The CARMENES search for exoplanets around M dwarfs: Convective shift and starspot constraints from chromatic radial velocities

Abstract

Context. Variability caused by stellar activity represents a challenge to the discovery and characterization of terrestrial exoplanets and complicates the interpretation of atmospheric planetary signals. Aims. We aim to use a detailed modeling tool to reproduce the effect of active regions on radial velocity measurements, which aids the identification of the key parameters that have an impact on the induced variability. Methods. We analyzed the effect of stellar activity on radial velocities as a function of wavelength by simulating the impact of the properties of spots, shifts induced by convective motions, and rotation. We focused our modeling effort on the active star YZ CMi (GJ 285), which was photometrically and spectroscopically monitored with CARMENES and the Telescopi Joan Oró. Results. We demonstrate that radial velocity curves at different wavelengths yield determinations of key properties of active regions, including spot filling factor, temperature contrast, and location, thus solving the degeneracy between them. Most notably, our model is also sensitive to convective motions. Results indicate a reduced convective shift for M dwarfs when compared to solar-type stars (in agreement with theoretical extrapolations) and points to a small global convective redshift instead of blueshift. Conclusions. Using a novel approach based on simultaneous chromatic radial velocities and light curves, we can set strong constraints on stellar activity, including an elusive parameter such as the net convective motion effect.

A&A, in press

References in corpus (20)

• The Gaia mission
• The Transiting Exoplanet Survey Satellite
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• VOSA: Virtual Observatory SED Analyzer. An application to the Collinder 69 open cluster
• Spectrum radial velocity analyser (SERVAL). High-precision radial velocities and two alternative spectral indicators
• Evolution of low-mass star and brown dwarf eclipsing binaries
• Stellar Activity Masquerading as Planets in the Habitable Zone of the M dwarf Gliese 581
• The First Direct Measurements of Magnetic Fields on Very Low-Mass Stars
• SOAP 2.0: A tool to estimate the photometric and radial velocity variations induced by stellar spots and plages
• Search for exoplanets with the radial-velocity technique: quantitative diagnostics of stellar activity
• The CARMENES search for exoplanets around M dwarfs: Different roads to radii and masses of the target stars
• CARMENES input catalogue of M dwarfs V. Luminosities, colours, and spectral energy distributions
• Accounting for velocity jitter in planet search surveys
• Magnetic fields in M dwarfs from the CARMENES survey
• Stellar activity as noise in exoplanet detection II. Application to M dwarfs
• Comparing different approaches to model the rotational modulation of the Sun as a star
• The HADES RV Programme with HARPS-N@TNG II. Data treatment and simulations
• Stellar Activity and its Implications for Exoplanet Detection on GJ 176
• Variability in stellar granulation and convective blueshift with spectral type and magnetic activity. II. From young to old main-sequence K-G-F stars
• Long-Term Cyclic Variability of YZ CMi in the Context of Solar and Stellar Physics

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• ESPRESSO Mass determination of TOI-263b: An extreme inhabitant of the brown dwarf desert
• The CARMENES search for exoplanets around M dwarfs. Rotational variation in activity indicators of Ross 318, YZ CMi, TYC 3529-1437-1, and EV Lac
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• Non-radial oscillations mimicking a brown dwarf orbiting the cluster giant NGC 4349 No. 127
• Astrometric radial velocities for nearby stars
• The CARMENES search for exoplanets around M dwarfs : Understanding the wavelength dependence of radial velocity measurements
• The SPIRou Legacy Survey: near-infrared and optical radial velocity analysis of Gl 480 and Gl 382 using SPIRou, HARPS and CARMENES spectrographs
• The CARMENES search for exoplanets around M dwarfs. A homogeneous catalogue of projected rotational velocities accounting for limb-darkening
• CARMENES input catalog of M dwarfs VI. A time-resolved Ca II H&K catalog from archival data