2000/06/30 by C. R. Canizares, D. P. Huenemoerder, D. S. Davis +10 · 4 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Binary star #Electron density #Emission spectrum #Extreme ultraviolet #Ionization #Plasma #Plasma diagnostics #Solar and Space Plasma Dynamics #Spectral line #Spectrometer #Stellar atmosphere #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/312823
9 pages, 3 figures (1 color) accepted for ApJL
arxiv created 2000/06/30 · openalex publication_date 2000/08/10 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
High-resolution spectra of the active binary Capella (G8 III + G1 III) covering the energy range of 0.4-8.0 keV (1.5-30 Å) show a large number of emission lines, demonstrating the performance of the High-Energy Transmission Grating Spectrometer. A preliminary application of plasma diagnostics provides information on coronal temperatures and densities. Lines arising from different elements in a range of ionization states indicate that Capella has plasma with a broad range of temperatures, from log T = 6.3 to 7.2, generally consistent with recent results from observations with the Extreme-Ultraviolet Explorer and the Advanced Satellite for Cosmology and Astrophysics . The electron density is determined from He-like O VII lines, giving the value of N e ~ 10 10 cm -3 at T e ~ 2 × 10 6 K; He-like lines formed at higher temperatures give only upper limits to the electron density. The density and emission measure from O VII lines together indicate that the coronal loops are significantly smaller than the stellar radius.