Calibration Target Selection for the SPARCS Satellite

Abstract

Abstract The Star–Planet Activity Research CubeSat (SPARCS) is an upcoming NASA mission to understand the impact of low-mass stellar radiation on exoplanets. SPARCS will obtain photometric observations of low-mass stars in two bands: 153–171 nm (Far-UV; FUV) and 258–308 nm (Near-UV; NUV). SPARCS’ absolute calibration will be derived by observing White Dwarfs (WDs). WD selected as SPARCS calibrators should vary ≤7%. Here we present a study of UV variability of potential WD calibrators, based on Galaxy Evolution Explorer and HST/UVIS photometric observations. We collected data on a sample of 29 WDs from the Mikulski Archive for Space Telescopes and identified 8 potential SPARCS calibration targets in the NUV and 5 in the FUV, for a total of 10 distinct targets. Statistical analysis shows variability <3% in both bands. For some stars, the intrinsic astrophysical variability is smaller than these limits.