The Structure of the Homunculus. I. Shape and Latitude Dependence from H2 and [Fe II] Velocity Maps of η Carinae

By N. Smith. 2006

222 citations recorded by the source corpus.

High-resolution long-slit spectra obtained with the Phoenix spectrograph on Gemini South provide our most accurate probe of the three-dimensional structure of the Homunculus Nebula around η Carinae. The new near-infrared spectra dramatically confirm the double-shell structure inferred previously from thermal dust emission, resolving the nebula into a very thin outer shell seen in H2 and a warmer, thicker inner layer seen in [Fe II]. The remarkably thin and uniform H 2 skin hints that the most important mass loss during the 19th century eruption had a very short duration of ≲5 yr. H2 emission traces the majority of the more than 10 M☉ of material in the nebula and has an average density of order nH ≳ 106.5 cm-3. This emission, in turn, yields our first definitive picture of the exact shape of the nebula, plus a distance of 2350 ± 50 pc and an inclination angle of ~41°. The distribution of the H2 emission provides the first measure of the latitude dependence of the speed, mass loss, and kinetic energy associated with η Car's 19th century explosion. Almost 75% of the total mass and more than 90% of the kinetic energy in the ejecta were released at high latitudes between 45° and the polar axis. This rules out a model for the bipolar shape in which an otherwise spherical explosion was pinched at the waist by a circumstellar torus. Instead, most of the mass appears to have been directed poleward by the explosion itself. H2 emission also provides our first reliable picture of the critical innermost waist of the Homunculus, yielding clues to the observed morphology of the core and the more extended equatorial debris.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/2bda7d1b15241fd7c9512376c899c4e467843b96

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In Astronomy and Astrophysics

1. N. Smith
2. A. Filippenko
3. S. Smartt
4. Ryan Chornock
5. J. C. Wheeler
6. Weidong Li
7. J. Silverman
8. Stan Woosley

Citations in the corpus

• SN 2006gy: Discovery of the Most Luminous Supernova Ever Recorded, Powered by the Death of an Extremely Massive Star like η Carinae (2006, background): “We do not know the electron density in the nebula around SN 2006gy, but values of 105–106 cm 3 are the highest densities typically seen in young LBV nebulae like the one around Carinae (Smith 2006).”
• Pulsational Pair-instability Supernovae (2016, background): “The duration of the major mass ejection was less than 5 years Smith (2006) and the velocity and energy in the ejecta is quite asymmetric (Smith 2006) with ∼90% of the explosion energy concentrated at latitudes above 45 degrees.”
• Luminous blue variable eruptions and related transients: diversity of progenitors and outburst properties (2010, methodology): “For η Car and P Cygni, values of Vexp were inferred from the kinematics of their expanding nebulae (Smith 2005, 2006, 2008; Smith & Hartigan 2006), and even this is incomplete (e.g., we only listed the polar expansion speed for the Homunculus nebula of 650 km s−1, while a latitude-dependent range…”
• SPECTRAL EVOLUTION OF THE EXTRAORDINARY TYPE IIn SUPERNOVA 2006gy (2009, background): “We have argued here and elsewhere (Smith et al. 2007, 2008a, 2008b; Smith 2006b) that the extreme progenitor mass-loss rates required to produce the dense CSM around luminous SNe IIn may suggest a link to LBV-like instability in the progenitor stars.”
• HIGH-DENSITY CIRCUMSTELLAR INTERACTION IN THE LUMINOUS TYPE IIn SN 2010jl: THE FIRST 1100 DAYS (2013, background): “The column density of the shell in Eta Carinae is ∼ 1024 cm−2 located at a radius between 3× 1016 cm and 3× 1017 cm (Smith 2006).”
• DISCOVERY OF PRECURSOR LUMINOUS BLUE VARIABLE OUTBURSTS IN TWO RECENT OPTICAL TRANSIENTS: THE FITFULLY VARIABLE MISSING LINKS UGC 2773-OT AND SN 2009ip (2009, background): “This speed is faster than the 300–370 km s−1 expansion observed in U2773-OT, V1 in NGC 2363 (Drissen et al. 2001), and V37/SN 2002kg (Van Dyk et al. 2006), and it is closer to the 600 km s−1 outflow speed around more massive LBVs like the Homunculus of η Car (Smith 2006).”
• Mass Loss: Its Effect on the Evolution and Fate of High-Mass Stars (2014, background): “Typical expansion speeds observed in outburst spectra are 100-1000 km s−1 (Smith et al. 2011a), although lower speeds can be seen along the line of sight if the ejection speed is latitude dependent (Smith 2006).”
• Ancient eruptions of η Carinae: a tale written in proper motions (2016, methodology): “Moreover,ηCar has a massive binary companion in an eccentric 5.5-year orbit (Damineli 1996; Damineli et al. 1997, 2000; Corcoran et al. 2001; Whitelock et al. 2004), and is located in the rich cluster Trumpler 16, home to dozens of O-type stars (Smith 2006a).”
• On the Role of Continuum-driven Eruptions in the Evolution of Very Massive Stars and Population III Stars (2006, background): “Even for peak luminosities of few 107L⊙ during η Car’s eruption, this limit is still several orders of magnitude below the mass-loss that created the Homunculus.”
• Dust Formation and He II λ4686 Emission in the Dense Shell of the Peculiar Type Ib Supernova 2006jc (2007, background): “We assume spherical symmetry for simplicity, but the discussion below does not preclude possible asymmetry in the SN ejecta or the bipolar geometry that is likely in circumstellar matter arising from LBV-style eruptions (e.g., Smith 2006; Owocki 2003).”
• The Galactic WC stars Stellar parameters from spectral analyses indicate a new evolutionary sequence (2012, background): “WR 23 is another a WC6 star and belongs to the Car OB1 association, for which Smith (2006) obtained a distance modulus of D.M. = 11.8 mag for the Homunculus nebula aroundηCar.”