The Ultraviolet Spectrum of η Carinae: Investigation of the Ejecta Absorption

Details The Ultraviolet Spectrum of η Carinae: Investigation of the Ejecta Absorption The Ultraviolet Spectrum of η Carinae: Investigation of the Ejecta Absorption

Mar 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005apjs..157..138n&link_type=abstract

The Astrophysical Journal Supplement Series, Volume 157, Issue 1, pp. 138-146.

Astronomy and Astrophysics

Astronomy

22

Stars: Circumstellar Matter, Line: Identification, Stars: Individual: Constellation Name: Η Carinae, Ultraviolet: Stars

Scientific paper

We have investigated the far- through mid-UV (1150-2360 Å) spectrum of η Carinae during the late stages of its broad maximum using the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) moderate dispersion echelle modes. The η Car spectrum is a mixture of absorption and emission lines from the surrounding nebula superimposed on broad stellar wind features. This paper provides a description of the observed spectrum including the wind features, the interstellar absorption, and the emission spectrum from the surrounding nebula, but with the emphasis on the absorption spectrum formed in the foreground ejecta. The ejecta absorption spectrum has a complicated velocity structure in which two velocity structures, at -146 and -513 km s-1, are easily distinguished. These two velocity components, formed in different regions of the η Car nebula, have in an earlier analysis been identified and demonstrated to have very different spectral characteristics. The slower velocity component is time variable over the spectroscopic period and is characterized by spectral lines from mainly singly ionized iron-peak elements, while the faster one shows transitions from neutral and singly ionized elements in addition to molecular lines from the hydrogen Lyman bands. The high-velocity H2 lines dominate great parts of the spectrum with over 800 identified transitions from energy levels up to 30,000 cm-1. The STIS MAMA data provide the tool for spatial investigations of the central parts of η Car. H I Lyα pumped and semiforbidden emission lines are observed to be formed east of the central source toward Weigelt blobs B and C, located up to 0.2" from the central source. The complete spectrum, with nebular and interstellar line identifications, is available in the electronic edition of the paper.
Laboratory for Astronomy and Solar Physics, Code 681, Goddard Space Flight Center, Greenbelt, MD 20771.

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