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

[vsnet-grb-info 38096] EP250404A: COLIBRÍ/DDRAGO Optical Observations
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40073 SUBJECT: EP250404A: COLIBRÍ/DDRAGO Optical Observations DATE: 25/04/05 08:31:34 GMT FROM: Ny Avo Rakotondrainibe at LAM <nyavo.rakotobe(a)gmail.com> Ny Avo Rakotondrainibe (LAM), Jean-Grégoire Ducoin (CPPM), Rosa L. Becerra (U Roma), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Sarah Antier (OCA/IJCLAB), Stéphane Basa (UAR Pytheas), Diego López-Cámara (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Ramandeep Gill (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Antonio de Ugarte Postigo (LAM) and Benjamin Schneider (LAM) report: We imaged the field of EP250404A (Hu et al., GCN Circ. 40051) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico on the night of 2025-04-05 UTC. We observed from 2025-04-05 05:39 to 06:18 UTC (T+15.3 to T+16.0 hours after the trigger) and obtained 1920 seconds of exposure in total in the r filter. Our observations were performed under regular weather conditions. The data were coadded with the COLIBRÍ pipeline and analysed in STDWeb/STDPipe (Karpov 2025), with photometric calibration against Pan-STARRS DR1. Our photometry is in the AB system and is not corrected for Galactic extinction. We detected the optical counterpart (Jiang et al., GCN Circ. 40052, Perez-Garcia et al., GCN Circ. 40053, Du et al., GCN Circ. 40058, Zhu et al., GCN Circ. 40061, Konno et al. GCN Circ. 40063, Odeh et al., GCN Circ. 40064, Lipunov et al., GCN Circ. 40066, He et al., GCN Circ. 40069, Perez-Fournon et al., GCN Circ. 40071, Jelinek et al., GCN Circ. 40072) with an AB magnitude of: r = 21.99 +/- 0.15. Compared with the values previously reported, we estimate the fading nature of the OT with a temporal index ~1.4 after T+1.7 hours. Further observations and analysis are ongoing. We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/40073. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38095] EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40072 SUBJECT: EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection DATE: 25/04/05 03:49:34 GMT FROM: Martin Jelinek at Astro.Inst-AVCR,Ondrejov <martin.jelinek(a)asu.cas.cz> M. Jelinek, J. Strobl, F. Novotny, R. Hudec (ASU CAS Ondrejov) report:We observed the field of EP250404a detected by EP (Hu et al., GCN 40051), which is temporally and spatially consistent with GRB 250404A (Fermi team, GCN 40050; Mukherjee et al., GCN 40067), using the D50 telescope of the Astronomical Institute Ondrejov, near Prague, Czech Republic. Our observations started at 15:50 UT on 2025-04-04, approximately 5.5 hours after the trigger. We performed a series of 120s exposures in the SDSS i' filter. The optical counterpart, previously reported by several teams (Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Konno et al., GCN 40063; Odeh et al., GCN 40064; He et al., GCN 40069; Pérez-Fournon et al., GCN 40071), is detected in our combined image of 25x120s exposures. The PanSTARRS-calibrated magnitude of the source is i' = 19.5 +/- 0.1, not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/40072. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38094] EP250404a: LCO optical counterpart detection
