Magnifying NASA Roman GBTDS exoplanet science with coordinated observations by ESA Euclid

TL;DR

Coordinated observations by ESA Euclid and NASA Roman can significantly enhance exoplanet detection, characterization, and demographics, especially through early pre-imaging and sustained joint campaigns.

Contribution

This paper proposes a coordinated observational strategy between Euclid and Roman to improve exoplanet science, including mass measurements and demographic surveys.

Findings

Euclid pre-imaging can improve Roman exoplanet mass estimates by up to five times.

Joint Euclid-Roman observations enable detection and characterization of exomoons.

Simultaneous observations facilitate direct mass measurements and false-positive discrimination.

Abstract

The ESA Euclid mission is scheduled to launch on July 1st 2023. This White Paper discusses how Euclid observations of the Galactic Bulge Time Domain Survey (GBTDS) area could dramatically enhance the exoplanet science output of the Nancy Grace Roman Space Telescope (Roman). An early Euclid pre-imaging survey of the Roman GBTDS fields, conducted soon after launch, can improve proper motion determinations for Roman exoplanet microlenses that can yield a factor of up to $\sim 5$ improvement in exoplanet mass measurements. An extended Euclid mission would also enable the possibility of sustained simultaneous observations of the GBTDS by Euclid and Roman that would achieve large gains in several areas of Roman exoplanet science, including science that is impossible to achieve with Roman alone. These include: a comprehensive demographic survey for free-floating planets that includes precision mass measurements to establish the true nature of individual candidates; detection, confirmation and mass measurements of exomoons; direct exoplanet mass measurements through parallax and finite source size effects for a large sample of bound exoplanets detected jointly by Euclid and Roman; enhanced false-positive discrimination for the large samples of transiting planets that Roman will detect. Our main recommendation to NASA and ESA is to initiate a Joint Study Group as early as possible that can examine how both missions could best conduct a coordinated campaign. We also encourage flexibility in the GBTDS scheduling.