Stellar Surface Magneto-Convection as a Source of Astrophysical Noise. I. Multi-component Parameterisation of Absorption Line Profiles

Abstract

We outline our techniques to characterise photospheric granulation as an astrophysical noise source. A four component parameterisation of granulation is developed that can be used to reconstruct stellar line asymmetries and radial velocity shifts due to photospheric convective motions. The four components are made up of absorption line profiles calculated for granules, magnetic intergranular lanes, non-magnetic intergranular lanes, and magnetic bright points at disc centre. These components are constructed by averaging Fe I $6302\mathring{\mathrm{A}}$ magnetically sensitive absorption line profiles output from detailed radiative transport calculations of the solar photosphere. Each of the four categories adopted are based on magnetic field and continuum intensity limits determined from examining three-dimensional magnetohydrodynamic simulations with an average magnetic flux of $200\mathrm{G}$. Using these four component line profiles we accurately reconstruct granulation profiles, produced from modelling 12 x 12 Mm${}^2$ areas on the solar surface, to within $\sim \pm$ 20 cm s${}^{-1}$ on a $\sim$ 100 m s${}^{-1}$ granulation signal. We have also successfully reconstructed granulation profiles from a $50\mathrm{G}$ simulation using the parameterised line profiles from the $200\mathrm{G}$ average magnetic field simulation. This test demonstrates applicability of the characterisation to a range of magnetic stellar activity levels.

8 pages, 9 figures, 1 table, accepted to ApJ

References in corpus (6)

• A solar surface dynamo
• A simple method to estimate radial velocity variations due to stellar activity using photometry
• The HARPS search for Earth-like planets in the habitable zone: I -- Very low-mass planets around HD20794, HD85512 and HD192310
• 'Ultimate' Information Content in Solar and Stellar Spectra: Photospheric line asymmetries and wavelength shifts
• Stokes diagnostics of simulated solar magneto-convection
• Stellar jitter from variable gravitational redshift: implications for RV confirmation of habitable exoplanets

Cited by in corpus (27)

• Measuring precise radial velocities on individual spectral lines. I. Validation of the method and application to mitigate stellar activity
• Three years of Sun-as-a-star radial-velocity observations on the approach to solar minimum
• Using the Sun to estimate Earth-like planets detection capabilities. V. Parameterizing the impact of solar activity components on radial velocities
• Ellerman Bombs - Evidence for Magnetic Reconnection in the Lower Solar Atmosphere
• Radial Velocity Fitting Challenge. I. Simulating the data set including realistic stellar radial-velocity signals
• Stellar Surface Magneto-Convection as a Source of Astrophysical Noise II. Center-to-Limb Parameterisation of Absorption Line Profiles and Comparison to Observations
• Modelling the Rossiter-McLaughlin Effect: Impact of the Convective Centre-to-Limb Variations in the Stellar Photosphere
• The Changing Face of $\alpha$ Centauri B: Probing plage and stellar activity in K-dwarfs
• Stellar Surface Magneto-Convection as a Source of Astrophysical Noise III. Sun-as-a-star Simulations and Optimal Noise Diagnostics
• Black Mirror: The impact of rotational broadening on the search for reflected light from 51 Pegasi b with high resolution spectroscopy
• Stellar signal components seen in HARPS and HARPS-N solar radial velocities
• The solar gravitational redshift from HARPS-LFC Moon spectra. A test of the General Theory of Relativity
• Small-scale dynamos: From idealized models to solar and stellar applications
• The Impact of Stellar Surface Magnetoconvection and Oscillations on the Detection of Temperate, Earth-Mass Planets Around Sun-Like Stars
• Spatially resolved spectroscopy across stellar surfaces. I. Using exoplanet transits to analyze 3-D stellar atmospheres
• The effects of granulation and supergranulation on Earth-mass planet detectability in the habitable zone around F6-K4 stars
• Long-term stellar activity variations and their effect on radial-velocity measurements
• Radial-velocity variations due to meridional flows in the Sun and solar-type stars: impact on exoplanet detectability
• 3D magneto-hydrodynamical simulations of stellar convective noise for improved exoplanet detection. I. Case of regularly sampled radial velocity observations
• Final Design and On-Sky Testing of the iLocater SX Acquisition Camera: Broadband Single-Mode Fiber Coupling
• Testing the Spectroscopic Extraction of Suppression of Convective Blueshift
• The magnetic properties of photospheric magnetic bright points with high resolution spectropolarimetry
• Unsigned magnetic flux proxy from solar optical intensity spectra
• YOUNG Star detrending for Transiting Exoplanet Recovery (YOUNGSTER) -- I. A search for young exoplanets in Sectors 1-5 of the TESS Full-Frame-Images
• GRASS II: Simulations of Potential Granulation Noise Mitigation Methods
• Granulation on a quiet K dwarf: HD 166620 I. Spectral signatures as a function of line-formation temperature
• Towards understanding stellar variability at the sub m/s level: granulation-induced variability across the optical spectrum