TITLE: GCN CIRCULAR NUMBER: 40108 SUBJECT: IceCube 250406A: DDOTI Optical Observations of the Refined Position DATE: 25/04/07 18:50:45 GMT FROM: Rosa L. Becerra at Tor Vergata, Roma rosa.becerra@roma2.infn.it

Rosa L. Becerra (U Roma), Alan M. Watson (UNAM), Eleonora Troja (U Roma), Camila Angulo Valdez (UNAM), Sahil Atri (U Roma), 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 IceCube 250406A (goldtrack) event (IceCube Collaboration, GCN Circ. 40103) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on the Sierra of San Pedro Martir (http://ddoti.astroscu.unam.mx) on the night of 2025-04-07 UTC from 03:12 UTC to 05:19 UTC (from T+4.4 h to T+6.5 h after the trigger) and obtained a total exposure of 1.2 hours.

In Becerra et al. (GCN Circ. 40101), we reported a 5-sigma upper limits in the original uncertainty region distributed as a GCN notice (https://gcn.gsfc.nasa.gov/notices_amon_g_b/140752_31006975.amon).

Here, we report observations of the updated uncertainty region (IceCube Collaboration, GCN Circ. 40103). In this region, we detect no uncataloged source to a 5-sigma AB limiting magnitude of:

w > 20.0

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.

View this GCN Circular online at https://gcn.nasa.gov/circulars/40108. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...