June 2025 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 38681] GRB 250605A: Swift-XRT refined Analysis
by GCN Circulars 06 Jun '25

06 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40644 SUBJECT: GRB 250605A: Swift-XRT refined Analysis DATE: 25/06/06 11:02:50 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), M.A. Williams (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 7.0 ks of XRT data for GRB 250605A, from 90 s to 50.2 ks after the trigger. The data comprise 149 s in Windowed Timing (WT) mode (the first 6 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=4.36 (+0.19, -0.15). At T+164 s the decay flattens to an alpha of 3.19 (+0.29, -0.32) before breaking again at T+326 s to a final decay with index alpha=0.79 (+/-0.07). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.12 (+0.06, -0.05). The best-fitting absorption column is 2.59 (+0.20, -0.19) x 10^21 cm^-2, in excess of the Galactic value of 4.3 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.10 (+0.13, -0.12) and a best-fitting absorption column of 2.9 (+/-0.5) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.6 x 10^-11 (5.5 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 2.9 (+/-0.5) x 10^21 cm^-2 Galactic foreground: 4.3 x 10^20 cm^-2 Excess significance: 8.7 sigma Photon index: 2.10 (+0.13, -0.12) If the light curve continues to decay with a power-law decay index of 0.79, the count rate at T+24 hours will be 0.085 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.0 x 10^-12 (4.7 x 10^-12) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01321323. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40644. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38680] EP/WXT 01709177873: GOTO observations confirm stellar variability
by GCN Circulars 06 Jun '25

06 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40643 SUBJECT: EP/WXT 01709177873: GOTO observations confirm stellar variability DATE: 25/06/06 10:10:51 GMT FROM: Amit Kumar at Royal Holloway - UoL/ U of Warwick, UK <amitkundu515(a)gmail.com> A. Kumar, D. O'Neill, G. Ramsay, B. P. Gompertz, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, B. Godson, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, and J. Casares report on behalf of the GOTO collaboration: We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to the EP/WXT alert 01709177873. Targeted observations were performed beginning at 2025-06-05 21:27:07 UT (+2.59 hr post trigger) and continued through to 2025-06-05 23:43:10 UT (+4.86 hr post trigger). Each observation consisted of 4x90 s exposures in the GOTO L-band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogs. Human vetting was carried out in real time on any candidates that passed the above checks. No new transients associated with the alert were identified, except for one source within the localisation region: RX J1553.0+4457, a low mass star + white binary at RA = 15:53:04.8, Dec = +44:57:44.6. This source exhibited significant variability, brightening by ~0.6 mag relative to the last pre-trigger image taken on 2025-05-30 at 00:18:22 UT (6.77 days pre-trigger), reaching 13.70 ± 0.01 mag in the first post-trigger image at 2025-06-05 21:27:07 UT (+2.59 hr). It then faded to 14.10  ±  0.01 mag by the final observation at 2025-06-05 23:43:10 UT (+4.86 hr post-trigger). All the reported magnitudes are in the GOTO L-band and the AB system. Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/40643. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38679] GRB 250605A: Enhanced Swift-XRT position
by GCN Circulars 06 Jun '25

06 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40642 SUBJECT: GRB 250605A: Enhanced Swift-XRT position DATE: 25/06/06 08:44:00 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team. Using 3740 s of XRT Photon Counting mode data and 7 UVOT images for GRB 250605A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 166.95715, -19.78841 which is equivalent to: RA (J2000): 11h 07m 49.72s Dec (J2000): -19d 47' 18.3" with an uncertainty of 2.0 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40642. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38678] Fermi GRB 250606A: Global MASTER-Net observations report
by GCN Circulars 06 Jun '25

