Signatures of Circum PLANETARY Disks

Accreting Circumplanetary Disks. I. Observational Signatures

Author:

Zhu

Abstract:

I calculate the spectral energy distributions (SEDs) of accreting circumplanetary disks using atmospheric radiative transfer models. Circumplanetary disks only accreting at 10−10M⊙yr−1 around a 1 MJ planet can be brighter than the planet itself. A moderately accreting circumplanetary disk (M˙∼10−8M⊙yr−1; enough to form a 10 MJ planet within 1 Myr) around a 1 MJ planet has a maximum temperature of ∼2000 K, and at near-infrared wavelengths (J, H, K bands), this disk is as bright as a late M-type brown dwarf or a 10 MJ planet with a "hot start". To distinguish the accretion disks around low mass planets (e.g., 1 MJ) from brown dwarfs or hot high mass planets, it is crucial to obtain photometry at mid-infrared bands (L′, M, N bands) because disk SEDs fall off more slowly at longer wavelengths than those of brown dwarfs or planets. If young planets have strong magnetic fields (≳100 G), fields may truncate slowly accreting circumplanetary disks (M˙≲10−9M⊙yr−1) and lead to magnetospheric accretion, which can provide additional accretion signatures, such as UV/optical excess from the accretion shock and line emission.