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[vsnet-grb-info 41038] Fermi GRB 251202B: Global MASTER-Net observations report
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42962 SUBJECT: Fermi GRB 251202B: Global MASTER-Net observations report DATE: 25/12/02 19:00:24 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) started inspect of the Fermi GRB 251202B ( Fermi GBM team, GCN 42961) errorbox 566 sec after notice time and 598 sec after trigger time at 2025-12-02 18:37:01 UT, with upper limit up to 19.2 mag. Observations started at twilight. The observations began at zenith distance = 24 deg. The sun altitude is -12.7 deg. The galactic latitude b = -67 deg., longitude l = 38 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3058648 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 629 | 2025-12-02 18:37:01 | MASTER-SAAO | (23h 04m 42.90s , -23d 23m 21.3s) | C | 60 | 17.6 | 629 | 2025-12-02 18:37:01 | MASTER-SAAO | (23h 06m 42.31s , -23d 38m 56.2s) | C | 60 | 18.4 | 689 | 2025-12-02 18:37:01 | MASTER-SAAO | (23h 06m 42.31s , -23d 38m 56.2s) | C | 180 | 19.2 | Coadd 708 | 2025-12-02 18:38:20 | MASTER-SAAO | (23h 04m 42.92s , -23d 23m 16.2s) | C | 60 | 17.6 | 708 | 2025-12-02 18:38:20 | MASTER-SAAO | (23h 06m 42.32s , -23d 38m 51.7s) | C | 60 | 18.4 | 787 | 2025-12-02 18:39:39 | MASTER-SAAO | (23h 04m 42.96s , -23d 23m 12.1s) | C | 60 | 17.7 | 787 | 2025-12-02 18:39:40 | MASTER-SAAO | (23h 06m 42.35s , -23d 38m 48.1s) | C | 60 | 18.4 | 866 | 2025-12-02 18:40:58 | MASTER-SAAO | (23h 04m 43.00s , -23d 23m 08.4s) | C | 60 | 17.7 | 866 | 2025-12-02 18:40:58 | MASTER-SAAO | (23h 06m 42.37s , -23d 38m 45.0s) | C | 60 | 18.5 | 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/42962. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41037] GRB 251202B: Fermi GBM Final Real-time Localization
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42961 SUBJECT: GRB 251202B: Fermi GBM Final Real-time Localization DATE: 25/12/02 18:37:45 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 18:27:03 UT on 2 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251202B (trigger 786392828.111108 / 251202769). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 347.2, Dec = -23.3 (J2000 degrees, equivalent to J2000 23h 08m, -23d 18'), with a statistical uncertainty of 4.5 degrees. The angle from the Fermi LAT boresight is 92.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251202769/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251202769/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251202769/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42961. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41036] IPN triangulation of GRB 251129B (short/hard)
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42960 SUBJECT: IPN triangulation of GRB 251129B (short/hard) DATE: 25/12/02 18:31:26 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the HEND/Mars Odyssey team, D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, E. Burns on behalf of the IPN, S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, A. Tohuvavohu, and J. DeLaunay on behalf of the Swift-BAT team, and W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr, and A.S. Gardner on on behalf of the GRS-Odyssey GRB team, report: The short-duration GRB 251129B (AstroSat-CZTI detection: Salunke et al., GCN 42958) was detected by Konus-Wind, Swift(BAT), Mars-Odyssey (HEND), and AstroSat (CZTI), at about 35494 s UT (09:51:34). The burst was outside the coded field of view of the BAT. We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 124.862 (08h 19m 27s) +76.391 (+76d 23' 28") Corners: 118.469 (07h 53m 53s) +78.048 (+78d 02' 53") 119.970 (07h 59m 53s) +77.774 (+77d 46' 26") 129.621 (08h 38m 29s) +74.606 (+74d 36' 22") 128.692 (08h 34m 46s) +74.931 (+74d 55' 51") --------------------------------------------- The error box area is 617 sq. arcmin, and its maximum dimension is 4.32 deg (the minimum one is 2.6 arcmin). The Sun distance was 117 deg. The localization may be improved. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB251129_T35496/IPN/ The HEALPix triangulation map is the multi-order HEALPix in units of probability density. The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/42960. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41035] GRB251129A/EP251129a: Swift UVOT detection