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40071 SUBJECT: EP250404a: LCO optical counterpart detection DATE: 25/04/05 00:52:37 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> I. Pérez-Fournon, F. Poidevin (IAC and ULL), D. Cano-Morales, A.E. Hernández-Díaz, I. Correa-Plasencia (ULL), D. Aguado, A. López-Oramas, D. Nespral (IAC and ULL), N.C. Sun (UCAS), W. Li, Y. Wang, and Z. Niu (NAOC) We report on Las Cumbres Observatory Global Telescope network (LCOGT) observations of the X-ray transient EP250404a (Hu et al., GCN circ. 40051), that is temporally and spatially consistent with the likely long GRB 250404A, detected by Fermi/GBM (Fermi GBM team, GCN 40050; and Mukherjee et al., GCN circ. 40067). We observed the field of EP250404a with the two LCOGT 1-m telescopes, equipped with Sinistro cameras, located at the LCOGT node at Teide Observatory (Tenerife, Spain) in the SDSS i, g, and r filters, starting at 2025-04-04 20:27:26 UTC, about 6.12 hours after the EP trigger. An uncatalogued source is clearly detected in the three images at the position of the optical counterpart first reported by Jiang et al. (GCN circ. 40052) and also detected by Perez-Garcia et al. (GCN circ. 40053), Du et al. (GCN circ. 40058), Zhu et al. (GCN circ. 40061), Konno et al. (GCN circ. 40063), Odeh et al. (GCN circ. 40064), and He et al. (GCN circ. 40069). A redshift of z = 2.63 has been reported by Zhu et al. (GCN circ. 40061). We measure the following preliminary magnitudes, calibrated against Pan-STARRS DR2 stars, that are not corrected for Galactic extinction: Date | UT start | mag | error | filter | exposure time (sec) --------------------------------------------------------------------- 2025-04-04 20:27:26 20.11 0.22 i 300 2025-04-04 22:01:01 20.65 0.16 g 300 2025-04-04 22:05:55 20.38 0.11 r 300 This work makes use of observations from the Las Cumbres Observatory global telescope network (LCOGT observing programme IAC2025A-009, SGLF). View this GCN Circular online at https://gcn.nasa.gov/circulars/40071. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38093] Fermi GRB 250404A: Global MASTER-Net observations report
by GCN Circulars 05 Apr '25

05 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40070 SUBJECT: Fermi GRB 250404A: Global MASTER-Net observations report DATE: 25/04/05 00:17:01 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, 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. 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-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 250404A ( Fermi GBM team, GCN 40050) errorbox 16599 sec after notice time and 16639 sec after trigger time at 2025-04-04 18:57:05 UT, with upper limit up to 19.5 mag. The observations began at zenith distance = 66 deg. The sun altitude is -28.6 deg. MASTER-OAFA robotic telescope located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 250404A errorbox 31880 sec after notice time and 31919 sec after trigger time at 2025-04-04 23:11:46 UT, with upper limit up to 19.3 mag. Observations started at twilight. The observations began at zenith distance = 67 deg. The sun altitude is -10.4 deg. The galactic latitude b = 32 deg., longitude l = 188 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2832903 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 16669 | 2025-04-04 18:57:05 | MASTER-Tunka | (08h 19m 51.88s , +36d 00m 34.0s) | C | 60 | 18.6 | 16729 | 2025-04-04 18:57:05 | MASTER-Tunka | (08h 19m 51.88s , +36d 00m 34.0s) | C | 180 | 19.3 | Coadd 16740 | 2025-04-04 18:58:16 | MASTER-Tunka | (08h 19m 58.07s , +36d 00m 34.7s) | C | 60 | 18.6 | 16812 | 2025-04-04 18:59:28 | MASTER-Tunka | (08h 19m 55.11s , +36d 02m 04.0s) | C | 60 | 18.6 | 16885 | 2025-04-04 19:00:41 | MASTER-Tunka | (08h 19m 55.07s , +36d 00m 32.5s) | C | 60 | 18.7 | 16945 | 2025-04-04 19:00:41 | MASTER-Tunka | (08h 19m 55.07s , +36d 00m 32.5s) | C | 180 | 19.4 | Coadd 16962 | 2025-04-04 19:01:58 | MASTER-Tunka | (08h 19m 57.66s , +36d 02m 04.7s) | C | 60 | 18.6 | 17033 | 2025-04-04 19:03:09 | MASTER-Tunka | (08h 19m 52.37s , +36d 01m 15.7s) | C | 60 | 18.7 | 17108 | 2025-04-04 19:04:24 | MASTER-Tunka | (08h 