TITLE: GCN CIRCULAR NUMBER: 39553 SUBJECT: EP250302a: Montarrenti Observatory optical detection DATE: 25/03/02 23:05:33 GMT FROM: Simone Leonini at Montarrenti Observatory (Siena, Italy) s.leonini@iol.it

S. Leonini, M. Conti, P. Rosi, L.M. Tinjaca Ramirez (Montarrenti Observatory, Siena, Italy, part of UAI/SSV-GRB section), M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy) and K. Kalinowski (Aarhus University, Department of Physics and Astronomy) report:

we observed the field of the X-ray transient EP250302a (Einstein Probe mission, Trigger ID 01709132186) with the automated and remoted 0.53m Ritchey-Chretien telescope at Montarrenti Observatory (Siena, Italy, IAU code C88). The observations were started at 2025-03-02 20:40:11 UT (approximately 5 hours after the EP-WXT trigger) stacking 50x40s calibrated Rc-band CCD images.

We detect an optical transient candidate at the position reported by Zhu et al. (GCN 39550). Preliminary photometry was obtained using nearby PanSTARRS stars as follows:

Observation Mid-Time T-T0 (hr) Exposure Filter Mag. Err. 2025-03-02 20:57:42 UT 5.35 50x40s Rc 20.36 +/-0.08

consistent with other observation reported by Busmann et al., GCN 39551.

Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied.

Further observations are ongoing.

View this GCN Circular online at https://gcn.nasa.gov/circulars/39553. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...