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[vsnet-grb-info 41731] Fermi trigger No 792135758: Global MASTER-Net observations report
by GCN Circulars 07 Feb '26

07 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43627 SUBJECT: Fermi trigger No 792135758: Global MASTER-Net observations report DATE: 26/02/07 06:16:25 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-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB260207.24 (trigger No 792135758,10h 41m 48.00s , -34d 26m 24.0s, R=3.29) errorbox 110 sec after notice time and 142 sec after trigger time at 2026-02-07 05:44:56 UT, with upper limit up to 20.7 mag. The observations began at zenith distance = 7 deg. The sun altitude is -41.7 deg. The galactic latitude b = 21 deg., longitude l = 275 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3124959 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 158 | 2026-02-07 05:44:56 | MASTER-OAFA | (10h 51m 33.24s , -33d 38m 46.3s) | C | 30 | 19.5 | 203 | 2026-02-07 05:44:56 | MASTER-OAFA | (10h 51m 33.24s , -33d 38m 46.4s) | C | 120 | 20.0 | Coadd 198 | 2026-02-07 05:45:32 | MASTER-OAFA | (10h 51m 33.30s , -33d 38m 44.9s) | C | 40 | 19.6 | 250 | 2026-02-07 05:46:18 | MASTER-OAFA | (10h 51m 33.38s , -33d 38m 43.0s) | C | 50 | 19.7 | 311 | 2026-02-07 05:47:14 | MASTER-OAFA | (10h 51m 33.48s , -33d 38m 40.8s) | C | 60 | 19.8 | 382 | 2026-02-07 05:48:20 | MASTER-OAFA | (10h 51m 33.59s , -33d 38m 38.3s) | C | 70 | 19.8 | 644 | 2026-02-07 05:52:17 | MASTER-OAFA | (10h 42m 03.76s , -34d 05m 23.7s) | C | 120 | 19.9 | 799 | 2026-02-07 05:52:17 | MASTER-OAFA | (10h 42m 03.76s , -34d 05m 23.7s) | C | 430 | 20.7 | Coadd 781 | 2026-02-07 05:54:24 | MASTER-OAFA | (10h 42m 04.00s , -34d 05m 19.4s) | C | 140 | 19.9 | 942 | 2026-02-07 05:56:50 | MASTER-OAFA | (10h 42m 04.28s , -34d 05m 14.5s) | C | 170 | 19.9 | 1064 | 2026-02-07 05:59:47 | MASTER-OAFA | (10h 42m 04.50s , -34d 05m 10.9s) | C | 60 | 19.7 | 1129 | 2026-02-07 06:00:52 | MASTER-OAFA | (10h 42m 04.62s , -34d 05m 08.8s) | C | 60 | 19.7 | 1194 | 2026-02-07 06:01:58 | MASTER-OAFA | (10h 42m 04.73s , -34d 05m 07.0s) | C | 60 | 19.7 | 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/43627. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41730] EP260131a: VLA detection
by GCN Circulars 06 Feb '26

06 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43626 SUBJECT: EP260131a: VLA detection DATE: 26/02/06 20:32:30 GMT FROM: Genevieve Schroeder at Cornell University <genevieveschroeder(a)u.northwestern.edu> Genevieve Schroeder (Cornell), Anna Ho (Cornell), Daniel Perley (LJMU) report: We observed the position of EP260131a (Ding et al., GCN 43574, Wu et al. GCN 43583), with the Karl G. Jansky Very Large Array (VLA) under program 26A-488 (PI: Ho) beginning on 2026 February 3 at 06:37 UT (3.15 days post discovery) at a mean frequency of 10 GHz. Based on preliminary analysis, we detect a ~40 uJy (~6 sigma) radio source at the position of EP260131a. At the assumed redshift of EP260131a of z = 0.937 (Schneider et al., GCN 43582), the VLA observation corresponds to a 10 GHz luminosity of ~1e30 erg/s/Hz. This is consistent with, but on the lower end of, a typical GRB radio afterglow (Chandra & Frail 2012, ApJ, 746, 156). Additional followup is planned. We thank the VLA staff for quickly approving and executing these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/43626. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41729] GRB 260206A: Tiled Swift observations
by GCN Circulars 06 Feb '26