19m 51.30s , +36d 02m 12.7s) | C | 60 | 18.7 | 17168 | 2025-04-04 19:04:24 | MASTER-Tunka | (08h 19m 51.30s , +36d 02m 12.8s) | C | 180 | 19.5 | Coadd 17393 | 2025-04-04 19:09:09 | MASTER-Tunka | (08h 19m 52.28s , +35d 59m 59.8s) | C | 60 | 18.7 | 17466 | 2025-04-04 19:10:22 | MASTER-Tunka | (08h 19m 58.20s , +36d 00m 10.2s) | C | 60 | 18.7 | 17540 | 2025-04-04 19:11:35 | MASTER-Tunka | (08h 19m 54.28s , +36d 01m 24.3s) | C | 60 | 18.7 | 17600 | 2025-04-04 19:11:35 | MASTER-Tunka | (08h 19m 54.28s , +36d 01m 24.2s) | C | 180 | 19.4 | Coadd 17612 | 2025-04-04 19:12:48 | MASTER-Tunka | (08h 19m 54.27s , +35d 59m 56.4s) | C | 60 | 18.6 | 17683 | 2025-04-04 19:13:59 | MASTER-Tunka | (08h 19m 57.20s , +36d 01m 34.1s) | C | 60 | 18.6 | 17756 | 2025-04-04 19:15:12 | MASTER-Tunka | (08h 19m 51.23s , +36d 00m 41.3s) | C | 60 | 18.5 | 17816 | 2025-04-04 19:15:12 | MASTER-Tunka | (08h 19m 51.23s , +36d 00m 41.3s) | C | 180 | 19.3 | Coadd 17829 | 2025-04-04 19:16:24 | MASTER-Tunka | (08h 19m 51.76s , +36d 01m 37.4s) | C | 60 | 18.6 | 17903 | 2025-04-04 19:17:39 | MASTER-Tunka | (08h 19m 57.64s , +36d 00m 34.5s) | C | 60 | 18.7 | 17975 | 2025-04-04 19:18:51 | MASTER-Tunka | (08h 19m 51.82s , +35d 59m 30.3s) | C | 60 | 18.6 | 18035 | 2025-04-04 19:18:51 | MASTER-Tunka | (08h 19m 51.82s , +35d 59m 30.3s) | C | 180 | 19.4 | Coadd 18048 | 2025-04-04 19:20:04 | MASTER-Tunka | (08h 19m 57.26s , +35d 59m 42.1s) | C | 60 | 18.6 | 18120 | 2025-04-04 19:21:16 | MASTER-Tunka | (08h 19m 53.77s , +36d 01m 07.0s) | C | 60 | 18.5 | 18192 | 2025-04-04 19:22:28 | MASTER-Tunka | (08h 19m 53.78s , +35d 59m 24.2s) | C | 60 | 18.6 | 18252 | 2025-04-04 19:22:28 | MASTER-Tunka | (08h 19m 53.78s , +35d 59m 24.1s) | C | 180 | 19.4 | Coadd 18263 | 2025-04-04 19:23:39 | MASTER-Tunka | (08h 19m 57.55s , +36d 00m 59.3s) | C | 60 | 18.7 | 18337 | 2025-04-04 19:24:53 | MASTER-Tunka | (08h 19m 50.49s , +36d 00m 11.6s) | C | 60 | 18.6 | 31925 | 2025-04-04 23:11:46 | MASTER-OAFA | (08h 08m 19.47s , +34d 59m 12.3s) | C | 10 | 14.9 | 31925 | 2025-04-04 23:11:46 | MASTER-OAFA | (08h 19m 21.81s , +35d 21m 51.8s) | C | 10 | 16.5 | 31967 | 2025-04-04 23:12:28 | MASTER-OAFA | (08h 08m 15.18s , +35d 00m 30.7s) | C | 10 | 14.9 | 31967 | 2025-04-04 23:12:28 | MASTER-OAFA | (08h 19m 17.72s , +35d 23m 08.7s) | C | 10 | 16.6 | 32005 | 2025-04-04 23:13:06 | MASTER-OAFA | (08h 08m 15.01s , +34d 58m 38.5s) | C | 10 | 14.9 | 32005 | 2025-04-04 23:13:06 | MASTER-OAFA | (08h 19m 17.32s , +35d 21m 15.2s) | C | 10 | 16.7 | 32044 | 2025-04-04 23:13:45 | MASTER-OAFA | (08h 08m 17.35s , +35d 00m 09.4s) | C | 10 | 15.1 | 32044 | 2025-04-04 23:13:45 | MASTER-OAFA | (08h 19m 19.90s , +35d 22m 45.2s) | C | 10 | 16.8 | 32086 | 2025-04-04 23:14:27 | MASTER-OAFA | (08h 08m 10.02s , +34d 59m 29.2s) | C | 10 | 15.2 | 32086 | 2025-04-04 23:14:27 | MASTER-OAFA | (08h 19m 12.52s , +35d 22m 04.1s) | C | 10 | 16.8 | 32127 | 2025-04-04 23:15:08 | MASTER-OAFA | (08h 08m 11.16s , +35d 00m 25.4s) | C | 10 | 15.2 | 32127 | 2025-04-04 23:15:08 | MASTER-OAFA | (08h 19m 13.83s , +35d 22m 59.5s) | C | 10 | 16.8 | 32165 | 2025-04-04 23:15:45 | MASTER-OAFA | (08h 08m 16.58s , +34d 59m 22.6s) | C | 10 | 15.3 | 32165 | 2025-04-04 23:15:46 | MASTER-OAFA | (08h 19m 19.15s , +35d 21m 56.2s) | C | 10 | 17.0 | 32204 | 2025-04-04 23:16:24 | MASTER-OAFA | (08h 08m 09.70s , +34d 58m 17.6s) | C | 10 | 15.3 | 32204 | 2025-04-04 23:16:25 | MASTER-OAFA | (08h 19m 12.12s , +35d 20m 50.5s) | C | 10 | 16.9 | 32241 | 2025-04-04 23:17:02 | MASTER-OAFA | (08h 08m 15.41s , +34d 58m 44.1s) | C | 10 | 15.3 | 32241 | 2025-04-04 23:17:02 | MASTER-OAFA | (08h 19m 17.91s , +35d 21m 16.7s) | C | 10 | 17.0 | 32280 | 2025-04-04 23:17:41 | MASTER-OAFA | (08h 08m 11.54s , +35d 00m 