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A brown dwarf feeds its star in an 87-minute orbit

A brown dwarf in ZTF J0440+2325 is transferring material to a small star as the pair circles every 87 minutes. The newly published research identifies a gradual route for a close companion that could otherwise be rapidly engulfed. A second system remains a strong candidate, and the possible longevity of the transfer comes from a physical interpretation rather than direct observation over that timespan.

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A narrow luminous gas stream links a bright red star on the left to a brown celestial companion on the right against black space.

A close companion loses material gradually

A small red dwarf is drawing material from its orbiting brown dwarf through a slow, steady transfer. The research published on October 5 identifies an alternative to the rapid destruction that can occur when a star consumes a close companion. The objects remain a pair while material moves between them.[1], [2]

The system, designated ZTF J0440+2325, completes an orbit in about 87 minutes. Its receiving star is an M dwarf, a small main-sequence star. Brown dwarfs occupy a different category: they can outweigh planets but cannot maintain the sustained hydrogen fusion of ordinary stars. The observations connect a theoretically possible long-lived transfer with a particular system.[1]

Brightness variations revealed the first system

The authors’ March preprint describes finding the first system through periodic brightness variations in the Zwicky Transient Facility sky survey. Rapid measurements in several colours and spectra from the Keck observatory were used to investigate a hot region on the star. Changes through the orbit were considered alongside physical models, rather than identifying the receiving object from its brightness curve alone. The simplified hot-region models left some features of those curves unexplained.[1]

The second system remains a candidate

The October peer-reviewed publication gives the second system a more cautious classification than the March preprint. ZTF J1444+4820, with an approximately 67-minute period, is a strong candidate for low-mass transfer within a hierarchical triple, in which a close pair belongs to a wider three-object arrangement. It therefore has a different evidential status from the first brown-dwarf system. Transfer potentially lasting billions of years is an interpretation of how such systems evolve; that duration has not been observed directly.[1]

References

  1. News sourceNature AstronomyA brown dwarf transfers material to a star in an 87-minute orbit
    Primary preprintarXivStars stably accreting from substellar objects
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  2. News sourceScientific AmericanAstronomers catch dwarf stars gobbling up their orbiting companions↩
Space and explorationEnergy transition and climate

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