Planet formation in slightly inclined binary systems

¹ Department of Astronomy, Nanjing University, Nanjing, Jiangsu 210093, China
² Department of Astronomy, University of Florida, Gainesville, FL 32611-2055, USA

^a e-mail: xiejiwei@gmail.com

Abstract

One of the major problems of planet formation in close binary systems, such as α Centauri AB, is the formation of planetary embryos or cores by mutual accretion of km-sized planetesimals. In this contribution, we test the planetesimal accretion in such close binary systems but with small inclinations i_B = 0.1–10° between the binary orbital plane and the gas disk plane. Compared to previous studies (coplanar case with i_B = 0), we find that (1) planetesimal disk is stratified in the vertical direction and planetesimals are redistributed on different orbit groups with respect to their sizes, thus (2) collisions between similar-sized bodies dominate, leading to low dV and favoring planetesimal accretion (3) the planetesimal collision timescale at 1–2 AU is estimated as: T ∼ (1 + 100i_B) × 10³ yrs, where 0 ≤ i_B ≤ 10°. As a conclusion, although planetesimal accretion are much more favored in slightly inclined binary systems, it is significantly less efficient and slowed-down as compared to the single-star case.