GCN Circular 39570
Subject
EP250302a: Swift/UVOT detection
Date
2025-03-03T12:58:05Z (6 days ago)
From
Sam Shilling at Lancaster University <shilling.sam@gmail.com>
Via
Web form
S. P. R. Shilling (Lancaster U.) and A. A. Breeveld (UCL-MSSL) reports on behalf of the
Swift UVOT team:
Swift/UVOT observed the field of EP250302a (Dai et al., GCN 39556) for 1029 seconds
in the U-band starting at 16:36:56 UT, 1 hour after the detection by Einstein Probe WXT.
A source consistent with the EP-FXT position (Dai et al., GCN 39556) is detected and
appears to be fading. The preliminary detection magnitudes reported below are calculated
using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373).
The magnitude at the start of the observation is 17.64 +/- 0.05 (1 hour post trigger)
and decays to 18.88 +/- 0.12 (~2 hours post trigger).
We note that an X-ray source at the EP-FXT position was independently observed by the
Swift/XRT (Page et al., GCN 39557). We also note that, in addition to the Swift/UVOT,
various other facilities have observed an optical counterpart at this position
(Zhu et al., GCN 39550; Busmann et al., GCN 39551; Leonini et al., GCN 39553;
Wu et al., GCN 39555; Xin et al., GCN 39558; Lipunov et al., GCN 39559;
Adami et al., GCN 39560; Becerra et al., GCN 39562; Pankov et al., GCN 39565;
Reguitti et al., GCN 39568; Komesh et al., GCN 39569).