Paper: astro-ph/0506426
Date: Fri, 17 Jun 2005 20:41:34 GMT (351kb)

Title: Astrometric Microlensing Constraints on a Massive Body in the Outer
Solar System with the Global Astrometric Interferometer for Astrophysics
(GAIA)

Authors: B. Scott Gaudi (CfA), Joshua S. Bloom (CfA, UC Berkeley)
Comments: 15 pages, 5 figures
\\
A body in Solar orbit beyond the Kuiper belt exhibits an annual parallax that
exceeds its apparent proper motion by up to many orders of magnitude. Apparent
motion of this body along the parallactic ellipse will deflect the angular
position of background stars due to astrometric microlensing ("induced
parallax"). By synoptically sampling the astrometric position of background
stars over the entire sky, constraints on the existence (and basic properties)
of a massive nearby body may be inferred. With a simple simulation, we estimate
the signal-to-noise for detecting such a body -- as function of mass,
heliocentric distance, and ecliptic latitude -- using the anticipated
sensitivity and temporal cadences from the Global Astrometric Interferometer
for Astrophysics (GAIA; launch 2011). A Jupiter-mass (M_Jup) object at 2000 AU
is detectable by GAIA over the whole sky above 5-sigma, with even stronger
constraints if it lies near the ecliptic plane. Hypotheses for the mass
(~3M_Jup), distance (~20,000 AU) and location of the proposed perturber
("Planet X") which gives rise to long-period comets may be testable.

http://arXiv.org/abs/astro-ph/0506426