Discovery of a companion candidate in the HD 169142 transition disk and the possibility of multiple planet formation

We present L′- and J-band high-contrast observations of HD 169142, obtained with the Very Large Telescope/NACO AGPM vector vortex coronagraph and the Gemini Planet Imager, respectively. A source located at 0.″156 ± 0.″032 north of the host star (P.A. = 7.°4 ± 11.°3) appears in the final reduced L′ image. At the distance of the star (145 pc), this angular separation corresponds to a physical separation of 22.7 ± 4.7 AU, locating the source within the recently resolved inner cavity of the transition disk. The source has a brightness of L′ = 12.2 ± 0.5 mag, whereas it is not detected in the J band (J >13.8 mag). If its L′ brightness arose solely from the photosphere of a companion and given the J-L′ color constraints, it would correspond to a 28-32 M Jupiter object at the age of the star, according to the COND models. Ongoing accretion activity of the star suggests, however, that gas is left in the inner disk cavity from which the companion could also be accreting. In this case, the object could be lower in mass and its luminosity enhanced by the accretion process and by a circumplanetary disk. A lower-mass object is more consistent with the observed cavity width. Finally, the observations enable us to place an upper limit on the L′-band flux of a second companion candidate orbiting in the disk annular gap at 50 AU, as suggested by millimeter observations. If the second companion is also confirmed, HD 169142 might be forming a planetary system, with at least two companions opening gaps and possibly interacting with each other.