Evidence for a Circumplanetary Disk around Protoplanet PDS 70 b

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 MJ 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 $\mathrm{log}(g)\sim 4.0$, radius ∼1.6RJ, mass ∼10MJ, and possible thick clouds. Models with variable extinction lead to slightly worse fits. However, the amplitude (ΔAV ≳ 3 mag) and timescale of variation (≲years) required for the extinction would also suggest circumplanetary material.