Astrophysics, abstract
astro-ph/0608279

From: Krzysztof Gozdziewski [view email]

Date: Mon, 14 Aug 2006 14:41:36 GMT (417kb)

About the extrasolar multi-planet system around HD160691

Authors: Krzysztof Gozdziewski, Andrzej J. Maciejewski, Cezary Migaszewski

Comments: 12 pages (total), 9 figures, 2 tables, submitted to ApJ; the manuscript with full-resolution figures is available from this http URL

We re-analyze the precision radial velocity (RV) observations of HD160691 (mu Ara) by the Anglo-Australian Planet Search Team. The star is supposed to host two Jovian companions (HD160691b, HD160691c) in long-period orbits (about 630 days and 2500 days, respectively) and a hot-Neptune (HD160691d) in about 9 days orbit. We perform a global search for the best fits in the orbital parameters space with a hybrid code employing the genetic algorithm and simplex method. The stability of Keplerian fits is verified with the N-body model of the RV signal that takes into account the dynamical constraints (so called GAMP method). Our analysis reveals a signature of the fourth, yet unknown and unconfirmed, 0.5 Jupiter-mass planet in about 307 days orbit. In overview, the global architecture of the four-planet configuration recalls the Solar system. All companions of HD160691 move in close to circular orbits. The orbits of the two inner Jovian planets are close to the 2:1 mean motion resonance (MMR). The alternative three-planet system involves two Jovian planets in eccentric orbits (with e about 0.3), close to the 4:1 MMR, but it yields a significantly worse fit to the data.

http://arxiv.org/abs/astro-ph/0608279