Secular changes in eta Carinae's wind 1998-2011

Andrea Mehner, Kris Davidson, Roberta M. Humphreys, Kazunori Ishibashi, John C. Martin, María Teresa Ruiz, Frederick M. Walter

Research output: Contribution to journalArticlepeer-review

29 Scopus citations

Abstract

Stellar wind-emission features in the spectrum of eta Carinae have decreased by factors of 1.5-3 relative to the continuum within the last 10 years. We investigate a large data set from several instruments (STIS, GMOS, UVES) obtained between 1998 and 2011 and analyze the progression of spectral changes in direct view of the star, in the reflected polar-on spectra at FOS4, and at the Weigelt knots. We find that the spectral changes occurred gradually on a timescale of about 10 years and that they are dependent on the viewing angle. The line strengths declined most in our direct view of the star. About a decade ago, broad stellar wind-emission features were much stronger in our line-of-sight view of the star than at FOS4. After the 2009 event, the wind-emission line strengths are now very similar at both locations. High-excitation He I and N II absorption lines in direct view of the star strengthened gradually. The terminal velocity of Balmer PCyg absorption lines now appears to be less latitude dependent, and the absorption strength may have weakened at FOS4. Latitude-dependent alterations in the mass-loss rate and the ionization structure of eta Carinae's wind are likely explanations for the observed spectral changes.

Original languageEnglish (US)
Article number73
JournalAstrophysical Journal
Volume751
Issue number1
DOIs
StatePublished - May 20 2012

Keywords

  • circumstellar matter
  • stars: emission-line, Be
  • stars: individual (Eta Carinae)
  • stars: variables: general
  • stars: winds, outflows

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