# Weighing in on the masses of retired A stars with asteroseismology: K2 observations of the exoplanet-host star HD 212771

## TL;DR

This study uses K2 asteroseismology to accurately measure the mass of the exoplanet-host star HD 212771, challenging previous estimates and refining our understanding of planetary system evolution around evolved stars.

## Contribution

It provides a precise asteroseismic mass measurement for HD 212771, testing and ultimately refuting the overestimation hypothesis of stellar masses in retired A stars.

## Key findings

- Asteroseismic mass (1.45 M_sun) is higher than previous estimates (1.15 M_sun).
- Results do not support the hypothesis of systematic overestimation of stellar masses.
- Implications for planetary system evolution depend critically on accurate stellar mass measurements.

## Abstract

Doppler-based planet surveys point to an increasing occurrence rate of giant planets with stellar mass. Such surveys rely on evolved stars for a sample of intermediate-mass stars (so-called retired A stars), which are more amenable to Doppler observations than their main-sequence progenitors. However, it has been hypothesised that the masses of subgiant and low-luminosity red-giant stars targeted by these surveys --- typically derived from a combination of spectroscopy and isochrone fitting --- may be systematically overestimated. Here, we test this hypothesis for the particular case of the exoplanet-host star HD 212771 using K2 asteroseismology. The benchmark asteroseismic mass ($1.45^{+0.10}_{-0.09}\:\text{M}_{\odot}$) is significantly higher than the value reported in the discovery paper ($1.15\pm0.08\:\text{M}_{\odot}$), which has been used to inform the stellar mass-planet occurrence relation. This result, therefore, does not lend support to the above hypothesis. Implications for the fates of planetary systems are sensitively dependent on stellar mass. Based on the derived asteroseismic mass, we predict the post-main-sequence evolution of the Jovian planet orbiting HD 212771 under the effects of tidal forces and stellar mass loss.