Extending the Planetary Mass Function to Earth Mass by Microlensing at Moderately High Magnification

TL;DR

This paper proposes a microlensing strategy to extend the planetary mass function measurement down to Earth masses, enabling detection of low-mass planets near the Einstein ring with modest telescopes.

Contribution

It introduces a new observational approach to detect Earth-mass planets via microlensing at moderately high magnifications.

Findings

Earth-mass planets cause ~5% deviations in microlensing peaks.

Detection is feasible for planets in specific annular regions around the Einstein ring.

Sub-Earths could be detected if sufficiently abundant.

Abstract

A measurement by microlensing of the planetary mass function of planets with masses ranging from 5M_E to 10M_J and orbital radii from 0.5 to 10 AU was reported recently. A strategy for extending the mass range down to (1-3)M_E is proposed here. This entails monitoring the peaks of a few tens of microlensing events with moderately high magnifications with 1-2m class telescopes. Planets of a few Earth masses are found to produce deviations of ~ 5% to the peaks of microlensing light curves with durations ~ (0.7-3)hr in events with magnification ~ 100 if the projected separation of the planet lies in the annular region (0.85-1.2)r_E. Similar deviations are produced by Earth mass planets in the annular region (0.95-1.05)r_E. It is possible that sub-Earths could be detected very close to the Einstein ring if they are sufficiently abundant, and also planetary systems with more than one low mass planet.