06 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43625 SUBJECT: GRB 260206A: Tiled Swift observations DATE: 26/02/06 17:39:59 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a series of observations, tiled on the sky, of the MAXI GRB 260206A. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/xrt_products/TILED_GRB00142 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. The probability of finding serendipitous sources, unrelated to the MAXI event is high: any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43625. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41728] GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
by GCN Circulars 06 Feb '26

06 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43624 SUBJECT: GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection DATE: 26/02/06 11:14:51 GMT FROM: Hitoshi Negoro at Nihon University/MAXI team <negoro.hitoshi(a)nihon-u.ac.jp> H. Negoro, M. Nakajima, K. Saito (Nihon U.), T. Usuki (Ehime U.), K. Takagi, H. Nishio (Nihon U.), T. Mihara, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, Y. Kawakubo, H. Hiramatsu, Y. Kondo, D. Iijima, A. Yoshida (AGU), Y. Tsuboi, H. Sugai, N. Nagashima, Y. Ishihara (Chuo U.), M. Shidatsu, C. Kang, T. Nakamoto, M. Uenishi, S. Yatsuzuka (Ehime U.),I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara, S. Kobayashi (Kyoto U.), M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), W. Iwakiri (Chiba U.), T. Kawamuro (Osaka U.), and S. Yamada (Tohoku U), The MAXI/GSC nova alert system triggered on a bright uncatalogued hard X-ray transient source at 08:47:33 UT on February 6, 2026. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (78.322 deg, -40.534 deg) = (05 13 17, -40 32 02) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.33 deg and 0.23 deg, respectively. The roll angle of the long axis from the north direction is 38.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (77.845, -39.759) deg = (05 11 22, -39 45 32) (J2000) (77.278, -40.246) deg = (05 09 06, -40 14 45) (J2000) (79.005, -41.397) deg = (05 16 01, -41 23 49) (J2000) (79.569, -40.903) deg = (05 18 16, -40 54 10) (J2000) The X-ray flux averaged over the scan was 244 +- 33 mCrab (4.0-10.0keV, 1 sigma error). There was no significant excess flux in the previous transit at 07:36 UT and in the next transit at 10:22 UT with an upper limit of 20 mCrab for each. We note that the X-ray burster 4U 0513-40 is close to the above position, but out of the error box. If the systematic error is large this time, the burst may come from 4U 0513-40. View this GCN Circular online at https://gcn.nasa.gov/circulars/43624. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41727] GRB 260204A: SVOM/VT confirms fading of the optical afterglow
by GCN Circulars 06 Feb '26

06 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43623 SUBJECT: GRB 260204A: SVOM/VT confirms fading of the optical afterglow DATE: 26/02/06 04:13:44 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, Y. N. Ma, C. Wu, Z. H. Yao, Y. L. Qiu, L.P. Xin, X. H. Han, J. Wang, Y. Xu, 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/Irfu), R. Z. Li (YNAO), C. W. Wang (IHEP) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observation to the GRB 260204A triggered by SVOM/ECLAIRs (sb26020403, Pillas et al., GCN 43613), which was also detected by Fermi (Fermi GBM team, GCN 43618) and followed by Swift (Evan et al., GCN 43622), LCO (Turpin et al., GCN 43616; Malesani et al. GCN 43621), GOTO (Kumar et al, GCN 43617) and MASTER (Lipunov et al., GCN 43619). The observation started at 2026-02-05T07:04:40 UTC, i.e., 16.27 hour post trigger in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. By stacking images of 47*50 sec in VT_R and 44*50 sec in VT_B, the counterpart (Li et al., GCN 43620; Malesani et al. GCN 43621) was confirmed to be fading with the brightness of VT_R~23.1+/-0.3 mag and VT_B>23.3 mag at the mid time of 18.0 hours post trigger. Combined with the earlier detection (Li et al., GCN 43620), the optical decay slope was -0.90. Our photometry was in AB magnitude and 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/43623. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41726] GRB 260204A: Swift-XRT observations
by GCN Circulars 05 Feb '26

