Stars stably accreting from substellar objects

TL;DR

This paper reports the first direct observations of stable mass transfer from substellar objects like brown dwarfs to main-sequence stars, showing some such objects can survive for billions of years instead of being destroyed.

Contribution

It provides the first evidence of stable, long-term mass transfer from substellar objects to stars, challenging previous assumptions about their fate.

Findings

Identified two binary systems with brown dwarfs transferring mass to M dwarfs.

Demonstrated that some substellar objects can survive for billions of years.

Showed that stable accretion from substellar objects is possible, contrary to prior expectations.

Abstract

Substellar objects such as brown dwarfs and planets are generally expected to remain detached from their main-sequence host stars unless orbital decay or stellar expansion brings them into contact, leading to rapid engulfment and destruction. Such a fate is predicted for the Earth and other rocky planets in our solar system; however, in certain cases, theory also allows for stable long-lived mass transfer from a substellar object onto its main-sequence host, though such accretion has never been directly observed. Here we report the first direct observations of stable mass transfer from a substellar object onto a main-sequence star. In particular, we identify two binaries, ZTF J0440+2325 and ZTF J1444+4820, with orbital periods of just 87 and 67 minutes, respectively, in which a brown dwarf stably transfers mass onto an M dwarf companion. These systems demonstrate that the fate of some substellar objects is not rapid engulfment and destruction, but instead gradual consumption for potentially billions of years.