Could the planets around HR 8799 be brown dwarfs?

TL;DR

This paper examines the orbital stability of HR 8799's companions, suggesting they are likely planets rather than brown dwarfs due to age and mass considerations, challenging previous assumptions based on astroseismology.

Contribution

It proposes a new interpretation of the system's age and companion masses, reconciling orbital stability with planetary classification.

Findings

Orbital stability favors a system age of ~100 Myr.

Companion masses are near the planet-brown dwarf boundary.

Discrepancy with previous age estimates likely due to star inclination assumptions.

Abstract

We consider the limiting case for orbital stability of the companions to HR 8799. This case is only consistent with ages for the system of ~100 Myr, not with the 1 Gyr age proposed from astroseismology. The discrepancy probably arises because the inclination of the star is smaller than assumed in analyzing the astroseismology data. Given this young age, the best estimates of the companion masses place them by a small margin on the planet side of the division between planets and brown dwarfs.