Searching for GEMS – Giant Exoplanets around M-dwarf Stars

Giant (gaseous) exoplanets around M-dwarf stars have been theorized to be difficult to form owing to low protoplanetary disk masses and longer orbital timescales associated with the low host star mass. Up until the launch of NASA’s TESS mission, the primary source of detecting these objects has been through radial velocity (RV) surveys, which suffer from small sample sizes, and the sini degeneracy. 


In this presentation, I will present the motivation and preliminary results for the Giant Exoplanets around M-dwarf Stars (GEMS) survey, that will utilize transiting planet candidates across a sample of a million M-dwarfs to provide the most precise and accurate estimate of the occurrence of GEMS across the M-dwarf spectral type as a function of stellar mass, and period. Using RVs from the Habitable-zone Planet Finder (HPF), NEID, the Planet Finding Spectrograph (PFS), we have already confirmed and characterized ~ 10 GEMS orbiting a range of M-dwarf spectral subtypes, and will increase this number to ~ 30 in the next three years. I will then discuss how this sample has started to challenge our understanding of giant planet formation around low-mass stars, thereby necessitating (i) revisiting the mass budget of protoplanetary disks and disk dust mass estimation techniques, (ii) exploring gravitational instability as a means of rapid formation of GEMS during the proto-stellar phase, (iii) better estimates on the bulk-metallicity (i.e., heavy-element content) of these GEMS. Finally, I will discuss future prospects and the promise of this sample, including our JWST Cycle 2 program to study 7 GEMS and characterize their atmospheric and bulk metallicity to perform a comparison of mass-metallicity trends both within the M-dwarf sample, and with FGK sample.