SECULAR CHANGES IN ETA CARINAE'S WIND 1998-2011
- ESO, Alonso de Cordova 3107, Vitacura, Santiago de Chile (Chile)
- Minnesota Institute for Astrophysics, University of Minnesota, Minneapolis, MN 55455 (United States)
- Global COE, Division of Particle Physics and Astrophysics, Nagoya University, Nagoya 464-8602 (Japan)
- Department of Physics and Astronomy, University of Illinois Springfield, Springfield, IL 62703 (United States)
- Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago de Chile (Chile)
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States)
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 P Cyg 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.
- OSTI ID:
- 22037218
- Journal Information:
- Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 751; ISSN ASJOAB; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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