# Astrometric exoplanet detectability and the Earth orbital motion

September 7, 2017
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Alexey G. Butkevich
(Submitted on 1 Sep 2017)

Astrometric exoplanet discovery relies on detection of stellar motion caused by planetary companions. Systems with orbital period close to one year may escape detection if orbital motion of their host stars are observationally indistinguishable from parallax effect. Additionally, astrometric solution may produce a biased parallax estimation for such systems. We examine effects of orbital motion of the Earth on astrometric detectability in terms of correlation between the Earth’s orbital position and position of the star relative to system barycentre. The χ2 statistic for parallax estimation is calculated analytically, leading to expressions that relate the decrease in detectability and accompanying parallax bias to the position correlation function. The effects of the Earth motion’s critically depend on orbital period, diminishing rapidly as period deviates from one year. Selection effects against one-year period systems is therefore expected. Statistical estimation shows that corresponding loss of sensitivity is equivalent to a 10 per cent increase in detection threshold. Consideration of eccentric orbits shows that the Earth’s motion has no effect on detectability for e≥0.5. Dependence of detectability on other parameters, such as orbital phases and inclination of the orbit plane to the ecliptic, are smooth and monotonic because they are described by simple trigonometric functions.

Comments:    9 pages, 5 figures. Submitted to MNRAS
Subjects:    Earth and Planetary Astrophysics (astro-ph.EP)
Cite as:    arXiv:1709.00290 [astro-ph.EP] (or arXiv:1709.00290v1 [astro-ph.EP] for this version)
Submission history
From: Alexey Butkevich G.
[v1] Fri, 1 Sep 2017 13:15:54 GMT (68kb,D)
https://arxiv.org/abs/1709.00290

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