A wide planetary-mass companion to a young low-mass brown dwarf in Ophiuchus

Abstract

We present the discovery of a planetary-mass companion to CFHTWIR-Oph 98, a low-mass brown dwarf member of the young Ophiuchus star-forming region, with a wide 200-au separation (1.46 arcsec). The companion was identified using Hubble Space Telescope images, and confirmed to share common proper motion with the primary using archival and new ground-based observations. Based on the very low probability of the components being unrelated Ophiuchus members, we conclude that Oph 98 AB forms a binary system. From our multi-band photometry, we constrain the primary to be an M9-L1 dwarf, and the faint companion to have an L2-L6 spectral type. For a median age of 3 Myr for Ophiuchus, fits of evolutionary models to measured luminosities yield masses of $15.4\pm 0.8$ M${}_{\mathrm{Jup}}$ for Oph 98 A and $7.8\pm 0.8$ M${}_{\mathrm{Jup}}$ for Oph 98 B, with respective effective temperatures of $2320\pm 40$ K and $1800\pm 40$ K. For possible system ages of 1-7 Myr, masses could range from 9.6-18.4 M${}_{\mathrm{Jup}}$ for the primary, and from 4.1-11.6 M${}_{\mathrm{Jup}}$ for the secondary. The low component masses and very large separation make this binary the lowest binding energy system imaged to date, indicating that the outcome of low-mass star formation can result in such extreme, weakly-bound systems. With such a young age, Oph 98 AB extends the growing population of young free-floating planetary-mass objects, offering a new benchmark to refine formation theories at the lowest masses.

Accepted for publication in ApJL. 4 figures, 2 tables

References in corpus (18)

• The Gaia mission
• Direct Imaging of Multiple Planets Orbiting the Star HR 8799
• The Evolution of L and T Dwarfs in Color-Magnitude Diagrams
• Young L Dwarfs Identified in the Field: A Preliminary Low-Gravity, Optical Spectral Sequence from L0 to L5
• The Hawaii Infrared Parallax Program. II. Young Ultracool Field Dwarfs
• Brown dwarf formation by gravitational fragmentation of massive, extended protostellar discs
• The Planetary Mass Companion 2MASS1207-3932 B: Temperature, Mass and Evidence for an Edge-On Disk
• The Solar Neighborhood XXXV: Distances to 1404 M Dwarf Systems Within 25 pc in the Southern Sky
• The Wide Brown Dwarf Binary Oph 1622-2405 and Discovery of A Wide, Low Mass Binary in Ophiuchus (Oph 1623-2402): A New Class of Young Evaporating Wide Binaries?
• Discovery of a wide companion near the deuterium burning mass limit in the Upper Scorpius association
• A Survey for New Members of the Taurus Star-Forming Region with the Sloan Digital Sky Survey
• Brown dwarf disks with ALMA: evidence for truncated dust disks in Ophiuchus
• The Young L Dwarf 2MASS J11193254-1137466 is a Planetary-Mass Binary
• A census of $\rho$ Oph candidate members from Gaia DR2
• A Survey for New Stars and Brown Dwarfs in the Ophiuchus Star-forming Complex
• Discovery of a Low-Luminosity, Tight Substellar Binary at the T/Y Transition
• WISE2150-7520AB: A very low mass, wide co-moving brown dwarf system discovered through the citizen science project Backyard Worlds: Planet 9
• A Novel Survey for Young Substellar Objects with the W-band Filter. I. Filter Design and New Discoveries in Ophiuchus and Perseus

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• A giant planet transiting a 3-Myr protostar with a misaligned disk
• A scaled-up planetary system around a supernova progenitor
• The JWST/NIRISS Deep Spectroscopic Survey for Young Brown Dwarfs and Free-Floating Planets
• TOI-1696 and TOI-2136: Constraining the Masses of Two Mini-Neptunes with HPF
• Formation of free-floating planetary mass objects via circumstellar disk encounters
• A Novel Survey for Young Substellar Objects with the W-band filter III: Searching for very low mass brown dwarfs in Serpens South and Serpens Core
• Lost in space: companions' fatal dance around massive dying stars
• NICMOS Kernel-Phase Interferometry II: Demographics of Nearby Brown Dwarfs
• On the survivability of a population of gas giant planets on wide orbits
• Keck Observations in the INfrared of Taurus and $\rho$ Oph Exoplanets And Ultracool dwarfs (KOINTREAU) II: Two Young Bound Companions to Ophiuchus Stars
• The Perkins INfrared Exosatellite Survey (PINES) I. Survey Overview, Reduction Pipeline, and Early Results