TITLE: GCN CIRCULAR NUMBER: 39733 SUBJECT: EP250315a: optical counterpart candidate detected by Gemini North DATE: 25/03/15 13:43:51 GMT FROM: Jonathan Quirola at Radboud University jaquirola1990@gmail.com
J. A. Quirola-Vasquez (Radboud Univ.), P. G. Jonker (Radboud Univ.), D. B. Malesani (DAWN/NBI & Radboud Univ.), J. van Dalen (Radboud Univ.), A. Martin-Carrillo (UCD), A. J. Levan (Radboud Univ. & Warwick Univ.), A. van Hoof (Radboud Univ.), J. Sanchez-Sierras (Radboud Univ.), F. E. Bauer (PUC), M. E. Ravasio (Radboud Univ.), J. Chacon (PUC) report on behalf of a larger collaboration:
We observed the field of EP250315a (Peng et al., GCN 39731), using the GMOS-N instrument mounted on the Gemini North Telescope. We obtained 3 x 40 s frames in the r band at a median time of 3.72 hr after the EP trigger. When compared to the Legacy Survey archive, we find an uncatalogued optical transient (OT) which is detected in the stacked image within the EP/FXT error circle (Peng et al., GCN 39731) at coordinates
R.A. (J2000) = 13:32:06.98 Dec. (J2000) = -09:31:49.0
with an uncertainty of ~0.3 arcsec. The OT has a magnitude r = 21.72+-0.10 AB mag, calibrated against the Pan-STARRS DR1 catalog, and not corrected for Galactic extinction. We thus conclude the OT is very likely the optical counterpart of EP250315a.
We acknowledge excellent support of the Gemini staff, especially Emanuele Farina.
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