The CARMENES search for exoplanets around M dwarfs. Dynamical characterization of the multiple planet system GJ 1148 and prospects of habitable exomoons around GJ 1148 b

Publication date: 
Main author: 
Trifonov, T.
IAA authors: 
Bauer, F. F.;Amado, P. J.;Rodríguez-López, C.
Trifonov, T.;Lee, M. H.;Kürster, M.;Henning, Th.;Grishin, E.;Stock, S.;Tjoa, J.;Caballero, J. A.;Wong, K. H.;Bauer, F. F.;Quirrenbach, A.;Zechmeister, M.;Ribas, I.;Reffert, S.;Reiners, A.;Amado, P. J.;Kossakowski, D.;Azzaro, M.;Béjar, V. J. S.;Cortés-Contreras, M.;Dreizler, S.;Hatzes, A. P.;Jeffers, S. V.;Kaminski, A.;Lafarga, M.;Montes, D.;Morales, J. C.;Pavlov, A.;Rodríguez-López, C.;Schmitt, J. H. M. M.;Solano, E.;Barnes, R.
Astronomy and Astrophysics
Publication type: 
Context. GJ 1148 is an M-dwarf star hosting a planetary system composed of two Saturn-mass planets in eccentric orbits with periods of 41.38 and 532.02 days. <BR /> Aims: We reanalyze the orbital configuration and dynamics of the GJ 1148 multi-planetary system based on new precise radial velocity measurements taken with CARMENES. <BR /> Methods: We combined new and archival precise Doppler measurements from CARMENES with those available from HIRES for GJ 1148 and modeled these data with a self-consistent dynamical model. We studied the orbital dynamics of the system using the secular theory and direct N-body integrations. The prospects of potentially habitable moons around GJ 1148 b were examined. <BR /> Results: The refined dynamical analyses show that the GJ 1148 system is long-term stable in a large phase-space of orbital parameters with an orbital configuration suggesting apsidal alignment, but not in any particular high-order mean-motion resonant commensurability. GJ 1148 b orbits inside the optimistic habitable zone (HZ). We find only a narrow stability region around the planet where exomoons can exist. However, in this stable region exomoons exhibit quick orbital decay due to tidal interaction with the planet. <BR /> Conclusions: The GJ 1148 planetary system is a very rare M-dwarf planetary system consisting of a pair of gas giants, the inner of which resides in the HZ. We conclude that habitable exomoons around GJ 1148 b are very unlikely to exist.
ADS Bibcode: 
planetary systems;stars: general;stars: late-type;planets and satellites: dynamical evolution and stability;stars: low-mass;Astrophysics - Earth and Planetary Astrophysics;Astrophysics - Solar and Stellar Astrophysics