GRB250404A

This page lists all entries on GRB250404A in GRBweb

Summary Fermi GBM GCN 40050 GCN 40051 GCN 40052 GCN 40061 GCN 40067 GCN 40070 GCN 40071 GCN 40072 GCN 40075 GCN 40080 GCN 40083 GCN 40084 GCN 40086 GCN 40087 GCN 40088 GCN 40089 GCN 40090 GCN 40093 GCN 40095 GCN 40236

Summary table
Variable Value Source
GRB_name_Fermi GRB250404597
T0 14:19:46 UTC GCN_circulars,Fermi GBM final loc
ra 125.0606° GCN_circulars,Optical
decl 35.5282° GCN_circulars,Optical
T90 91.394 s Fermi_GBM
T90_error 0.724 s Fermi_GBM
T90_start 14:19:50.188 UTC Fermi_GBM
fluence 3.46e-05 erg/cm² Fermi_GBM
fluence_error 3.57e-08 erg/cm² Fermi_GBM
redshift 2.6270
T100 95.582 s
GBM_located False
mjd 60769.59706018519 GCN_circulars,Fermi GBM final loc
Fermi GBM table
GRB_name_Fermi GRB250404597
trigger_name bn250404597
ra 123.3700°
decl 34.1000°
pos_error 2.51e+00°
datum 2025-04-04
t_trigger 14:19:46.348 UTC
T90 91.394 s
T90_error 0.724 s
T90_start 14:19:50.188 UTC
fluence 3.46e-05 erg/cm²
fluence_error 3.57e-08 erg/cm²
flux_1024 1.29e+01 erg/cm²/s
flux_1024_error 3.27e-01 erg/cm²/s
flux_1024_time 2.07e+01 erg/cm²/s
flux_64 1.50e+01 erg/cm²/s
flux_64_error 1.47e+00 erg/cm²/s
GCN 40050 table
GRB_name GRB250404A
GCN_number 40050
Detection_method Fermi GBM final loc
t_trigger 14:19:46 UTC
ra 123.4000°
decl 34.1000°
Circular_text TITLE: GCN CIRCULAR NUMBER: 40050 SUBJECT: GRB 250404A: Fermi GBM Final Real-time Localization DATE: 25/04/04 14:30:25 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM The Fermi GBM team reports the detection of a likely LONG GRB At 14:19:46 UT on 4 Apr 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250404A (trigger 765469191.347644 / 250404597). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 123.4, Dec = 34.1 (J2000 degrees, equivalent to J2000 08h 13m, 34d 06'), with a statistical uncertainty of 1.2 degrees. The angle from the Fermi LAT boresight is 42.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250404597/quicklook/glg_skymap_all_bn250404597.png The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250404597/quicklook/glg_healpix_all_bn250404597.fit The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250404597/quicklook/glg_lc_medres34_bn250404597.gif
GCN 40051 table
GRB_name GRB250404A
GCN_number 40051
Detection_method Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 40051 SUBJECT: EP250404a: Einstein Probe detection of an X-ray transient DATE: 25/04/04 15:03:49 GMT FROM: EP Team at NAOC/CAS J. W. Hu (NAO, CAS), Q. C. Liu (THU), B. B. Zhang (BNU), Y. L. Hua (PMO, CAS), Y. Liu (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 EP250404a. The transient triggered EP-WXT (ID: 01709133918) at 2025-04-04T14:19:59 (UTC). The WXT position of the source is R.A. = 125.064 deg, DEC = 35.511 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 125.0575 deg, DEC = 35.5305 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). It is noted that EP250404a is temporally and spatially coincident with GRB 250404A (Fermi team, GCN Circ. 40050). Further information will be updated when the telemetry data is received. 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).
