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[vsnet-grb-info 39947] GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020)
by GCN Circulars 18 Sep '25

18 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41881 SUBJECT: GRB 250919A: BALROG localization (Fermi Trigger 779934537 / GRB 250919020) DATE: 25/09/19 05:41:12 GMT FROM: Jochen Greiner at MPE <jcgrog(a)mpe.mpg.de> T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report: The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 779934537 at 00:28:52 on 19 Sept. 2025 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60). The best-fit position is: RA(2000.0) = 300.5 deg Decl.(2000.0) = -49.1 deg The 1 sigma statistical error radius is 0.3 deg. We estimate an additional systematic error of 2 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB250919020/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB250919020/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB250919020/json View this GCN Circular online at https://gcn.nasa.gov/circulars/41881. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39946] EP250919a: Global MASTER-Net observations report
by GCN Circulars 18 Sep '25

18 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41880 SUBJECT: EP250919a: Global MASTER-Net observations report DATE: 25/09/19 04:54:19 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 (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP250919a ( EP Team et al., GCN 41879) errorbox 1286 sec after trigger time at 2025-09-19 02:36:21 UT, with upper limit up to 20.4 mag. The observations began at zenith distance = 28 deg. The sun altitude is -50.4 deg. MASTER-SAAO robotic telescope located in South Africa (South African Astronomical Observatory) was pointed to the EP250919a errorbox 2640 sec after trigger time at 2025-09-19 02:58:55 UT, with upper limit up to 17.7 mag. The observations began at zenith distance = 85 deg. The sun altitude is -20.6 deg. The galactic latitude b = -31 deg., longitude l = 350 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2994829 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 1317 | 2025-09-19 02:36:21 | MASTER-OAFA | (20h 01m 51.73s , -50d 10m 08.0s) | C | 60 | 20.4 | 1393 | 2025-09-19 02:37:38 | MASTER-OAFA | (20h 01m 45.42s , -50d 11m 06.5s) | C | 60 | 20.4 | 1468 | 2025-09-19 02:38:53 | MASTER-OAFA | (20h 01m 51.69s , -50d 11m 05.3s) | C | 60 | 20.4 | 1771 | 2025-09-19 02:43:56 | MASTER-OAFA | (20h 02m 12.87s , -48d 15m 58.0s) | C | 60 | 20.3 | 1848 | 2025-09-19 02:45:13 | MASTER-OAFA | (20h 02m 12.38s , -48d 14m 56.9s) | C | 60 | 20.3 | 1923 | 2025-09-19 02:46:28 | MASTER-OAFA | (20h 02m 18.99s , -48d 15m 56.3s) | C | 60 | 20.3 | 2652 | 2025-09-19 02:58:37 | MASTER-OAFA | (19h 53m 50.03s , -48d 54m 47.0s) | C | 60 | 20.1 | 2671 | 2025-09-19 02:58:55 | MASTER-SAAO | (19h 53m 22.97s , -48d 53m 39.0s) | C | 60 | 17.3 | 2731 | 2025-09-19 02:58:55 | MASTER-SAAO | (19h 53m 23.03s , -48d 53m 39.6s) | C | 180 | 17.7 | Coadd 2718 | 2025-09-19 02:59:42 | MASTER-OAFA | (19h 53m 50.12s , -48d 54m 46.3s) | C | 60 | 20.2 | 2750 | 2025-09-19 03:00:14 | MASTER-SAAO | (19h 53m 22.90s , -48d 53m 35.3s) | C | 60 | 17.2 | 2783 | 2025-09-19 03:00:48 | MASTER-OAFA | (19h 53m 50.30s , -48d 54m 45.8s) | C | 60 | 20.2 | 2829 | 2025-09-19 03:01:33 | MASTER-SAAO | (19h 53m 22.92s , -48d 53m 29.8s) | C | 60 | 16.4 | 2849 | 2025-09-19 03:01:54 | MASTER-OAFA | (19h 53m 50.44s , -48d 54m 45.2s) | C | 60 | 20.2 | 2908 | 2025-09-19 03:02:52 | MASTER-SAAO | (19h 53m 22.65s , -48d 53m 20.6s) | C | 60 | 17.0 | 2915 | 2025-09-19 03:02:59 | MASTER-OAFA | (19h 53m 50.57s , -48d 54m 44.6s) | C | 60 | 20.3 | 2980 | 2025-09-19 03:04:05 | MASTER-OAFA | (19h 53m 50.70s , -48d 54m 43.9s) | C | 60 | 20.3 | 3047 | 2025-09-19 03:05:11 | MASTER-OAFA | (19h 53m 50.85s , -48d 54m 43.5s) | C | 60 | 20.3 | 3112 | 2025-09-19 03:06:17 | MASTER-OAFA | (19h 53m 51.00s , -48d 54m 43.3s) | C | 60 | 20.2 | 3178 | 2025-09-19 03:07:22 | MASTER-OAFA | (19h 53m 51.10s , -48d 54m 42.9s) | C | 60 | 20.2 | 3244 | 2025-09-19 03:08:29 | MASTER-OAFA | (19h 53m 51.26s , -48d 54m 42.6s) | C | 60 | 20.2 | 3310 | 2025-09-19 03:09:34 | MASTER-OAFA | (19h 53m 51.38s , -48d 54m 42.1s) | C | 60 | 20.3 | 3375 | 2025-09-19 03:10:39 | MASTER-OAFA | (19h 53m 51.55s , -48d 54m 41.6s) | C | 60 | 20.2 | 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/41880. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39945] EP250919a: Einstein Probe detection of an X-ray transient
by GCN Circulars 18 Sep '25

