J. C. Yee, Y. Shvartzvald, A. Gal-Yam, I. A. Bond, A. Udalski, S. Kozlowski, C. Han, A. Gould, J. Skowron, D. Suzuki, the MOA Collaboration, the OGLE Collaboration, the MicroFUN Collaboration
Microlensing planet searches are transitioning from "survey+followup" mode to
"pure survey" mode, wherein events will be monitored without reference to the
presence of planets, which will enable a more rigorous statistical
interpretation. Such surveys will be able to monitor many more events but at a
lower cadence than typical followup observations, meaning that the significance
of the planets detected in this manner will be lower. It would be useful to
test these pure survey detections to ensure that even with sparser data, the
planets can be reliably detected. MOA-2011-BLG-293 provides one such test. This
planet is robustly detected in survey+followup data (DeltaChi^2~5400). The
planet/host mass ratio is q=5.1 +/- 0.2*10^(-3). The best fit projected
separation is s=0.545 +/- 0.005 Einstein radii. However, due to the s -> 1/s
degeneracy, projected separations of 1/s are only marginally disfavored at
DeltaChi^2=2. A Bayesian estimate of the host mass gives M_L =
0.44^{+0.27}_{-0.17} M_Sun, with a sharp upper limit of M_L < 1.2 M_Sun from
upper limits on the lens flux. Hence, the best estimate of the planet mass is
m_p=2.4^{+1.4}_{-0.9} M_Jup, and the physical projected separation is either
r_perp ~ 1.0 AU or r_perp ~ 3.5 AU. We show that survey data alone correctly
predict this solution and are able to characterize the planet even though the
signal from the planet is close to the limit of detectability (DeltaChi^2~500).
Analyzing a large sample of events like MOA-2011-BLG-293, which have both
followup data and high cadence survey data, will provide a guide for the
interpretation of pure survey microlensing data.
View original:
http://arxiv.org/abs/1201.1002
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