GCN 40052 table
GRB_name GRB250404A
GCN_number 40052
Detection_method Optical
ra 125.0606°
decl 35.5282°
Circular_text TITLE: GCN CIRCULAR NUMBER: 40052 SUBJECT: EP250404a: Nanshan/HMT optical counterpart detection DATE: 25/04/04 15:12:14 GMT FROM: Dong Xu at NAOC/CAS S.Q. Jiang, Z.P. Zhu, J. An, X. Liu, D. Xu (NAOC), S.Y. Fu (HUST), X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report: We observed the field of EP250404a detected by EP (Hu et al., GCN 40051), which is temporally and spatially consistent with GRB 250404A detected by Fermi/GBM (GBM team, GCN 40050), using the HMT-0.5m telescope located at Nanshan, Xinjiang, China. Observations started at 14:24:59 UT on 2025-04-04, i.e., 300 s after the EP/WXT trigger time, and a series of unfiltered frames with different exposures were obtained. An uncatalogued and varying optical source is detected within the EP/FXT error circle at coordinates: R.A.(J2000) = 08:20:14.54 Dec.(J2000) = +35:31:41.57 with an uncertainty of ~0.5 arcsec. The source has R ~ 16.1 mag in the first image, calibrated with the nearby Pan-STARRS field and not corrected for Galactic extinction. Observations are still ongoing.
GCN 40061 table
GRB_name GRB250404A
GCN_number 40061
Detection_method Optical
redshift 2.2550
Circular_text TITLE: GCN CIRCULAR NUMBER: 40061 SUBJECT: EP250404a: Xinglong-2.16m spectroscopic redshift DATE: 25/04/04 18:05:48 GMT FROM: Dong Xu at NAOC/CAS Z.P. Zhu, J. An, X. Liu, S.Q. Jiang, J.J. Jin, Z. Fan, D. Xu (NAOC), S.Y. Fu (HUST), report on behalf of a large collaboration: We carried out spectroscopy of the optical counterpart (e.g., Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058) of EP250404a (Hu et al., GCN 40051), likely the identical event to GRB 250404A (GBM team, GCN 40050), using the 2.16-m telescope equipped with the BFOSC instrument, located at Xinglong, Hebei, China. Our spectra cover the wavelength range 3800 - 9000 AA, and consist of 2 exposures of 1800 s each. The continuum is throughout the spectrum. From the detection of a broad Lya absorption feature at ~ 4400 AA and relatively weak absorption features, which interpreted as being due to Si IV and Al III, we infer a common redshift of z = 2.63. We conclude this is the likely redshift of the event. An intervening system is also detected with absorption features, interpreted as being due to Mg II and Fe II, we inferred its redshift of z = 1.88. We acknowledge the expert support from the Xinglong-2.16m staff, in particular Junjun Jia and Jie Zheng.
GCN 40067 table
GRB_name GRB250404A
GCN_number 40067
Detection_method Fermi GBM Det
t_trigger 14:19:46.350 UTC
ra 123.3700°
decl 34.1000°
Circular_text TITLE: GCN CIRCULAR NUMBER: 40067 SUBJECT: GRB 250404A: Fermi GBM Detection DATE: 25/04/04 19:52:20 GMT FROM: oindabimukherjee@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/"
GCN 40070 table
GRB_name GRB250404A
GCN_number 40070
Detection_method Fermi GBM Other
Circular_text 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 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.
GCN 40071 table
GRB_name GRB250404A
GCN_number 40071
Detection_method Optical
redshift 2.6300
Circular_text 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 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).
GCN 40072 table
GRB_name GRB250404A
GCN_number 40072
Detection_method Optical
Circular_text 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 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.
GCN 40075 table
GRB_name GRB250404A
GCN_number 40075
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40075 SUBJECT: EP250404a: REM optical/NIR observations DATE: 25/04/05 09:32:41 GMT FROM: Riccardo Brivio at INAF-OAB R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of EP250404a (Hu et al., GCN 40051), likely associated with GRB 250404A detected by Fermi/GBM (Fermi GBM team, GCN 40050) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, and K bands, started on 2025 April 04 at 23:26:12 UT (i.e. 9.1 hr after the burst), and lasted for about 1 hour. From preliminary inspection, we do not detect any counterpart at the position of the optical afterglow (Jiang et al., GCN. 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Zhu et al., GCN 40061; Konno et al., GCN 40063; Odeh et al., GCN 40064; He et al., GCN 40069; Pérez-Fournon et al., GCN 40071; Jelinek et al., GCN 40072; Rakotondrainibe et al., GCN 40073; Taguchi et al., GCN 40074) down to the following 3sigma limits: r > 19.7 (AB; calibrated against the Pan-STARRS catalogue), at a mid-time of 9.6 hours after the trigger; H > 16.3 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 9.5 hours after the trigger.
