2025/06/17 by Bouy, H., Duchêne, G., Strampelli, G. +11
#Astrophysics of Galaxies (astro-ph.GA) #Earth and Planetary Astrophysics (astro-ph.EP) #FOS: Physical sciences #Solar and Stellar Astrophysics (astro-ph.SR)
paper · doi:10.48550/arxiv.2506.14380
Free-floating planetary mass objects-worlds that roam interstellar space untethered to a parent star-challenge conventional notions of planetary formation and migration, but also of star and brown dwarf formation. We focus on the multiplicity among free-floating planets. By virtue of their low binding energy (compared to other objects formed in these environments), these low-mass substellar binaries represent a most sensitive probe of the mechanisms at play during the star formation process. We use the Hubble Space Telescope and its Wide Field Camera 3 and the Very Large Telescope and its ERIS adaptive optics facility to search for visual companions among a sample of 77 objects members of the Upper Scorpius and Taurus young nearby associations with estimated masses in the range between approximately 5-33 M\rm Jup. We report the discovery of one companion candidate around a Taurus member with a separation of 111.9±0.4 mas, or ∼18 au assuming a distance of 160pc, with an estimated primary mass in the range between 3-6 M\rm Jup and a secondary mass between 2.6-5.2 M\rm Jup, depending on the assumed age. This corresponds to an overall binary fraction of 1.8+2.6-1.3% among free-floating planetary mass objects over the separation range ≥7 au. Despite the limitations of small-number statistics and variations in spatial resolution and sensitivity, our results, combined with previous high-spatial-resolution surveys, suggest a notable difference in the multiplicity properties of objects below ∼25 M\rm Jup between Upper Sco and Taurus. In Taurus, five companions were identified among 78 observed objects (4.9+2.8-2.0%), whereas none were found among 97 objects in Upper Sco (≤1.2%).