The CARMENES search for exoplanets around M dwarfs. Benchmarking the impact of activity in high-precision radial velocity measurements

DOI: 
10.1051/0004-6361/202141880
Publication date: 
08/07/2022
Main author: 
Jeffers, S. V.
IAA authors: 
Amado, P. J.;Fernández, M.;Rodríguez, E.
Authors: 
Jeffers, S. V.;Barnes, J. R.;Schöfer, P.;Quirrenbach, A.;Zechmeister, M.;Amado, P. J.;Caballero, J. A.;Fernández, M.;Rodríguez, E.;Ribas, I.;Reiners, A.;Cardona Guillén, C.;Cifuentes, C.;Czesla, S.;Hatzes, A. P.;Kürster, M.;Montes, D.;Morales, J. C.;Pedraz, S.;Sadegi, S.
Journal: 
Astronomy and Astrophysics
Publication type: 
Article
Volume: 
663
Pages: 
A27
Abstract: 
Context. Current exoplanet surveys using the radial velocity (RV) technique are targeting M dwarfs because any habitable zone terrestrial-mass planets will induce a high RV and orbit on shorter periods than for more massive stars. One of the main caveats is that M dwarfs show a wide range of activity levels from inactive to very active, which can induce an asymmetry in the line profiles and, consequently, a spurious RV measurement. <BR /> Aims: We aim to benchmark the impact of stellar activity on high-precision RV measurements using regular-cadence CARMENES visible and near-infrared observations of the active M3.5 dwarf <ASTROBJ>EV Lac</ASTROBJ>. <BR /> Methods: We used the newly developed technique of low-resolution Doppler imaging to determine the centre-of-light, or spot-induced RV component, for eight observational epochs. <BR /> Results: We confirm a statistically significant and strong correlation between the independently measured centre-of-light and the chromatic index, which is a measure of the amplitude variation with wavelength of the RVs. We also find circular "closed-loop" relations of several activity indices with RV for a subset of data that covers only several rotation periods. We also investigate the implications of large phase gaps in the periodograms of activity indicators. Finally, by removing the spot-induced RV component we improve the planet-mass sensitivity by a factor of at least three. <BR /> Conclusions: We conclude that for active M stars, a regular-cadence observing strategy is the most efficient way to identify and eliminate sources of correlated noise.
Database: 
ADS
SCOPUS
URL: 
https://ui.adsabs.harvard.edu/#abs/2022A&A...663A..27J/abstract
ADS Bibcode: 
2022A&A...663A..27J
Keywords: 
stars: activity;stars: individual: EV Lac;stars: low-mass;starspots;techniques: radial velocities;stars: magnetic field;Astrophysics - Earth and Planetary Astrophysics;Astrophysics - Solar and Stellar Astrophysics