Establish whether the SO2 shoreline applies to planets orbiting hotter stars

Determine whether the SO2 shoreline separating detectable and undetectable SO2 as a function of equilibrium temperature and atmospheric metallicity remains valid for planets orbiting hotter stars, and characterize how the host-star spectral energy distribution and the atmospheric pressure range probed by observations alter its location and shape.

Background

The SO2 shoreline framework was developed primarily for warm planets orbiting K-type stars. HD 106315 c instead orbits an F-type star with a substantially different ultraviolet spectrum, making it unclear whether the same temperature–metallicity boundary can be transferred to hotter-host systems.

The authors compute new VULCAN model grids and find that the resulting shorelines differ significantly from those obtained for K-type stellar atmospheres. This motivates resolving whether the shoreline is universal or instead depends on stellar spectral type, chemical-network assumptions, and the pressure levels sampled by transmission spectroscopy.