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42959 SUBJECT: GRB251129A/EP251129a: Swift UVOT detection DATE: 25/12/02 18:31:14 GMT FROM: Paul Kuin at MSSL <npkuin(a)gmail.com> N.P.M. Kuin (UCL-MSSL) and B. Cenko (NASA/GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began observations of the field of GRB 251129A 16.8 ks after the SVOM trigger (Tan et al., GCN Circ. 42877). GRB251129A was also detected by the EP (Wu et al, GCN Circ. 16828). The optical afterglow consistent with the SVOM/COLIBRI position (Angulo et al. GCN Circ. 42880; Watson, GCN Circ. 42883) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) are:: Filter T_start(s) T_stop(s) Exp(s) Mag white 16828 17147 315 19.63 +/- 0.07 white 27564 28089 502 19.69 +/- 0.12 white 111007 117142 1044 20.22 +/- 0.12 white 227072 234439 2745 20.92 +/- 0.17 u 16503 16823 315 20.06 +/- 0.30 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.025 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42959. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41034] GRB251129A/EP251129a: Swift UVOT detection
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42959 SUBJECT: GRB251129A/EP251129a: Swift UVOT detection DATE: 25/12/02 18:31:14 GMT FROM: Paul Kuin at MSSL <npkuin(a)gmail.com> N.P.M. Kuin (UCL-MSSL) and B. Cenko (NASA/GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began observations of the field of GRB 251129A 16.8 ks after the SVOM trigger (Tan et al., GCN Circ. 42877). GRB251129A was also detected by the EP (Wu et al, GCN Circ. 16828). The optical afterglow consistent with the SVOM/COLIBRI position (Angulo et al. GCN Circ. 42880; Watson, GCN Circ. 42883) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) are:: Filter T_start(s) T_stop(s) Exp(s) Mag white 16828 17147 315 19.63 +/- 0.07 white 27564 28089 502 19.69 +/- 0.12 white 111007 117142 1044 20.22 +/- 0.12 white 227072 234439 2745 20.92 +/- 0.17 u 16503 16823 315 20.06 +/- 0.30 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.025 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42959. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41033] GRB 251129B: AstroSat CZTI detection
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42958 SUBJECT: GRB 251129B: AstroSat CZTI detection DATE: 25/12/02 18:22:35 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> S. Salunke (IUCAA), M. Tembhurnikar (IUCAA), Harsha K. H. (IUCAA), A. Arya (IITB), A. Goyal (IITB), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a short-duration GRB 251129B which was also detected by Konus Wind (IPN Notices). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed a peak of emission with the strongest peak at 2025-11-29T09:51:34 UTC. The measured peak count rate associated with the burst is 1480 (+927, -83) counts/s above the background in the combined data of three quadrants (out of four), with a total of 128 (+30, -29) counts. The local mean background count rate was 212 (+20, -44)) counts/s. Using cumulative rates, we measure a T90 of 0.14 (+0.04, -0.03) s. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/42958. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41032] GRB 251202A: Fermi GBM Observation
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42957 SUBJECT: GRB 251202A: Fermi GBM Observation DATE: 25/12/02 16:57:29 GMT FROM: Suman Bala at USRA <sumanbala2210(a)gmail.com> S. Bala (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 01:50:52.31 UT on 02 December 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251202A (GCN trigger 786333057/251202077), which was also detected by Einstein Probe (Y. J. Zhang et al. 2025, GCN 42937), Swift XRT (B. Sbarufatti et al. 2025, GCN 42943), Swift UVOT (N.P.M. Kuin et al. 2025, GCN 42956) GOTO (D. O’Neill et al. 2025, GCN 42947) and LCO (J. Quirola-Vasquez et al. 2025, GCN 42948). The spectroscopic redshift of GRB 251202A is found to be 2.785 by NOT (Z.P. Zhu et al. 2025, GCN 42939). The Fermi GBM Final Real-time Localization (GCN 42933) is consistent with the position reported by other instruments. The angle from the Fermi LAT boresight is 73 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 43 s (50-300 keV). The time-averaged spectrum from T0-10 to T0+55 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.07 +/- 0.06 and the cutoff energy, parameterized as Epeak, is 350 +/- 50 keV. The event fluence (10-1000 keV) in this time interval is (9.9 +/- 0.6)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+8.8 s in the 10-1000 keV band is 4.2 +/- 0.2 ph/s/cm^2. 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/42957. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41031] GRB 251202A: Swift/UVOT Detection
