LBT observations of the HR 8799 planetary system⋆
First detection of HR 8799e in H band
INAF – Osservatorio Astrofisico di Arcetri L.go E. Fermi 5,
2 INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
3 Steward Observatory, Department of Astronomy, University of Arizona, Tucson, AZ 85721, USA
4 INAF – Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
5 Dipartimento di Fisica e Astronomia – Universitá di Padova, via Marzolo 8, Padova, Italy
6 LBT Observatory, Univ. of Arizona, 933 North Cherry Ave., Tucson, AZ 85721, USA
7 INAF – Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monteporzio ( RM), Italy
8 Minnesota Institute of Astrophysics, University of Minnesota, Minneapolis, MN 5455, USA
Accepted: 1 August 2012
We have performed H and KS band observations of the planetary system around HR 8799 using the new AO system at the Large Binocular Telescope and the PISCES Camera. The excellent instrument performance (Strehl ratios up to 80% in H band) enabled the detection of the innermost planet, HR 8799e, at H band for the first time. The H and KS magnitudes of HR 8799e are similar to those of planets c and d, with planet e being slightly brighter. Therefore, HR 8799e is likely slightly more massive than c and d. We also explored possible orbital configurations and their orbital stability. We confirm that the orbits of planets b, c and e are consistent with being circular and coplanar; planet d should have either an orbital eccentricity of about 0.1 or be non-coplanar with respect to b and c. Planet e can not be in circular and coplanar orbit in a 4:2:1 mean motion resonances with c and d, while coplanar and circular orbits are allowed for a 5:2 resonance. The analysis of dynamical stability shows that the system is highly unstable or chaotic when planetary masses of about 5 MJ for b and 7 MJ for the other planets are adopted. Significant regions of dynamical stability for timescales of tens of Myr are found when adopting planetary masses of about 3.5, 5, 5, and 5 MJ for HR 8799b, c, d, and e respectively. These masses are below the current estimates based on the stellar age (30 Myr) and theoretical models of substellar objects.
Key words: stars: individual: HR 8799 / planetary systems / instrumentation: adaptive optics / techniques: high angular resolution / planets and satellites: dynamical evolution and stability / planets and satellites: physical evolution
The LBT is an international collaboration among institutions in the United States, Italy and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona university system; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, the Astrophysical Institute Potsdam, and Heidelberg University; The Ohio State University, and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota and University of Virginia.
© ESO, 2012