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[vsnet-grb-info 41492] Fermi-LAT Gamma-ray Observations of IceCube-260111A
by GCN Circulars 14 Jan '26

14 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43397 SUBJECT: Fermi-LAT Gamma-ray Observations of IceCube-260111A DATE: 26/01/14 12:42:22 GMT FROM: Leo Pfeiffer at University of Würzburg <pfeiffer.leo(a)gmail.com> L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg) and S. Garrappa (Weizmann Institute of Science) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC-260111A neutrino event (GCN 43374) with all-sky survey data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 26-01-11 at 20:10:33.91 UTC (T0) with J2000 position RA = 70.88 (+1.55, -1.40) deg, Decl. = 34.59 (+0.76, -0.64 ) deg 90% PSF containment. One cataloged >100 MeV gamma-ray source is located within the 90% IC-260111A localization error, at a distance of roughly 0.3 deg (Fourth Fermi-LAT catalog, 4FGL-DR4, The Fermi-LAT collaboration 2023, arXiv:2307.12546). This is the object 4FGL J0444.6+3425 associated with the blazar of uncertain type B2 0441+34. Based on a preliminary analysis of the LAT data over the timescale of one day and one month prior T0, this object is not significantly detected at gamma-rays. We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (> 100 MeV) within the IC-260111A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IceCube best-fit position, the >100 MeV flux upper limit (95% confidence) is 3.0e-10 ph cm^-2 s^-1 for ~17-years (2008-08-04 / T0), <9.3e-09 (1.6 e-07) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. For this analysis, the Fermi-LAT contact person is L. Pfeiffer (leonard.pfeiffer at uni-wuerzburg.de). The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/43397. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41491] GRB 260114A: Swift detection of a short burst
by GCN Circulars 14 Jan '26

14 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43396 SUBJECT: GRB 260114A: Swift detection of a short burst DATE: 26/01/14 11:55:28 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. A. J. Eyles-Ferris (U Leicester), J. A. Kennea (PSU), H. A. Krimm (NSF), N. P. M. Kuin (UCL-MSSL), K. L. Page (U Leicester) and B. Sbarufatti (INAF-OAB) report on behalf of the Neil Gehrels Swift Observatory Team: At 11:40:26 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 260114A (trigger=1440319). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 74.602, -7.994 which is RA(J2000) = 04h 58m 25s Dec(J2000) = -07d 59' 37" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 0.5 sec. The peak count rate was ~16000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 11:42:28.4 UT, 122.2 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 74.59830, -8.01433 which is equivalent to: RA(J2000) = 04h 58m 23.59s Dec(J2000) = -08d 00' 51.6" with an uncertainty of 3.3 arcseconds (radius, 90% containment). This location is 74 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 5.72 x 10^20 cm^-2 (Willingale et al. 2013). UVOT took a finding chart exposure of 150 seconds with the White filter starting 126 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.080. Burst Advocate for this burst is R. A. J. Eyles-Ferris (raje1 AT leicester.ac.uk). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) View this GCN Circular online at https://gcn.nasa.gov/circulars/43396. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41490] GRB 260114A: Swift detection of a short burst
by GCN Circulars 14 Jan '26

14 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43396 SUBJECT: GRB 260114A: Swift detection of a short burst DATE: 26/01/14 11:55:28 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. A. J. Eyles-Ferris (U Leicester), J. A. Kennea (PSU), H. A. Krimm (NSF), N. P. M. Kuin (UCL-MSSL), K. L. Page (U Leicester) and B. Sbarufatti (INAF-OAB) report on behalf of the Neil Gehrels Swift Observatory Team: At 11:40:26 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 260114A (trigger=1440319). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 74.602, -7.994 which is RA(J2000) = 04h 58m 25s Dec(J2000) = -07d 59' 37" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 0.5 sec. The peak count rate was ~16000 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 11:42:28.4 UT, 122.2 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 74.59830, -8.01433 which is equivalent to: RA(J2000) = 04h 58m 23.59s Dec(J2000) = -08d 00' 51.6" with an uncertainty of 3.3 arcseconds (radius, 90% containment). This location is 74 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 5.72 x 10^20 cm^-2 (Willingale et al. 2013). UVOT took a finding chart exposure of 150 seconds with the White filter starting 126 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.080. Burst Advocate for this burst is R. A. J. Eyles-Ferris (raje1 AT leicester.ac.uk). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) View this GCN Circular online at https://gcn.nasa.gov/circulars/43396. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41489] GRB 260114A: Fermi GBM Final Real-time Localization
by GCN Circulars 14 Jan '26

