TITLE:   GCN CIRCULAR
NUMBER:  40391
SUBJECT: EP250508a: COLIBRÍ Optical Limit
DATE:    25/05/08 07:01:07 GMT
FROM:    Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo@gmail.com>

Antonio de Ugarte Postigo (LAM), Noémie Globus (UNAM), Rosa L. Becerra (U Roma), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Fredd Alvarez (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), and Benjamin Schneider (LAM):

We imaged the field of the EP250508a (ID: 01709175339; Liang et al. GCN Circ. 40390) using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2025-05-08 06:15 to 06:34 UTC (from 0.2 to 0.5 hours after the trigger) and obtained 16 minutes of exposure in the i filter.

The data were reduced and coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.

In the stacked image, we do not detect any new source at the WXT source position (Liang et al. GCN Circ. 40390) down to the following 3-sigma limit:

i > 21.7 mag

Further observations and analysis are ongoing.

We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams.

COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.