9:45 AM - 10:00 AM
[PCG19-04] The First effective Constraint on Dependence of Microlensing Planet Frequency on The Host Star Mass
Keywords:Exoplanet, Gravitational Microlensing, Planet Formation Theory
More than 5500 exoplanets have been discovered to date and gravitational microlensing is one of the most effective methods to detect planets.
Gravitational microlensing is a unique method that can detect planets residing in a wide range of parameter space, such as planets in the Galactic disk or bulge, planets around late M-dwarfs or G-dwarfs, and even planets around white dwarfs. Measuring the planet frequency as a function of host star mass and location in our Galaxy via microlensing enables us to study the comprehensive picture of planet formation throughout our Galaxy.
We examine a dependence of planet frequency on the host star mass, ML, and distance from the Galactic center, RL, using a sample of planets discovered by gravitational microlensing.
We compare the two-dimensional distribution of the lens-source proper motion, murel, and the Einstein radius crossing time, tE, measured for the 22 planetary events from Suzuki et al 2016 with the distribution from the Galactic model.
Assuming that the planet-hosting probability of a star is proportional to MLm * RLr, we calculate the likelihood distribution of (m,r). We estimate that r = 0.10+0.51-0.37, m = 0.50+0.90-0.70 under the assumption that the planet-hosting probability is independent of the mass ratio.
The effective constraint on the host mass dependence is the first result for microlensing planets.
We also divide the planet sample into subsamples based on their mass ratio, q, and estimate that m=-0.08+0.95-0.65 for q < 10-3 and 1.25+1.07-1.14 for q > 10-3.
Although uncertainties are still large, this result implies a possibility that massive planets are more likely to exist around more massive stars whereas low-mass planets exist regardless of their host star mass.
These results are not only informative for planet formation theory but also helpful for microlensing events analysis that will be discovered by Roman Space Telescope.
Gravitational microlensing is a unique method that can detect planets residing in a wide range of parameter space, such as planets in the Galactic disk or bulge, planets around late M-dwarfs or G-dwarfs, and even planets around white dwarfs. Measuring the planet frequency as a function of host star mass and location in our Galaxy via microlensing enables us to study the comprehensive picture of planet formation throughout our Galaxy.
We examine a dependence of planet frequency on the host star mass, ML, and distance from the Galactic center, RL, using a sample of planets discovered by gravitational microlensing.
We compare the two-dimensional distribution of the lens-source proper motion, murel, and the Einstein radius crossing time, tE, measured for the 22 planetary events from Suzuki et al 2016 with the distribution from the Galactic model.
Assuming that the planet-hosting probability of a star is proportional to MLm * RLr, we calculate the likelihood distribution of (m,r). We estimate that r = 0.10+0.51-0.37, m = 0.50+0.90-0.70 under the assumption that the planet-hosting probability is independent of the mass ratio.
The effective constraint on the host mass dependence is the first result for microlensing planets.
We also divide the planet sample into subsamples based on their mass ratio, q, and estimate that m=-0.08+0.95-0.65 for q < 10-3 and 1.25+1.07-1.14 for q > 10-3.
Although uncertainties are still large, this result implies a possibility that massive planets are more likely to exist around more massive stars whereas low-mass planets exist regardless of their host star mass.
These results are not only informative for planet formation theory but also helpful for microlensing events analysis that will be discovered by Roman Space Telescope.