Astrophysical Journal Letters
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 μJy 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 12CO(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 μJy.
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© 2022. The Author(s)
Wu, Ya Lin; Bowler, Brendan P.; Sheehan, Patrick D.; Close, Laird M.; Eisner, Joshua A.; Best, William M.J.; Ward-Duong, Kimberly; Zhu, Zhaohuan; and Kraus, Adam L., "ALMA Discovery of a Disk around the Planetary-Mass Companion Sr 12 C" (2022). Astronomy: Faculty Publications, Smith College, Northampton, MA.