01.8s) | C | 10 | 15.3 | 32280 | 2025-04-04 23:17:41 | MASTER-OAFA | (08h 19m 14.23s , +35d 22m 33.8s) | C | 10 | 17.0 | 32318 | 2025-04-04 23:18:19 | MASTER-OAFA | (08h 08m 11.34s , +34d 58m 27.0s) | C | 10 | 15.3 | 32318 | 2025-04-04 23:18:19 | MASTER-OAFA | (08h 19m 13.81s , +35d 20m 58.4s) | C | 10 | 17.1 | 32356 | 2025-04-04 23:18:57 | MASTER-OAFA | (08h 08m 13.99s , +34d 59m 41.3s) | C | 10 | 15.4 | 32357 | 2025-04-04 23:18:57 | MASTER-OAFA | (08h 19m 16.67s , +35d 22m 12.7s) | C | 10 | 17.2 | 33140 | 2025-04-04 23:32:01 | MASTER-OAFA | (08h 07m 59.46s , +34d 58m 26.5s) | C | 10 | 15.7 | 33150 | 2025-04-04 23:32:01 | MASTER-OAFA | (08h 19m 01.71s , +35d 21m 07.7s) | C | 30 | 18.4 | 33186 | 2025-04-04 23:32:47 | MASTER-OAFA | (08h 07m 58.57s , +34d 59m 30.7s) | C | 10 | 15.8 | 33197 | 2025-04-04 23:32:47 | MASTER-OAFA | (08h 19m 01.06s , +35d 22m 10.1s) | C | 30 | 18.4 | 33235 | 2025-04-04 23:33:35 | MASTER-OAFA | (08h 08m 03.56s , +34d 58m 34.6s) | C | 10 | 15.8 | 33245 | 2025-04-04 23:33:36 | MASTER-OAFA | (08h 19m 05.95s , +35d 21m 12.1s) | C | 30 | 18.5 | 33280 | 2025-04-04 23:34:21 | MASTER-OAFA | (08h 07m 56.35s , +34d 57m 37.5s) | C | 10 | 15.8 | 33290 | 2025-04-04 23:34:21 | MASTER-OAFA | (08h 18m 58.65s , +35d 20m 14.0s) | C | 30 | 18.4 | 33328 | 2025-04-04 23:35:09 | MASTER-OAFA | (08h 08m 02.36s , +34d 58m 09.7s) | C | 10 | 15.9 | 33338 | 2025-04-04 23:35:09 | MASTER-OAFA | (08h 19m 04.81s , +35d 20m 45.1s) | C | 30 | 18.6 | 33373 | 2025-04-04 23:35:54 | MASTER-OAFA | (08h 07m 58.28s , +34d 59m 32.8s) | C | 10 | 15.8 | 33384 | 2025-04-04 23:35:54 | MASTER-OAFA | (08h 19m 00.96s , +35d 22m 07.7s) | C | 30 | 18.5 | 33424 | 2025-04-04 23:36:45 | MASTER-OAFA | (08h 07m 57.86s , +34d 58m 00.1s) | C | 10 | 15.8 | 33434 | 2025-04-04 23:36:45 | MASTER-OAFA | (08h 19m 00.34s , +35d 20m 33.9s) | C | 30 | 18.5 | 33464 | 2025-04-04 23:36:45 | MASTER-OAFA | (08h 19m 00.33s , +35d 20m 33.8s) | C | 90 | 19.3 | Coadd 33471 | 2025-04-04 23:37:32 | MASTER-OAFA | (08h 08m 01.00s , +34d 59m 22.3s) | C | 10 | 15.8 | 33481 | 2025-04-04 23:37:32 | MASTER-OAFA | (08h 19m 03.70s , +35d 21m 55.5s) | C | 30 | 18.5 | 33519 | 2025-04-04 23:38:20 | MASTER-OAFA | (08h 07m 54.12s , +34d 58m 51.0s) | C | 10 | 15.9 | 33529 | 2025-04-04 23:38:20 | MASTER-OAFA | (08h 18m 56.76s , +35d 21m 23.8s) | C | 30 | 18.5 | 33566 | 2025-04-04 23:39:07 | MASTER-OAFA | (08h 07m 52.92s , +34d 59m 53.3s) | C | 10 | 15.9 | 33576 | 2025-04-04 23:39:07 | MASTER-OAFA | (08h 18m 55.71s , +35d 22m 25.5s) | C | 30 | 18.5 | 33606 | 2025-04-04 23:39:07 | MASTER-OAFA | (08h 18m 55.72s , +35d 22m 25.5s) | C | 90 | 19.3 | Coadd 33613 | 2025-04-04 23:39:54 | MASTER-OAFA | (08h 07m 58.66s , +34d 58m 55.1s) | C | 10 | 15.9 | 33624 | 2025-04-04 23:39:54 | MASTER-OAFA | (08h 19m 01.35s , +35d 21m 27.0s) | C | 30 | 18.5 | 33659 | 2025-04-04 23:40:40 | MASTER-OAFA | (08h 07m 51.06s , +34d 57m 56.5s) | C | 10 | 15.9 | 33669 | 2025-04-04 23:40:40 | MASTER-OAFA | (08h 18m 53.65s , +35d 20m 28.1s) | C | 30 | 18.4 | 33721 | 2025-04-04 23:41:27 | MASTER-OAFA | (08h 07m 56.45s , +34d 58m 08.6s) | C | 40 | 16.6 | 33731 | 2025-04-04 23:41:27 | MASTER-OAFA | (08h 18m 59.04s , +35d 20m 38.8s) | C | 60 | 18.4 | 33799 | 2025-04-04 23:42:45 | MASTER-OAFA | (08h 07m 52.46s , +34d 59m 53.5s) | C | 40 | 16.6 | 33809 | 2025-04-04 23:42:45 | MASTER-OAFA | (08h 18m 55.24s , +35d 22m 22.0s) | C | 60 | 18.6 | 33874 | 2025-04-04 23:44:00 | MASTER-OAFA | (08h 07m 51.72s , +34d 58m 08.4s) | C | 40 | 16.5 | 33885 | 2025-04-04 23:44:00 | MASTER-OAFA | (08h 18m 54.29s , +35d 20m 36.9s) | C | 60 | 18.6 | 33950 | 2025-04-04 23:45:16 | MASTER-OAFA | (08h 07m 52.58s , +34d 59m 42.2s) | C | 40 | 16.6 | 33961 | 2025-04-04 23:45:16 | MASTER-OAFA | (08h 18m 55.38s , +35d 22m 10.2s) | C | 60 | 18.6 | 34029 | 2025-04-04 23:46:35 | MASTER-OAFA | (08h 07m 46.04s , +34d 59m 09.7s) | C | 40 | 16.5 | 34039 | 2025-04-04 23:46:35 | MASTER-OAFA | (08h 18m 48.79s , +35d 21m 37.5s) | C | 60 | 18.6 | 34105 | 2025-04-04 23:47:51 | MASTER-OAFA | (08h 07m 44.23s , +35d 00m 11.7s) | C | 40 | 16.6 | 34116 | 2025-04-04 23:47:51 | MASTER-OAFA | (08h 18m 47.13s , +35d 22m 39.2s) | C | 60 | 18.6 | 34183 | 2025-04-04 23:49:09 | MASTER-OAFA | (08h 07m 50.81s , +34d 59m 13.6s) | C | 40 | 16.6 | 34193 | 2025-04-04 23:49:09 | MASTER-OAFA | (08h 18m 53.60s , +35d 21m 41.4s) | C | 60 | 18.6 | 34258 | 2025-04-04 23:50:24 | MASTER-OAFA | (08h 07m 43.46s , +34d 58m 15.9s) | C | 40 | 16.7 | 34268 | 2025-04-04 23:50:24 | MASTER-OAFA | (08h 18m 46.23s , +35d 20m 43.3s) | C | 60 | 18.9 | 34334 | 2025-04-04 23:51:40 | MASTER-OAFA | (08h 07m 49.53s , +34d 58m 37.1s) | C | 40 | 16.7 | 34344 | 2025-04-04 23:51:40 | MASTER-OAFA | (08h 18m 52.40s , +35d 21m 04.5s) | C | 60 | 19.0 | 34412 | 2025-04-04 23:52:58 | MASTER-OAFA | (08h 07m 45.63s , +34d 59m 52.0s) | C | 40 | 16.7 | 34422 | 2025-04-04 23:52:58 | MASTER-OAFA | (08h 18m 48.68s , +35d 22m 19.3s) | C | 60 | 19.0 | 34490 | 2025-04-04 23:54:16 | MASTER-OAFA | (08h 07m 45.61s , +34d 58m 24.1s) | C | 40 | 16.7 | 34500 | 2025-04-04 23:54:16 | MASTER-OAFA | (08h 18m 48.48s , +35d 20m 51.3s) | C | 60 | 19.0 | 34568 | 2025-04-04 23:55:34 | MASTER-OAFA | (08h 07m 47.51s , +34d 59m 56.5s) | C | 40 | 16.7 | 34578 | 2025-04-04 23:55:34 | MASTER-OAFA | (08h 18m 50.62s , +35d 22m 23.7s) | C | 60 | 19.0 | 34694 | 2025-04-04 23:57:00 | MASTER-OAFA | (08h 18m 44.27s , +35d 21m 54.2s) | C | 120 | 19.3 | 34823 | 2025-04-04 23:59:19 | MASTER-OAFA | (08h 07m 41.05s , +35d 00m 30.6s) | C | 100 | 16.9 | 34833 | 2025-04-04 23:59:19 | MASTER-OAFA | (08h 18m 44.29s , +35d 22m 57.6s) | C | 120 | 19.3 | 34970 | 2025-04-05 00:01:46 | MASTER-OAFA | (08h 07m 46.89s , +34d 59m 33.9s) | C | 100 | 17.1 | 34981 | 2025-04-05 00:01:46 | MASTER-OAFA | (08h 18m 50.01s , +35d 22m 01.1s) | C | 120 | 19.3 | 35095 | 2025-04-05 00:04:06 | MASTER-OAFA | (08h 07m 41.46s , +34d 58m 36.8s) | C | 70 | 16.9 | 35105 | 2025-04-05 00:04:06 | MASTER-OAFA | (08h 18m 44.44s , +35d 21m 04.0s) | C | 90 | 19.1 | 35202 | 2025-04-05 00:05:53 | MASTER-OAFA | (08h 07m 45.68s , +34d 58m 59.5s) | C | 70 | 17.0 | 35212 | 2025-04-05 00:05:53 | MASTER-OAFA | (08h 18m 48.74s , +35d 21m 26.6s) | C | 90 | 19.1 | 35308 | 2025-04-05 00:07:39 | MASTER-OAFA | (08h 07m 42.99s , +35d 00m 18.1s) | C | 70 | 16.9 | 35319 | 2025-04-05 00:07:39 | MASTER-OAFA | (08h 18m 46.22s , +35d 22m 44.9s) | C | 90 | 19.1 | 35398 | 2025-04-05 00:09:24 | MASTER-OAFA | (08h 07m 42.93s , +34d 59m 00.1s) | C | 40 | 16.7 | 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/40070. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38092] EP250404a: Xinglong decaying optical counterpart
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40069 SUBJECT: EP250404a: Xinglong decaying optical counterpart DATE: 25/04/04 22:17:12 GMT FROM: Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong(a)nao.cas.cn> Min-He (NAOC), Yiming-Mao (NAOC), Junjie-Jin (NAOC), Haiyang-Mu (NAOC), Jinlei-Zhang (NAOC), Junjun-Jia (NAOC), Pengliang-Du (NAOC), Zhou-Fan (NAOC), Hong-Wu (NAOC) report: We observed the field of the X-ray transient, EP 250404a, detected by EP/WXT using the Xinglong 0.8-m, 2.16-m telescope located at Xinglong, Hebei, China. We obtained 6 x 300 s g'-band frames for 0.8-m telescope, 5 * 300s clear-band frames for 2.16-m telescope during the time between 2025-04-04T14:32:21.91 and 2025-04-04T17:08:42 as soon as the EP trigger. We have found the optical counterpart of EP 250404a in these