Can Lava Lakes from Planetary Debris form on Low-mass M Dwarfs?

Abstract A recent Research Note observes that late-type M dwarf average densities are two orders of magnitude higher than that of lava, and suggests that planetary debris from tidal disruption events (TDEs) could form long-lived and potentially detectable lava lakes on the surfaces of cool M dwarfs. This would represent a very valuable observational avenue for studying TDEs and any other mechanisms that might give rise to planetary engulfment on cool dwarfs. However, examining the density structure of low-mass M dwarfs reveals that lava would only become buoyant at depths well below photospheric, and where plasma temperatures are of the order of 10 5 K. Infalling lava would be rapidly evaporated on timescales of hours, but could form evanescent and detectable metal-enhanced regions with lifetimes of the order of the surface convective turnover time of a day or so.