2001/03/26 by Scott J. Kenyon, Daniel Proga, C. D. Keyes +1 · 2 citations
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Star Formation Studies #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/321107
17 pages, 7 pages, 5 tables; to be published in the Astronomical Journal, July 2001
arxiv created 2001/03/26 · openalex publication_date 2001/07/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/30
We analyze optical and ultraviolet observations of the symbiotic binary AG Pegasi acquired during 1992–1997. The bolometric luminosity of the hot component declined by a factor of 2–3 from 1980–1985 to 1997. Since 1992, the effective temperature of the hot component may have declined by 10%–20%, but this decline is comparable to the measurement errors. Optical observations of Hβ and He I emission show a clear illumination effect, where high-energy photons from the hot component ionize the outer atmosphere of the red giant. Simple illumination models generally account for the magnitude of the optical and ultraviolet emission-line fluxes. High-ionization emission lines—[Ne V], [Mg V], and [Fe VII]—suggest mechanical heating in the outer portions of the photoionized red giant wind. This emission probably originates in a low-density region ∼30–300 AU from the central binary.