TITLE: GCN CIRCULAR NUMBER: 39348 SUBJECT: GRB 250215A / EP250215a: LCO detection of the afterglow DATE: 25/02/16 21:11:38 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 field of the Fermi long GRB 250215A (Fermi GBM Team, GCN Circ. 39327), detected also by Einstein Probe WXT and FXT (EP250215a, Wang et al., GCN Circ. 39329), INTEGRAL SPI-ACS (Barria et al., GCN Circ. 39331), AstroSat CZTI (Tembhurnikar et al., GCN Circ. 39334), SVOM/GRM (Zheng et al., GCN Circ. 39335), and Swift XRT (Page et al., GCN Circ. 39336) with the two Las Cumbres Observatory Global Telescope network (LCOGT) 1-m telescopes, equipped with Sinistro cameras, at the LCOGT node at the Siding Spring Observatory (Australia). We obtained two 600-sec exposures in the SDDS-i' filter starting at 2025-02-15 11:08:48 and 12:58:59 UT, respectively. The optical afterglow detected first by Liu et al. (GCN Circ. 39330) at a redshift of z = 4.61 (Sánchez-Ramírez et al., GCN Circ. 39343) is clearly detected in our LCOGT images with magnitudes of i' = 20.10 +/- 0.15 in the first observation (starting 8.615 after the trigger) and i' = 20.59 +/- 0.23 in the second one (starting 10.451 hr after trigger), with a clear fading between the two observations. The photometry has been calibrated against Pan-STARRS DR2 and is not corrected for Galactic extinction. These results are consistent with other optical detections of the afterglow (Liu et al., GCN Circ. 39330; Xie et al., GCN Circ. 39333; Malesani et al., GCN Circ. 39339; and Malesani et al. GCN Circ. 39341).
This work makes use of observations from the Las Cumbres Observatory global telescope network (LCOGT observing programme IAC2025A-009, SGLF).
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