387 | 2026-01-21 11:43:03 | MASTER- | (17h 17m 03.38s , +06d 50m 02.6s) | C | 60 | 18.5 | 45457 | 2026-01-21 11:44:13 | MASTER- | (17h 26m 15.40s , +06d 16m 14.1s) | C | 60 | 18.5 | 45457 | 2026-01-21 11:44:13 | MASTER- | (17h 25m 12.21s , +06d 50m 13.9s) | C | 60 | 18.4 | 46057 | 2026-01-21 11:54:13 | MASTER- | (17h 17m 05.56s , +06d 51m 19.0s) | C | 60 | 18.6 | 46057 | 2026-01-21 11:54:13 | MASTER- | (17h 18m 09.53s , +06d 17m 03.8s) | C | 60 | 18.8 | 46127 | 2026-01-21 11:55:23 | MASTER- | (17h 25m 09.25s , +06d 49m 58.4s) | C | 60 | 18.5 | 46127 | 2026-01-21 11:55:23 | MASTER- | (17h 26m 12.91s , +06d 15m 41.0s) | C | 60 | 18.6 | 46661 | 2026-01-21 12:04:17 | MASTER- | (17h 18m 10.15s , +06d 16m 41.1s) | C | 60 | 19.0 | 46661 | 2026-01-21 12:04:17 | MASTER- | (17h 17m 05.20s , +06d 51m 05.2s) | C | 60 | 18.7 | 46730 | 2026-01-21 12:05:26 | MASTER- | (17h 25m 08.92s , +06d 49m 31.9s) | C | 60 | 18.5 | 46730 | 2026-01-21 12:05:26 | MASTER- | (17h 26m 13.45s , +06d 15m 06.0s) | C | 60 | 18.8 | 47327 | 2026-01-21 12:15:23 | MASTER- | (17h 17m 06.31s , +06d 49m 15.8s) | C | 60 | 18.7 | 47327 | 2026-01-21 12:15:23 | MASTER- | (17h 18m 11.40s , +06d 14m 44.7s) | C | 60 | 19.0 | 47398 | 2026-01-21 12:16:33 | MASTER- | (17h 25m 11.28s , +06d 50m 36.4s) | C | 60 | 18.6 | 47398 | 2026-01-21 12:16:34 | MASTER- | (17h 26m 16.13s , +06d 16m 02.5s) | C | 60 | 18.9 | 47994 | 2026-01-21 12:26:30 | MASTER- | (17h 17m 04.57s , +06d 49m 46.2s) | C | 60 | 18.7 | 47994 | 2026-01-21 12:26:30 | MASTER- | (17h 18m 10.96s , +06d 15m 15.9s) | C | 60 | 19.1 | 48064 | 2026-01-21 12:27:40 | MASTER- | (17h 25m 06.47s , +06d 50m 37.4s) | C | 60 | 18.7 | 48064 | 2026-01-21 12:27:40 | MASTER- | (17h 26m 12.55s , +06d 16m 04.5s) | C | 60 | 19.1 | 90457 | 2026-01-22 00:14:13 | MASTER-Kislovodsk | (16h 55m 40.00s , +10d 25m 13.1s) | C | 60 | 16.7 | 90573 | 2026-01-22 00:16:09 | MASTER-Kislovodsk | (17h 02m 50.35s , +12d 18m 51.1s) | C | 60 | 16.7 | 90811 | 2026-01-22 00:20:07 | MASTER-Kislovodsk | (16h 45m 12.41s , +06d 36m 17.1s) | C | 60 | 16.8 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43494. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41591] GRB 260120B: Swift-BAT refined analysis
by GCN Circulars 21 Jan '26

21 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43493 SUBJECT: GRB 260120B: Swift-BAT refined analysis DATE: 26/01/21 23:08:12 GMT FROM: D. R. Sadaula at NASA GSFC <dev.r.sadaula(a)nasa.gov> D. M. Palmer (LANL), S. D. Barthelmy (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-769 to T+303 sec from the recent telemetry downlink, we report further analysis of BAT GRB 260120B (trigger #1442454) (Ferro et al., GCN Circ. 43479). The BAT ground-calculated position is RA, Dec = 284.701, 61.905 deg which is RA(J2000) = 18h 58m 48.3s Dec(J2000) = +61d 54' 19.2" with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 9%. The BAT light curve showed a single-peaked structure with a duration of about 10 sec. T90 (15-350 keV) is 4.48 +- 0.94 sec (estimated error including systematics). The time-averaged spectrum from T-0.34 to T+4.59 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index -0.93 +- 1.35, and Epeak of 103.9 +- 38.6 keV (chi squared 48.41 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.2 +- 0.1 x 10^-06 erg/cm2 and the 1-sec peak flux measured from T+0.48 sec in the 15-150 keV band is 3.1 +- 0.8 ph/cm2/sec. A fit to a simple power law gives a photon index of 0.95 +- 0.21 (chi squared 57.22 for 57 d.o.f.). 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/1442454 View this GCN Circular online at https://gcn.nasa.gov/circulars/43493. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41590] GRB 260120B: Swift-XRT refined Analysis
by GCN Circulars 21 Jan '26

