{
  "subject": "EP260221a: Gemini South z-band upper limit",
  "submitter": "Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo@ucd.ie>",
  "createdOn": 1771760577752,
  "submittedHow": "web",
  "body": "Andrew J. Levan (Radboud), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), J. A. Quirola-Vasquez (Radboud), R. A. J. Eyles-Ferris (Leicester), J. Sanchez-Sierras (Radboud), D. Xu (NAOAC), report on behalf of a larger collaboration\n\nWe observed the field of the fast X-ray transient EP260221a (Zhang et al., GCN 43791; Liu et al., GCN 43802) using the GMOS-S instrument mounted on the Gemini South telescope (Cerro Pachon, Chile). A single 300 s z-band observation was secured starting on 2026 Feb 22 at 08:20 UT (20.62 hr after trigger).\n\nNo new source is detected within the EP/FXT error circle, down to a limiting magnitude z = 24.8 (AB, calibrated against nearby sources from the Pan-STARRS catalog, and not corrected for Galactic extinction). A number of faint sources are visible consistent with the EP/FXT position, but they are all present in archival imaging from the Legacy survey and from DECam.\n\nOur results are consistent with other non-detection reports (Mandarakas et al., GCN 43793; Kumar et al., GCN 43794; He et al., GCN 43798; Lipunov et al., GCN 43803).\n\nWe thank excellent support from the Gemini staff, in particular Lindsay Magill.",
  "eventId": "EP260221a",
  "bibcode": "2026GCN.43805....1L",
  "circularId": 43805,
  "format": "text/plain"
}