Creating low planetary mass-functions with Euclid and Roman

Speaker: Natalia Rektsini
Series: Exoplanet Seminars
Also open online: the joining details are on the talk's page.

Gravitational microlensing has proven to be a powerful technique for probing exoplanet populations even in the darkest corners of our Galaxy, as long as sufficiently bright background sources are sampled. The detection depends on the chance alignment between two distant stars and the observer. Due to the difficulty in predicting the time and the location of an event, the number of exoplanet detections via this technique remains modest, but this is about to change. The Nancy Grace Roman Space Telescope is expected to detect more than 1,400 bound planets and hundreds of free-floating planet candidates via microlensing, promising a real breakthrough in our understanding of our Galaxy’s planetary population.

Observing a microlensing event alone cannot always guarantee a precise mass measurement of the planet and its host star. High-angular-resolution follow-up observations of the target in the decade that follows the source–lens alignment have proven to be a very efficient way to derive precise mass and separation measurements for planetary systems. With this motivation, ESA’s space telescope Euclid conducted a 29-hour set of observations of the upcoming Roman fields in late March 2025. This is the largest high-resolution Galactic Bulge survey dedicated to microlensing to this day. This data became public on the 24th June, as part of the Euclid Q2 Data Release.

Here I will begin by presenting an overview of the Euclid Galactic Bulge Survey and its data products. I will introduce the first microlensing systems that we have been working on and explain how Euclid can help use derive the physical parameters of these systems. Finally, I will explain how these observations, in combination with the ongoing HST Galactic Bulge survey (Terry et al 2024), will play a key role in confirming and characterising the planetary systems discovered by Roman.