The extended interacting wind structure of Eta Carinae

Details The extended interacting wind structure of Eta Carinae The extended interacting wind structure of Eta Carinae

Jul 2009

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009mnras.396.1308g&link_type=abstract

Monthly Notices of the Royal Astronomical Society, Volume 396, Issue 3, pp. 1308-1328.

Astronomy and Astrophysics

Astronomy

21

Binaries: Spectroscopic, Stars: Individual: Eta Carinae, Stars: Winds, Outflows

Scientific paper

The highly eccentric binary system, η Car, provides clues to the transition of massive stars from hydrogen-burning via the CNO cycle to a helium-burning evolutionary state. The fast-moving wind of η Car B creates a cavity in η Car A's slower, but more massive, stellar wind, providing an in situ probe. The Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS), with its high spatial and spectral resolutions, is well matched to follow temporal spatial and velocity variations of multiple wind features. We use observations obtained across 1998-2004 to produce a rudimentary three-dimensional model of the wind interaction in the η Car system. Broad (+/-500 km s-1) [FeII] emission line structures extend 0.7arcsec (~1600 au) from the stellar core. In contrast, [FeIII], [ArIII], [NeIII] and [SIII] lines extend only 0.3arcsec (700 au) from NE to SW and are blue shifted from -500 to +200 km s-1. All observed spectral features vary with the 5.54-year orbital period. The highly ionized, forbidden emission disappears during the low state, associated with periastron passage. The high-ionization emission originates in the outer wind interaction region that is directly excited by the far-ultraviolet radiation from η Car B. The HST/STIS spectra reveal a time-varying, distorted paraboloidal structure, caused by the interaction of the massive stellar winds. The model and observations are consistent with the orbital plane aligned with the skirt of the Homunculus. However, the axis of the distorted paraboloid, relative to the major axis of the binary orbit, is shifted in a prograde rotation along the plane, which projected on the sky is from NE to NW.
Based on observations made with the National Aeronautics and Space Agency/European Space Agency (NASA/ESA) HST. Support for Programme numbers 7302, 8036, 8483, 8619, 9083, 9337, 9420, 9973, 10957 and 11273 was provided by NASA directly to the Space Telescope Imaging Spectrograph Science Team and through grants from the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. Based on observations made with European Southern Observatory telescopes at the La Silla or Paranal Observatories under programme IDs 070.D-0607, 071.D-0168, 074.D-0141, 077.D-0618 and 380.D-0036.
E-mail: theodore.r.gull@nasa.gov

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