TITLE:   GCN CIRCULAR
NUMBER:  45679
SUBJECT: EP260920a: VLT/HAWK-I near-infrared candidate
DATE:    26/09/21 10:34:38 GMT
FROM:    Valerio D'Elia at ASDC <valerio.delia@ssdc.asi.it>

J. An (NAOC), D. Xu (NAOC), V. D’Elia (ASI/SSDC), M. Garnichey (LUX-Paris Obs.) G. Corcoran (UCD), A. J. Levan (Radboud and Warwick), N. R. Tanvir (U. Leicester), A. L. Thakur (INAF/IAPS), S. D. Vergani (LUX-Paris Obs.), M. Garnichey (LUX-Paris Obs.), report on behalf of the Stargate collaboration:

We observed the field of the EP260920a (Ni et al., GCN 45649) using the ESO/VLT UT4 equipped with the HAWK-I instrument. Observation started at 2026-09-21 02:43:54 UT, i.e., 1.11 days after the trigger, and 20 x 60 s of J-band frames were obtained.

We detect an uncatalogued source in the stacked image at the following coordinates, located within the EP/FXT error circle:
R.A. (J2000) = 01:46:06.91 (26.5288 deg)
Dec. (J2000) = -13:58:49.83 (-13.9805 deg)
with an uncertainty of ~ 0.5 arcsec.

The source had J ~ 20.72+/-0.08 mag (Vega) at a median time of ~ 26.87 hr post-trigger, calibrated with 2MASS and not corrected for Galactic extinction. The target position has no known detections in either the Legacy or Vista Hemisphere Survey historical survey images. No NEO would be at the above position at the observational time by checking MPC. We thus think the source could be the candidate of EP260920a, and this hints at its high-redshift nature.

We acknowledge excellent support from the ESO staff in Paranal.