2004/12/21 by Nathan Smith, N. Smith · 2 citations
Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Astrophysics and Star Formation Studies #Classical mechanics #Doppler effect #Ejecta #Kinetic energy #Physics #Spectral line #Stellar, planetary, and galactic studies #Supernova #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2005.08750.x
published as 2005, MNRAS, 357, 1330 · 7 pages, 4 Figs, Fig 4 in color; Accepted by MNRAS
arxiv created 2004/12/21 · openalex publication_date 2005/03/02 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
High-resolution spectra of [Fe ii]λ16 435 around η Carinae provide powerful diagnostics of the geometry and kinematics of the ‘Little Homunculus’ (LH) growing inside the larger Homunculus nebula. The LH expansion is not perfectly homologous: while low latitudes are consistent with linear expansion since 1910, the polar caps imply ejection dates around 1920–1930. However, the expansion speed of the LH is much slower than the post-eruption wind, so the star's powerful wind may accelerate the LH. With an initial ejection speed of 200 km s−1 in 1890, the LH would have been accelerated to its present speed if the mass is roughly 0.1 M⊙. This agrees with an independent estimate of the LH mass based on its density and volume. In any case, an ejection after 1930 is ruled out. Using the LH as a probe of the 1890 event then, it is evident that its most basic physical parameters (total mass and kinetic energy, which are 0.1 M⊙ and 1046.9 erg, respectively) are orders of magnitude less than during the giant eruption in the 1840s. Thus, the ultimate energy sources were different for these two events – yet their ejecta have the same bipolar geometry. This clue may point toward a collimation mechanism separate from the underlying causes of the outbursts.