New Methods for Finding Activity-Sensitive Spectral Lines: Combined Visual Identification and an Automated Pipeline Find a Set of 40 Activity Indicators

Abstract

Starspots, plages, and activity cycles cause radial velocity variations that can either mimic planets or hide their existence. To verify the authenticity of newly discovered planets, observers may search for periodicity in spectroscopic activity indices such as Ca H & K and H$\alpha$, then mask out any Doppler signals that match the activity period or its harmonics. However, not every spectrograph includes Ca H & K, and redder activity indicators are needed for planet searches around low-mass stars. Here we show how new activity indicators can be identified by correlating spectral line depths with a well-known activity index. We apply our correlation methods to archival HARPS spectra of $\epsilon$ Eri and $\alpha$ Cen B and use the results from both stars to generate a master list of activity-sensitive lines whose core fluxes are periodic at the star's rotation period. Our newly discovered activity indicators can in turn be used as benchmarks to extend the list of known activity-sensitive lines toward the infrared or UV. With recent improvements in spectrograph illumination stabilization, wavelength calibration, and telluric correction, stellar activity is now the biggest noise source in planet searches. Our suite of $>40$ activity-sensitive lines is a first step toward allowing planet hunters to access all the information about spots, plages, and activity cycles contained in each spectrum.

arXiv comment26 pages, 10 figures, accepted to AJ on August 27, 2018

References in corpus (36)

• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• The CORALIE survey for southern extra-solar planets VII. Two short-period Saturnian companions to HD108147 and HD168746
• Planets and Stellar Activity: Hide and Seek in the CoRoT-7 system
• New Grids of ATLAS9 Model Atmospheres
• A Gaussian process framework for modelling stellar activity signals in radial velocity data
• Assessing statistical significance of periodogram peaks
• The HARPS-TERRA project I. Description of the algorithms, performance and new measurements on a few remarkable stars observed by HARPS
• A simple method to estimate radial velocity variations due to stellar activity using photometry
• Using the Sun to estimate Earth-like planets detection capabilities II. Impact of plages
• SOAP 2.0: A tool to estimate the photometric and radial velocity variations induced by stellar spots and plages
• Solar-like oscillations in alpha Centauri B
• The low-level radial velocity variability in Barnard's star (=GJ 699). Secular acceleration, indications for convective redshift, and planet mass limits
• Abundances of refractory elements in the atmospheres of stars with extrasolar planets
• EXPRES: A Next Generation RV Spectrograph in the Search for Earth-like Worlds
• Asteroseismology and calibration of alpha Cen binary system
• H-alpha Activity of Old M Dwarfs: Stellar Cycles and Mean Activity Levels For 93 Low-Mass Stars in the Solar Neighborhood
• Planetary detection limits taking into account stellar noise. II. Effect of stellar spot groups on radial-velocities
• Magnetic Activity Cycles in the Exoplanet Host Star epsilon Eridani
• The HARPS search for southern extra-solar planets. XXXI. Magnetic activity cycles in solar-type stars: statistics and impact on precise radial velocities
• The effect of M dwarf starspot activity on low-mass planet detection thresholds
• Evolution of coexisting long and short period stellar activity cycles
• Stellar activity as noise in exoplanet detection II. Application to M dwarfs
• The Alpha Centauri Binary System: Atmospheric Parameters and Element Abundances
• Precision radial velocities of 15 M5 - M9 dwarfs
• Variability of stellar granulation and convective blueshift with spectral type and magnetic activity. I. K and G main sequence stars
• Empirically Constrained Color-Temperature Relations. II. uvby
• Insights on the Spectral Signatures of Stellar Activity and Planets from PCA
• X-Ray, FUV, and UV Observations of alpha Centauri B: Determination of Long-term Magnetic Activity Cycle and Rotation Period
• Stellar Activity and its Implications for Exoplanet Detection on GJ 176
• The Changing Face of $\alpha$ Centauri B: Probing plage and stellar activity in K-dwarfs
• A new method of correcting radial velocity time series for inhomogeneous convection
• A combined spectroscopic and photometric stellar activity study of Epsilon Eridani
• The Temperature Diagnostic Properties of the MG I 457.1 NM Line
• The Mg I b triplet and the 4571 Å line as diagnostics of stellar chromospheric activity
• Do Long-Lived Features Really Exist in the Solar Photosphere? II. Contrast of Time-Averaged Granulation Images