21 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43492 SUBJECT: GRB 260120B: Swift-XRT refined Analysis DATE: 26/01/21 20:20:55 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), A. D'Ai (INAF-IASFPA), S. Lanava (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 5.6 ks of XRT data for GRB 260120B, from 130 s to 29.5 ks after the trigger. The data comprise 13 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The light curve can be modelled with a power-law decay with a decay index of alpha=0.84 (+/-0.06). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.97 (+0.29, -0.27). The best-fitting absorption column is 2.1 (+1.2, -1.0) x 10^21 cm^-2, in excess of the Galactic value of 7.4 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.7 x 10^-11 (5.1 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 2.1 (+1.2, -1.0) x 10^21 cm^-2 Galactic foreground: 7.4 x 10^20 cm^-2 Excess significance: 2.4 sigma Photon index: 1.97 (+0.29, -0.27) The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/01442454. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43492. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41589] EP260116a: COLIBRÍ further observations
by GCN Circulars 21 Jan '26

21 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43491 SUBJECT: EP260116a: COLIBRÍ further observations DATE: 26/01/21 19:38:30 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (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), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), 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 observed the field of EP260116a (Wang et al., GCN Circ. 43424) with the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope from 2026-01-21 03:47 to 07:39 UTC (from 123.6 to 127.5 hours after the trigger) and obtained 99 and 171 minutes of exposure in the r and z filters, respectively. The observing conditions were good. The data were reduced, coadded, calibrated, and analyzed with the COLIBRÍ 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. The source we have previously reported (Butler et al., GCN Circ 43459; Watson et al., GCN Circ 43480) is clearly detected with preliminary magnitudes of r = 23.09 +/- 0.06, z = 23.10 +/- 0.13. Considering all of our data, the rebrightening we tentatively reported (Watson et al., GCN Circ 43480) is not confirmed and the data seem to be best explained by a simple flattening. We also note that while this source is within the WXT error regions, it is not within the FXT error region (Wang et al., GCN Circ. 43424). We do not consider it to be associated with EP 260116a. 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/43491. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41588] GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
by GCN Circulars 21 Jan '26

21 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43490 SUBJECT: GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765 DATE: 26/01/21 17:54:30 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> B. Schneider (LAM), A. Saccardi (CEA/Irfu), J. T. Palmerio (CEA/Irfu), S. D. Vergani (LUX-Paris Obs.), D. B. Malesani (DAWN/NBI and Radboud), M. Ferro (INAF/OAB), G. Corcoran (UCD), C. Lachaud (APC), Z.-Y. Lin (APC), report on behalf of the Stargate collaboration: At the position of the optical counterpart (Cheng et al., GCN 42803; Li et al., GCN 42806; Sun et al., GCN 42807; Ma et al., GCN 42811; Gupta et al., GCN 42813; Busman et al., GCN 42814; Volnova et al., GCN 42950) of the high-energy transient GRB 251122A / EP251122a (Wang et al., GCN 42799; Lin et al., GCN 42800), a galaxy is visible in the Legacy survey, with magnitude r ~ 24.6, which is also detected in archival images from the Hyper Suprime-Cam Legacy Archive (Tanaka et al. 2021, doi:10.1093/pasj/psab034) A spectrum of this object was secured using the ESO VLT UT3 (Melipal) equipped with the X-shooter spectrograph. The spectrum covers the wavelength range 3000-25000 AA, and consists of 4 exposures of 1200 s each. The observation mid time is 2025 Dec 23.08 UT (30.5 days after the GRB). A single, very clear emission line is detected at 18140 Å. We discuss its interpretation below. - At the X-shooter resolution we would expect to resolve it if it was the [O II] 3727/3729 doublet (at z = 3.87). While the line is indeed resolved in wavelength space, it does not show a doublet profile; there is also no hint of Lyalpha nor [O III] 5008 in emission at this redshift. - The line cannot be [O III] 5008 (at z = 2.62), otherwise we would also detect [O III] 4959, which is expected from first principles to be ~1/3 as intense, and is excluded by our data. We also do not detect Halpha in the K band, a region clean of atmospheric absorption. - The line is however consistent with Halpha at z = 1.765; at this redshift, both Hbeta and [O III] fall at observed wavelengths with poor atmospheric transmission, and their non-detection is thus not unexpected. The [O II] doublet is not detected at this redshift, although it falls in a noisy region of the spectrum (at the interface between the X-shooter VIS and NIR arms). Dust extinction could also contribute to the faintness of this line. We conclude that z = 1.765 is most likely the redshift of GRB 251122A / EP251122a. We acknowledge excellent support from the observing staff at Paranal, in particular Claudia Cid, Florian Rodler, Jonathan Smoker and Thomas Rivinius. 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/43490. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41587] GRB 260120B: Fermi GBM Observation
by GCN Circulars 21 Jan '26

