Subpercent Photometry: Faint DA White Dwarf Spectrophotometric Standards for Astrophysical Observatories

Abstract

We have established a network of 19 faint (16.5 mag < V < 19 mag) northern and equatorial DA white dwarfs (WDs) as spectrophotometric standards for present and future wide-field observatories. Our analysis infers spectral energy distribution (SED) models for the stars that are tied to the three CALSPEC primary standards. Our SED models are consistent with panchromatic Hubble Space Telescope photometry to better than 1%. The excellent agreement between observations and models validates the use of non-LTE DA WD atmospheres extinguished by interstellar dust as accurate spectrophotometric references. Our standards are accessible from both hemispheres and suitable for ground- and space-based observatories covering the ultraviolet to the near-infrared. The high precision of these faint sources makes our network of standards ideally suited for any experiment that has very stringent requirements on flux calibration, such as studies of dark energy using the Large Synoptic Survey Telescope and the Wide-field Infrared Survey Telescope.