GCN 40080 table
GRB_name GRB250404A
GCN_number 40080
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40080 SUBJECT: GRB 250404A / EP250404a: NOT optical observations DATE: 25/04/05 15:27:15 GMT FROM: Antonio Martin-Carrillo at UCD,Space Science Group A. Martin-Carrillo (UCD), B. Schneider (LAM), A. de Ugarte Postigo (LAM), D. B. Malesani (DAWN/NBI and Radboud Univ.), J. An (NAOC), D. Xu (NAOC), G. Corcoran (UCD), Dimple (U. Birmingham), M. A. Diaz Teodori (NOT and Turku Univ.), report on behalf of a larger collaboration: We observed the field of EP250404a (Hu et al., GCN 40051), likely associated with GRB 250404A detected by Fermi/GBM (Fermi GBM team, GCN 40050; Mukherjee & Meegan, GCN 40067) using the ALFOSC camera mounted on the Nordic Optical Telescope (NOT). We obtained exposures in the SDSS-r (3x180 s) and SDSS-z (2x180 s) bands, starting at 22:09:17 UT on 2025-04-04 (7.82 hr after the EP trigger). The optical counterpart reported by Jiang et al. (GCN. 40052), Perez-Garcia et al. (GCN 40053), Du et al. (GCN 40058), Zhu et al. (GCN 40061), Konno et al. (GCN 40063), Odeh et al. (GCN 40064), He et al. (GCN 40069), Pérez-Fournon et al. (GCN 40071), Jelinek et al. (GCN 40072), Rakotondrainibe et al. (GCN 40073), Taguchi et al. (GCN 40074), Ruocco et al. (GCN 40076) is well detected in the stacked images, with the following preliminary magnitudes: r = 20.43 +/- 0.05 (7.90 hr after trigger); z = 19.79 +/- 0.06 (8.04 hr after trigger). The photometric calibration was performed using nearby stars from the Pan-STARRS catalog and the magnitudes are not corrected for Galactic extinction.
GCN 40083 table
GRB_name GRB250404A
GCN_number 40083
Detection_method Optical
ra 125.0583°
decl 35.5281°
Circular_text TITLE: GCN CIRCULAR NUMBER: 40083 SUBJECT: GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection DATE: 25/04/05 22:56:51 GMT FROM: leavittob@gmail.com E. Pavoni, L. Moretti (Leavitt Observatory, Italy) Members of: GRB/UAI - Gamma Ray Burst Section of Unione Astrofili Italiani ATA - Associazione Tuscolana di Astronomia In a large collaboration with: M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy), K. Kalinowski (Aarhus University, Department of Physics and Astronomy), report: We observed the field of EP250404a detected by Einstein Probe (Hu et al., GCN 40051), which is temporally and spatially consistent with GRB 250404A (Fermi team, GCN 40050), with our RC telescope (D=250 mm, F/D=8) of Leavitt Observatory, Manciano, Italy. Median moon illumination of 47% was present. The observations started approximately 5.1 hours after the trigger time, stacking a series of R-Cousins filtered exposures, for a total integration time of approximately 88 minutes. All images were processed using the astropy package (Astropy Collaboration et al., 2022ApJ...935..167A). We detected the optical counterpart (Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Zhu et al., GCN 40061; Konno et al. GCN 40063; Odeh et al., GCN 40064; Lipunov et al., GCN 40066; He et al., GCN 40069; Perez-Fournon et al., GCN 40071; Jelinek et al., GCN 40072; Rakotondrainibe et al., GCN 40073; Taguchi et al., GCN 40074; Ruocco, GCN 40076; Martin-Carrillo et al., GCN 40080) in the stacked image at the following coordinates +/- 2 arcsec: R.A. (J2000) = 08:20:14:59 Dec. (J2000) = +35:31:41:75 with the following photometry: Date UT at mid-exposure: 2025-04-04 20:24:18 UTC Mag (R Cousins) 19.47 Error +/- 0.2 Magnitudes were estimated with the Pan-STARRS cat. and converted using Lupton (2005) equations. No corrected for galactic dust extinction. The message may be cited. Reference: https://leavittobservatory.altervista.org
