We present precise photometry and spectroscopy for 23 candidate spectrophotometric standard white dwarfs. The selected stars are distributed in the Northern hemisphere and around the celestial equator, and are all fainter than r~16.5mag. This network of stars, when established as standards and together with the three Hubble Space Telescope primary CALSPEC white dwarfs, will provide a set of spectrophotometric standards to directly calibrate data products to better than 1%. In future deep photometric surveys and facilities, these new faint standard white dwarfs will have enough signal-to-noise ratio to be measured accurately while still avoiding saturation. They will also fall within the dynamic range of large telescopes and their instruments for the foreseeable future. This paper discusses the provenance of the observational data for our candidate standard stars.

Cone search capability for table J/ApJ/872/199/table4 (Log of the observations collected with the Wide Field Camera 3 (WFC3) on board the Hubble Space Telescope (HST) during cycles 20 and 22)

Cone search capability for table J/ApJ/872/199/candidates (properties of the three HST primary CALSPEC standards and the 23 candidate spectrophotometric standard DA WDs (Table 1), Pan-STARRS1 photometry (Table 2) and GAIA DR2 photometry (Table 3))