14 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43395 SUBJECT: GRB 260114A: Fermi GBM Final Real-time Localization DATE: 26/01/14 11:51:03 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 SHORT GRB At 11:40:26 UT on 14 Jan 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260114A (trigger 790083631.309942 / 260114486). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 74.1, Dec = -15.2 (J2000 degrees, equivalent to J2000 04h 56m, -15d 11'), with a statistical uncertainty of 1.7 degrees. The angle from the Fermi LAT boresight is 63.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260114486/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260114486/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260114486/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43395. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41488] EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
by GCN Circulars 14 Jan '26

14 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43394 SUBJECT: EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare DATE: 26/01/14 00:30:43 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Z. Kang (CHO), C. Wu, L.P. Xin, X.H. Han, P.P. Zhang, X.M. Lu (NAOC), Z.W. Li, Y. Lv (CHO), R.S. Zhang, Y.J. Xiao, Y.L. Qiu, J. Wang, J.S. Deng, L. Huang, J.Y. Wei (NAOC) report on behalf of the SVOM/C-GFT team: We observed the field of trigger 01709251266 detected by EP/WXT (Wang et al., GCN 43383) with LATIOS on SVOM/C-GFT. Observations started at 2026-01-12T18:15:35 UTC, ~5.63 min after the trigger. A sequence of g-, r-, and i-band images was obtained over ~1.5 hr. Photometry of the suggested flare star LSPM J0924+304 shows a decline from ~13.3 to ~14.0 mag in g-band over ~90 min. The fading was initially fast, then slowed, and was flatter in the r and i bands. This confirms the EP X-ray trigger is associated with a stellar flare. We thank the observation assistants Yin-Huai Hao and Chun-Lei Guo at Jilin observatory for their excellent support. The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcsec x 21 arcsec FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching. View this GCN Circular online at https://gcn.nasa.gov/circulars/43394. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41487] IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 13 Jan '26

13 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43393 SUBJECT: IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube DATE: 26/01/13 20:32:34 GMT FROM: Alicia Mand at IceCube/UW-Madison <aemand(a)wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-260111A (https://gcn.nasa.gov/circulars/43374) in a time range of 1000 seconds centered on the alert event time (2026-01-11 20:02:13.888 UTC to 2026-01-11 20:18:53.888 UTC) during which IceCube was collecting good quality data. Excluding the event that prompted the alert, zero track-like events are found within the 90% containment region of IceCube-260111A. We report a p-value of 1.00 in this time window. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, is 1.4e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-260111A in a 1000 second time window. 90% of events IceCube would detect from a source at this declination with an E^-2.5 spectrum have energies in the approximate energy range between 2e+02 GeV and 6e+04 GeV. A subsequent search was performed including 2 days of data centered on the alert event time (2026-01-10 20:10:33.888 UTC to 2026-01-12 20:10:33.888 UTC). In this case, we report a p-value of 1.00, consistent with no significant excess of track events. IceCube’s sensitivity to neutrino point sources with an E^-2.5 spectrum, expressed as E^2 dN/dE evaluated at 1 TeV, ranges from 1.6e-01 to 1.7e-01 GeV cm^-2 within the 90% spatial containment region of IceCube-260111A in a 2 day time window. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu. [1] IceCube Collaboration, R. Abbasi et al., ApJ 910 4 (2021) View this GCN Circular online at https://gcn.nasa.gov/circulars/43393. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41486] Swift GRB260113.43: Global MASTER-Net observations report
by GCN Circulars 13 Jan '26