GCN 40084 table
GRB_name GRB250404A
GCN_number 40084
Detection_method Optical
redshift 2.6270
Circular_text TITLE: GCN CIRCULAR NUMBER: 40084 SUBJECT: GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627 DATE: 25/04/06 03:57:18 GMT FROM: Rui-Zhi Li at Yunnan Observatories, CAS R.-Z. Li, B.-T. Wang, F.-F. Song, J. Mao, H.-C. Feng and J.-M. Bai (YNAO, CAS) report: GRB 250404A / EP250404a was detected by Fermi GBM (Fermi GBM team, GCN 40050) and by EP/WXT (Hu et al., GCN 40051). We observed the optical counterpart of GRB 250404A / EP250404a (Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Zhu et al., GCN 40061; Konno et al., GCN 40063; Odeh et al., GCN 40064; He et al., GCN 40069; Pérez-Fournon et al., GCN 40071; Jelinek et al., GCN 40072; Rakotondrainibe et al., GCN 40073; Taguchi et al., GCN 40074; Brivio et al., GCN 40075; Ruocco et al., GCN 40076; Martin-Carrillo et al., GCN 40080; Pavoni et al., GCN 40083). The spectroscopic observation was conducted using the GMG-2.4m telescope with Grism #14, which provides a wavelength coverage of 3600–7460 AA. A single 1800s spectrum was obtained, with exposure beginning at 2025-04-04T15:18:24, about 0.98 hours after the Fermi/GBM and EP/WXT trigger (Fermi GBM team, GCN 40050; Hu et al., GCN 40051). Two absorption systems were identified in the spectrum. For the first absorption system, we detected multiple metal absorption features, including Si II at 1527 AA, Al II at 1671 AA, Al III at 1855 AA and 1863 AA, Zn II/Cr II at 2026 AA and 2062 AA, and Fe II at 2344 AA, 2374 AA, and 2383 AA. These features consistently indicate a redshift of z ~ 1.881. For the second absorption system, the spectrum shows multiple metal absorption lines from Si II/S II at 1260 AA, O I/Si II at 1303 AA, C II at 1335 AA, Si IV at 1394 AA, Si II at 1527 AA, Fe II at 1608 AA, and Al III at 1863 AA. These absorption features correspond to a redshift of z ~ 2.627. These results support a redshift of z ~ 2.627 for the transient, consistent with the measurement reported by Xinglong-2.16m (Zhu et al., GCN 40061). We thank the staff at the Lijiang Observatory for their support in conducting the observation.
GCN 40086 table
GRB_name GRB250404A
GCN_number 40086
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40086 SUBJECT: GRB 250404A / EP250404a: Mondy optical observations DATE: 25/04/06 11:27:55 GMT FROM: Alexei Pozanenko at IKI, Moscow N. Pankov (HSE), E. Klunko (ISTP), A. Pozanenko (IKI) report on behalf of IKI GRB-FuN: We observed GRB 250404A / EP250404a (Fermi GBM team, GCN 40050; Hu et al., GCN 40051). The optical counterpart (Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Zhu et al., GCN 40061; Konno et al., GCN 40063; Odeh et al., GCN 40064; He et al., GCN 40069; Pérez-Fournon et al., GCN 40071; Jelinek et al., GCN 40072; Rakotondrainibe et al., GCN 40073; Taguchi et al., GCN 40074; Brivio et al., GCN 40075; Ruocco et al., GCN 40076; Martin-Carrillo et al., GCN 40080; Pavoni et al., GCN 40083; Li et al., GCN 40084; Yin et al., GCN 40085) is early detected on 2025-04-04 and was observed between (UT) 14:50:52 and 17:09:01. We obtained an upper limit on 2025-04-05. Preliminary photometry of some stacked images is the following Date UT start t-T0 Filter Exp. OT Err. UL(3sigma) (mid, days) (s) 2025-04-04 14:50:52 0.04244 R 40*90 16.53 0.02 22.4 2025-04-04 16:01:21 0.08999 R 28*120 17.96 0.03 22.2 2025-04-05 15:08:33 1.05611 R 42*90 n/d n/d 21.5 The photometry is based on nearby USNO-B1.0 stars.
