A YOUNG PROTOPLANET CANDIDATE EMBEDDED IN THE CIRCUMSTELLAR DISK OF HD 100546

Abstract

We present high-contrast observations of the circumstellar environment of the\nHerbig Ae/Be star HD100546. The final 3.8 micron image reveals an emission\nsource at a projected separation of 0.48"+-0.04" (corresponding to ~47+-4 AU at\na position angle of 8.9+-0.9 degree. The emission appears slightly extended\nwith a point source component with an apparent magnitude of 13.2+-0.4 mag. The\nposition of the source coincides with a local deficit in polarization fraction\nin near-infrared polarimetric imaging data, which probes the surface of the\nwell-studied circumstellar disk of HD100546. This suggests a possible physical\nlink between the emission source and the disk. Assuming a disk inclination of\n~47 degree the de-projected separation of the object is ~68 AU. Assessing the\nlikelihood of various scenarios we favor an interpretation of the available\nhigh-contrast data with a planet in the process of forming. Follow-up\nobservations in the coming years can easily distinguish between the different\npossible scenarios empirically. If confirmed, HD100546 "b" would be a unique\nlaboratory to study the formation process of a new planetary system, with one\ngiant planet currently forming in the disk and a second planet possibly\norbiting in the disk gap at smaller separations.\n