GCN Circular 37930

J. A. Quirola-Vasquez (Radboud Univ.), D. B. Malesani (DAWN/NBI & Radboud Univ.), A. J. Levan (Radboud), F. E. Bauer (PUC), P. G. Jonker (Radboud Univ.), report on behalf of a larger collaboration:

We observed the optical counterpart of EP241021a (Fu et al., GCN 37840
Not found
 
 
; Gompertz et al., GCN 37835
Not found
 
 
; Lipunov et al., GCN 37839
Not found
 
 
; Fu et al., GCN 37842
Not found
 
 
; Yang et al., GCN 37843
Not found
 
 
; Li et al., GCN 37844
Not found
 
 
; Li et al., GCN 37846
Not found
 
 
; Zheng et al., GCN 37849
Not found
 
 
; Moskvitin et al., GCN 37850
Not found
 
 
; Pugliese et al., GCN 37852
Not found
 
 
; Pérez-Fournon et al., GCN 37858
Not found
 
 
; Bochenek et al., GCN 37869
Not found
 
 
; Kumar et al., GCN 37875
Not found
 
 
; Jin et al., GCN 37892
Not found
 
 
), using the Gemini-South (GS) telescope equipped with the GMOS instrument.

We obtained 4x180 s exposures in the r-band, starting on 2024-10-28 at 00:21:06 UT, i.e., approximately ~6.8 days after the X-ray trigger. We detect the source at an r-band magnitude of ~21.90 AB mag, calibrated against nearby Pan-STARRS objects. Compared to both reports from the literature (e.g., Bochenek & Perley, GCN 37869
Not found
 
 
; Busmann et al., GCN 37878
Not found
 
 
) and our own data, this shows that the source has brightened. Such a brightening is reminiscent of that shown by EP240414a (Shubham et al. 2024, arXiv:2409.19070
Not found
 
 
; van Dalen et al. 2024, arXiv:2409.19056
Not found
 
 
), though occurring at a slightly later epoch.

We thank the staff of the Gemini-South for excellent support.