13 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43392 SUBJECT: Swift GRB260113.43: Global MASTER-Net observations report DATE: 26/01/13 18:52:27 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 [1] located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB260113.43 (trigger No 1439093,23h 49m 29.21s , +09d 02m 28.7s, R=0.05) errorbox 30419 sec after notice time and 30437 sec after trigger time at 2026-01-13 18:41:23 UT, with upper limit up to 17.8 mag. Observations started at twilight. The observations began at zenith distance = 68 deg. The sun altitude is -10.6 deg. The galactic latitude b = -51 deg., longitude l = 99 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3101140 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 30527 | MASTER-SAAO | C | 180 | 13.4 | 30739 | MASTER-SAAO | C | 180 | 17.8 | 30739 | MASTER-SAAO | C | 180 | 17.1 | 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/43392. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41485] EP260110a: NOT and GTC Optical and Near-Infrared Observations
by GCN Circulars 13 Jan '26

13 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43391 SUBJECT: EP260110a: NOT and GTC Optical and Near-Infrared Observations DATE: 26/01/13 16:52:27 GMT FROM: Gregory Corcoran at University College Dublin <gregory.corcoran(a)ucdconnect.ie> G. Corcoran (UCD), P. G. Jonker (Radboud), J. Sanchez-Sierras (Radboud), A. Martin-Carrillo (UCD), J. A. Quirola-Vasquez (Radboud), A. van Hoof (Radboud), D. Mata Sanchez (IAC), D. Slumstrup (GTC), N. Castro Rodríguez (GTC), V. Vuolteenaho (NOT and Oulu Univ.) report on behalf of a larger collaboration: We observed the field of the fast X-ray transient EP260110a (Zhang et al., GCNs 43363, 43367) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera as well as in the near infrared with the Gran Telescopio Canarias (GTC) equipped with the EMIR instrument. Our observations consisted of two epochs of 3 x 300 s in SDSS-r band and 5 x 200 s in SDSS-z, taken from the NOT, and a single epoch in H with a total exposure time of 1280 s taken from the GTC. Performing image subtraction with PyZOGY on our r-band stacked images and visually comparing the other bands to a stack of archival r-band CFHT images we do not detect any new sources within the EP/FXT uncertainty region in any of our images. We obtain the following upper limits: | Mid time (UT) | Time since trigger (hr) | Band | 3 sigma UL (AB) | | ----- | ----- | ----- | ----- | | 2026-01-11 01:46:32 | 13.80 | r | 23.5 | | 2026-01-11 02:04:27 | 14.10 | z | 22.3 | | 2026-01-11 06:35:44 | 19.02 | H | 23.3 | | 2026-01-12 03:03:04 | 39.08 | r | 24.2 | | 2026-01-12 03:20:59 | 39.38 | z | 22.7 | The r and z band upper limits were calibrated using nearby stars from the Pan-STARRS catalog while the 2MASS catalog was used for the H-band observations and the photometry is not corrected for Galactic extinction. Our upper limits are consistent with Perez-Garcia et al. (GCN 43364), Kang et al. (GCN 43365), Antier et al. (GCN 43366), Zheng et al. (GCN 43368), Lipunov et al. (GCN 43372), Li et al. (GCN 43375), and Zhu et al. (GCN 43390). We note the presence of two faint sources within the EP/FXT uncertainty region in both our r- and H-band images, which are also seen in the archival CFHT imagery. While no residual is visible at their position in the r-band subtraction, due to the lack of sufficiently deep H-band templates we cannot test for NIR variability at this time. View this GCN Circular online at https://gcn.nasa.gov/circulars/43391. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41484] EP260110a: TRT optical upper limits
by GCN Circulars 13 Jan '26

