ALMA Discovery of a Disk around the Planetary-mass Companion SR 12 c

• Published in: Astrophysical journal. Letters Vol. 930; no. 1; p. L3
• Main Authors: Wu, Ya-Lin, Bowler, Brendan P., Sheehan, Patrick D., Close, Laird M., Eisner, Joshua A., Best, William M. J., Ward-Duong, Kimberly, Zhu, Zhaohuan, Kraus, Adam L.
• Format: Journal Article
• Language: English
• Published: Austin The American Astronomical Society 01-05-2022; IOP Publishing
• Subjects: Accretion; Accretion disks; Dust; Dust emission; Extrasolar gaseous giant planets; Extrasolar planets; Flux density; Radio continuum emission; Radio interferometry; Radio telescopes
• ISSN: 2041-8205; 2041-8213
• DOI: 10.3847/2041-8213/ac6420

Abstract
We report an Atacama Large Millimeter/submillimeter Array 0.88 mm (Band 7) continuum detection of the accretion disk around SR 12 c, an ∼11
M
Jup
planetary-mass companion (PMC) orbiting its host binary at 980 au. This is the first submillimeter detection of a circumplanetary disk around a wide PMC. The disk has a flux density of 127 ± 14
μ
Jy and is not resolved by the ∼0.″1 beam, so the dust disk radius is likely less than 5 au and can be much smaller if the dust continuum is optically thick. If, however, the dust emission is optically thin, then the SR 12 c disk has a comparable dust mass to the circumplanetary disk around PDS 70 c but is about five times lower than that of the ∼12
M
Jup
free-floating OTS 44. This suggests that disks around bound and unbound planetary-mass objects can span a wide range of masses. The gas mass estimated with an accretion rate of 10
−11
M
☉
yr
−1
implies a gas-to-dust ratio higher than 100. If cloud absorption is not significant, a nondetection of
12
CO(3–2) implies a compact gas disk around SR 12 c. Future sensitive observations may detect more PMC disks at 0.88 mm flux densities of ≲100
μ
Jy.