TITLE: GCN CIRCULAR NUMBER: 42000 SUBJECT: GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula DATE: 25/09/26 12:19:19 GMT FROM: Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra@roma2.infn.it> Rosa L. Becerra (U Roma), Alan M. Watson (UNAM), Sahil Atri (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), Margarita Pereyra (UNAM) and Eleonora Troja (U Roma) report: We observed the field of GRB 250926A detected by Fermi/GBM (Fermi GBM Team GCN Circ. 41993) 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 2025-09-26 UTC. DDOTI imaged the GBM error region (Fermi GBM Team, GCN Circ. 41993) from 09:06 to 11:53 UTC (T+8.6 to T+11.5 hours after the trigger), covering the entire region and obtaining a total exposure of 64 minutes. Comparing our observations to the USNO-B1 and Pan-STARRS PS1 DR2 catalogues, we detect no uncatalogued fading sources within the observed field down to a 10-sigma limiting AB magnitude of: w > 20.3 This value is not corrected for Galactic extinction. We note that the Orion Nebula (d ~400 pc) lies within the error region reported by the Fermi/GBM Team. Given the possible association with this nearby star-forming region and the moderate duration of the signal (T90 ~ 5 s), we strongly encourage follow-up observations of this event. Further analysis is ongoing. We thank the staff of the Observatorio Astronómico Nacional at the Sierra de San Pedro Mártir, especially María H. Riesgo Tirado, for their invaluable assistance during the night. View this GCN Circular online at https://gcn.nasa.gov/circulars/42000. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...