13 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43390 SUBJECT: EP260110a: TRT optical upper limits DATE: 26/01/13 16:28:35 GMT FROM: Zipei Zhu at NAOC <zpzhu(a)nao.cas.cn> Z.P. Zhu (NAOC), S. Tinyanont, K. Noysena, K. Chanchaiworawit, S. Tinyanont (NARIT), J. An, X. Liu, S.Q. Jiang, L.B. He, N.C. Sun, W.X. Li, D. Xu (NAOC), S.Y. Fu (HUST) report on behalf of a large collaboration: We observed the field of EP260110a detected by the Einstein Probe (EP) (Zhang et al., GCN 43367), using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Sierra Remote Observatories in California. We obtained several 360 s frames in the R filter. Observations started at 07:38:55 UTC on 2026-01-11, i.e., 0.44 day after the EP/WXT trigger time. No new source is detected within or at the border of the EP/FXT error region (Zhang et al., GCN 43363), being consistent with the non-detection reported at other telescopes (Perez-Garcia et al., GCN 43364; Kang et al., GCN 43365; Antier et al., GCN 43366; Zheng et al., GCN 43368; Lipunov et al., GCN 43372; Li et al., GCN 43375). From the stacked images we obtain the following 5-sigma upper limits in Vega magnitude: | Mid-time(d) | filter | upper limit | site | | ------------- | -------- | ------------- | ------ | | 0.46 | R | > 19.6 | SRO | | 1.45 | R | > 20.9 | SRO | | 2.44 | R | > 21.0 | SRO | calibrated using nearby stars from the Pan-STARRS DR1 catalog and are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43390. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41483] Konus-Wind detection of GRB 260101A
by GCN Circulars 13 Jan '26

13 Jan '26

TITLE: GCN CIRCULAR NUMBER: 43389 SUBJECT: Konus-Wind detection of GRB 260101A DATE: 26/01/13 15:31:48 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, A. Tsvetkova, M. Ulanov, and T. Cline on behalf of the Konus-Wind team, report: The long-duration GRB 260101A (Fermi-GBM detection: The Fermi GBM team, GCN 43284; Hristov and Meegan, GCN 43297; Swift-BAT detection: Cenko et al., GCN 43285; Markwardt et al., GCN 43354; SVOM-GRM detection: Yu et al., GCN 43292; GECAM-B detection: Wang et al., GCN 43294) triggered Konus-Wind at T0=3419.619 s UT (00:56:59.619). The burst light curve shows a multipeaked structure which starts at ~T0-26 s and has a total duration of ~30 s. The emission is seen up to ~1 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260101_T03419/ As observed by Konus-Wind, the burst had the total fluence of 7.47(-0.65,+0.77)x10^-6 erg/cm2, and the 64-ms peak flux, measured from T0+0.210 s, of 1.95(-0.42,+0.44)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). Since the main fraction of burst counts was detected before the trigger, the spectral analysis was performed using the KW 3-channel light curve data. Modelling the KW 3-channel time-integrated spectrum (measured from T0-26.365 s to T0+3.168 s) by a power law with exponential cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep), yields alpha = -1.50(-0.11,+0.13) and Ep = 176(-30,+45) keV. Modelling the KW 3-channel spectrum near the maximum count rate (measured from T0-5.757 s to T0+3.168 s) by the CPL model yields alpha = -1.44(-0.15,+0.20) and Ep = 129(-18,+25) keV. Assuming the redshift z=2.623 (de Ugarte Postigo et al., GCN 43287) and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014), we estimate the following rest-frame parameters: the isotropic energy release E_iso is 1.21(-0.11,+0.12)x10^53 erg, the peak luminosity L_iso is 1.15(-0.25,+0.26)x10^53 erg/s, the rest-frame peak energy of the time-averaged spectrum Ep,i,z is 637(-109,+162) keV and the spectrum near the maximum count rate Ep,p,z is 467(-65,+90) keV. With the obtained estimates, GRB 260101A is inside 68% prediction bands for both the 'Amati' and the 'Yonetoku' relations derived for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021), see http://www.ioffe.ru/LEA/GRBs/GRB260101_T03419/GRB260101A_rest_frame.pdf 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/43389. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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