06 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40641 SUBJECT: Fermi GRB 250606A: Global MASTER-Net observations report DATE: 25/06/06 06:31:54 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 (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 250606A ( Fermi GBM team, GCN 40640) errorbox 91 sec after trigger time at 2025-06-06 04:30:12 UT, with upper limit up to 19.3 mag. Observations started at twilight. The observations began at zenith distance = 50 deg. The sun altitude is -13.2 deg. MASTER-OAFA robotic telescope located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 250606A errorbox 133 sec after trigger time at 2025-06-06 04:30:55 UT, with upper limit up to 19.0 mag. The observations began at zenith distance = 69 deg. The sun altitude is -81.6 deg. The galactic latitude b = -38 deg., longitude l = 298 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2894070 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 101 | 2025-06-06 04:30:12 | MASTER-SAAO | (02h 08m 41.74s , -77d 25m 10.8s) | C | 20 | 18.5 | 136 | 2025-06-06 04:30:12 | MASTER-SAAO | (02h 08m 41.71s , -77d 25m 10.8s) | C | 90 | 19.3 | Coadd 101 | 2025-06-06 04:30:12 | MASTER-SAAO | (02h 17m 05.10s , -77d 40m 08.2s) | C | 20 | 18.4 | 136 | 2025-06-06 04:30:12 | MASTER-SAAO | (02h 17m 05.14s , -77d 40m 08.2s) | C | 90 | 19.2 | Coadd 145 | 2025-06-06 04:30:51 | MASTER-SAAO | (02h 08m 41.54s , -77d 25m 10.8s) | C | 30 | 18.7 | 145 | 2025-06-06 04:30:51 | MASTER-SAAO | (02h 17m 04.94s , -77d 40m 08.4s) | C | 30 | 18.6 | 149 | 2025-06-06 04:30:55 | MASTER-OAFA | (02h 17m 57.07s , -77d 44m 13.6s) | C | 30 | 16.1 | 185 | 2025-06-06 04:31:31 | MASTER-OAFA | (02h 17m 56.58s , -77d 44m 12.6s) | C | 30 | 15.8 | 199 | 2025-06-06 04:31:40 | MASTER-SAAO | (02h 08m 41.15s , -77d 25m 10.8s) | C | 40 | 18.9 | 199 | 2025-06-06 04:31:40 | MASTER-SAAO | (02h 17m 04.63s , -77d 40m 08.5s) | C | 40 | 18.8 | 226 | 2025-06-06 04:32:07 | MASTER-OAFA | (02h 17m 56.05s , -77d 44m 11.8s) | C | 40 | 16.1 | 263 | 2025-06-06 04:32:40 | MASTER-SAAO | (02h 08m 40.59s , -77d 25m 10.4s) | C | 50 | 18.9 | 263 | 2025-06-06 04:32:40 | MASTER-SAAO | (02h 17m 04.32s , -77d 40m 08.4s) | C | 50 | 18.8 | 277 | 2025-06-06 04:32:53 | MASTER-OAFA | (02h 17m 55.51s , -77d 44m 10.8s) | C | 50 | 17.0 | 337 | 2025-06-06 04:33:48 | MASTER-SAAO | (02h 08m 40.02s , -77d 25m 10.1s) | C | 60 | 18.9 | 337 | 2025-06-06 04:33:48 | MASTER-SAAO | (02h 17m 03.91s , -77d 40m 08.3s) | C | 60 | 18.8 | 376 | 2025-06-06 04:34:22 | MASTER-OAFA | (02h 17m 54.36s , -77d 44m 09.3s) | C | 70 | 16.6 | 457 | 2025-06-06 04:35:38 | MASTER-OAFA | (02h 17m 53.34s , -77d 44m 08.1s) | C | 80 | 16.0 | 552 | 2025-06-06 04:37:04 | MASTER-OAFA | (02h 17m 52.34s , -77d 44m 06.6s) | C | 100 | 17.2 | 633 | 2025-06-06 04:38:44 | MASTER-SAAO | (02h 01m 01.33s , -78d 21m 33.4s) | C | 60 | 18.4 | 693 | 2025-06-06 04:38:44 | MASTER-SAAO | (02h 01m 01.32s , -78d 21m 33.4s) | C | 180 | 18.9 | Coadd 633 | 2025-06-06 04:38:44 | MASTER-SAAO | (02h 10m 05.68s , -78d 36m 27.8s) | C | 60 | 18.2 | 693 | 2025-06-06 04:38:44 | MASTER-SAAO | (02h 10m 05.70s , -78d 36m 27.8s) | C | 180 | 18.9 | Coadd 702 | 2025-06-06 04:39:19 | MASTER-OAFA | (02h 10m 51.22s , -78d 38m 24.3s) | C | 130 | 17.1 | 712 | 2025-06-06 04:40:03 | MASTER-SAAO | (02h 01m 00.54s , -78d 21m 33.2s) | C | 60 | 18.2 | 712 | 2025-06-06 04:40:03 | MASTER-SAAO | (02h 10m 05.03s , -78d 36m 27.9s) | C | 60 | 18.1 | 791 | 2025-06-06 04:41:22 | MASTER-SAAO | (02h 00m 59.70s , -78d 21m 32.7s) | C | 60 | 18.1 | 791 | 2025-06-06 04:41:22 | MASTER-SAAO | (02h 10m 04.49s , -78d 36m 27.5s) | C | 60 | 17.9 | 849 | 2025-06-06 04:41:35 | MASTER-OAFA | (02h 10m 49.35s , -78d 38m 22.1s) | C | 150 | 17.0 | 870 | 2025-06-06 04:42:41 | MASTER-SAAO | (02h 00m 58.99s , -78d 21m 32.4s) | C | 60 | 17.8 | 870 | 2025-06-06 04:42:41 | MASTER-SAAO | (02h 10m 03.94s , -78d 36m 27.3s) | C | 60 | 17.8 | 1020 | 2025-06-06 04:44:12 | MASTER-OAFA | (02h 10m 47.45s , -78d 38m 19.3s) | C | 180 | 17.4 | 1206 | 2025-06-06 04:47:18 | MASTER-OAFA | (02h 10m 44.99s , -78d 38m 15.8s) | C | 180 | 14.2 | 3930 | 2025-06-06 05:32:42 | MASTER-OAFA | (02h 02m 27.41s , -77d 24m 58.8s) | C | 180 | 18.4 | 4117 | 2025-06-06 05:35:48 | MASTER-OAFA | (02h 02m 25.46s , -77d 24m 53.1s) | C | 180 | 18.4 | 4304 | 2025-06-06 05:38:55 | MASTER-OAFA | (02h 02m 23.74s , -77d 24m 48.4s) | C | 180 | 19.0 | 4490 | 2025-06-06 05:42:01 | MASTER-OAFA | (02h 02m 21.86s , -77d 24m 43.4s) | C | 180 | 18.9 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40641. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38677] GRB 250606A: Fermi GBM Final Real-time Localization
by GCN Circulars 06 Jun '25

