Three spiral arms and a possible giant planet caught at birth

Transition disks offer the extraordinary opportunity to look for newly born planets and investigate the early stages of planet formation. In this poster, we present our observations of the Herbig A5 star MWC 758 with the L'-band vector vortex coronagraph installed in NIRC2, the near-infrared camera of Keck II. Our high-contrast imaging observations show a bright point-like emission, south of MWC 758 at a deprojected separation of ~20 au (r= 0.111''+-0.004'') from the central star. We also recover the two spiral arms previously imaged in polarized light, and discover a third one to the south-west of the star. No additional companions were detected in the system down to 5 Jupiter masses beyond 0.6'' from the star. We propose that the bright L'-band emission could be caused by the presence of an embedded and accreting protoplanet, although the possibility of it being an asymmetric disk feature cannot be excluded. In this poster, we also discuss different possibilities for the origin of the observed spiral structure.