Confirmation and characterization of the protoplanet HD100546 b - Direct   evidence for gas giant planet formation at 50 au
  We present the first multi-wavelength, high-contrast imaging study confirming the protoplanet embedded in the disk around the Herbig Ae/Be star HD100546. The object is detected at $L'$ ($\sim 3.8\,\mu m$) and $M'$ ($\sim 4.8\,\mu m$), but not at $K_s$ ($\sim 2.1\,\mu m$), and the emission consists of a point source component surrounded by spatially resolved emission. For the point source component we derive apparent magnitudes of $L'=13.92\pm0.10$ mag, $M'=13.33\pm0.16$ mag, and $K_s>15.43\pm0.11$ mag (3$\sigma$ limit), and a separation and position angle of $(0.457\pm0.014)"$ and $(8.4\pm1.4)^\circ$, and $(0.472\pm0.014)"$ and $(9.2\pm1.4)^\circ$ in $L'$ and $M'$, respectively. We demonstrate that the object is co-moving with HD100546 and can reject any (sub-)stellar fore-/background object. Fitting a single temperature blackbody to the observed fluxes of the point source component yields an effective temperature of $T_{eff}=932^{+193}_{-202}$ K and a radius for the emitting area of $R=6.9^{+2.7}_{-2.9}$ R$_{\rm Jupiter}$. The best-fit luminosity is $L=(2.3^{+0.6}_{-0.4})\cdot 10^{-4}\,L_{\rm Sun}$. We quantitatively compare our findings with predictions from evolutionary and atmospheric models for young, gas giant planets, discuss the possible existence of a warm, circumplanetary disk, and note that the de-projected physical separation from the host star of $(53\pm2)$ au poses a challenge standard planet formation theories. Considering the suspected existence of an additional planet orbiting at $\sim$13--14 au, HD100546 appears to be an unprecedented laboratory to study the formation of multiple gas giant planets empirically. 
Sascha P. Quanz (1), Adam Amara (1), Michael R. Meyer (1), Julien H.   Girard (2), Matthew A. Kenworthy (3), Markus Kasper (...
astro-ph.SR astro-ph.EP