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Eta Carinae's Dusty...
Eta Carinae's Dusty Homunculus Nebula from Near-infrared to Submillimeter Wavelengths: Mass, Composition, and Evidence for Fading Opacity
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- Morris, P. W. (författare)
- California Institute of Technology (Caltech)
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- Gull, T. R. (författare)
- NASA Goddard Space Flight Center
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- Hillier, D. J. (författare)
- University of Pittsburgh
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- Barlow, M. J. (författare)
- University College London (UCL)
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- Royer, P. (författare)
- Katholieke Universiteit Leuven
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- Nielsen, K. (författare)
- Catholic University of America
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- Black, John H, 1949 (författare)
- Chalmers tekniska högskola,Chalmers University of Technology
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- Swinyard, B. (författare)
- STFC Rutherford Appleton Laboratory
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(creator_code:org_t)
- 2017-06-15
- 2017
- Engelska.
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 842:2, s. Article no. 79 -
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Abstract
Ämnesord
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- Infrared observations of the dusty, massive Homunculus Nebula around the luminous blue variable eta Carinae are crucial to characterize the mass-loss history and help constrain the mechanisms leading to the great eruption. We present the 2.4-670 mu m spectral energy distribution, constructed from legacy Infrared Space Observatory observations and new spectroscopy obtained with the Herschel Space Observatory. Using radiative transfer modeling, we find that the two best-fit dust models yield compositions that are consistent with CNO-processed material, with iron, pyroxene and other metal-rich silicates, corundum, and magnesium-iron sulfide in common. Spherical corundum grains are supported by the good match to a narrow 20.2 mu m feature. Our preferred model contains nitrides AlN and Si3N4 in low abundances. Dust masses range from 0.25 to 0.44 M-circle dot, but M-tot. 45M(circle dot) in both cases, due to an expected high Fe gas-to-dust ratio. The bulk of dust is within a 5 '' x 7 '' central region. An additional compact feature is detected at 390 mu m. We obtain L-IR = 2.96 x 10(6) L-circle dot, a 25% decline from an average of mid-IR photometric levels observed in 1971-1977. This indicates a reduction in circumstellar extinction in conjunction with an increase in visual brightness, allowing 25%-40% of optical and UV radiation to escape from the central source. We also present an analysis of (CO)-C-12 and (CO)-C-13 J = 5-4 through 9-8 lines, showing that the abundances are consistent with expectations for CNO-processed material. The [C-12 II] line is detected in absorption, which we suspect originates in foreground material at very low excitation temperatures.
Ämnesord
- NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
Nyckelord
- stars: massive
- circumstellar matter
- dust
- stars: individual (eta Carinae)
- extinction
- stars: mass-loss
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- ref (ämneskategori)
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