TITLE:   GCN CIRCULAR
NUMBER:  37911
SUBJECT: EP241021a: SOAR observations of the optical counterpart
DATE:    24/10/27 15:21:13 GMT
FROM:    James Freeburn at Swinburne University of Technology <jamesfreeburn54@gmail.com>

J. Freeburn (Swinburne/OzGrav), I. Andreoni (UNC), J. Quirola-Vasquez (Radboud Univ.), D. B. Malesani (DAWN/NBI and Radboud Univ.), F. E. Bauer (PUC), P. G. Jonker (Radboud Univ)

We observed the field of EP241021a (Hu et al., GCN 37834) with the Goodman High Throughput Spectrograph mounted on the SOAR telescope in imaging mode (Prop. ID: SOAR2024B-021, SOAR2024B-016). We took four 300s exposures i-band between 2024-10-27T04:56:18 and 2024-10-27T05:16:54 UTC. 

We detect the optical counterpart associated with EP241021a (Fu et al., GCN 37840; Gompertz et al., GCN 37835; Lipunov et al., GCN 37839; Fu et al., GCN 37842; Yang et al., GCN 37843; Li et al., GCN 37844; Li et al., GCN 37846; Zheng et al., GCN 37849; Moskvitin et al., GCN 37850; Pugliese et al., GCN 37852; Pérez-Fournon et al., GCN 37858; Bochenek et al., GCN 37869; Kumar et al., GCN 37875; Jin et al., GCN 37892).  With photometric calibration using the Pan-STARRS1 catalogue, we measure an r=2.5” aperture magnitude of:

i = 22.355 +/- 0.066 AB mag