Towards Understanding Stellar Radial Velocity Jitter as a Function of Wavelength: The Sun as a Proxy

TL;DR

This study estimates how stellar activity-induced radial velocity noise varies with wavelength for the Sun, showing that near-infrared observations can significantly reduce stellar noise compared to visible wavelengths, aiding planet detection.

Contribution

It demonstrates that near-infrared spectrographs can lower stellar activity noise in RV measurements of Sun-like stars, highlighting their potential in exoplanet searches.

Findings

NIR RV noise is up to 4 times lower than visible RV noise.

Stellar activity effects are wavelength-dependent and reduced in NIR.

Future NIR instruments can improve low-mass planet detection around FGK stars.

Abstract

Using solar spectral irradiance measurements from the SORCE spacecraft and the F/F' technique, we have estimated the radial velocity (RV) scatter induced on the Sun by stellar activity as a function of wavelength. Our goal was to evaluate the potential advantages of using new near-infrared (NIR) spectrographs to search for low-mass planets around bright F, G, and K stars by beating down activity effects. Unlike M dwarfs, which have higher fluxes and therefore greater RV information content in the NIR, solar-type stars are brightest at visible wavelengths, and, based solely on information content, are better suited to traditional optical RV surveys. However, we find that the F/F' estimated RV noise induced by stellar activity is diminished by up to a factor of 4 in the NIR versus the visible. Observations with the upcoming future generation of NIR instruments can be a valuable addition to the search for low-mass planets around bright FGK stars in reducing the amount of stellar noise affecting RV measurements.