A Likely Detection of a Twoplanet System in a Lowmagnification Microlensing Event
Abstract
We report on the analysis of a microlensing event, OGLE2014BLG1722, that showed two distinct shortterm anomalies. The bestfit model to the observed light curves shows that the two anomalies are explained with two planetary mass ratio companions to the primary lens. Although a binarysource model is also able to explain the second anomaly, it is marginally ruled out by 3.1σ. The twoplanet model indicates that the first anomaly was caused by planet “b” with a mass ratio of q=({4.5}_{0.6}^{+0.7})× {10}^{4} and projected separation in units of the Einstein radius, s = 0.753 ± 0.004. The second anomaly reveals planet “c” with a mass ratio of {q}_{2}=({7.0}_{1.7}^{+2.3})× {10}^{4} with ∆χ ^{2} ∼ 170 compared to the singleplanet model. Its separation has two degenerated solutions: the separation of planet c is s _{2} = 0.84 ± 0.03 and 1.37 ± 0.04 for the close and wide models, respectively. Unfortunately, this event does not show clear finitesource and microlensing parallax effects; thus, we estimated the physical parameters of the lens system from Bayesian analysis. This gives the masses of planets b and c as {m}_{{{b}}}={56}_{33}^{+51} and {m}_{{{c}}}={85}_{51}^{+86} {M}_{\oplus }, respectively, and they orbit a latetype star with a mass of {M}_{host}} ={0.40}_{0.24}^{+0.36} {M}_{☉ } located at {D}_{{{L}}}={6.4}_{1.8}^{+1.3} {kpc} from us. The projected distances between the host and planets are {r}_{\perp ,{{b}}}=1.5+/ 0.6 {au} for planet b and {r}_{\perp ,{{c}}}={1.7}_{0.6}^{+0.7} {au} and {r}_{\perp ,{{c}}}={2.7}_{1.0}^{+1.1} {au} for the close and wide models of planet c. If the twoplanet model is true, then this is the third multipleplanet system detected using the microlensing method and the first multipleplanet system detected in lowmagnification events, which are dominant in the microlensing survey data. The occurrence rate of multiple cold gas giant systems is estimated using the two such detections and a simple extrapolation of the survey sensitivity of the 6 yr MOA microlensing survey combined with the 4 yr μFUN detection efficiency. It is estimated that 6% ± 2% of stars host two cold giant planets.
 Publication:

The Astronomical Journal
 Pub Date:
 June 2018
 DOI:
 10.3847/15383881/aabd7a
 arXiv:
 arXiv:1803.05238
 Bibcode:
 2018AJ....155..263S
 Keywords:

 gravitational lensing: micro;
 planetary systems;
 Astrophysics  Earth and Planetary Astrophysics
 EPrint:
 Submitted to AAS