GCN 40087 table
GRB_name GRB250404A
GCN_number 40087
Detection_method Konus-Wind Det
t_trigger 14:20:05.773 UTC
redshift 2.6270
Circular_text TITLE: GCN CIRCULAR NUMBER: 40087 SUBJECT: Konus-Wind detection of GRB 250404A / EP250404a DATE: 25/04/06 12:08:53 GMT FROM: Dmitry Frederiks at Ioffe Institute D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 250404A (Fermi-GBM detection: The Fermi GBM team, GCN 40050; Mukherjee & Meegan, GCN 40067), coincident with the X-ray transient EP250404a (Hu et al., GCN 40051), triggered Konus-Wind (KW) at T0=51605.773 s UT (14:20:05.773). The burst light curve shows a multi-peaked structure which starts at ~T0-21 s and has a total duration of ~105 s. The emission is seen up to ~1 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250404_T51605/ As observed by Konus-Wind, the burst had a fluence of (2.83 ± 0.09)x10^-5 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 0.832 s, of (1.78 ± 0.22)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+81.186 s) is best fit in the 20 keV - 15 MeV range by a power law with exponential cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.38(-0.13,+0.14) and Ep = 56(-5,+4) keV (chi2 = 76/98 dof). Fitting this spectrum by a Band function yields the same values of alpha and Ep, and an upper limit on the high energy photon index beta of -3.5 (chi2 = 76/97 dof). The spectrum near the peak count rate(measured from T0 to T0+8.448 s) is best fit in the 20 keV - 15 MeV range by a CPL with alpha = -1.16(-0.17,+0.19) and Ep = 68(-9,+8) keV (chi2 = 90/96 dof). Fitting this spectrum by a Band function yields the same values of alpha and Ep, and an upper limit on the high energy photon index beta of -4.2 (chi2 = 90/95 dof). Assuming the redshift z ~ 2.627 ( Li et al., GCN 40084) and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014), we estimate the burst isotropic energy release E_iso to (4.60 ± 0.14)x10^53 erg, the isotropic peak luminosity L_iso to (1.05 ± 0.13)x10^53 erg/s, the rest-frame peak energy of the time-integrated spectrum Ep,i,z to (203 ± 18) keV, and the rest-frame peak energy at the peak of the emission Ep,p,z to (247 ± 30) keV. With the obtained estimates, GRB 250404A lies at the lower edge, but is consistent with 90% prediction bands of the 'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021), see http://www.ioffe.ru/LEA/GRBs/GRB250404_T51605/GRB250404A_rest_frame.pdf All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary.
GCN 40088 table
GRB_name GRB250404A
GCN_number 40088
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40088 SUBJECT: EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope DATE: 25/04/06 12:26:24 GMT FROM: Chun Chen at Sun Yat-sen University, SYSU 80cm telescope team Chun Chen, Xia Li, Zhong-Nan Dong, Jia-Qi Lin, Wei-Sen Huang, Jin-Ji Li, Pu Lin, Hao-Nan Yang, Yan Yu, Hao-Ran Zhang, Hao-Yuan Zheng, P H Thomas Tam, Rong-Feng Shen, Bin Ma (Sun Yat-sen University) report on behalf of the SYSU 80cm telescope team: We observed the field of EP250404a detected by Einstein Probe (Hu et al., GCN 40051), which is temporally and spatially consistent with GRB250404A (Fermi GBM team, GCN40050; Fermi GBM team, GCN40067), using the Sun Yat-sen University 80cm infrared telescope with 183 x 20 s exposures in J band. The calculated position is R.A. = 125.0575 deg, DEC = 35.5305 deg J2000, from EP/FXT observation. Our observations began at 2025-4-4 15:25:20 UTC, 1.09 hours after the EP trigger. We detected a counterpart at the position of the optical afterglow (Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Zhu et al., GCN 40061; Konno et al. GCN 40063; Odeh et al., GCN 40064; Lipunov et al., GCN 40066; He et al., GCN 40069; Perez-Fournon et al., GCN 40071; Jelinek et al., GCN 40072; Rakotondrainibe et al., GCN 40073; Taguchi et al., GCN 40074; Ruocco, GCN 40076; Martin-Carrillo et al., GCN 40080; Pavoni et al., GCN 40083; Li et al., GCN 40084) in the stacked images. The preliminary photometric magnitudes in J band are below: Start Time (UTC) |Band | Exp | Mag (Vega) --------------------|-----|-------|------------------ 2025/4/4 15:25:20 | J | 200s | 15.30+/-0.08 2025/4/4 15:28:40 | J | 200s | 15.28+/-0.09 2025/4/4 15:32:20 | J | 200s | 15.47+/-0.10 2025/4/4 15:35:40 | J | 200s | 15.76+/-0.11 2025/4/4 15:39:00 | J | 360s | 15.83+/-0.10 2025/4/4 15:50:20 | J | 400s | 16.05+/-0.12 2025/4/4 15:57:00 | J | 400s | 15.99+/-0.12 2025/4/4 16:03:40 | J | 400s | 15.99+/-0.12 2025/4/4 16:10:40 | J | 400s | 16.29+/-0.15 2025/4/4 16:17:40 | J | 1100s | 16.21+/-0.11 The photometric calibration was performed using nearby stars from the 2MASS catalog and the magnitudes are not corrected for Galactic extinction.