05 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43622 SUBJECT: GRB 260204A: Swift-XRT observations DATE: 26/02/05 13:29:09 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P.A. Evans (U. Leicester), J.A. Kennea (PSU), E. Ambrosi (INAF-IASFPA) , A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB), D.N. Burrows (PSU), S. Campana (INAF-OAB), M. Capalbi (INAF-OAR), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), M. Ferro (INAF-OAB), A. Melandri (INAF-OAR), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M. Perri (SSDC & INAF-OAR), C. Salvaggio (INAF-OAB), T. Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), M.A. Williams (PSU) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the SVOM/ECLAIRs-detected GRB 260204A, collecting 1.7 ks of Photon Counting (PC) mode data between T0+23 ks and T0+25 ks after the trigger. We have detected 4 sources. These have been automatically classified as follows: * 0 likely counterparts * 0 candidate counterparts * 3 uncatalogued X-ray sources * 1 known X-ray source As already reported source 1 is consistent with an optical source (Li et al., GCN Circ. 43620; Malesani et al., GCN Circ. 43621). We note that, in the X-rays, this source is not well separated from source 3 and cannot rule out that these arise not from point sources but from a patch of diffuse emission. We note also the presence of a source in the XMM Slew survey XMMSL3 catalogue, XMMSL3 J134023.8+015613 at RA,Dec = 205.0888, +1.9370 degrees (J2000), with a 1-sigma error of 4.3" (statistical) and an estimated systematic error of ~8" (see http://xmmssc.irap.omp.eu/Catalogue/XMMSL3/XMMSL3_Catalogue_User_Guide.html… ry). This source is 33" from the position of source 1. Source 2 is consistent with the position of HD 118981, a high proper motion star, while source 4 is a known quasar. Further observations are planned. Uncatalogued X-ray sources -------------------------- Source 1 (SWIFT J134025.4+015552): ================================== RA (J2000.0): 205.1060 = 13 40 25.44 Dec (J2000.0): +1.9313 = +01 55 52.7 Error: 5.0 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 5.4 arcmin from the SVOM/ECLAIRs position. Mean rate: 0.0235 +/- 0.0046 ct s^-1 Mean flux: (8.7 +/- 1.7)e-13 erg cm^-2 s^-1 Peak rate: 0.0235 +/- 0.0046 ct s^-1 Peak flux: (8.7 +/- 1.7)e-13 erg cm^-2 s^-1 ECF: 3.71e-11 erg cm^-2 ct^-1 assuming NH=1.90e+20 cm^-2, gamma=1.76 determined from a spectral fit. RASS UL: 4.1e-02 ct s^-1 (converted to XRT; 0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. Source 2 (SWIFT J134026.9+020905): ================================== RA (J2000.0): 205.1125 = 13 40 27.00 Dec (J2000.0): +2.1515 = +02 09 05.4 Error: 5.0 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 7.9 arcmin from the SVOM/ECLAIRs position. Mean rate: 0.0136 +/- 0.0036 ct s^-1 Mean flux: (2.28 +/- 0.61)e-13 erg cm^-2 s^-1 Peak rate: 0.0136 +/- 0.0036 ct s^-1 Peak flux: (2.28 +/- 0.61)e-13 erg cm^-2 s^-1 ECF: 1.67e-11 erg cm^-2 ct^-1 assuming NH=1.30e+22 cm^-2, gamma=9.94 determined from a spectral fit. RASS UL: 3.3e-02 ct s^-1 (converted to XRT; 0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. A SIMBAD object `HD 118981' is 0.7" away. There is 1 2MASS object within the source's 3-sigma error radius. Source 4 (SWIFT J134043.1+020310): ================================== RA (J2000.0): 205.1796 = 13 40 43.10 Dec (J2000.0): +2.0530 = +02 03 10.8 Error: 6.6 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 4.2 arcmin from the SVOM/ECLAIRs position. Mean rate: (7.2 [+2.9, -2.3])e-3 ct s^-1 Mean flux: (1.49 [+0.60, -0.48])e-13 erg cm^-2 s^-1 Peak rate: (7.2 [+2.9, -2.3])e-3 ct s^-1 Peak flux: (1.49 [+0.60, -0.48])e-13 erg cm^-2 s^-1 ECF: 2.07e-11 erg cm^-2 ct^-1 assuming NH=6.90e+21 cm^-2, gamma=9.20 determined from a spectral fit. RASS UL: 2.1e-02 ct s^-1 (converted to XRT; 0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. A SIMBAD object `[VV2006] J134042.9+020307' is 4.5" away. Known X-ray sources ------------------- Source 3 (SWIFT J134023.6+015612): ================================== RA (J2000.0): 205.0984 = 13 40 23.62 Dec (J2000.0): +1.9369 = +01 56 12.8 Error: 6.1 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 5.1 arcmin from the SVOM/ECLAIRs position. Mean rate: 0.0225 +/- 0.0058 ct s^-1 Mean flux: (2.54 +/- 0.65)e-12 erg cm^-2 s^-1 Peak rate: 0.0225 +/- 0.0058 ct s^-1 Peak flux: (2.54 +/- 0.65)e-12 erg cm^-2 s^-1 ECF: 1.13e-10 erg cm^-2 ct^-1 assuming NH=1.89e+20 cm^-2, gamma=1.04 determined from a spectral fit. This matches a catalogued X-ray source XMMSL3 J134023.8+015613 in the XMM-NEWTON/XMMSLEWCLN catalogue. Details: Separation: 1.6" from the XRT source Cat Rate: 4.8e-01 +/- 2.6e-01 ct s^-1 Cat Flux: 7.7e-12 +/- 4.1e-12 erg cm^-2 s^-1 (0.3-10 keV) so the source is not above the catalogued flux. There is no evidence for fading. There is 1 2MASS object within the source's 3-sigma error radius. All fluxes are 0.3-10 keV, observed. For all flux conversions and comparisons with catalogues and upper limits from other missions, we assumed a power-law spectrum with NH=3x10^20 cm^-2 and photon index (Gamma)=1.7 unless otherwise stated. The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/SVOM/SVOM_FIELD00057. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43622. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41725] GRB 260204A: LCO optical afterglow detection
by GCN Circulars 05 Feb '26