06 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40640 SUBJECT: GRB 250606A: Fermi GBM Final Real-time Localization DATE: 25/06/06 04:39:12 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 LONG GRB At 04:28:41 UT on 6 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250606A (trigger 770876926.822872 / 250606187). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 32.3, Dec = -78.2 (J2000 degrees, equivalent to J2000 02h 09m, -78d 12'), with a statistical uncertainty of 2.8 degrees. The angle from the Fermi LAT boresight is 50.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250606187/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250606187/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250606187/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40640. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38676] Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
by GCN Circulars 06 Jun '25

06 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40639 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB DATE: 25/06/06 04:37:18 GMT FROM: oindabimukherjee(a)gmail.com Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB O. Mukherjee (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 770867684/250606080 at 01:54:39.00 UT on 06 June 2025, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to local particles." View this GCN Circular online at https://gcn.nasa.gov/circulars/40639. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38675] Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
by GCN Circulars 06 Jun '25

06 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40638 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB DATE: 25/06/06 04:33:56 GMT FROM: oindabimukherjee(a)gmail.com Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB O. Mukherjee (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 770867684/250606080 at 01:54:39.00 UT on 06 June 2025, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to local particles." View this GCN Circular online at https://gcn.nasa.gov/circulars/40638. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38674] Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
by GCN Circulars 06 Jun '25

06 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40638 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB DATE: 25/06/06 04:33:56 GMT FROM: oindabimukherjee(a)gmail.com Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB O. Mukherjee (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 770867684/250606080 at 01:54:39.00 UT on 06 June 2025, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to local particles." View this GCN Circular online at https://gcn.nasa.gov/circulars/40638. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38673] GRB 250602A: GECAM detection
by GCN Circulars 06 Jun '25

06 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40637 SUBJECT: GRB 250602A: GECAM detection DATE: 25/06/06 04:33:43 GMT FROM: zhengchao_astro(a)foxmail.com Chao Zheng, Chen-Wei Wang, Yan-Qiu Zhang, Shao-Lin Xiong, Yue Huang (IHEP) report on behalf of GECAM team: GECAM-A detected burst GRB 250602A at 2025-06-02T03:04:31.310 UTC (denoted as T0), which was also detected by Fermi/GBM (Fermi GBM team, GCN #40602). According to the GECAM-A light curves in about 70-6000 keV, this burst mainly consists of a single pulse with a duration (T90) of about 8.68 s. The GECAM-A light curve can be found here: https://www.bursthub.cn//admin/static/gecamgrb250602A.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/40637. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38672] Fermi trigger No 770867684: Global MASTER-Net observations report
by GCN Circulars 06 Jun '25

