TITLE:   GCN CIRCULAR
NUMBER:  42241
SUBJECT: GRB 251013C: DDOTI detection of the optical afterglow
DATE:    25/10/14 03:26:13 GMT
FROM:    Alan Watson at UNAM <alan@astro.unam.mx>

Alan M. Watson (UNAM), Camila Angulo Valdez (UNAM), Rosa L. Becerra (U Roma), 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 251013C detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 42221) and SVOM/ECLAIRS (Rakotondrainibe et al., GCN Circ. 42222) with the DDOTI wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir (http://ddoti.astroscu.unam.mx) from 2025-10-14 02:41 to 03:08 (8.80 to 9.45 hours after the trigger) and obtained a total of 23 minutes of exposure in the w filter.

We detect the optical afterglow (Palmerio et al., GCN Circ. 42223; Perez-Garcia et al., GCN Circ. 42225; Konno et al., GCN Circ. 42226; Martin-Carrillo et al., GCN Circ. 42227; Masi et al., GCN Circ. 42228; Palmerio et al., GCN Circ. 42229; Moskvitin et al., GCN Circ. 42230; Gompertz et al., GCN Circ. 42231; Lipunov et al., GCN Circ. 42235; and Garnavich et al., GCN Circ. 42240) with a preliminary magnitude of

w = 18.95 +/- 0.04

Our photometry is calibrated against the USNO-B1 and Pan-STARRS PS1 DR2 catalogues and is not corrected for Galactic extinction.

Observations are continuing.

We thank the staff of the Observatorio Astronómico Nacional at the Sierra de San Pedro Mártir for their excellent support.