05 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43621 SUBJECT: GRB 260204A: LCO optical afterglow detection DATE: 26/02/05 10:45:38 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> D. B. Malesani (DAWN/NBI and Radboud), D. Turpin (CEA/Irfu), A. Saccardi (CEA/Irfu), B. Cordier (CEA/Irfu), M. Pillas, M. Dennefeld (IAP), report on behalf of the SVOM mission team: Following the report of an optical counterpart (Li et al., GCN 43620; see also the X-ray detection at https://www.swift.ac.uk/SVOM/SVOM_FIELD00057/) of the SVOM GRB 260204A (Pillas et al. GCN 43613), we inspected again our images taken with the LCO telescope at the Siding Spring Observatory (Turpin et al., GCN 43616). The optical counterpart is detected in our images, and we measure the following magnitudes: r = 20.26 +- 0.21 AB (mid-time 25.7 min after the trigger); z = 19.49 +- 0.25 AB (mid-time 38.4 min after the trigger). We note that these measurements are close to the sensitivity limit of our images, and consistent with the 5-sigma upper limits reported in our previous circular (Turpin et al., GCN 43616). The above measurements are not corrected for Galactic extinction. Compared to the SVOM/VT measurement (taken at a mean epoch ~74 min after the GRB), our data indicate only marginal decay between the two observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/43621. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41724] GRB 250204A: SVOM/VT optical candidate
by GCN Circulars 05 Feb '26

05 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43620 SUBJECT: GRB 250204A: SVOM/VT optical candidate DATE: 26/02/05 02:02:27 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H.L. Li , C. Wu, Y.N. Ma, Z.H. Yao, Y. L. Qiu, L.P. Xin, X. H. Han, J. Wang, Y. Xu, 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/Irfu), M. Pillas (IAP), M. Dennefeld (IAP) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observation to the field of GRB 260204A triggered by SVOM/ECLAIRs (sb26020403, Pillas et al., GCN 43613). The observation started at 2026-02-04T15:37:26UTC, i.e., 49 minutes post trigger in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. An uncatalogued source was detected within the error box of ECLAIRs (Pillas et al., GCN 43613) and source 1 of Swift-XRT (https://www.swift.ac.uk/SVOM/SVOM_FIELD00057) compared to the Legacy survey catalog. The position is at R.A., Dec. = 205.106167, 1.930114 degrees, equivalent to: R.A. (J2000) = 13:40:25.48 Dec. (J2000) = +1:55:48.41 with an uncertainty of 0.5 arcsec. The measurements in AB magnitudes are given below: Mid_time Band Exposure Time Magnitude (AB) 1.23 hour VT_R 27*50 sec 20.5+/-0.1 mag 1.23 hour VT_B 26*50 sec 21.3+/-0.1 mag Our photometry was in AB magnitude and 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/43620. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41723] GRB 260204A : MASTER Global robotic net optical observations
by GCN Circulars 05 Feb '26

