Direct detection and orbital analysis of the exoplanets HR8799bcd from archival 2005 KECK/NIRC2 data

Abstract

We present previously unpublished 2005 July H-band coronagraphic data of the young, planet-hosting star HR8799from the newly released Keck/NIRC2 archive. Despite poor observing conditions, we detect three of the planets (HR8799bcd), two of them (HR8799bc) without advanced image processing. Comparing these data with previously published 1998-2011 astrometry and that from re-reduced 2010 October Keck data constrains the orbits of the planets. Analyzing the planets' astrometry separately, HR8799d's orbit is likely inclined at least 25° from face-on and the others may be on inclined orbits. For semimajor axis ratios consistent with a 4:2:1 mean-motion resonance, our analysis yields precise values for HR8799bcd's orbital parameters and strictly constrains the planets' eccentricities to be less than 0.18-0.3. However, we find no acceptable orbital solutions with this resonance that place the planets in face-on orbits; HR8799d shows the largest deviation from such orbits. Moreover, few orbits make HR8799d coplanar with b and c, whereas dynamical stability analyses used to constrain the planets' masses typically assume coplanar and/or face-on orbits. This Letter illustrates the significant science gain enabled with the release of the NIRC2 archive. © © 2012. The American Astronomical Society. All rights reserved.