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42956 SUBJECT: GRB 251202A: Swift/UVOT Detection DATE: 25/12/02 16:35:43 GMT FROM: Paul Kuin at MSSL <npkuin(a)gmail.com> N.P.M. Kuin (UCL-MSSL) and M. J. Moss (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of EP251202a/GRB 251202A 17,500s after the EP trigger (Zhang et al., GCN Circ. No 42937). A source consistent with Li et al. (GCN Circ No 42934) and the XRT position (Sbarufatti et al. GCN Circ. No. 42943) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 08:08:27.5 = 122.11420 (deg.) Dec (J2000) = 40:36:45.3 = 40.61244 (deg.) with an estimated uncertainty of 0.48 arc sec. (radius, 90% confidence). Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag u 17500 18104 509 19.80 +/- 0.20 u 23697 24044 342 20.26 +/- 0.39 u 28710 28841 129 20.06 +/- 0.53 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.043 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42956. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41030] GRB 251201B: Kilonova-Catcher optical afterglow detection
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42955 SUBJECT: GRB 251201B: Kilonova-Catcher optical afterglow detection DATE: 25/12/02 16:14:17 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> M. Freeberg (KNC), D. Turpin (CEA-Saclay/Irfu), C. Andrade(UMN), S. Antier (OCA/IJCLab), M. Coughlin (UMN), S. Karpov (FZU), P. Hello (IJCLAB), M. Pillas (IAP) on behalf of the GRANDMA/Kilonova-Catcher collaboration: We observed the field of GRB 251201B detected by Swift/BAT (Moss et al., GCN 42924) and Fermi/GBM (Fermi GBM team, GCN 42923) with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with the iTelescope 72 located in Chile and operated by M. Freeberg. Our observations started at TGRB+8.4h and were taken with Rc filter. In our stacked frames, subtracted from the Legacy Survey DR10 template image, we detect the optical counterpart reported by Swift/UVOT(Moss et al., GCN 42924, Kuin et al., GCN 42954), LCO/1m (Cerón et al., GCN 42929), MASTER (Buckley et al., GCN 42930), SVOM/VT (Li et al., GCN 42931). We report our follow-up results in the table below: +---------------+-----------+-----------+----------------+-------------+ | Tmid-TGRB (hr)| Exp (s) | Filter | Magnitude | Instrument | +===============+===========+===========+================+=============+ | 8.89 | 17 x 180s | Rc (Vega) | 20.33 +/- 0.09 | iT72 | +---------------+-----------+-----------+----------------+-------------+ All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the Johnson-Cousins filters were calibrated using the GAIA DR3 Synphot catalog. We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023). GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/). View this GCN Circular online at https://gcn.nasa.gov/circulars/42955. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41029] GRB 251201B: Swift/UVOT Detection
by GCN Circulars 02 Dec '25

02 Dec '25

TITLE: GCN CIRCULAR NUMBER: 42954 SUBJECT: GRB 251201B: Swift/UVOT Detection DATE: 25/12/02 15:52:28 GMT FROM: Paul Kuin at MSSL <npkuin(a)gmail.com> N.P.M. Kuin (UCL-MSSL) and M. J. Moss (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251201B 101 s after the BAT trigger (Moss et al., GCN Circ. 42924). A source consistent with the XRT position is detected in the initial UVOT exposures. Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 101 251 147 17.31 +/- 0.03 v 644 663 19 15.97 +/- 0.12 b 570 589 20 16.71 +/- 0.10 u 314 564 246 16.48 +/- 0.04 w1 693 1808 117 18.35 +/- 0.18 m2 668 1093 39 >18.7 w2 1196 1562 39 >18.8 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.008 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42954. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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