Title: Frequency of Solar-Like Systems and of Ice and Gas Giants Beyond the Snow Line from High-Magnification Microlensing Event
We present the first measurement of planet frequency beyond the "snow line"
for planet/star mass-ratios[-4.5<log q<-2]: d^2 N/dlog q/dlog
s=(0.36+-0.15)/dex^2 at mean mass ratio q=5e-4, and consistent with being flat
in log projected separation, s. Our result is based on a sample of 6 planets
detected from intensive follow-up of high-mag (A>200) microlensing events
during 2005-8. The sample host stars have typical mass M_host 0.5 Msun, and
detection is sensitive to planets over a range of projected separations
(R_E/s_max,R_E*s_max), where R_E 3.5 AU sqrt(M_host/Msun) is the Einstein
radius and s_max (q/5e-5)^{2/3}, corresponding to deprojected separations ~3
times the "snow line". Though frenetic, the observations constitute a
"controlled experiment", which permits measurement of absolute planet
frequency. High-mag events are rare, but the high-mag channel is efficient:
half of high-mag events were successfully monitored and half of these yielded
planet detections. The planet frequency derived from microlensing is a factor 7
larger than from RV studies at factor ~25 smaller separations [2<P<2000 days].
However, this difference is basically consistent with the gradient derived from
RV studies (when extrapolated well beyond the separations from which it is
measured). This suggests a universal separation distribution across 2 dex in
semi-major axis, 2 dex in mass ratio, and 0.3 dex in host mass. Finally, if all
planetary systems were "analogs" of the Solar System, our sample would have
yielded 18.2 planets (11.4 "Jupiters", 6.4 "Saturns", 0.3 "Uranuses", 0.2
"Neptunes") including 6.1 systems with 2 or more planet detections. This
compares to 6 planets including one 2-planet system in the actual sample,
implying a first estimate of 1/6 for the frequency of solar-like systems.
A. Gould (OSU),
Subo Dong (IAS),
B.S. Gaudi (OSU),
A. Udalski (Warsaw U.),
I.A. Bond (Massey U.),
J. Greenhill (U. of Tasmania),
R.A.Right Ascension, abbreviated R.A., is a measure of distance on the celestial sphere measured eastward along the celestial equator. It is similar to longitude and is measured in hours, minutes and seconds. Street (LCOGTLas Cumbres Observatory Global Telescope Network),
M. Dominik (U. St. Andrews),
T. Sumi (Nagoya U.),
M.K. Szymanski (Warsaw U.),
C. Han (Chungbuk U.),
MicroFUN Collaboration,
OGLE Collaboration,
MOA Collaboration,
PLANET Collabroation,
RoboNet Collaboration,
MiNDSTEp Consortium
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