06 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40636 SUBJECT: Fermi trigger No 770867684: Global MASTER-Net observations report DATE: 25/06/06 04:16:29 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 (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB250606.08 (trigger No 770867684,11h 54m 36.00s , -54d 01m 12.0s, R=8.02) errorbox 145 sec after notice time and 170 sec after trigger time at 2025-06-06 01:57:29 UT, with upper limit up to 18.0 mag. The observations began at zenith distance = 81 deg. The sun altitude is -44.9 deg. MASTER-OAFA robotic telescope located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB250606.08 errorbox 146 sec after notice time and 171 sec after trigger time at 2025-06-06 01:57:30 UT, with upper limit up to 19.4 mag. The observations began at zenith distance = 33 deg. The sun altitude is -54.5 deg. The galactic latitude b = 8 deg., longitude l = 295 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2893923 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 185 | 2025-06-06 01:57:29 | MASTER-SAAO | (12h 05m 40.89s , -53d 37m 11.1s) | C | 30 | 16.5 | 235 | 2025-06-06 01:57:29 | MASTER-SAAO | (12h 05m 40.89s , -53d 37m 11.2s) | C | 130 | 17.2 | Coadd 185 | 2025-06-06 01:57:29 | MASTER-SAAO | (12h 08m 35.38s , -53d 52m 45.4s) | C | 30 | 17.3 | 235 | 2025-06-06 01:57:29 | MASTER-SAAO | (12h 08m 35.39s , -53d 52m 45.4s) | C | 130 | 18.0 | Coadd 187 | 2025-06-06 01:57:30 | MASTER-OAFA | (12h 08m 13.05s , -53d 38m 46.7s) | C | 30 | 18.6 | 228 | 2025-06-06 01:58:06 | MASTER-OAFA | (12h 08m 13.09s , -53d 38m 46.8s) | C | 40 | 18.8 | 239 | 2025-06-06 01:58:18 | MASTER-SAAO | (12h 05m 41.09s , -53d 37m 07.5s) | C | 40 | 16.7 | 239 | 2025-06-06 01:58:18 | MASTER-SAAO | (12h 08m 35.55s , -53d 52m 43.0s) | C | 40 | 17.5 | 279 | 2025-06-06 01:58:53 | MASTER-OAFA | (12h 08m 13.22s , -53d 38m 46.8s) | C | 50 | 19.0 | 308 | 2025-06-06 01:59:17 | MASTER-SAAO | (12h 05m 41.36s , -53d 37m 03.8s) | C | 60 | 16.8 | 308 | 2025-06-06 01:59:17 | MASTER-SAAO | (12h 08m 35.78s , -53d 52m 40.3s) | C | 60 | 17.6 | 341 | 2025-06-06 01:59:49 | MASTER-OAFA | (12h 08m 13.38s , -53d 38m 46.5s) | C | 60 | 18.9 | 387 | 2025-06-06 02:00:36 | MASTER-SAAO | (12h 05m 41.68s , -53d 37m 00.3s) | C | 60 | 16.8 | 387 | 2025-06-06 02:00:36 | MASTER-SAAO | (12h 08m 36.14s , -53d 52m 38.0s) | C | 60 | 17.6 | 419 | 2025-06-06 02:01:08 | MASTER-OAFA | (12h 31m 47.57s , -49d 44m 44.7s) | C | 60 | 19.0 | 754 | 2025-06-06 02:06:43 | MASTER-OAFA | (12h 44m 15.34s , -49d 44m 12.4s) | C | 60 | 19.2 | 932 | 2025-06-06 02:09:40 | MASTER-OAFA | (12h 31m 52.61s , -49d 44m 50.8s) | C | 60 | 19.3 | 1008 | 2025-06-06 02:10:57 | MASTER-OAFA | (12h 38m 34.16s , -51d 38m 58.0s) | C | 60 | 19.1 | 1341 | 2025-06-06 02:16:30 | MASTER-OAFA | (12h 51m 33.85s , -51d 38m 22.8s) | C | 60 | 19.0 | 1417 | 2025-06-06 02:17:46 | MASTER-OAFA | (12h 44m 10.98s , -49d 45m 06.6s) | C | 60 | 19.3 | 1596 | 2025-06-06 02:20:44 | MASTER-OAFA | (12h 31m 50.62s , -49d 43m 18.2s) | C | 60 | 19.1 | 1672 | 2025-06-06 02:22:01 | MASTER-OAFA | (12h 38m 36.25s , -51d 38m 57.0s) | C | 60 | 18.6 | 1999 | 2025-06-06 02:27:28 | MASTER-OAFA | (12h 51m 34.74s , -51d 38m 15.9s) | C | 60 | 19.4 | 2077 | 2025-06-06 02:28:46 | MASTER-OAFA | (12h 44m 12.10s , -49d 45m 00.3s) | C | 60 | 19.3 | 2255 | 2025-06-06 02:31:43 | MASTER-OAFA | (12h 31m 52.06s , -49d 43m 09.8s) | C | 60 | 18.6 | 2331 | 2025-06-06 02:33:00 | MASTER-OAFA | (12h 38m 37.81s , -51d 38m 37.7s) | C | 60 | 18.2 | 2665 | 2025-06-06 02:38:33 | MASTER-OAFA | (12h 51m 36.64s , -51d 38m 08.1s) | C | 60 | 18.5 | 2740 | 2025-06-06 02:39:48 | MASTER-OAFA | (12h 44m 14.95s , -49d 44m 53.5s) | C | 60 | 18.8 | 2916 | 2025-06-06 02:42:45 | MASTER-OAFA | (12h 31m 53.39s , -49d 43m 00.2s) | C | 60 | 18.8 | 2992 | 2025-06-06 02:44:00 | MASTER-OAFA | (12h 38m 39.38s , -51d 38m 29.8s) | C | 60 | 18.7 | 3322 | 2025-06-06 02:49:30 | MASTER-OAFA | (12h 51m 38.28s , -51d 38m 00.7s) | C | 60 | 18.9 | 3398 | 2025-06-06 02:50:46 | MASTER-OAFA | (12h 44m 15.32s , -49d 44m 46.9s) | C | 60 | 19.1 | 3575 | 2025-06-06 02:53:43 | MASTER-OAFA | (12h 31m 54.88s , -49d 42m 52.8s) | C | 60 | 19.1 | 3650 | 2025-06-06 02:54:59 | MASTER-OAFA | (12h 38m 40.97s , -51d 38m 22.6s) | C | 60 | 19.1 | 3985 | 2025-06-06 03:00:34 | MASTER-OAFA | (12h 51m 38.79s , -51d 37m 54.3s) | C | 60 | 18.7 | 4066 | 2025-06-06 03:01:55 | MASTER-OAFA | (12h 44m 18.16s , -49d 44m 41.8s) | C | 60 | 18.6 | 4245 | 2025-06-06 03:04:54 | MASTER-OAFA | (12h 31m 56.32s , -49d 42m 44.8s) | C | 60 | 18.0 | 4323 | 2025-06-06 03:06:12 | MASTER-OAFA | (12h 38m 42.60s , -51d 38m 21.7s) | C | 60 | 17.8 | 4653 | 2025-06-06 03:11:42 | MASTER-OAFA | (12h 51m 41.88s , -51d 37m 49.9s) | C | 60 | 16.9 | 4729 | 2025-06-06 03:12:57 | MASTER-OAFA | (12h 44m 17.92s , -49d 44m 38.6s) | C | 60 | 17.4 | 4915 | 2025-06-06 03:16:04 | MASTER-OAFA | (12h 31m 57.78s , -49d 42m 33.6s) | C | 60 | 17.7 | 4993 | 2025-06-06 03:17:21 | MASTER-OAFA | (12h 38m 44.26s , -51d 38m 29.4s) | C | 60 | 17.7 | 5321 | 2025-06-06 03:22:50 | MASTER-OAFA | (12h 51m 43.99s , -51d 37m 46.6s) | C | 60 | 18.0 | 5398 | 2025-06-06 03:24:07 | MASTER-OAFA | (12h 44m 19.80s , -49d 44m 36.2s) | C | 60 | 17.8 | 5573 | 2025-06-06 03:27:02 | MASTER-OAFA | (12h 31m 59.29s , -49d 42m 59.2s) | C | 60 | 17.6 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40636. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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