GRB 250411A

The Fermi GBM team reports the detection of a likely LONG GRB

At 18:17:09 UT on 11 Apr 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250411A (trigger 766088234.189348 / 250411762).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 245.7, Dec = -13.9 (J2000 degrees, equivalent to J2000 16h 22m, -13d 54'), with a statistical uncertainty of 3.4 degrees.

The angle from the Fermi LAT boresight is 98.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250411762/quicklook/glg_skymap_all_bn250411762.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/bn250411762/quicklook/glg_healpix_all_bn250411762.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250411762/quicklook/glg_lc_medres34_bn250411762.gif

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-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 250411A ( Fermi GBM team, GCN 40136
Loading...
 
 ) errorbox  7115 sec after notice time and 7149 sec after trigger time at 2025-04-11 20:16:18 UT, with upper limit up to  17.6 mag. The observations began at zenith distance = 75 deg. The sun  altitude  is -49.3 deg. 

The galactic latitude b = 24 deg., longitude l =  1 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=2840071

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

    7179 | 2025-04-11 20:16:18 |         MASTER-SAAO | (16h 18m 59.95s , -13d 56m 46.1s) |   C |    60 | 17.6 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.

Sahil Atri (U Roma), Rosa L. Becerra (U Roma), Alan M. Watson (UNAM), Eleonora Troja (U Roma), Camila Angulo Valdez (UNAM), Nat Butler (ASU), Simone Dichiara (Penn State University), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Océlotl López (UNAM) and Margarita Pereyra (UNAM) report:

We observed the field of the GRB 250411A detected by Fermi/GBM (Fermi GBM Team, GCN 40136
Loading...
 
 ) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir (http://ddoti.astroscu.unam.mx) on the night of 2025-04-12 UTC from 07:13 UTC to 12:05 UTC (from T+12.9 h to T+17.8 h after the trigger) and obtained a total exposure of 1.94 hours. 

Comparing our observations to the USNO-B1 and Pan-STARRS PS1 DR2 catalogues, we detect no evident uncatalogued sources within the observed field to a 10-sigma limiting AB magnitude of: 

w > 18.93-19.65

This value is not corrected for the Galactic extinction.

We thank the staff of the Observatorio Astronómico Nacional on the Sierra of San Pedro Mártir.