A quarter century of spectroscopic monitoring of the nearby M dwarf Gl 514. A super-Earth on an eccentric orbit moving in and out of the habitable zone

Publication date: 
Main author: 
Damasso, M.
IAA authors: 
Pérez-Torres, M.;Amado, P. J.
Damasso, M.;Perger, M.;Almenara, J. M.;Nardiello, D.;Pérez-Torres, M.;Sozzetti, A.;Hara, N. C.;Quirrenbach, A.;Bonfils, X.;Zapatero Osorio, M. R.;Astudillo-Defru, N.;González Hernández, J. I.;Suárez Mascareno, A.;Amado, P. J.;Forveille, T.;Lillo-Box, J.;Alibert, Y.;Caballero, J. A.;Cifuentes, C.;Delfosse, X.;Figueira, P.;Galadí-Enríquez, D.;Hatzes, A. P.;Henning, Th.;Kaminski, A.;Mayor, M.;Murgas, F.;Montes, D.;Pinamonti, M.;Reiners, A.;Ribas, I.;Béjar, V. J. S.;Schweitzer, A.;Zechmeister, M.
Astronomy and Astrophysics
Publication type: 
Context. Statistical analyses based on Kepler data show that most of the early-type M dwarfs host multi-planet systems consisting of Earth- to sub-Neptune-sized planets with orbital periods of up to ~250 days, and that at least one such planet is likely located within the habitable zone. M dwarfs are therefore primary targets to search for potentially habitable planets in the solar neighbourhood. <BR /> Aims: We investigated the presence of planetary companions around the nearby (7.6 pc) and bright (V = 9 mag) early-type M dwarf Gl 514, analysing 540 radial velocities collected over nearly 25 yr with the HIRES, HARPS, and CARMENES spectrographs. <BR /> Methods: The data are affected by time-correlated signals at the level of 2-3 m s<SUP>−1</SUP> due to stellar activity, which we filtered out, testing three different models based on Gaussian process regression. As a sanity cross-check, we repeated the analyses using HARPS radial velocities extracted with three different algorithms. We used HIRES radial velocities and Hipparcos-Gaia astrometry to put constraints on the presence of long-period companions, and we analysed TESS photometric data. <BR /> Results: We find strong evidence that Gl 514 hosts a super-Earth on a likely eccentric orbit, residing in the conservative habitable zone for nearly 34% of its orbital period. The planet Gl 514b has minimum mass m<SUB>b</SUB> sin i<SUB>b</SUB> = 5.2 ± 0.9 M<SUB>⊕</SUB>, orbital period P<SUB>b</SUB> = 140.43 ± 0.41 days, and eccentricity e<SUB>b</SUB> = 0.45<SUB>−0.14</SUB><SUP>+0.15</SUP>. No evidence for transits is found in the TESS light curve. There is no evidence for a longer period companion in the radial velocities and, based on astrometry, we can rule out a ~0.2 M<SUB>Jup</SUB> planet at a distance of ~3-10 astronomical units, and massive giant planets and brown dwarfs out to several tens of astronomical units. We discuss the possible presence of a second low-mass companion at a shorter distance from the host than Gl 514 b. <BR /> Conclusions: Gl 514 b represents an interesting science case for studying the habitability of planets on eccentric orbits. We advocate for additional spectroscopic follow-up to get more accurate and precise planetary parameters. Further follow-up is also needed to investigate the presence of additional planetary signals of less than 1 m s<SUP>−1</SUP>. <P />Tables A.1-A.4 are only available at the CDS via anonymous ftp to ftp://cdsarc.u-strasbg.fr (<A href=""></A>) or via <A href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/666/A187">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/666/A187</A>
ADS Bibcode: 
techniques: radial velocities;techniques: photometric;planetary systems;stars: activity;stars: individual: Gl 514;Astrophysics - Earth and Planetary Astrophysics