GCN 40089 table
GRB_name GRB250404A
GCN_number 40089
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40089 SUBJECT: GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations DATE: 25/04/06 12:27:20 GMT FROM: Chen Liang-Jun at Guangxi University L. J. Chen(GXU), L. P. Xin(NAOC), Y. G. Yang(HNU), X. H. Han, C. WU, Y. L. Qiu, J. Wang, H. L. Li, X .M. Lu, R. S. Zhang, Y. Xu, L. Huang, H. B. Cai, Y. J. Xiao, P. P. Zhang, L. Lan, W. J. Xie, Z. H. Yao, J. Y. Wei(NAOC), X. G. Wang, E. W. Liang(GXU) report on behalf of the SVOM follow-up team: We observed the field of EP250404a detected by Einstein Probe (Hu et al., GCN 40051), which is temporally and spatially consistent with GRB 250404A (Fermi team, GCN 40050), with the GWAC-F50A and GWAC-F60 at Xinglong Observatory, China. F50 started observing at 2025-04-04T14:25:34 UTC and lasted until 2025-04-04T15:36:36 with 9 frames in R-band and 15 frames in I-band. F60A started observing at 2025-04-04T14:24:56 UTC and lasted until 2025-04-04T15:24:21 with 25 frames in R-band. F60B started observing at 2025-04-04T14:25:05 UTC and lasted until 2025-04-04T15:24:28 with 25 frames in R-band. The optical counterpart of GRB 250404A / EP250404a (Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Zhu et al., GCN 40061; Konno et al., GCN 40063; Odeh et al., GCN 40064; He et al., GCN 40069; Pérez-Fournon et al., GCN 40071; Jelinek et al., GCN 40072; Rakotondrainibe et al., GCN 40073; Taguchi et al., GCN 40074; Brivio et al., GCN 40075; Ruocco et al., GCN 40076; Martin-Carrillo et al., GCN 40080; Pavoni et al., GCN 40083; Li et al., GCN 40084; Pankov et al., GCN 40086), was clearly detected in our images. The afterglow shows a first brightening and then a single decay with a peak magnitude of R~14.3 mag, calibrated to the USNO B1.0 catalog, at about 1000 sec after the burst. Two 60cm GWAC-F60(A/B) are operated by Guangxi University and NAOC, CAS, at Xinglong Observatory, China. The field of view is 19*19 arcmin. The 50cm telescope (F50A) is operated by Huaibei Normal University and NAOC, CAS, at Xinglong Observatory, China. The field of view is 27*27 arcmin.
