A New Channel for the Detection of Planetary Systems Through Microlensing

TL;DR

This paper proposes a new microlensing strategy to detect wide-orbit planets, especially low-mass ones, with high expected detection rates, enabling detailed studies of planetary populations in the Galactic Bulge.

Contribution

It introduces a novel approach for detecting wide-orbit planets via microlensing and provides detailed simulations to evaluate its effectiveness and benefits.

Findings

Detection rates for wide-orbit planets could be 2-10% of current single-star microlensing events.

The strategy could significantly constrain the prevalence of planetary systems in the Galactic Bulge.

High detection rates may enable follow-up studies and insights into planetary habitability.

Abstract

We propose and evaluate the feasibility of a new strategy to search for planets via microlensing observations. This new strategy is designed to detect planets in "wide" orbits, i.e., with orbital separation, a, greater than ~1.5 R_E. Planets in wide orbits may provide the dominant channel for the discovery of planets via microlensing, particularly low-mass (e.g., Earth-mass) planets. Because the ongoing microlensing observations and extensions of them should be able to discover planets in wide orbits, we provide a foundation for the search through detailed calculations and simulations that quantify the expected results and compare the relative benefits of various search strategies. If planetary systems similar to our own or to some of the known extra-solar systems are common, then the predicted detection rates of wide-orbit events are high, generally in the range 2-10% of the present detection rate for apparently single events by stars. The expected high rates should allow the microlensing observing teams to either place significant limits on the presence of planetary systems in the Galactic Bulge, or begin to probe the population in detail within the next few years. We also address the issues of (1) whether planets discovered via microlensing are likely to harbor life, (2) the feasibility of follow-up observations to learn more about planet microlenses, and (3) the contamination due to stellar populations of any microlensing signal due to low-mass MACHOs.