18 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41879 SUBJECT: EP250919a: Einstein Probe detection of an X-ray transient DATE: 25/09/19 04:34:49 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. F. Liang (PMO), R. D. Liang, C. L. Guo, W. J. Hu, Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP250919a. The transient triggered EP-WXT (ID: 01709243841). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. At 2025-09-19T02:14:55 (UTC), an uncatalogued X-ray source was detected at R.A. = 298.5520 deg, DEC = -48.8395 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). An uncataloged optical source was detected within FXT error circle (GCN 41877, 41878). EP250919a is located within the 1-sigma error region of GRB 250919A (GCN 41874). However, the temporal offset exceeds 2 hours, and thus we cannot rule out the possibility of a chance spatial coincidence. Further information will be updated when the telemetry data is received. Further follow-up observations are encouraged. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/41879. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39944] Correction for GCN 41877: EP-WXT ID is 01709243841
by GCN Circulars 18 Sep '25

18 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41878 SUBJECT: Correction for GCN 41877: EP-WXT ID is 01709243841 DATE: 25/09/19 03:38:33 GMT FROM: Wenxiong Li at NAOC <liwenxiong1992(a)gmail.com> Wenxiong Li (NAOC), Iair Arcavi (TAU), Ido Keinan (TAU), David Sand (U of Arizona) The correct EP-WXT trigger ID in GCN 41877 is 01709243841. We apologize for any confusion. View this GCN Circular online at https://gcn.nasa.gov/circulars/41878. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39943] The EP-WXT trigger 01709240768: Las Cumbres discovery of the optical counterpart
by GCN Circulars 18 Sep '25

18 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41877 SUBJECT: The EP-WXT trigger 01709240768: Las Cumbres discovery of the optical counterpart DATE: 25/09/19 03:28:55 GMT FROM: Wenxiong Li at NAOC <liwenxiong1992(a)gmail.com> Wenxiong Li (NAOC), Iair Arcavi (TAU), Ido Keinan (TAU), David Sand (U of Arizona) We observed the position of EP-WXT trigger 01709240768 with a Las Cumbres 1m telescope at Cerro Tololo Inter-American Observatory 0.8 hours after the Einstein Probe WXT trigger. We took 2x300s exposures in the broad optical w band. We find an uncataloged source at RA=298.55383, Dec=-48.8378 within the EP/WXT error circle and measure the following preliminary photometry calibrated to the r band: MJD 60937.127 Mag 17.0 Additional followup is encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/41877. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39942] GRB 250916A: Fermi GBM Observation
by GCN Circulars 18 Sep '25

18 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41876 SUBJECT: GRB 250916A: Fermi GBM Observation DATE: 25/09/19 02:43:19 GMT FROM: Matt Godwin <msg0028(a)uah.edu> Matt Godwin (UAH) and C. Meegan (UAH) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 13:29:21.01 UT on 16 September 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250916A (trigger 779722166/250916562). which was also detected by AstroSat ( Arya et al. 2025, GCN 41843) with an optical counterpart by GOTO (Belkin et al. 2025, GCN 41847). The angle from the Fermi LAT boresight is 66 degrees. GBM triggered on what appears to be precursor and the main emission episode begins about 150 seconds after the precursor. The lightcurve has a duration (T90) of about 80 s (50-300 keV). The time-averaged spectrum of the main emission from T0+230 to T0+290 s is best fit by a Band function with Epeak = 144 +/- 9 keV, alpha = -1.08 +/- 0.03, and beta = -2.00 +/- 0.03. The event fluence (10-1000 keV) within this time interval is (4.61 +/- 0.07)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+270 s in the 10-1000 keV band is 5.65 +/- 0.4 ph/s/cm^2. The time-averaged spectrum of the percursor from T0-12 to T0+05 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.92 +/- 0.3 and the cutoff energy, parameterized as Epeak, is 110 +/- 22 keV. The event fluence (10-1000 keV) within this time interval is (1.31 +/- 0.15)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+270 s in the 10-1000 keV band is 0.67 +/- 0.05 ph/s/cm^2. The localization for the preliminary pulse is uncertain, but consistent with the secondary pulse. The event fluence (10-1000 keV) within the whole time interval is (4.73 +/- 0.16)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+270 s in the 10-1000 keV band is 4.57 +/- 0.3 ph/s/cm^2. The localization for the preliminary pulse is uncertain, but consistent with the secondary pulse. 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/41876. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39941] Fermi GRB 250919A: Global MASTER-Net observations report
by GCN Circulars 18 Sep '25

