Microlensing planet detection via geosynchronous and low Earth orbit satellites

TL;DR

This paper investigates how satellites in geosynchronous and low Earth orbits can improve microlensing planet detection, especially for short timescale events and low-mass planets, by measuring microlens parallax.

Contribution

It extends previous analyses to shorter Einstein timescales and evaluates the capabilities of low Earth orbit satellites for detecting Earth-mass free-floating planets.

Findings

Geosynchronous satellites can detect parallaxes for Jupiter-mass free floaters.

Low Earth orbit satellites could discover Earth-mass free-floating planets.

Detection capabilities depend on photometry quality, blending, and Earth's umbra effects.

Abstract

Planet detection through microlensing is usually limited by a well-known degeneracy in the Einstein timescale $t_E$, which prevents mass and distance of the lens to be univocally determined. It has been shown that a satellite in geosynchronous orbit could provide masses and distances for most standard planetary events ($t_E \approx 20$ days) via a microlens parallax measurement. This paper extends the analysis to shorter Einstein timescales, $t_E \approx 1$ day, when dealing with the case of Jupiter-mass lenses. We then study the capabilities of a low Earth orbit satellite on even shorter timescales, $t_E \approx 0.1$ days. A Fisher matrix analysis is employed to predict how the 1-$\sigma$ error on parallax depends on $t_E$ and the peak magnification of the microlensing event. It is shown that a geosynchronous satellite could detect parallaxes for Jupiter-mass free floaters and discover planetary systems around very low-mass brown dwarfs. Moreover, a low Earth orbit satellite could lead to the discovery of Earth-mass free-floating planets. Limitations to these results can be the strong requirements on the photometry, the effects of blending, and in the case of the low orbit, the Earth's umbra.