A red dwarf is slowly consuming its brown-dwarf companion
MIT astronomers have identified ZTF J0440+2325, a system about 300 light-years away where a red dwarf is drawing material from a closely orbiting brown dwarf. The first observed case of a low-mass star steadily accreting from another low-mass object offers a slower alternative to a star rapidly engulfing its companion.
Bottom line — The brown dwarf transfers about one hundred-thousandth of an Earth mass each year, and the process may continue for billions of years.
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The MIT team found the objects orbit each other every 87 minutes, within a span smaller than the Sun’s diameter.
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The star has about 85 times Jupiter’s mass; the brown dwarf has about 25 times Jupiter’s mass.
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MIT researchers say the material strikes the star directly, rather than forming the disc often seen around accreting black holes.
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The team traced the system’s repeating triangular brightness pattern to a hot spot where the incoming material hits the star, rotating in and out of view.
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SSBCrack News reports a second candidate system, ZTF J1444+4820, with a 67-minute orbit; it may be part of a three-star system.
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The MIT team hopes to find more systems in which a star gradually draws material from a close companion.