The CARMENES search for exoplanets around M dwarfs. Two Saturn-mass planets orbiting active stars

DOI: 
10.1051/0004-6361/202142915
Publication date: 
08/07/2022
Main author: 
Quirrenbach, A.
IAA authors: 
Amado, P. J.;Aceituno, J.;López-González, M. J.;Rodríguez, E.;López, C. Rodríguez
Authors: 
Quirrenbach, A.;Passegger, V. M.;Trifonov, T.;Amado, P. J.;Caballero, J. A.;Reiners, A.;Ribas, I.;Aceituno, J.;Béjar, V. J. S.;Chaturvedi, P.;González-Cuesta, L.;Henning, T.;Herrero, E.;Kaminski, A.;Kürster, M.;Lalitha, S.;Lodieu, N.;López-González, M. J.;Montes, D.;Pallé, E.;Perger, M.;Pollacco, D.;Reffert, S.;Rodríguez, E.;López, C. Rodríguez;Shan, Y.;Tal-Or, L.;Osorio, M. R. Zapatero;Zechmeister, M.
Journal: 
Astronomy and Astrophysics
Refereed: 
Yes
Publication type: 
Article
Volume: 
663
Pages: 
A48
Abstract: 
The CARMENES radial-velocity survey is currently searching for planets in a sample of 387 M dwarfs. Here we report on two Saturn-mass planets orbiting TYC 2187-512-1 (M<SUB>*</SUB> = 0.50 M<SUB>⊙</SUB>) and TZ Ari (M<SUB>*</SUB> = 0.15 M<SUB>⊙</SUB>), respectively. We obtained supplementary photometric time series, which we use along with spectroscopic information to determine the rotation periods of the two stars. In both cases, the radial velocities also show strong modulations at the respective rotation period. We thus modeled the radial velocities as a Keplerian orbit plus a Gaussian process representing the stellar variability. TYC 2187-512-1 is found to harbor a planet with a minimum mass of 0.33 M<SUB>Jup</SUB> in a near-circular 692-day orbit. The companion of TZ Ari has a minimum mass of 0.21 M<SUB>Jup</SUB>, orbital period of 771 d, and orbital eccentricity of 0.46. We provide an overview of all known giant planets in the CARMENES sample, from which we infer an occurrence rate of giant planets orbiting M dwarfs with periods up to 2 yr in the range between 2 and 6%. TZ Ari b is only the second giant planet discovered orbiting a host with mass less than 0.3 M<SUB>⊙</SUB>. These objects occupy an extreme location in the planet mass versus host mass plane. It is difficult to explain their formation in core-accretion scenarios, so they may possibly have been formed through a disk fragmentation process. <P />The CARMENES radial-velocity data are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr">cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/663/A48">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/663/A48</A>
Database: 
ADS
SCOPUS
URL: 
https://ui.adsabs.harvard.edu/#abs/2022A&A...663A..48Q/abstract
ADS Bibcode: 
2022A&A...663A..48Q
Keywords: 
planets and satellites: detection;planets and satellites: formation;stars: individual: TZ Ari;stars: individual: TYC 2187-512-1;stars: low-mass;techniques: radial velocities;Astrophysics - Earth and Planetary Astrophysics;Astrophysics - Solar and Stellar Astrophysics