GCN Circular 40428
Subject
EP250508a: Gemini NIR upper limits
Event
Date
2025-05-11T07:27:31Z (6 months ago)
From
Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani@nbi.ku.dk>
Via
email
A. J. Levan (Radboud and Warwick), J. C. Rastinejad (Northwestern), A.
Martin-Carrillo (UCD), J. A. Quirola-Vasquez (Radboud), F. E. Bauer (SSI
and UTA), G. Corcoran (UCD), R. A. J. Eyles-Ferris (Leicester), P. G.
Jonker (Radboud), D. B. Malesani (DAWN/NBI and Radboud), report on
behalf of a larger collaboration:
We observed the field of the fast X-ray transient EP250508a (Liang et
al., GCN 40390; Zhao et al., GCN 40399) using the Gemini-South telescope
equipped with the FLAMINGOS-2 near-infrared imager (program
GS-2025A-FT-106, PI Bauer). Observations were started on 2025 May 9 at
02:08:01 UT (20.07 hr after the EP trigger), and we secured 9 and 4.8
min imaging in the J and Ks bands, respectively. The seeing was modest
at ~1.7" in the J-band image.
No source is detected at the coordinates of the optical afterglow
reported by SVOM/VT (Xin et al., GCN 40402; Li et al., GCN 40412), down
to 5-sigma limiting magnitudes:
J > 22.9 (AB system, 20.28 hr after trigger);
Ks > 22.2 (AB system, 22.58 hr after trigger).
These upper limits were calibrated using nearby stars from the VISTA
Hemisphere Survey (VHS) catalogue.
We thank excellent support from the observing staff at Gemini, in
particular Venu Kalari and Henrique Reggiani.