The CARMENES search for exoplanets around M dwarfs. Detection of a mini-Neptune around LSPM J2116+0234 and refinement of orbital parameters of a super-Earth around GJ 686 (BD+18 3421)

DOI: 
10.1051/0004-6361/201935534
Publication date : 
11/07/2019
Main author: 
Lalitha, S.
IAA authors: 
Bauer, F. F.; Amado, P. J.; López-González, M. J.; Rodríguez, E.; Rodríguez-López, C.
Authors: 
Lalitha, S.; Baroch, D.; Morales, J. C.; Passegger, V. M.; Bauer, F. F.; Cardona Guillén, C.; Dreizler, S.; Oshagh, M.; Reiners, A.; Ribas, I.; Caballero, J. A.; Quirrenbach, A.; Amado, P. J.; Béjar, V. J. S.; Colomé, J.; Cortés-Contreras, M.; Galadí-Enríquez, D.; González-Cuesta, L.; Guenther, E. W.; Hagen, H. -J. Henning, T.; Herrero, E.; Husser, T. -O.; Jeffers, S. V.; Kaminski, A.; Kürster, M.; Lafarga, M.; Lodieu, N.; López-González, M. J.; Montes, D.; Perger, M.; Rosich, A.; Rodríguez, E.; Rodríguez-López, C.; Schmitt, J. H. M. M.; Tal-Or, L.; Zechmeister, M.
Journal: 
ASTRONOMY & ASTROPHYSICS
Refereed: 
Yes
Publication type: 
Article
Volume: 
627
Pages: 
21 pp.
Number: 
A116
Abstract: 
Although M dwarfs are known for high levels of stellar activity, they are ideal targets for the search of low-mass exoplanets with the radial velocity (RV) method. We report the discovery of a planetary-mass companion around LSPM J2116+0234 (M3.0 V) and confirm the existence of a planet orbiting GJ 686 (BD+18 3421; M1.0 V). The discovery of the planet around LSPM J2116+0234 is based on CARMENES RV observations in the visual and near-infrared channels. We confirm the planet orbiting around GJ 686 by analyzing the RV data spanning over two decades of observationsfrom CARMENES VIS, HARPS-N, HARPS, and HIRES. We find planetary signals at 14.44 and 15.53 d in the RV data for LSPM J2116+0234 and GJ 686, respectively. Additionally, the RV, photometric time series, and various spectroscopic indicators show hints of variations of 42 d for LSPM J2116+0234 and 37 d for GJ 686, which we attribute to the stellar rotation periods. The orbital parameters of the planets are modeled with Keplerian fits together with correlated noise from the stellar activity. A mini-Neptune with a minimum mass of 11.8 M⊕ orbits LSPM J2116+0234 producing a RV semi-amplitude of 6.19 m s-1, while a super-Earth of mass 6.6 M⊕ orbits GJ 686 and produces a RV semi-amplitude of 3.0 m s-1. Both LSPM J2116+0234 and GJ 686 have planetary companions populating the regime of exoplanets with masses lower than 15 M⊕ and orbital periods <20 d.
Database: 
ADS
URL: 
https://www.aanda.org/articles/aa/full_html/2019/07/aa35534-19/aa35534-19.html
ADS Bibcode: 
2019A&A...627A.116L
Keywords: 
stars: individual: LSPM J2116+0234 / stars: individual: GJ 686 / stars: low-mass / techniques: radial velocities / planetary systems / stars: activity