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

Abstract

The CARMENES instrument is searching for periodic radial-velocity (RV) variations of M dwarfs, which are induced by orbiting planets. However, there are other potential sources of such variations, including rotational modulation caused by stellar activity. We aim to investigate four M dwarfs (Ross 318, YZ CMi, TYC 3529-1437-1, and EV Lac) with different activity levels and spectral sub-types. Our goal is to compare the periodicities seen in 22 activity indicators and the stellar RVs, and to examine their stability over time. For each star, we calculated GLS periodograms of pseudo-equivalent widths of chromospheric lines, indices of photospheric bands, the differential line width as a measure of the width of the average photospheric absorption line, the RV, the chromatic index that describes the wavelength dependence of the RV, and CCF parameters. We also calculated periodograms for subsets of the data and compared our results to TESS photometry. We find the rotation periods of all four stars to manifest themselves in the RV and photospheric indicators, particularly the TiO~7050 index, whereas the chromospheric lines show clear signals only at lower activity levels. For EV Lac and TYC 3529-1437-1, we find episodes during which indicators vary with the rotation period, and episodes during which they vary with half the rotation period, similarly to photometric light curves. The changing periodicities reflect the evolution of stellar activity features on the stellar surface. We therefore conclude that our results not only emphasise the importance of carefully analysing indicators complementary to the RV in RV surveys, but they also suggest that it is also useful to search for signals in activity indicators in subsets of the dataset, because an activity signal that is present in the RV may not be visible in the activity indicators all the time, in particular for the most active stars.

arXiv comment8 pages + 9 pages appendix, 5+4 figures, 1+4 tables, accepted for publication in A&A

References in corpus (38)

• The Transiting Exoplanet Survey Satellite
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• No planet for HD 166435
• Spectrum radial velocity analyser (SERVAL). High-precision radial velocities and two alternative spectral indicators
• Large-scale magnetic topologies of mid-M dwarfs
• The rotation and Galactic kinematics of mid M dwarfs in the Solar Neighborhood
• Time-Resolved Properties and Global Trends in dMe Flares from Simultaneous Photometry and Spectra
• The CARMENES search for exoplanets around M dwarfs: High-resolution optical and near-infrared spectroscopy of 324 survey stars
• On the angular momentum evolution of fully-convective stars: rotation periods for field M-dwarfs from the MEarth transit survey
• Magnetic Cycles and Rotation Periods of Late Type Stars from photometric time series
• The CARMENES search for exoplanets around M dwarfs: Different roads to radii and masses of the target stars
• Rotation periods of late-type dwarf stars from time-series high-resolution spectroscopy of chromospheric indicators
• CARMENES input catalogue of M dwarfs. I. Low-resolution spectroscopy with CAFOS
• CARMENES input catalogue of M dwarfs V. Luminosities, colours, and spectral energy distributions
• The CARMENES search for exoplanets around M dwarfs -- Planet occurrence rates from a subsample of 71 stars
• The CARMENES search for exoplanets around M dwarfs. First visual-channel radial-velocity measurements and orbital parameter updates of seven M-dwarf planetary systems
• New periodic variable stars coincident with ROSAT sources discovered using SuperWASP
• Flat-relative optimal extraction. A quick and efficient algorithm for stabilised spectrographs
• The M dwarf planet search programme at the ESO VLT + UVES. A search for terrestrial planets in the habitable zone of M dwarfs
• Radial Velocity Detection of Earth-mass Planets in the Presence of Activity Noise: The Case of Alpha Centauri Bb
• Correcting HIRES radial velocities for small systematic errors
• The CARMENES search for exoplanets around M dwarfs. Activity indicators at visible and near-infrared wavelengths
• CARMENES input catalogue of M dwarfs IV. New rotation periods from photometric time series
• Magnetic fields in M dwarfs from the CARMENES survey
• The CARMENES search for exoplanets around M dwarfs. Radial velocities and activity indicators from cross-correlation functions with weighted binary masks
• HADES RV Programme with HARPS-N at TNG. VII. Rotation and activity of M-Dwarfs from time-series high-resolution spectroscopy of chromospheric indicators
• Starspot distributions on fully convective M dwarfs: implications for radial velocity planet searches
• Precision radial velocities of 15 M5 - M9 dwarfs
• The CARMENES search for exoplanets around M dwarfs: Radial-velocity variations of active stars in visual-channel spectra
• Double-Dipping: A New Relation between Stellar Rotation and Starspot Activity
• Properties of flares and CMEs on EV Lac: Possible erupting filament
• The CARMENES search for exoplanets around M dwarfs. Mapping stellar activity indicators across the M dwarf domain
• Exoplanet Imitators: A test of stellar activity behavior in radial velocity signals
• The CARMENES search for exoplanets around M dwarfs: Convective shift and starspot constraints from chromatic radial velocities
• The CARMENES search for exoplanets around M dwarfs. Period search in H$\alpha$, Na I D, and Ca II IRT lines
• The CARMENES search for exoplanets around M dwarfs: Benchmarking the impact of activity in high-precision radial velocity measurements
• Variability Timescales of H$\alpha$ on Active Mid-to-Late M dwarfs
• Photometric rotation periods for 107 M dwarfs from the APACHE survey

Cited by in corpus (10)

• APO & SMARTS flare star campaign observations I. Blue wing asymmetries in chromospheric lines during mid M dwarf flares from simultaneous spectroscopic and photometric observation data
• The CARMENES search for exoplanets around M dwarfs: Benchmarking the impact of activity in high-precision radial velocity measurements
• TOI-1468: A system of two transiting planets, a super-Earth and a mini-Neptune, on opposite sides of the radius valley
• Universal Scaling Laws for Solar and Stellar Atmospheric Heating: Catalog of Power-law Index between Solar Activity Proxies and Various Spectral Irradiances
• The CARMENES search for exoplanets around M dwarfs. Behaviour of the Paschen lines during flares and quiescence
• The CARMENES search for exoplanets around M dwarfs. Line-by-line sensitivity to activity in M dwarfs
• Exploring the short-term variability of H$\alpha$ and H$\beta$ emissions in a sample of M dwarfs
• A Seven-Day Multi-Wavelength Flare Campaign on AU Mic III: Quiescent and Flaring Properties of the X-ray Spectra and Chromospheric lines
• The CARMENES search for exoplanets around M dwarfs : Understanding the wavelength dependence of radial velocity measurements
• The RoPES project with HARPS and HARPS-N II. A third planet in the multi-planet system HD 176986