TITLE:   GCN CIRCULAR
NUMBER:  35791
SUBJECT: Transient EPW20240219aa: GECKO: LOAO Optical Upper Limits
DATE:    24/02/25 16:11:06 GMT
FROM:    Gregory Paek at Seoul National University <gregorypaek94@gmail.com>

Gregory S.H. Paek (SNU ARC/SNU), Myungshin Im (SNU ARC/SNU), Chung-Uk Lee (KASI), Seung-Lee Kim (KASI), Hyun-Il Sung (KASI) on behalf of a larger collaboration

We searched for the optical counterpart of the bright X-ray flare, EPW20240219aa (Zhang et al., ATel #16463; Zhang et al., GCN #35773) with the 1-m class telescope in Lemonsan Optical Astronomy Observatory (LOAO), one of the facilities of the GW EM-Counterpart Korean Observatory (GECKO).

We observed the localization center provided by the Wide-field X-ray Telescope (WXT) modules aboard the Einstein Probe (EP) mission at RA, Dec = 80.016 deg, 25.541 deg, but could not find any transient within the field of view of LOAO (28.1'x28.1'). We calibrated flux with the PS1 catalog and used an AB magnitude system.

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Filter Date-obs[UT] Exp.time[s] Depth(5sigma)
R 2024-02-23T02:46:34 60*30 20.562

We thank the LOAO operator for performing the observation. Gravitational-wave Electromagnetic-wave Counterpart Korean Observatory (GECKO) is a network of 10+ 0.5m to 1m class telescopes over the world.