GCN 40090 table
GRB_name GRB250404A
GCN_number 40090
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40090 SUBJECT: GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit DATE: 25/04/06 13:05:06 GMT FROM: Alexei Pozanenko at IKI, Moscow N. Pankov (HSE), A.N. Tarasenkov (INASAN), A. Pozanenko (IKI) report on behalf of IKI GRB-FuN: We observed GRB 250404A / EP250404a (Fermi GBM team, GCN 40050; Hu et al., GCN 40051; Frederiks et al., GCN 40087) with RC500 telescope of the INASAN-Kislovodsk observatory. The optical counterpart (Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Zhu et al., GCN 40061; Konno et al., GCN 40063; Odeh et al., GCN 40064; He et al., GCN 40069; Pérez-Fournon et al., GCN 40071; Jelinek et al., GCN 40072; Rakotondrainibe et al., GCN 40073; Taguchi et al., GCN 40074; Brivio et al., GCN 40075; Ruocco et al., GCN 40076; Martin-Carrillo et al., GCN 40080; Pavoni et al., GCN 40083; Li et al., GCN 40084; Yin et al., GCN 40085; Pankov et al., GCN 40086; Chen et al., GCN 40088;) is not detected starting on 2025-04-04 (UT) 21:10:11. Preliminary upper limit of the stacked image is the following Date UT start t-T0 Filter Exp. OT Err. UL(3sigma) (mid, days) (s) 2025-04-04 21:10:11 0.33362 R 70*120 n/d n/d 20.1 The photometry is based on nearby USNO-B1.0 stars.
GCN 40093 table
GRB_name GRB250404A
GCN_number 40093
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40093 SUBJECT: EP250404a / GRB 250404A: Montarrenti Observatory optical observations DATE: 25/04/06 13:49:11 GMT FROM: Simone Leonini at Montarrenti Observatory (Siena, Italy) S. Leonini, A. Lorini, 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 the X-ray transient EP250404a (Einstein Probe mission, Trigger ID 01709133918) probably associated with GRB 250404A (Fermi team, GCN 40050) with the automated and remoted 0.53m Ritchey-Chretien telescope at Montarrenti Observatory (Siena, Italy, IAU code C88). The observations were started at 2025-04-04 18:36:04 UT (approximately 4 hours after burst) ending at 2025-04-04 22:00:50 UT stacking a set of Rc-band CCD images. Observations were performed under thin cloud cover in the second part of the night. The optical afterglow (Jiang et al., GCN 40052; Perez-Garcia et al., GCN 40053; Du et al., GCN 40058; Zhu et al., GCN 40061; Konno et al., GCN 40063; Odeh et al, GCN 40064; He et al., GCN 40069; Perez-Fournon et al., GCN 40071; Jelinek et al., GCN 40072; Rakotondrainibe et al, GCN 40073; Taguchi et al., GCN 40074; Ruocco et al., GCN 40076; Martin-Carrillo et al., GCN 40080; Pavoni et al., GCN 40083; Li et al., GCN 40084; Yin et al., GCN 40085; Pankov et al., GCN 40086; Chu Chen et al., GCN 40088 and Chen et al., GCN 40089) was clearly detected at the following position: RA (J2000) 08h 20m 14.57s +/-0.06 Decl. (J2000) +35° 31' 42.0" +/-0.04 Preliminary photometry was obtained using nearby PanSTARRS stars as follows: Observation Mid-Time T-T0 (hr) Exposure Filter Mag. Err. 2025-04-04 18:36:24 UT 4.27 50x40s Rc 19.60 +/-0.10 2025-04-04 19:11:30 UT 4.85 50x40s Rc 19.67 +/-0.10 2025-04-04 19:46:31 UT 5.43 50x40s Rc 19.81 +/-0.15 2025-04-04 20:21:33 UT 6.02 54x40s Rc 20.25 +/-0.20 2025-04-04 21:07:10 UT 6.78 78x40s Rc 20.16 +/-0.12 Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied. Along the span of our observations and within our uncertainties, the afterglow evolves in agreement with a power-law decay with a rate alpha ~1.40.
