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

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.
Bibliographical reference

Astronomy and Astrophysics

Advertised on:
6
2020
Number of authors
32
IAC number of authors
1
Citations
21
Refereed citations
20
Description
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.
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.
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.
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.
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.
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