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Eta Carinae: Orientation of The Orbital PlaneEvidence continues to build that Eta Carinae is a massive binary system with a hidden hot companion in a highly elliptical orbit. We present imaging and spectroscopic evidence that provide clues to the orientation of the orbital plane. The circumstellar ejecta, known as the Homunculus and Little Homunculus, are hourglass-shaped structures, one encapsulated within the other, tilted at about 45 degrees from the sky plane. A disk region lies between the bipolar lobes. Based upon their velocities and proper motions, Weigelt blobs B, C and D, very bright emission clumps 0.1 to 0.3" Northwest from Eta Carinae, lie in the disk. UV flux from the hot companion, Eta Car B, photoexcites the Weigelt blobs. Other clumps form a complete chain around the star, but are not significantly photoexcited. The strontium filament, a 'neutral' emission structure, lies in the same general direction as the Weigelt blobs and exhibits peculiar properties indicative that much mid-UV, but no hydrogen-ionizing radiation impinges on this structure. It is shielded by singly-ionized iron. P Cygni absorptions in Fe I I lines, seen directly in line of sight from Eta Carinae, are absent in the stellar light scattered by the Weigelt blobs. Rather than a strong absorption extending to -600 km/s, a low velocity absorption feature extends from -40 to -150 km/s. No absorbing Fe II exists between Eta Carinae and Weigelt D, but the outer reaches of the wind are intercepted in line of sight from Weigelt D to the observer. This indicates that the UV radiation is constrained by the dominating wind of Eta Car A to a small cavity carved out by the weaker wind of Eta Car B. Since the high excitation nebular lines are seen in the Weigelt blobs at most phases, the cavity, and hence the major axis of the highly elliptical orbit, must lie in the general direction of the Weigelt blobs. The evidence is compelling that the orbital major axis of Eta Carinae is projected at -45 degrees position angle on the sky. Moreover the milliarcsecond-scale extended structure of Eta Carinae, recently detected by VLTI, may be evidence of the binary companion in the disk plane, not necessarily of a single star as a prolate spheroid extending along the ejecta polar axis.
Document ID
20060012180
Acquisition Source
Goddard Space Flight Center
Document Type
Conference Paper
Authors
Gull, T. R.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Nielsen, K. E.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Ivarsson, S.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Corcoran, M. F.
(Universities Space Research Association Greenbelt, MD, United States)
Verner, E.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Hillier, J. D.
(Pittsburgh Univ. PA, United States)
Date Acquired
August 23, 2013
Publication Date
January 1, 2006
Publication Information
Publication: Bulletin of the American Astronomical Society
Volume: 37
Issue: 4
Subject Category
Astronomy
Meeting Information
Meeting: AAS 207th Meeting: Massive Binaries
Location: Washington, DC
Country: United States
Start Date: January 8, 2006
End Date: January 12, 2006
Sponsors: American Astronomical Society
Distribution Limits
Public
Copyright
Other

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