Secondary Standards in the UKIRT Faint Standard Fields

We present precise J- and K-band photometric measurements for 128 near-infrared (NIR) secondary standard stars, located in the 19 United Kingdom Infrared Telescope/Maunakea Observatories (UKIRT/MKO) primary faint standard fields. The data were collected over more than 50 nights, covering a decade of observations between 2008 and 2018 at the ESO La Silla Observatory, using the New Technology Telescope equipped with the SOFI NIR camera. Presented magnitudes are calibrated onto the MKO photometric system. The J- and K-band magnitudes range from 10 to 15.8 mag, with median values of J˜ = 13.5 mag and K˜ = 13 mag. The selection process ensured high photometric quality, with a precision better than 0.01 mag for all stars. The catalog excludes stars with close neighbors, high proper motion, or variable stars. Using these fields for standardization can improve the precision and accuracy of photometric calibrations without increasing the observational time cost.