05 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43619 SUBJECT: GRB 260204A : MASTER Global robotic net optical observations DATE: 26/02/05 01:13:33 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.M.Lipunov (Lomonosov MSU), O.A.Gress, N.M.Budnev (ISU), V.A.Senik, I.Panchenko, P.Balanutsa, A.Kuznetsov, E.Gorbovskoy, G.Antipov, N. Tiurina, Ya.Kechin,A.Chasovnikov, D.Vlasenko, I.Ionov,Yu.Tselik(Lomonosov MSU), R.Mirgazov, A.Diachok, O.Ershova (Irkutsk State University), R. Podesta, C.Francile, F. Podesta, E. Gonzalez (OAFA, San JuanUni.,Argentina); D.Buckley (SAAO), A. Sosnovskij (CrAO RAS), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino, J.Martinez, A.R.Corella, J.G. Tanori, L. F. Villalobos, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysic Observatory, Mexico) V.M.Pillet, R.Rebolo Lopez (The Instituto de Astrofisica de Canarias,Spain) At alert and notice time the error-box of SVOM GRB 260204A (Pillas et al. GCN 43613, also by Fermi-GBM GCN 43618; in optic observed by LCO (Turpin et al. GCN 43616), GOTO (Kumar et al. GCN 43617)) altitude was -8deg at MASTER-Tunka (the nearest MASTER for observation). So we started observe it several hours later. MASTER-Tunka robotic telescope [1-3] located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the SVOM GRB260204A (trigger No 1770219433,13h 40m 56.04s , +01d 58m 50.2s, R=0.0662) errorbox 12301 sec after notice time (13245 sec after trigger time) at 2026-02-04 19:17:57 UT, with upper limit up to 18.1 mag at single images and 19.9 at summary. MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the SVOM GRB 260204A errorbox 16703 sec after notice time and 17647 sec after trigger time at 2026-02-04 20:31:20 UT, with upper limit up to 17.1 mag. The observations began at zenith distance = 81 deg. The sun altitude was -60.8 deg. The galactic latitude b = 62 deg., longitude l = 331 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3122418 Observation and reduction will continue. [1] Lipunov et al. 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html [2] Lipunov et al. 2022, Universe, 8, id.271 [3] Lipunov et al. 2023, Astronomy Reports, 67, p.S140 View this GCN Circular online at https://gcn.nasa.gov/circulars/43619. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41722] Fermi GBM Sub-Threshold Detection of GRB 260204A
by GCN Circulars 04 Feb '26

04 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43618 SUBJECT: Fermi GBM Sub-Threshold Detection of GRB 260204A DATE: 26/02/04 21:43:34 GMT FROM: Matt Godwin <msg0028(a)uah.edu> Matt Godwin (UAH) reports on behalf of the Fermi-GBM Team: SVOM/ECLAIRs detected the GRB 260204A on 2026-02-04 at 14:48:49 UTC (Pillas et al. 2026, GCN 43613). There was no Fermi-GBM onboard trigger around this event time. An automated, blind search for gamma-ray bursts below the onboard triggering threshold in Fermi-GBM identified a candidate. The GBM Targeted Search [1], the most sensitive coherent search for GRB-like signals in GBM, identified a transient starting -35 seconds before the SVOM best SNR time at 2026-02-04T14:48:28 most significantly on the 16 s timescale, with a false alarm rate of 3.8e-05 Hz. The Fermi-MET of this transient is 791909278.714 s. The Targeted Search localization is found to be spatially consistent with the ECLAIRs localization Additionally, the GBM Targeted Search event was found with the highest significance using a "normal" spectrum (Band function with Epeak = 230 keV, alpha = -1.0, beta = -2.3) for a GRB. [1] Goldstein et al. 2019 arXiv:1903.12597 View this GCN Circular online at https://gcn.nasa.gov/circulars/43618. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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