2019/06/30 by Brett M. Morris, Jason L. Curtis, Charli Sakari +2 · 34 citations
Engineering · Physics and Astronomy · #Astronomy and Astrophysical Research #Chromosphere #Observatory #Space Technology and Applications #Spectral line #Spectrograph #Stars #Starspot #Stellar classification #Stellar, planetary, and galactic studies #Telescope #astro-ph.SR
paper · pdf · open access · doi:10.3847/1538-3881/ab2e04
published in The Astronomical Journal 158(3), 101 (Institute of Physics) · Accepted for publication in AJ
arxiv created 2019/06/30 · openalex created_date 2019/07/12 · openalex publication_date 2019/08/08 · arxiv updated 2019/08/14 · openalex updated_date 2026/08/05
We gathered high resolution spectra for an ensemble of 55 bright active and inactive stars using the ARC 3.5 m Telescope Echelle Spectrograph at Apache Point Observatory (R≈31,500). We measured spectroscopic effective temperatures, surface gravities and metallicities for most stars in the sample with SME and MOOG. Our stellar property results are consistent with the photometric effective temperatures from the Gaia DR2 pipeline. We also measured their chromospheric S and log R^′HK indices to classify the stars as active or inactive and study the connection between chromospheric activity and starspots. We then attempted to infer the starspot covering fractions on the active stars by modeling their spectra as a linear combination of hot and cool inactive stellar spectral templates. We find that it is critical to use precise colors of the stars to place stringent priors on the plausible spot covering fractions. The inferred spot covering fractions generally increase with the chromospheric activity indicator log R^′HK, though we are largely insensitive to spot coverages smaller than fS \lesssim 20%. We find a dearth of stars with small log R^′HK and significant spot coverages.