On the existence of brown dwarfs more massive than the hydrogen burning limit

TL;DR

This paper challenges the traditional view by proposing that brown dwarfs can have masses exceeding the hydrogen burning limit through slow mass accretion, forming a continuous sequence with traditional brown dwarfs.

Contribution

It introduces the concept of overmassive brown dwarfs formed via mass transfer, expanding the understanding of brown dwarf mass limits.

Findings

Overmassive brown dwarfs can exist above 0.07 solar masses.

Mass transfer in binary systems via gravitational waves can produce these objects.

Overmassive brown dwarfs share properties with traditional brown dwarfs.

Abstract

Almost by definition brown dwarfs are objects with masses below the hydrogen burning limit, around $0.07\ M_\odot$. Below this mass, objects never reach a steady state where they can fuse hydrogen. Here we demonstrate, in contrast to this traditional view, that brown dwarfs with masses greater than the hydrogen burning limit may in principle exist in the universe. These objects, which we term "overmassive brown dwarfs" form a continuous sequence with traditional brown dwarfs in any property (mass, effective temperature, radius, luminosity). To form an overmassive brown dwarf, mass must be added sufficiently slowly to a sufficiently old traditional brown dwarf below the hydrogen burning limit. We identify mass transfer in binary brown dwarf systems via Roche lobe overflow driven by gravitational waves to be the most plausible mechanism to produce the bulk of the putative overmassive brown dwarf population.