TITLE: GCN CIRCULAR NUMBER: 38638 SUBJECT: EP241217a : Leavitt Observatory optical upper limit DATE: 24/12/19 19:26:00 GMT FROM: leavittob@gmail.com

E. Pavoni and L. Moretti (Leavitt Observatory, Italy),

Members of: GRB/UAI - Gamma Ray Burst section of Unione Astrofili Italiani ATA - Associazione Tuscolana di Astronomia

In a large collaboration with: M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy), K. Kalinowski (Aarhus University, Department of Physics and Astronomy), report:

We observed the field of EP241217a (Zhou et al., GCN 38586) with the RC telescope (D=250 mm, F/D=8) of Leavitt Observatory, Italy.

Our observations started about 11.25 hours after the EP-WXT trigger, at the following position: RA (J2000): 03h 07m 46s Dec(J2000): +30d 55' 47"

Weather conditions were good.

We utilized the astropy package (Astropy Collaboration et al., 2022ApJ...935..167A) to align and stack 39 individual frames of 120 sec each, with a median time of 2024-12-17T17:36:16 (UTC). All images are unfiltered.

In the stacked frame, we did not detect any optical counterpart at the position of the optical afterglow, with the following upper limit:

Time (UTC) Limit (clear filter) 2024-12-17T17:36:16 >20.8

Magnitudes were estimated with the BP-band of Gaia DR3 catalogue (*) and are not corrected for galactic dust extinction.

The upper limit is consistent with other already reported (Lipunov et al., GCN 38603; Junjie-Jin et al. GCN 38607; Mohan et al. GCN 38612; Brivio et al. GCN 38618).

The message may be cited.

Reference: https://leavittobservatory.altervista.org

(*) https://gea.esac.esa.int/archive/documentation/GEDR3/Data_processing/chap_cu...

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