{
  "submitter": "Malte Busmann at Ludwig-Maximilians-Universität München <m.busmann@physik.lmu.de>",
  "bibcode": "2024GCN.35724....1B",
  "eventId": "GRB 240209A",
  "submittedHow": "web",
  "subject": "GRB 240209A: Wendelstein Optical Observations",
  "body": "Malte Busmann (LMU), Daniel Gruen (LMU),  Brendan O’Connor (CMU), Antonella Palmese (CMU), Lei Hu (CMU), Arno Riffeser (LMU/MPE) report:\n\nWe observed the position of the optical afterglow candidate (AT2024cew / GOTO24pw;  Belkin et al. GCN 35715; de Ugarte Postigo et al. GCN 35716) for GRB 240209A (Fermi GBM team, GCN 35712) with the 2.1 m Fraunhofer telescope at Wendelstein Observatory, Germany. Observations were obtained using the 3kk imager in the r, i, and J bands simultaneously, starting at 2024-02-13 at 17:42 UT, and again in the g, i and J bands, starting at 04:46 UT.\n\nAt the position of the transient (Belkin et al. GCN 35715), we clearly detect the source in g-band, r-band and i-band in the individual epochs. We measure a brightness of r~19.5+/-0.1 AB mag calibrated to the PS1 catalog. We marginally detect it in J-band co-adding both epochs, at J~20.2+/-0.4 calibrated to the 2MASS catalog. Compared to previous NOT r-band photometry (de Ugarte Postigo et al. GCN 35716) this represents an increase in brightness, further suggesting that this transient is unlikely to be associated with the GRB, as does the blue color r-i~0.3 mag. \n\nFurther observations to uncover the nature of the transient are encouraged. \n\nWe thank the staff of the Wendelstein Observatory for obtaining these observations.\n",
  "circularId": 35724,
  "createdOn": 1707907336167
}