TITLE: GCN CIRCULAR NUMBER: 39440 SUBJECT: EP250223a: LCO detection of the afterglow DATE: 25/02/23 23:49:41 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias ipf@iac.es
I. Pérez-Fournon, F. Poidevin, D. Aguado, J.A. Acosta-Pulido, A. López-Oramas, D. Nespral (IAC and ULL), F. Acero (CEA Saclay and IAC), N.C. Sun (UCAS), W. Li, Y. Wang, Z. Niu (NAOC), D. Cano-Morales, I. Correa-Plasencia, and A.E. Hernández-Díaz (ULL)
We observed the location of EP250223a (Lian et al., GCN circ. 39429), detected also by Swift XRT (Kennea et al., GCN circ. 39437), with two Las Cumbres Observatory Global Telescope network (LCOGT) 1-m telescopes, equipped with Sinistro cameras, located at the LCOGT node at Sutherland Observatory (South Africa). We obtained first a 600-sec exposure in the SDSS r' filter, that started at 2025-02-23 19:47:12 UT, e.g. 4.71 hr after the EP trigger, followed by 300-sec exposures in the SDSS i' and g' filters. The optical afterglow candidate reported by Hauptmann et al. (GCN circ. 39436) is clearly detected in the three images.
We measured the following magnitudes, calibrated against PanSTARRS DR2 stars and not corrected for Galactic extinction:
Date | UT start | T (mid) - T0 (hours) | mag | error | filter | ---------------------------------------------------------------------- 2025-02-23 19:47:12 4.79 19.73 0.03 r' 2025-02-23 21:38:41 6.61 19.74 0.06 i' 2025-02-23 21:42:28 6.67 20.77 0.10 g'
A redshift of z = 2.756 has been reported by Levan et al. (GCN circ. 39438).
This work makes use of observations from the Las Cumbres Observatory global telescope network (LCOGT observing programme IAC2025A-009, SGLF).
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