Astronomers have conducted high-resolution spectroscopic observations of the brown dwarf HD 206893 B, revealing significant details about its nature and properties. The findings were presented on January 23 on the arXiv pre-print server.
Brown dwarfs, which are intermediate objects between planets and stars, range from 13 to 80 Jupiter masses. HD 206893 B is a substellar companion to the star HD 206893, located approximately 133 light-years away. This star, classified as F5V, is about 40% larger and 24% more massive than the Sun, with an effective temperature of 6,680 K and an estimated age of 1.1 billion years.
HD 206893 hosts two exoplanets and a circumstellar debris disk extending from about 30 to 180 AU. HD 206893 B, estimated to be 26 times more massive than Jupiter, resides within this debris disk. Previous studies suggest that the gravity of HD 206893 B may influence the disk's inner edge.
Led by Ben Sappey from the University of California, San Diego, the team utilized the Keck Planet Imager and Characterizer (KPIC) to observe HD 206893 B at high spectral resolution. They inferred the brown dwarf's atmospheric parameters and radial velocity through a Bayesian framework.
The observations revealed that HD 206893 B has a radius of approximately 1.11 Jupiter radii and a mass of about 22.7 Jupiter masses, with an effective temperature of 1,634 K. The atmospheric carbon-to-oxygen (C/O) ratio was calculated to be 0.57, close to the solar value, indicating a possible core accretion or disk fragmentation scenario for its formation.
HD 206893 B orbits its host star at a distance of approximately 11.62 AU, suggesting it was likely not formed through disk fragmentation, which typically occurs at greater distances. The researchers recommend further investigation using the Near Infrared Spectrograph (NIRSpec) on the James Webb Space Telescope (JWST) to obtain additional data on the carbon-to-sulfur (C/S) ratio, which could provide more insight into its formation.