images, and the light of this object had been decreased rapidly. The magnitude of this object firstly be ~ 15.68+/- 0.014 at 2025-04-04T14:32:21.91 with 0.8-m telescope in g'-band, and then decrease to ~ 19.7+/-0.102 with 2.16-m telescope at a median time of 2025-04-04T17:03:42, which measured by a stacked clear-band image and calibrated with the Pan-STARRS r' band field. The stacked clear-band image using the 2.16-m telescope has a 5-sigma limiting magnitude of ~21.64 mag, calibrated with the Pan-STARRS r'-band field. Within the 20 arcsec error circle of the FXT, we identified an optical transient (OT) localized at R. A. = 08:20:11.41 , Dec. = 35:31:27.68 (J2000). We summarize our observation results as follows: Obs. No. | Start Time (UTC) | End Time (UTC) | Exposure Time (s) | Filter | Apparent mag (AB) |Telescope Name 1 | 2025-04-04 14:32:21.91 | 2025-04-04 14:37:21.91 | 300s | g' | 15.681 +/- 0.014 | Xinglong 0.8-m Telescope. 2 | 2025-04-04 14:37:27.81 | 2025-04-04 14:42:27.81 | 300s | g' | 15.717 +/- 0.013 | Xinglong 0.8-m Telescope. 3 | 2025-04-04 14:42:33.76 | 2025-04-04 14:47:33.76 | 300s | g' | 16.124 +/- 0.019 | Xinglong 0.8-m Telescope. 4 | 2025-04-04 15:11:06.35 | 2025-04-04 15:16:06.35 | 300s | g' | 17.864 +/- 0.070 | Xinglong 0.8-m Telescope. 5 | 2025-04-04 15:16:12.26 | 2025-04-04 15:21:12.26 | 300s | g' | 18.149 +/- 0.088 | Xinglong 0.8-m Telescope. 6 | 2025-04-04 15:21:18.16 | 2025-04-04 15:26:18.16 | 300s | g' | 19.015 +/- 0.112 | Xinglong 0.8-m Telescope. 7 | 2025-04-04 14:37:24 | 2025-04-04 14:42:24 | 300s |clear| 14.882 +/- 0.001 (calibrated to r') | Xinglong 2.16-m Telescope. 8 | 2025-04-04 14:42:32 | 2025-04-04 14:47:32 | 300s |clear| 15.363 +/- 0.002 (calibrated to r')| Xinglong 2.16-m Telescope. 9 | 2025-04-04 16:58:22 | 2025-04-04 17:13:42 | 3x300s |clear| 19.703 +/- 0.102 (calibrated to r')| Xinglong 2.16-m Telescope Further observations are encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/40069. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38091] GRB 250403A: Montarrenti Observatory optical detection
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40068 SUBJECT: GRB 250403A: Montarrenti Observatory optical detection DATE: 25/04/04 21:35:28 GMT FROM: Simone Leonini at Montarrenti Observatory (Siena, Italy) <s.leonini(a)iol.it> S. Leonini, M. Conti, P. Rosi, L.M. Tinjaca Ramirez (Montarrenti Observatory, Siena, Italy, part of UAI/SSV-GRB section), M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy) and K. Kalinowski (Aarhus University, Department of Physics and Astronomy) report: we observed the field of GRB 250403A detected by Fermi/GBM (Fermi team, GCN 40025), SVOM/ECLAIRs (Julakanti et al., GCN 40026) and SWIFT (Dichiara et al., GCN 40037; Shilling et al., GCN 40048) with the automated and remoted 0.53m Ritchey-Chretien telescope at Montarrenti Observatory (Siena, Italy, IAU code C88). The observations were started at 2025-04-03 21:56:50 UT (approximately 7 hours after burst) stacking a set of Rc-band CCD images. The elevation of the field decreased from 19 degrees above the horizon. The optical afterglow (Starling et al., GCN 40028; Wu et al., GCN 40029; Du et al., GCN 40031; Li et al., GCN 40032; Julakanti et al., GCN 40034; Ghosh et al, GCN 40039; Jiang et al., GCN 40041; Perez-Fournon et al., GCN 40043; Brivio et al., GCN 40044; Xin et al, GCN 40045 and Zheng et al., GCN 40065) was barely detected (S/N=2.4) at the following position: RA (J2000.0) 12h 58m 27.72s +/-0.15 Decl. (J2000.0) -24° 22' 46.5" +/-0.19 Preliminary photometry was obtained using nearby PanSTARRS stars as follows: Observation Mid-Time T-T0 (hr) Exposure Filter Mag. Err. UL (3-sigma) 2025-04-03 21:57:10 UT 6.68 94x40s Rc 20.10 S/N =2.4 >19.90 Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied. View this GCN Circular online at https://gcn.nasa.gov/circulars/40068. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38090] GRB 250404A: Fermi GBM Detection
