Sebastien Lepine, Rosanne DiStefano
Extrapolation of the astrometric motion of the nearby low-mass star VB 10 indicates that sometime in late December 2011 or early January 2012, the star will approach to within short angular distance of a background point source. Based on astrometric uncertainties, we estimate a 1 in 2 chance that the distance of closest approach rho_{min} will be less than 100 mas, a 1 in 5 chance that rho_{min} < 50 mas, and a 1 in 10 chance that rho_{min} < 20 mas. The latter would result in a microlensing event with a magnification larger than 6% in the light from the background source, with an astrometric shift of about 3.3 mas. The lensing signal will however be significantly diluted by the light from VB 10, which is 1.5 mag brighter that the background source in the blue (B), 5 mag brighter in the red (I), and 10 mag brighter in the infrared (K), making the event undetectable in all but the bluer bands. However, we show that if VB 10 happens to harbor a ~1 M_Jup planet on a moderately wide (>0.3 AU) orbit, this planet could pass closer to the background source up to several weeks preceding or following the primary event, and produce a secondary event of significantly higher magnification (tens of percent or higher). The secondary events have timescales of several days but detectable, high-magnification peaks lasting only about 5-10 hours. We argue that an intensive, multi-site monitoring campaign using 1-meter class telescopes would be required to detect secondary events due to orbiting planets.
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http://arxiv.org/abs/1111.5850
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