Astrometric orbit of a low-mass companion to an ultracool dwarf

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Astrometric orbit of a low-mass companion to an ultracool dwarf

Post by Led_Zep on 16th June 2013, 9:04 pm

One of the very first results with astrometric method !
Conclusion page 6 : " Finally, the astrometric performance demonstrated here is sucient to discover planetary companions of nearby ultracool dwarfs with masses as low as one Neptune mass at separations & 0.4 AU."

http://arxiv.org/abs/1306.3225

Astrometric orbit of a low-mass companion to an ultracool dwarf

Little is known about the existence of extrasolar planets around ultracool dwarfs. Furthermore, binary stars with Sun-like primaries and very low-mass binaries composed of ultracool dwarfs show differences in the distributions of mass ratio and orbital separation that can be indicative of distinct formation mechanisms. Using FORS2/VLT optical imaging for high precision astrometry we are searching for planets and substellar objects around ultracool dwarfs to investigate their multiplicity properties for very low companion masses. Here we report astrometric measurements with an accuracy of two tenths of a milli-arcsecond over two years that reveal orbital motion of the nearby L1.5 dwarf DENIS-P J082303.1-491201 located at 20.77 +/- 0.08 pc caused by an unseen companion that revolves about its host on an eccentric orbit in 246.4 +/- 1.4 days. We estimate the L1.5 dwarf to have 7.5 +/- 0.7 % of the Sun's mass that implies a companion mass of 28 +/- 2 Jupiter masses. This new system has the smallest mass ratio (0.36 +/- 0.02) of known very low-mass binaries with characterised orbits. With this discovery we demonstrate 200 micro-arcsecond astrometry over an arc-minute field and over several years that is sufficient to discover sub-Jupiter mass planets around ultracool dwarfs. We also show that the achieved parallax accuracy of < 0.4 % makes it possible to remove distance as a dominant source of uncertainty in the modelling of ultracool dwarfs.
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Re: Astrometric orbit of a low-mass companion to an ultracool dwarf

Post by Edasich on 17th June 2013, 5:20 am

I wonder if this is going to be included as extrasolar planet, with true mass of 28 +/- 2 MJup...
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