TITLE:   GCN CIRCULAR
NUMBER:  37438
SUBJECT: EP240908a: optical afterglow candidate
DATE:    24/09/09 19:09:59 GMT
FROM:    Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo@ucd.ie>

J. Quirola-Vasquez (Radboud Univ.), D. B. Malesani (DAWN/NBI and Radboud Univ.), A. J. Levan (Radboud Univ. & Warwick Univ.), P. G. Jonker (Radboud Univ), F. E. Bauer (PUC), J. van Dalen (Radboud Univ.), M. E. Ravasio (Radboud Univ.), D. Mata Sanchez (IAC), M. A. P. Torres (IAC), A. Martin-Carrillo (UCD), report on behalf of a larger collaboration:

We observed the position of the X-ray counterpart of EP 240908a (Mao et al., GCN 37432) using the Gemini-North telescope equipped with the GMOS-N imager. A total of 4 exposures by 180 s each were secured, with mid time 2024 Sep 9.561 UT (0.777 days after the EP detection time).

Within the FXT error circle (Mao et al., GCN 37432), we detect a source not readily visible in the Legacy survey images. We measure its position (J2000):

RA = 00:56:00.88
Dec = +08:04:31.9

The source is pointlike (in a seeing of 0.6") and well detected in our data with an AB magnitude r ~ 24. Sources of comparable brightness are visible in the Legacy survey, which has a detection limit of r ~ 24.5 in this area of the sky. We thus propose this as a candidate afterglow of EP 240908a, though further observations are planned in order to confirm variability.

We acknowledge rapid and expert support of the observing staff at the Gemini telescope.