ZTF Finds 57‑Minute Mass‑Transferring Brown Dwarf Binary
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- ZTF identified a new binary system of two brown dwarfs, ZTF J1239+8347, located about 1,100 light‑years away, via its variability survey.
- The binary comprises two brown dwarfs each 60–80 Jupiter masses, orbiting every 57.41 minutes, and is undergoing stable mass transfer.
- The accretor has a radius of ~1.2 Jupiter radii and an atmospheric temperature near 1,500 K, while the donor is estimated at 0.9–1.4 Jupiter radii and <1,200 K.
- Optical observations reveal extremely high‑amplitude variability at short wavelengths, suggesting a buried hotspot on the accretor’s atmosphere.
- Near‑ and mid‑infrared data show the accretion luminosity is low enough that thermal emission from the brown dwarf atmospheres dominates the spectrum.
- The authors recommend JWST follow‑up to refine the accretor’s temperature, detect the donor’s atmosphere, and directly measure the system’s mass ratio, which ground‑based near‑IR spectra cannot resolve.
Why it matters: The system offers astronomers a uniquely observable case of stable mass transfer between brown dwarfs, enabling direct measurement of temperatures, radii, and mass ratios that can validate substellar evolution models and accretion physics, while JWST follow‑up could finally resolve the donor’s atmosphere.
