Seminario: Andrea Bonfanti (Austrian Academy of Sciences, Graz, Austria)

Speaker: Andrea Bonfanti (Austrian Academy of Sciences, Graz, Austria)
Title: Insights into the M-dwarf radius and density valley
M dwarfs are quite attractive in the domain of exoplanetology: Because of their low mass and small
radius, it is easier to detect low-mass planets with the transit method and the radial velocity (RV)
technique. In addition, it is more likely that the hosted planets are within the so-called habitable
zone (HZ). In fact, the HZ around M dwarfs is located closer to the host star than in stars of earlier
spectral type, and it is well known that both the transit method and the RV technique preferentially
detect close-in planets.
The first part of my talk will focus on the case of TOI-732, an M dwarf orbited by an ultra-short
period super-Earth and an outer mini-Neptune likely rich in volatiles. I will specifically show you
the full characterisation of the system with the determination of the stellar parameters followed by a
MCMC joint analysis of ground- and space-based lightcurves and RV time series. In particular, the
analysed dataset contain CHEOPS, TESS, and MAROON-X observations, among others.
TOI-732 is an interesting system also because its planets are located on the two opposite sides of
the so called radius valley. The nature of the radius valley has been deeply investigated in the
literature by mainly focusing on FGK stars, while only a few works specifically drew attention to
low-mass stars. These considerations open the second part of my talk, where I will compare both
evolution and formation mechanisms in shaping the M-dwarf radius valley. By complementing the
results of TOI-732 with literature data of well characterised M-dwarf exoplanets, I will explore the
topology of both the radius and the density valleys using a support vector machine procedure. I will
show you that the formation likely shapes the radius and density gaps more strongly than the
evolution mechanisms.