Unveiling the nature of the protoplanet PDS70 b

Unveiling the nature of the protoplanet PDS70 b

Two main families of models (the so-called “cold-start” and “hot-start” models) describe the formation process of gas giant planets, and they differ primarily in the amount of entropy retained by the planet at the end of its formation. The initial entropy is a key quantity that has a large impact on many other planet parameters like temperature and radius. After ~100 Myr the model predictions for radius and temperature converge and it is no longer possible to reconstruct the formation history of planets at these ages. Hence, it is crucial to identify and characterize young companions in the first phase of their life. In this context, one of the most promising systems is PDS70, which is hosting at least two companions in the gap of its transitional disk. The two protoplanetary candidates show H-alpha emission, a sign of ongoing accretion, indicating that they are still in the formation phase. In this talk, I will present new results on the protoplanetary candidate PDS70 b obtained with the SINFONI medium resolution spectrograph at the VLT. Based on new R~5000 K-band spectra we applied molecular mapping to identify molecular species in the environment of the object, determine their relative abundances, and put strong constraints on key atmospheric parameters like temperature and surface gravity. Also, we performed a comprehensive analysis of the SED of the companion, including two new photometric points at 4.05 and 4.8 microns, revealing new insights on the nature of the companion and its possible surroundings. The comparison and the combination of molecular mapping and SED fitting provides a unique opportunity to empirically study the formation of planetary systems and to evaluate the available planet formation theories.

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