2001/07/02 by Brian E. Wood, Margarita Karovska, Warren Hack · 1 citation
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Astrophysics and Star Formation Studies #astro-ph
paper · pdf · doi:10.1086/322871
12 pages, 4 figures; AASTEX v5.0 plus EPSF extensions in mkfig.sty; accepted by ApJ Letters
arxiv created 2001/07/02 · openalex publication_date 2001/07/20 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/01
We present ultraviolet spectra of Mira's companion star from the Space Telescope Imaging Spectrograph (STIS) instrument on board the Hubble Space Telescope ( HST ). The companion is generally assumed to be a white dwarf surrounded by an accretion disk fed by Mira's wind, which dominates the UV emission from the system. The STIS UV spectrum is dominated by numerous, narrow H 2 lines fluoresced by H I Lyα, which were not detected in any of the numerous observations of Mira B by the International Ultraviolet Explorer ( IUE ). The high-temperature lines detected by IUE (e.g., C IV λ1550) still exist in the STIS spectrum but with dramatically lower fluxes. The continuum fluxes in the STIS spectra are also much lower, being more than an order of magnitude lower than ever observed by IUE and also an order of magnitude lower than fluxes observed in more recent HST Faint Object Camera objective prism spectra from 1995. Thus, the accretion rate onto Mira B was apparently much lower when STIS observed the star, and this change altered the character of Mira B's UV spectrum.