Protostars and Planets VI, Heidelberg, July 15-20, 2013

Poster 2K015

Imaged companions: not as eccentric as they appear?

Pearce, Tim (IoA)
Wyatt, Mark (IoA)
Kennedy, Grant (IoA)

Increasing numbers of sub-stellar companions are now being discovered via direct imaging. Orbital elements for some of these objects have been derived using star–companion astrometry, and several of these appear to have eccentricities significantly greater than zero. We show that stellar motion caused by an undetected inner body may result in the companion elements derived in such a way being incorrect, which could lead to an overestimation of the eccentricity. The magnitude of this effect is quantified in several regimes, and criteria for identifying systems potentially susceptible to this scenario are presented. In particular, this effect could be relevant for systems within 100 pc with companions at >50 AU, if they also harbour an unseen ∼ 10MJupiter object at >10 AU.

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