WFIRST Planet Masses from Microlens Parallax

TL;DR

This paper proposes a ground-based method to measure microlens parallaxes for WFIRST events in L2 orbit, enabling routine determination of lens and planet masses, including dark objects, with minimal additional observations.

Contribution

It introduces a simple, effective approach to measure microlens parallaxes using limited ground-based data for WFIRST events in L2, enhancing mass determination capabilities.

Findings

Method can measure parallaxes for all events with Amax > 30

Enables routine mass measurements of lenses and planets

Applicable to dark and isolated objects like brown dwarfs

Abstract

I present a method using only a few ground-based observations of magnified microlensing events to routinely measure the parallaxes of WFIRST events if WFIRST is in an L2 orbit. This could be achieved for all events with Amax > 30 using target-ofopportunity observations of select WFIRST events, or with a complementary, ground-based survey of the WFIRST field, which can push beyond this magnification limit. When combined with a measurement of the angular size of the Einstein ring, which is almost always measured in planetary events, these parallax measurements will routinely give measurements of the lens masses and hence, the absolute masses of the planets. They can also lead to mass measurements for dark, isolated objects such as brown dwarfs, free-floating planets, and stellar remnants if the size of the Einstein ring is measured.