18 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41875 SUBJECT: Fermi GRB 250919A: Global MASTER-Net observations report DATE: 25/09/19 01:30:59 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 250919A ( Fermi GBM team, GCN 41874) errorbox 557 sec after notice time and 592 sec after trigger time at 2025-09-19 00:38:44 UT, with upper limit up to 19.3 mag. The observations began at zenith distance = 63 deg. The sun altitude is -47.5 deg. MASTER-OAFA robotic telescope located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 250919A errorbox 658 sec after notice time and 693 sec after trigger time at 2025-09-19 00:40:26 UT, with upper limit up to 20.3 mag. The observations began at zenith distance = 19 deg. The sun altitude is -28.7 deg. The galactic latitude b = -34 deg., longitude l = 350 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2994728 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 622 | 2025-09-19 00:38:44 | MASTER-SAAO | (20h 12m 52.30s , -49d 54m 57.2s) | C | 60 | 19.3 | 622 | 2025-09-19 00:38:44 | MASTER-SAAO | (20h 10m 02.82s , -49d 39m 38.7s) | C | 60 | 19.2 | 764 | 2025-09-19 00:40:26 | MASTER-OAFA | (20h 13m 10.49s , -49d 55m 27.8s) | C | 140 | 20.2 | 925 | 2025-09-19 00:42:52 | MASTER-OAFA | (20h 13m 10.79s , -49d 55m 23.7s) | C | 170 | 20.3 | 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/41875. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39940] GRB 250919A: Fermi GBM Final Real-time Localization
by GCN Circulars 18 Sep '25

18 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41874 SUBJECT: GRB 250919A: Fermi GBM Final Real-time Localization DATE: 25/09/19 00:39:24 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 00:28:52 UT on 19 Sep 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250919A (trigger 779934537.284108 / 250919020). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 303.5, Dec = -49.8 (J2000 degrees, equivalent to J2000 20h 14m, -49d 47'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 57.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250919020/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250919020/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250919020/… View this GCN Circular online at https://gcn.nasa.gov/circulars/41874. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39939] GRB 250916A: KAIT optical observations
by GCN Circulars 18 Sep '25

18 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41873 SUBJECT: GRB 250916A: KAIT optical observations DATE: 25/09/18 22:13:06 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB) and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, observed the field of GRB 250916A (Fermi GBM team, GCN 41839; Arya et al., GCN 41843; Cheung et al., GCN 41855; Waratkar et al., GCN 41871) starting at ~0.783d and again at ~1.738d after the burst. A set of clear (roughly R) filter images were obtained. We clearly detected the optical afterglow (Belkin et al., GCN 41847; Mohan et al., GCN 41858; Moskvitin et al., GCN 41859; Burkhonov et al., GCN 41860; de Ugarte Postigo et al., GCN 41863; Moskvitin et al., GCN 41870) in our coadd images. We estimate the afterglow to be 19.35 +/- 0.1 and 20.10 +/- 0.1 mag (Vega) at a mid time of ~0.824d and ~1.807d respectively. View this GCN Circular online at https://gcn.nasa.gov/circulars/41873. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39938] GRB 250917B: VLT/HAWK-I near-infrared observations
by GCN Circulars 18 Sep '25

18 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41872 SUBJECT: GRB 250917B: VLT/HAWK-I near-infrared observations DATE: 25/09/18 20:03:34 GMT FROM: muskan.yadav(a)students.uniroma2.eu Muskan Yadav (U. Rome), Rosa L. Becerra (U. Rome) and Eleonora Troja (U. Rome) report on behalf of the ERC BHianca team: We observed the field of GRB 250917B (Fermi GBM Team et al., GCN 41846; Caputo et al., GCN 41848) with the HAWKI imager on the ESO VLT UT4 (Yepun). Observations started on 2025-09-17 at 23:52:22 UT, approximately 0.7 days after the trigger, and were carried out in the Ks filter at an average seeing of 0.6". Image subtraction against 2MASS Catalogue (Skrutskie et al. 2006) shows no new uncataloged source down to K~18.5 AB. Several fainter objects are visible within the BAT refined position (Parsotan et al., GCN 41868), however additional observations are required to assess their variability. At the position of the Source 1 reported by Kennea et al. GCN 41851, our observation is dominated by the close bright star TYC 1059-317-1. We thank the staff at the VLT, for the rapid execution of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/41872. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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