Measuring microlensing parallax via simultaneous observations from Chinese Space Station Telescope and Roman Telescope

TL;DR

This paper explores how simultaneous observations from the Chinese Space Station Telescope and Roman Telescope can effectively measure microlensing parallax, especially for short-duration events like free-floating planets, enhancing mass determination accuracy.

Contribution

It demonstrates the potential of joint space-based observations to measure microlensing parallax for a wide range of short-duration events, including free-floating planets and binary systems.

Findings

Joint observations can measure parallax for nearly all FFP events with $t_E \\lesssim 10$ days.

CSST alone has potential for parallax measurement, discussed in the paper.

The separation between the two telescopes is ideal for short and ultra-short microlensing events.

Abstract

Simultaneous observations from two spatially well-separated telescopes can lead to the measurements of the microlensing parallax parameter, an important quantity toward the determinations of the lens mass. The separation between Earth and Sun-Earth L2 point, $\sim0.01$ AU, is ideal for parallax measurements of short and ultra-short ($\sim$1\,hr to 10\,days) microlensing events, which are candidates of free-floating planet (FFP) events. In this work, we study the potential of doing so in the context of two proposed space-based missions, the Chinese Space Station Telescope (CSST) in a Leo orbit and the Nancy Grace Roman Space Telescope (\emph{Roman}) at L2. We show that the joint observations of the two can directly measure the microlensing parallax of nearly all FFP events with timescales $t_{\rm E}\lesssim$ 10\,days as well as planetary (and stellar binary) events that show caustic crossing features. The potential of using CSST alone in measuring microlensing parallax is also discussed.