TITLE: GCN CIRCULAR NUMBER: 38019 SUBJECT: GRB 241030A / EP241030a: FTW Optical and NIR observations of the optical counterpart DATE: 24/10/31 22:50:07 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 optical counterpart of GRB 241030A (Fermi GBM team, GCN 37955; Klingler et al., GCN 37956; Watson et al., GCN 37957; Fernández-Rodríguez et al., GCN 37958; Zheng et al., GCN 37959, An et al., GCN 37960, Higuchi at al., GCN 3763; Qui et al., GCN 37965; Lin et al., GCN 37966 and similar) which was also detected as an X-ray transient by Swift (Klingler et al., GCN 37956) and Einstein Probe (Wu et al., GCN 37997) as EP241030a with the Three Channel Imager (3KK) at the Fraunhofer Telescope Wendelstein (FTW) in the r, i and J band simultaneously for 20 x 180 s starting at 2024-10-31T17:18:20 UT (1.48 days after the trigger). We detect the counterpart at r = (20.89 +/- 0.02) mag i = (20.62 +/- 0.02) mag J = (20.11 +/- 0.04) mag. The r and i band magnitudes are calibrated against the PanSTARRS1 catalog and provided in the AB system. The J band magnitude is calibrated against the 2MASS catalog and converted to the AB system with Blanton and Roweis, 2007, doi:10.1086/510127. Magnitudes are not corrected for Galactic extinction. We thank the staff of the Wendelstein Observatory for obtaining these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/38019. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...