We investigate the formation of double-peaked asymmetric line profiles of CO in the fundamental band spectra emitted by young ( 1 \textrm { - - } 5 Myr ) protoplanetary disks hosted by a 0.5 \textrm { - - } 2 M _ { \odot } star .
Distortions of the line profiles can be caused by the gravitational perturbation of an embedded giant planet with q = 4.7 \times 10 ^ { -3 } stellar-to-planet mass ratio .
Locally isothermal , two-dimensional hydrodynamic simulations show that the disk becomes globally eccentric inside the planetary orbit with stationary \sim 0.2 \textrm { - - } 0.25 average eccentricity after \sim 2000 orbital periods .
For orbital distances 1 \textrm { - - } 10 AU , the disk eccentricity is peaked inside the region where the fundamental band of CO is thermally excited .
Hence , these lines become sensitive indicators of the embedded planet via their asymmetries ( both in flux and wavelength ) .
We find that the line shape distortions ( e.g. , distance , central dip , asymmetry , and positions of peaks ) of a given transition depend on the excitation energy ( i.e. , on the rotational quantum number J ) .
The magnitude of line asymmetry is increasing/decreasing with J if the planet orbits inside/outside the CO excitation zone ( R _ { \mathrm { CO } } \leq 3 , 5 and 7 AU for a 0.5 , 1 , and 2 M _ { \odot } star , respectively ) , thus one can constrain the orbital distance of a giant planet by determining the slope of the peak asymmetry– J profile .
We conclude that the presented spectroscopic phenomenon can be used to test the predictions of planet formation theories by pushing the age limits for detecting the youngest planetary systems .