TITLE: GCN CIRCULAR NUMBER: 38064 SUBJECT: EP241101a: Possible detection of an optical counterpart with FTW DATE: 24/11/03 17:56:13 GMT FROM: Malte Busmann at Ludwig-Maximilians-Universität München <m.busmann@physik.lmu.de> Malte Busmann (LMU), Daniel Gruen (LMU), Brendan O’Connor (Carnegie Mellon U.) and Antonella Palmese (Carnegie Mellon U.) report: We observed the 90% localization area of EP241101a (Liang et al., GCN 38039) with the Three Channel Imager (3KK) at the Fraunhofer Telescope Wendelstein (FTW) for 40 x 180 s in the r, i and J band simultaneously. Observations started at 2024-11-03T01:36:19 UT (1.07 days after the EP-WXT trigger). Our observations are calibrated against the PS1 catalog and reach 24.5 AB mag in the r band and 24.0 AB mag in the i band at the 3σ limit. We performed difference imaging in the r band with images from the DESI Legacy Survey DR10. In the difference image, we detect a source at RA, DEC (J2000) = 02:31:10.85, +22:44:54.75 corresponding to PSO J037.7952+22.7485 in the PS1 catalog, which is labeled as a variable source and a possible AGN/QSO. Compared to the mean magnitude in PS1 the source is brighter by ~0.5 mag in r-band and ~0.4 mag in i-band. This detection is consistent with the upper limits from Perez-Garcia et al., GCN 38047; Lipunov et al., GCN 38049 and Aryan et al., GCN 38061. While it is difficult to explain the short duration flare of EP241101a in the context of an AGN/QSO, we do not uncover any other variable sources to depth r>24.5 AB mag and i>24.0 AB mag over the entire 90% WXT localization. Further observations are encouraged to determine the nature of the source. We thank the staff of the Wendelstein Observatory for obtaining these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/38064. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...