{
  "bibcode": "2026GCN.43698....1C",
  "body": "G. Corcoran (UCD) and J. A. Quirola-Vasquez (Radboud) report on behalf of a larger collaboration:\n\nWe observed the field of the fast X-ray transient EP260209a (Zhang et al., GCN 43693) using the LCO 1m telescope located at the McDonald Observatory (Texas, USA) equipped with the SINISTRO instrument. Our observations consisted of a sequence of 4x300 s exposures in the SDSS r-band starting on 2026-02-11 at 12:22:56 UT (~1.44 days after the WXT trigger).\n\nWe do not detect any sources within the EP/FXT uncertainty region (Zhang et al., GCN 43693). From the stacked image, we obtain the following 3-sigma upper limiting magnitude:
\n\nr > 22.5\n\nThis limit is in the AB system, calibrated using nearby stars from the Pan-STARRS catalog, and not corrected for Galactic extinction.\n",
  "eventId": "EP260209a",
  "subject": "EP260209a: LCO optical upper limits",
  "submitter": "Gregory Corcoran  at University College Dublin  <gregory.corcoran@ucdconnect.ie>",
  "format": "text/plain",
  "submittedHow": "web",
  "circularId": 43698,
  "createdOn": 1770828061608
}