The origins of the substellar companion to GQ Lupi

Department of Astronomy & Astrophysics, Pennsylvania State University, University Park, PA 16802, USA e-mail: debes@astro.psu.edu

Received: 3 January 2006
Accepted: 2 February 2006

Abstract

The recently discovered substellar companion to GQ Lup possibly represents a direct test of current planet formation theories. We examine the possible formation scenarios for the companion to GQ Lup assuming it is a ~2 M_Jup object. We determine that GQ Lup B most likely was scattered into a large, eccentric orbit by an interaction with another planet in the inner system. If this is the case, several directly observable predictions can be made, including the presence of a more massive, secondary companion that could be detected through astrometry, radial velocity measurements, or sculpting in GQ Lup's circumstellar disk. This scenario requires a highly eccentric orbit for the companion already detected. These predictions can be tested within the next decade or so. Additionally, we look at scenarios of formation if the companion is a brown dwarf. One possible formation scenario may involve an interaction between a brown dwarf binary and GQ Lup. We look for evidence of any brown dwarfs that have been ejected from the GQ Lup system by searching the 2MASS all-sky survey.