A universal brown dwarf desert formed between planets and stars

Area of Science:

• Astronomy and astrophysics
• Exoplanetary science
• Stellar evolution

Background:

• Giant planets and brown dwarfs bridge the gap between planets and stars, with formation mechanisms requiring further investigation.
• Previous studies lacked comprehensive samples of wide-orbit giant planets and substellar companions, hindering boundary research.
• Radial velocity and astrometry data combined offer a larger, unified sample for analysis.

Purpose of the Study:

• To statistically analyze the occurrence rates of brown dwarfs and giant planets around FGK stars.
• To investigate the formation boundary between planets and stars.
• To test the dual formation hypothesis for substellar objects.

Main Methods:

• Combined analysis of radial velocity and astrometry data.
• Statistical analysis of a sample of 55 giant planets, brown dwarfs, and low-mass stellar companions.
• Population synthesis modeling.

Main Results:

• Identified a distinct brown dwarf desert around 30 Jupiter masses (M_J) with no observed decline up to 20 astronomical units (au).
• Discovered a population of giant planets and low-mass brown dwarfs beyond the water-ice line, contrary to previous predictions.
• Observed metallicity and eccentricity trends suggesting two distinct formation pathways.

Conclusions:

• The findings support the dual formation hypothesis for substellar objects.
• The study refines our understanding of the occurrence rates and formation mechanisms of giant planets and brown dwarfs.
• The identified brown dwarf desert and planetary population beyond the water-ice line provide crucial data for formation models.