Astronomers reported the discovery of a new large brown dwarf using the Zwicky Transient Facility (ZTF). The newly discovered object orbits a low-mass star about 80 times larger than Jupiter. The discovery was detailed in an article posted on the preprint server July 28. arXiv.

Brown dwarfs (BDs) are intermediate objects between planets and stars, occupying a mass range between 13 and 80 Jupiter masses (0.012 and 0.076 solar masses). While many brown dwarfs have been discovered to date, these objects orbiting other stars are a rare find.

Recently, a group of astronomers led by Karim El-Badri of the California Institute of Technology (Caltech) found such a rare brown dwarf. While searching for low-mass shaded binaries, they discovered a system called ZTF J2020+5033, consisting of an M-dwarf star and a brown dwarf.

“This paper presents the discovery of a BD in a binary system with a much shorter orbital period than any system discovered to date. The discovery was made possible thanks to the Zwicky Transient Facility (ZTF), which provides high-quality light curves for much dimmer stars. more than any other survey used to detect transitioning BD,” he explained.

The brown dwarf in ZTF J2020+5033 is the size of Jupiter, but has a mass of about 80.1 times that of the Solar System’s largest planet, placing it just below the hydrogen-burning limit at the stellar/substellar boundary. The effective temperature of the object is estimated to be 1691 K.

The star in the system is an M-dwarf of M6 spectral type with a radius of 0.176 solar radii and a mass of 0.134 solar masses. It has been determined that the effective temperature of this star is 2856 K.

According to the research, the binary system is located about 445 light-years from Earth. The system is estimated to be between 5 and 13 billion years old and has an orbital period of just 1.9 hours, making the smaller component the shortest transiting brown dwarf known.

With such a short orbital period, the astronomers noted that ZTF J2020+5033 is much more compact than other known transiting brown dwarf pairs.

“Both components must have been much larger than they are today when they were young, which means that the orbit has shrunk considerably due to magnetic braking. This is a strong indication that, contrary to the common assumption in many models of binary evolution, magnetic braking continues to be effective, at least in some stars, completely below the convective limit. it shows.”

They added that ZTF J2020+5033 is closer than 34 of the other 39 known transitional brown dwarf systems, suggesting that BDs in short-period orbits are not particularly rare. Source