OGLE-2008-BLG-355Lb: A Massive Planet around a Late-type Star
Abstract
We report the discovery of a massive planet, OGLE-2008-BLG-355Lb. The light curve analysis indicates a planet:host mass ratio of q = 0.0118 ± 0.0006 at a separation of 0.877 ± 0.010 Einstein radii. We do not measure a significant microlensing parallax signal and do not have high angular resolution images that could detect the planetary host star. Therefore, we do not have a direct measurement of the host star mass. A Bayesian analysis, assuming that all host stars have equal probability to host a planet with the measured mass ratio, implies a host star mass of M_{h} = 0.37_{-0.17}^{+0.30}\ M_{\odot } and a companion of mass M_{P} = 4.6^{+3.7}_{-2.2} M_{J}, at a projected separation of r_{\perp } = 1.70^{+0.29}_{-0.30} AU. The implied distance to the planetary system is D L = 6.8 ± 1.1 kpc. A planetary system with the properties preferred by the Bayesian analysis may be a challenge to the core accretion model of planet formation, as the core accretion model predicts that massive planets are far more likely to form around more massive host stars. This core accretion model prediction is not consistent with our Bayesian prior of an equal probability of host stars of all masses to host a planet with the measured mass ratio. Thus, if the core accretion model prediction is right, we should expect that follow-up high angular resolution observations will detect a host star with a mass in the upper part of the range allowed by the Bayesian analysis. That is, the host would probably be a K or G dwarf.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2014
- DOI:
- 10.1088/0004-637X/788/2/128
- arXiv:
- arXiv:1403.7005
- Bibcode:
- 2014ApJ...788..128K
- Keywords:
-
- gravitational lensing: micro;
- planetary systems;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 42 pages, 12 figures, submitted for publication in ApJ