JHK standard stars for large telescopes:: the UKIRT Fundamental and Extended lists

We present high-precision JHK photometry with the 3.8-m UK Infrared Telescope (UKIRT) of 82 standard stars, 28 from the widely used preliminary list known as the 'UKIRT Faint Standards', referred to here as the Fundamental List, and 54 additional stars referred to as the Extended List. The stars have 9.4 < K < 15.0 and all or most should be readily observable with imaging array detectors in normal operating modes on telescopes of up to 10-m aperture. Many are accessible from the southern hemisphere. Arcsec-accuracy positions (J2000, epoch similar to 1998) are given, together with optical photometry and spectral types from the literature, where available, or inferred from the J - K colour. K-band finding charts are provided for stars with proper motions exceeding 0.3 arcsec yr(-1). We discuss some pitfalls in the construction of flat-fields for array imagers and a method to avoid them. On 30 nights between late 1994 and early 1998 the stars from the Fundamental List, which were used as standards for the whole programme, were observed on an average of 10 nights each, and those from the Extended List on an average of six nights. The average internal standard error of the mean results for the K magnitudes is 0.005 mag; for the J - H colours it is 0.003 mag for the Fundamental List stars and 0.005 mag for those of the Extended List; for H - K the average is 0.004 mag. The results are on the natural system of the IRCAM3 imager, which used a 256 x 256 InSb detector array with 'standard' JHK filters, behind gold-coated fore-optics and a gold- or silver-dielectric coated dichroic. We give colour transformations on to the CIT, Arcetri and LCO/Palomar NICMOS systems, and preliminary transformations on to the system defined by the new Mauna Kea Observatory near-infrared filter set.