TITLE: GCN CIRCULAR NUMBER: 39593 SUBJECT: EP250302A: 1.3m DFOT optical afterglow detection DATE: 25/03/04 15:36:13 GMT FROM: ANSHIKA GUPTA at ARIES anshika05180@gmail.com

Anshika Gupta, Amit K. Ror, Kuntal Misra, and Shashi B. Pandey (ARIES) report:

We observed the field of EP250302A detected by EP-WXT (Trigger ID: 01709132186) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2025-03-02 at 20:15:46 UT, i.e., ~ 4.66 hours after the EP-WXT trigger. We have taken multiple frames with an exposure time of 300 s in the R filter. We stacked the images after the alignment. We clearly detected optical afterglow in our stacked image within the error box of the EP/WXT coordinates (GCN 39550). We obtained the following preliminary magnitude in the stacked image:

Date Start_UT T_start-T0 (hour) Filter Exp time (s) magnitude

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2025-03-02 20:15:46 ~4.66 hour R 300*12 19.990 +- 0.004

Our detection is consistent with Zhu et al. 2025 (GCN 39550); Busmann et al. 2025 (GCN 39551); Leonini et al. 2025 (GCN 39553); WU et al. 2025 (GCN 39555); Xin et al. 2025 (GCN 39558); Lipunov et al. 2025 (GCN 39559); Adami et al. 2025 (GCN 39560); Yang et al. 2025 (GCN 39561); Becerra et al. 2025 (GCN 39562); Izzo et al. 2025 (GCN 39564); Pankov et al. 2025(GCN 39565); Reguitti et al. 2025 (GCN 39568); Komesh et al. 2025 (GCN 39569); Shilling et al. 2025 (GCN 39570); Aryan et al. 2025 (GCN 39572); Eappachen wt al. 2025 (GCN 39575); Moskvitin et al. 2025(GCN 39576); Wu et al. 2025 (GCN 39578) and Pankov et al. 2025 (GCN 39586).

The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalog. This circular may be cited.

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