21 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43489 SUBJECT: GRB 260120B: Fermi GBM Observation DATE: 26/01/21 16:21:32 GMT FROM: Matt Godwin <msg0028(a)uah.edu> Matt Godwin (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 18:00:26.05 UT on 20 January 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260120B (trigger 790624831/260120750), which was also detected by Swift BAT (Ferro et al. 2026, GCN 43479), Swift XRT (Goad et al. 2026, GCN 43484), and SVOM/C-GFT (Wu et al. 2026, GCN 43483). The Fermi GBM real-time localization (GCN 43477) is consistent with the Swift BAT position. The angle from the Fermi LAT boresight is 10 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 7 s (50-300 keV). The time-averaged spectrum from T0-1.1 to T0+9.9 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.19 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 214 +/- 4 keV. The event fluence (10-1000 keV) in this time interval is (3.1 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.38 s in the 10-1000 keV band is 5.8 +/- 0.3 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak= 152 +/- 2 keV, alpha = 0.36 +/- 0.02 and beta = -2.26 +/- 0.05. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/43489. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41586] EP260105a: GTC/HiPERCAM optical observations
by GCN Circulars 21 Jan '26

21 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43488 SUBJECT: EP260105a: GTC/HiPERCAM optical observations DATE: 26/01/21 16:05:28 GMT FROM: javisansie(a)gmail.com J. Sanchez-Sierras (Radboud), G. Corcoran (UCD), P. G. Jonker (Radboud), D. B. Malesani (DAWN/NBI and Radboud), D. Mata Sanchez (IAC), A. L. Cabrera Lavers (GTC), report on behalf of a larger collaboration: We observed the field of EP260105a (Zhou et al., GCN 43327) with the HiPERCAM instrument attached to the Gran Telescopio Canarias (GTC; La Palma, Spain). The observation simultaneously covered the u, g, r, i and z bands with a total exposure time of 1612 s (150 x 10.75 s), starting on 2026-01-15 at 05:49:40 UT (i.e. 10 days after the trigger). Several sources are detected within the EP/FXT error circle, but comparison with archival i-band imaging from the Hyper Suprime-Cam Legacy Archive (Tanaka et al. 2021, doi:10.1093/pasj/psab034) shows all of them to be pre-existing. We carried out subtraction in the i-band with PyZOGY (Guevel et al. 2021), using the HSC image as a template. The subtraction does not show any new source inside the EP-FXT error region (Zhou et al., GCN 43333) down to a limiting AB magnitude of i > 25.5, not corrected by Galactic extinction. This non-detection is consistent with the others reported by Lipunov et al. (GCN 43328), Corcoran et al. (GCN 43332), Li et al. (GCN 43337) and Busmann et al. (GCN 43345). View this GCN Circular online at https://gcn.nasa.gov/circulars/43488. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41585] EP260105a: GTC/HiPERCAM optical observations
by GCN Circulars 21 Jan '26

21 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43488 SUBJECT: EP260105a: GTC/HiPERCAM optical observations DATE: 26/01/21 16:05:28 GMT FROM: javisansie(a)gmail.com J. Sanchez-Sierras (Radboud), G. Corcoran (UCD), P. G. Jonker (Radboud), D. B. Malesani (DAWN/NBI and Radboud), D. Mata Sanchez (IAC), A. L. Cabrera Lavers (GTC), report on behalf of a larger collaboration: We observed the field of EP260105a (Zhou et al., GCN 43327) with the HiPERCAM instrument attached to the Gran Telescopio Canarias (GTC; La Palma, Spain). The observation simultaneously covered the u, g, r, i and z bands with a total exposure time of 1612 s (150 x 10.75 s), starting on 2026-01-15 at 05:49:40 UT (i.e. 10 days after the trigger). Several sources are detected within the EP/FXT error circle, but comparison with archival i-band imaging from the Hyper Suprime-Cam Legacy Archive (Tanaka et al. 2021, doi:10.1093/pasj/psab034) shows all of them to be pre-existing. We carried out subtraction in the i-band with PyZOGY (Guevel et al. 2021), using the HSC image as a template. The subtraction does not show any new source inside the EP-FXT error region (Zhou et al., GCN 43333) down to a limiting AB magnitude of i > 25.5, not corrected by Galactic extinction. This non-detection is consistent with the others reported by Lipunov et al. (GCN 43328), Corcoran et al. (GCN 43332), Li et al. (GCN 43337) and Busmann et al. (GCN 43345). View this GCN Circular online at https://gcn.nasa.gov/circulars/43488. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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