Optimal Survey Strategies and Predicted Planet Yields for the Korean Microlensing Telescope Network

TL;DR

This paper optimizes the observing strategy for the Korean Microlensing Telescope Network (KMTNet) to maximize exoplanet detection, predicting it will detect around 20 planets per year across a wide mass range, including free-floating planets.

Contribution

It presents a detailed simulation-based optimization of KMTNet's survey strategy and provides predictions for its exoplanet and free-floating planet yields.

Findings

KMTNet will detect approximately 2,200 microlensing events annually.

It will find about 20 planets per year per dex in mass between 5 and 1000 Earth masses.

KMTNet is predicted to detect about 1 Earth-mass free-floating planet per year.

Abstract

The Korean Microlensing Telescope Network (KMTNet) will consist of three 1.6m telescopes each with a 4 deg^{2} field of view (FoV) and will be dedicated to monitoring the Galactic Bulge to detect exoplanets via gravitational microlensing. KMTNet's combination of aperture size, FoV, cadence, and longitudinal coverage will provide a unique opportunity to probe exoplanet demographics in an unbiased way. Here we present simulations that optimize the observing strategy for, and predict the planetary yields of, KMTNet. We find preferences for four target fields located in the central Bulge and an exposure time of t_{exp} = 120s, leading to the detection of ~2,200 microlensing events per year. We estimate the planet detection rates for planets with mass and separation across the ranges 0.1 <= M_{p}/M_{Earth} <= 1000 and 0.4 <= a/AU <= 16, respectively. Normalizing these rates to the cool-planet mass function of Cassan (2012), we predict KMTNet will be approximately uniformly sensitive to planets with mass 5 <= M_{p}/M_{Earth} <= 1000 and will detect ~20 planets per year per dex in mass across that range. For lower-mass planets with mass 0.1 <= M_{p}/M_{Earth} < 5, we predict KMTNet will detect ~10 planets per year. We also compute the yields KMTNet will obtain for free-floating planets (FFPs) and predict KMTNet will detect ~1 Earth-mass FFP per year, assuming an underlying population of one such planet per star in the Galaxy. Lastly, we investigate the dependence of these detection rates on the number of observatories, the photometric precision limit, and optimistic assumptions regarding seeing, throughput, and flux measurement uncertainties.