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40067 SUBJECT: GRB 250404A: Fermi GBM Detection DATE: 25/04/04 19:52:20 GMT FROM: oindabimukherjee(a)gmail.com O. Mukherjee (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 14:19:46.35 UT on 04 April 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250404A (trigger 765469191/250404597). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 123.37, Dec = 34.10 (J2000 degrees, equivalent to J2000 8h 13m, +34d 6'), with a statistical uncertainty of 1.20 degrees. (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a mixture of two Gaussians, one with a radius of 1.8 degrees (52% contribution) and one with a radius of 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1]). The angle from the Fermi LAT boresight is 42 degrees. The GBM light curve consists of multiple peaks with a duration (T90) of about 91.4 s (50-300 keV). The time-averaged spectrum from T0-3.6 to T0+124.4 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.10 +/- 0.02 and the cutoff energy, parameterized as Epeak, is 55.7 +/- 0.5 keV. The event fluence (10-1000 keV) in this time interval is (3.33 +/- 0.02)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+21 s in the 10-1000 keV band is 12.9 +/- 0.3 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/40067. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38089] EP250404a: Global MASTER-Net observations report
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40066 SUBJECT: EP250404a: Global MASTER-Net observations report DATE: 25/04/04 19:27:39 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, 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. 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-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the EP250404a ( EP Team et al., GCN 40051) errorbox 13675 sec after notice time and 16626 sec after trigger time at 2025-04-04 18:57:05 UT, with upper limit up to 19.5 mag. The observations began at zenith distance = 66 deg. The sun altitude is -28.6 deg. The galactic latitude b = 33 deg., longitude l = 187 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2832935 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 16657 | 2025-04-04 18:57:05 | MASTER-Tunka | (08h 19m 51.88s , +36d 00m 34.0s) | C | 60 | 18.6 | 16717 | 2025-04-04 18:57:05 | MASTER-Tunka | (08h 19m 51.88s , +36d 00m 34.0s) | C | 180 | 19.3 | Coadd 16728 | 2025-04-04 18:58:16 | MASTER-Tunka | (08h 19m 58.07s , +36d 00m 34.7s) | C | 60 | 18.6 | 16800 | 2025-04-04 18:59:28 | MASTER-Tunka | (08h 19m 55.11s , +36d 02m 04.0s) | C | 60 | 18.6 | 16872 | 2025-04-04 19:00:41 | MASTER-Tunka | (08h 19m 55.07s , +36d 00m 32.5s) | C | 60 | 18.7 | 16932 | 2025-04-04 19:00:41 | MASTER-Tunka | (08h 19m 55.07s , +36d 00m 32.5s) | C | 180 | 19.4 | Coadd 16950 | 2025-04-04 19:01:58 | MASTER-Tunka | (08h 19m 57.66s , +36d 02m 04.7s) | C | 60 | 18.6 | 17021 | 2025-04-04 19:03:09 | MASTER-Tunka | (08h 19m 52.37s , +36d 01m 15.7s) | C | 60 | 18.7 | 17095 | 2025-04-04 19:04:24 | MASTER-Tunka | (08h 19m 51.30s , +36d 02m 12.7s) | C | 60 | 18.7 | 17155 | 2025-04-04 19:04:24 | MASTER-Tunka | (08h 19m 51.30s , +36d 02m 12.8s) | C | 180 | 19.5 | Coadd 17381 | 2025-04-04 19:09:09 | MASTER-Tunka | (08h 19m 52.28s , +35d 59m 59.8s) | C | 60 | 18.7 | 17454 | 2025-04-04 19:10:22 | MASTER-Tunka | (08h 19m 58.20s , +36d 00m 10.2s) | C | 60 | 18.7 | 17527 | 2025-04-04 19:11:35 | MASTER-Tunka | (08h 19m 54.28s , +36d 01m 24.3s) | C | 60 | 18.7 | 17587 | 