Astronomy and Astrophysics – Astronomy
Scientific paper
May 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21823005k&link_type=abstract
American Astronomical Society, AAS Meeting #218, #230.05; Bulletin of the American Astronomical Society, Vol. 43, 2011
Astronomy and Astrophysics
Astronomy
Scientific paper
Epsilon Aurigae is an eclipsing binary with a 27-year period that has baffled investigators for almost two centuries. The data from present and prior eclipses have strengthened our understanding of the system, but a comprehensive understanding of it's evolutionary state has remained illusive. There are presently two competing views: (1)the F-star primary is a supergiant of 15 Mo with a companion that is equally massive, yet obviously much smaller, that has yet to evolve off the MS or (2)the F-star is a post-AGB object of 4 Mo with a MS companion of 6-7 Mo that is enshrouded in an accretion disk of debris from the F-star.
Deciding between the two models depends on having an accurate distance to the system. Published parallaxes all agree within their formal uncertainties, but have error bars larger than the nominal value. We have found that all astrometric results either neglected orbital motion or relied on orbital elements that are not congruent with spectroscopy (Stefanik et al. 2010) and with the recent in-eclipse interferometric observations (Kloppenborg et al. 2010). For example, all astrometric orbital solutions (van de Kamp 1978, Strand 1959, Heintz and Cantor 1994) assumed an eccentricity that does not agree with present value, e = 0.22-0.26 (Stefanik et al. 2010, Chadima et al. 2010), rather than solving for it. Likewise the HIPPARCOS parallax used Heintz's orbit that we argue is incorrect.
We are deriving new orbital solutions for both components in the system. The solution for the F-star will use radial velocity and astrometric observations. The solution for the eclipsing object comes from the relative motion of the components implied by interferometric imaging.
The University of Denver participants are grateful for support under NSF grant 10-16678 and the bequest of William Hershel Womble in support of astronomy at the University of Denver.
Hemenway Paul
Jensen Eric
Kloppenborg Brian K.
Osborn Wayne
Stencel Robert
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