GCN 40095 table
GRB_name GRB250404A
GCN_number 40095
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 40095 SUBJECT: GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations. DATE: 25/04/06 17:44:24 GMT FROM: Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, Messina, Italy Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, (Messina) Italy Member of: GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani. Report: We observed the field of GRB 250404A detected by Fermi Gamma-ray Burst Monitor (GBM team, GCN 40050) with the 11 inches Schmidt-Cassegrain (Celestron 11) telescope F/D=6,3. The observations were started at 2025-04-04 22:45 UT (approximately 8.42 hours after burst) stacking a set of unfiltered CCD image. The observations were made with modest visibility conditions: passing clouds and Moon (illumin. 48%, dist. 19°) The OT was detected at the following position (+/- 0.3 arcsec): RA (J2000) 08h 20m 14.59s Decl. (J2000) +35° 31' 41.5" Photometry was obtained using nearby PanSTARRS stars as follows: Observation Mid-Time T-T0 (hr) Exposure Filter Mag. Err. 2025-04-04 23:27:00 UT 9.12 82x60s CR 20.16 +/-0.2 Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied. Our observations are consistent with other already reported Jiang et al. (GCN 40052), Perez-Garcia et al. (GCN 40053), Du et al. (GCN 40058), Zhu et al. (GCN 40061), Konno et al. (GCN 40063), Odeh et al. (GCN 40064), Lipunov et al. (GCN 40066), Min-He et al. (GCN 40069), Lipunov et al. (GCN 40070), Perez-Fournon et al. (GCN 40071), Jelinek et al. (GCN 40072), Rakotondrainibe et al. (GCN 40073), Taguchi et al. (GCN 40074), Brivio et al. (GCN 40075), Ruocco (GCN 40076), Martin-Carrillo et al. (GCN 40080), Pavoni et al. (GCN 40083), Li et al. (GCN 40084), Yin et al. (GCN 40085), Pankov et al. (GCN 40086), Chen et al. (GCN 40088), Chen et al. (GCN 40089), Pankov et al. (GCN 40090), Leonini et al. (GCN 40093). The message may be cited.
GCN 40236 table
GRB_name GRB250404A
GCN_number 40236
Detection_method Fermi GBM Det
t_trigger 14:20:37.400 UTC
Circular_text TITLE: GCN CIRCULAR NUMBER: 40236 SUBJECT: GRB 250404A / EP250404a: GRBAlpha detection DATE: 25/04/24 15:03:18 GMT FROM: Marianna Dafčíková at Masaryk University <500025@mail.muni.cz> M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner (Masaryk U.), M. Ohno, H. Takahashi (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), N. Husarikova, F. Munz , M. Topinka, M. Duriskova, M. Kolar, L. Szakszonova, J.-P. Breuer, F. Hroch (Masaryk U.), T. Urbanec, M. Kasal, A. Povalac (Brno U. of Technology), J. Hudec, J. Kapus, M. Frajt (Spacemanic s.r.o), R. Laszlo, M. Koleda (Needronix s.r.o), M. Smelko, P. Hanak, P. Lipovsky (Technical U. of Kosice), G. Galgoczi (Wigner Research Center/Eotvos U.), Y. Uchida, H. Poon, H. Matake (Hiroshima U.), N. Uchida (ISAS/JAXA), T. Bozoki (Eotvos U.), G. Dalya (Eotvos U.), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), G. Friss (Eotvos U.), Y. Fukazawa, K. Hirose (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), K. Kapas (Eotvos U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), J. Takatsy (Eotvos U.), K. Torigoe (Hiroshima U.), N. Kogiso, M. Yoneyama (Osaka Metropolitan U.), M. Moritaki (U. Tokyo), T. Kano (U. Michigan) -- the GRBAlpha collaboration. The long-duration GRB 250404A / EP250404a (Fermi/GBM detection: GCN 40050; EP/WXT detection: GCN 40051; Wind/Konus detection: GCN 40087) was observed by the GRBAlpha 1U CubeSat (Pal et al. 2023, A&A, 677, 40; https://ui.adsabs.harvard.edu/abs/2023A%26A...677A..40P/abstract). The detection was confirmed at the peak time 2025-04-04 14:20:37.4 UTC. The T90 duration measured by GRBAlpha is 67 s and the overall significance during T90 reaches 19 sigma. The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB250404A_GCN.pdf All GRBAlpha detections are listed at: https://monoceros.physics.muni.cz/hea/GRBAlpha/ GRBAlpha, launched on 2021 March 22, is a demonstration mission for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). The detector of GRBAlpha consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~50 keV to ~1000 keV. To increase the duty cycle and the downlink rate, the upgrade of the on-board data acquisition software stack is in progress. The ground segment is also supported by the radio amateur community and it takes advantage of the SatNOGS network for increased data downlink volume.