Cited by in corpus (39)

• Measuring precise radial velocities on individual spectral lines. I. Validation of the method and application to mitigate stellar activity
• Observational constraints on the origin of the elements. I. 3D NLTE formation of Mn lines in late-type stars
• Measuring precise radial velocities on individual spectral lines : II. Dependance of stellar activity signal on line depth
• Separating planetary reflex Doppler shifts from stellar variability in the wavelength domain
• The CARMENES search for exoplanets around M dwarfs. Radial velocities and activity indicators from cross-correlation functions with weighted binary masks
• YARARA: Significant improvement of RV precision through post-processing of spectral time-series
• Diving Beneath the Sea of Stellar Activity: Chromatic Radial Velocities of the Young AU Mic Planetary System
• How magnetic activity alters what we learn from stellar spectra
• RASSINE: Interactive tool for normalising stellar spectra I. Description and performance of the code
• The EXPRES Stellar Signals Project II. State of the Field in Disentangling Photospheric Velocities
• Statistical methods for exoplanet detection with radial velocities
• Decoding the radial velocity variations of HD41248 with ESPRESSO
• Stellar activity correction using PCA decomposition of shells
• Target Prioritization and Observing Strategies for the NEID Earth Twin Survey
• The CARMENES search for exoplanets around M dwarfs: Stable radial-velocity variations at the rotation period of AD~Leonis -- A test case study of current limitations to treating stellar activity
• Modeling the Echelle Spectra Continuum with Alpha Shapes and Local Regression Fitting
• Impact of Correlated Noise on the Mass Precision of Earth-analog Planets in Radial Velocity Surveys
• The spectral impact of magnetic activity on disk-integrated HARPS-N solar observations: exploring new activity indicators
• Rotational modulation of spectroscopic Zeeman signatures in low-mass stars
• 3D magneto-hydrodynamical simulations of stellar convective noise for improved exoplanet detection. I. Case of regularly sampled radial velocity observations
• Magnitude-squared coherence: A powerful tool for disentangling Doppler planet discoveries from stellar activity
• Activity and telluric contamination in HARPS observations of Alpha Centauri B
• The death of Vulcan: NEID reveals the planet candidate orbiting HD 26965 is stellar activity
• Spectral Line Depth Variability in Radial Velocity Spectra
• Into the Depths: a new activity metric for high-precision radial velocity measurements based on line depth variations
• Magnetic activity of red giants: correlation between the amplitude of solar-like oscillations and chromospheric indicators
• The Measured Impact of Chromatic Atmospheric Effects on Barycentric Corrections: Results from the EXtreme PREcision Spectrograph
• The CARMENES search for exoplanets around M dwarfs. Line-by-line sensitivity to activity in M dwarfs
• Solar photospheric spectrum microvariability II. Observed relations to magnetic activity and radial-velocity modulation
• A Stellar Activity F-statistic for Exoplanet Surveys (SAFE)
• Quiet Please: Detrending Radial Velocity Variations from Stellar Activity with a Physically Motivated Spot Model
• Deriving Iodine-free spectra for high-resolution echelle spectrographs
• Exploring the robustness of Keplerian signals to the removal of active and telluric features
• Minimal Data Fidelity for Detection of Stellar Features or Companions
• Revisiting $\epsilon$ Eridani with NEID: Identifying New Activity-Sensitive Lines in a Young K Dwarf Star
• Spectral Ratio Analysis: probing of a new suite of stellar activity indicators as a tool for astrophysical noise mitigation
• Leveraging space-based data from the nearest Solar-type star to better understand stellar activity signatures in radial velocity data
• An Hα Transit of HD 189733b to Assess Stellar Activity Across the Transit Chord Close to JWST Observations
• Spin-Orbit Geometry of AU Mic b and c from Back-to-Back Transits Observed Contemporaneously with Magellan PFS, LCOGT, and CHEOPS