2019ApJ...877L..33C

We present the first observational evidence for a circumplanetary disk (CPD) around the protoplanet PDS 70 b, based on a new spectrum in the K-band acquired with Very Large Telescope/SINFONI. We tested three hypotheses to explain the spectrum: atmospheric emission from the planet with either (1) a single value of extinction, (2) a variable extinction, and (3) a combined atmospheric and CPD model. Goodness-of-fit indicators favor the third option, suggesting that circumplanetary material contributes excess thermal emission-most prominent at λ >= 2.3 µm. Inferred accretion rates (∼10^–7.8-10^–7.3 M_J yr^–1) are compatible with observational constraints based on the Hα and Brγ lines. For the planet, we derive an effective temperature of 1500-1600 K, surface gravity log(g)∼4.0, radius ∼1.6R_J, mass ∼10M_J, and possible thick clouds. Models with variable extinction lead to slightly worse fits. However, the amplitude (ΔA_V >= 3 mag) and timescale of variation (<=years) required for the extinction would also suggest circumplanetary material.