2025-04-04 19:11:35 | MASTER-Tunka | (08h 19m 54.28s , +36d 01m 24.2s) | C | 180 | 19.4 | Coadd 17599 | 2025-04-04 19:12:48 | MASTER-Tunka | (08h 19m 54.27s , +35d 59m 56.4s) | C | 60 | 18.6 | 17670 | 2025-04-04 19:13:59 | MASTER-Tunka | (08h 19m 57.20s , +36d 01m 34.1s) | C | 60 | 18.6 | 17743 | 2025-04-04 19:15:12 | MASTER-Tunka | (08h 19m 51.23s , +36d 00m 41.3s) | C | 60 | 18.5 | 17803 | 2025-04-04 19:15:12 | MASTER-Tunka | (08h 19m 51.23s , +36d 00m 41.3s) | C | 180 | 19.3 | Coadd 17816 | 2025-04-04 19:16:24 | MASTER-Tunka | (08h 19m 51.76s , +36d 01m 37.4s) | C | 60 | 18.6 | 17890 | 2025-04-04 19:17:39 | MASTER-Tunka | (08h 19m 57.64s , +36d 00m 34.5s) | C | 60 | 18.7 | 17962 | 2025-04-04 19:18:51 | MASTER-Tunka | (08h 19m 51.82s , +35d 59m 30.3s) | C | 60 | 18.6 | 18035 | 2025-04-04 19:20:04 | MASTER-Tunka | (08h 19m 57.26s , +35d 59m 42.1s) | C | 60 | 18.6 | 18108 | 2025-04-04 19:21:16 | MASTER-Tunka | (08h 19m 53.77s , +36d 01m 07.0s) | C | 60 | 18.5 | 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/40066. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38088] GRB 250403A: KAIT optical observations
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40065 SUBJECT: GRB 250403A: KAIT optical observations DATE: 25/04/04 18:53:09 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) 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 250403A (Julakanti et al., GCN 40026; Fermi GBM team, GCN 40025) with a set of 120x60s images in the clear (roughly R) filters, at a mid time of 16.0 hours after the trigger. We marginally detected the optical afterglow (Starling et al., GCN 40028; Wu et al., GCN 40029; Du et al., GCN 40031; Li et al., GCN 40032, Julakanti et al., GCN 40034; Ghosh et al., GCN 40039; Jiang et al., GCN 40041; Pérez-Fournon et al., GCN 40043; Brivio et al., GCN 40044; Xin et al., GCN Circ. 40045) in the coadd image with a brightness of 21.2 +/- 0.4 mag (Vega). View this GCN Circular online at https://gcn.nasa.gov/circulars/40065. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38087] EP250404a: AKO Optical Afterglow Detection
by GCN Circulars 04 Apr '25

04 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40064 SUBJECT: EP250404a: AKO Optical Afterglow Detection DATE: 25/04/04 18:35:28 GMT FROM: Mohammad Odeh at Al Khatim Observatory M44 <mshodeh(a)gmail.com> Mohammad Odeh (Al-Khatim Observatory, AKO, operated by the International Astronomical Center in Abu Dhabi, UAE), and Shaikha Alshamsi and Nidhal Guessoum (American University of Sharjah, UAE), report: We observed the field of EP250404a detected by EP (Hu et al., GCN 40051), using our 0.36m f/7.7 robotic telescope. The observation session began on 04 April 2025 at 15:47 UT and continued until 16:56 UT, with a midpoint at 16:22 UT, approximately 2 hours after the trigger. We obtained multiple 180-second exposures using the Ic filter. The optical afterglow was clearly detected at: R.A. (J2000): 08:20:14.59 Dec. (J2000): +35:31:42.3 Our detection is consistent with the results of (Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Konno et al., GCN 40063). The following observation was calculated using the Atlas catalogue as a reference: ---------------------------------------------------------------------------- - ObsTime (mid), Exposure (sec), Filter, Mag ---------------------------------------------------------------------------- - 2025-04-04T16:21:38Z, 20 x 180s (stacked), Ic, 17.5 +/- 0.35 ---------------------------------------------------------------------------- - The magnitude is not corrected for galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/40064. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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