2015ApJ...799...16Z

I calculate the spectral energy distributions of accreting circumplanetary disks using atmospheric radiative transfer models. Circumplanetary disks only accreting at 10^–10 M_☉/yr around a 1 M_J planet can be brighter than the planet itself. A moderately accreting circumplanetary disk ({dot}M ∼ 10^–8 M_☉/yr; enough to form a 10 M_Jplanet within 1 Myr) around a 1 M_Jplanet 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 M_Jplanet with a "hot start." To use direct imaging to find the accretion disks around low-mass planets (e.g., 1 M_J) and distinguish them from brown dwarfs or hot high-mass planets, it is crucial to obtain photometry at mid-infrared bands (L', M, N bands) because the emission from circumplanetary disks falls off more slowly toward 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 ({dot}M ≲ 10^–9 M_☉/yr) and lead to magnetospheric accretion, which can provide additional accretion signatures, such as UV/optical excess from the accretion shock and line emission.