B-type host stars revealed by exoplanets around massive secondary-clump giant stars.

Abstract

Exoplanets around massive young stars, including hot spectral-class B (B-type) stars, are rare but important for understanding how planets form and survive. Most known examples are either very distant companions found by direct imaging or extremely close-in planets found by transit surveys, leaving planets at intermediate orbital distances largely unexplored. Here, we show that this missing population can be revealed through evolved stars. Using space-based stellar oscillations and stellar-evolution models, we identify four known planet-hosting catalogue stars, HD 2952, HD 120084, HIP 65891, and HIP 67537 (Henry Draper and Hipparcos catalogue identifiers), as massive helium-burning giant stars. We reconstruct their birth properties and find that all four were originally B-type stars hosting giant planets at intermediate orbital distances. Orbital-evolution calculations show that the present systems can survive the expansion of their host stars after the main sequence. These systems uncover a hidden population of planets around B-type stars and extend tests of planet formation and survival into a previously inaccessible regime.