Multiwavelength Mitigation of Stellar Activity in Astrometric Planet Detection

Abstract

Astrometry has long been a promising technique for exoplanet detection. At the theoretical limits, astrometry would allow for the detection of smaller planets than previously seen by current exoplanet search methods, but stellar activity may make these theoretical limits unreachable. Astrometric jitter of a Sun-like star due to magnetic activity in its photosphere induces apparent variability in the photocenter of order $0.5\text{m}{R}_{\odot }$. This jitter creates a fundamental astrophysical noise floor preventing detection of lower-mass planets in a single spectral band. By injecting planet orbits into simulated solar data at five different passbands, we investigate mitigation of this fundamental astrometric noise using correlations across passbands. For a true solar analog and a planet at 1 au semimajor axis, the $6\sigma$ detection limit set by stellar activity for an ideal telescope at the best single passband is $0.01$ Earth masses. We found that pairs of passbands with highly correlated astrometric jitter due to stellar activity, but with less motion in the redder band, enable higher-precision measurements of the common signal from the planet. Using this method improves detectable planet masses at 1 au by up to a factor of $10$, corresponding to at best $0.005$ Earth masses for a Sun-like star with a perfect telescope. Given these results, we recommend that future astrometry missions consider proceeding with two or more passbands to reduce noise due to stellar activity.

arXiv comment11 pages, 9 figures. Published in AJ

References in corpus (18)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• The Gaia mission
• Understanding the Lomb-Scargle Periodogram
• Astrometric exoplanet detection with Gaia
• Reconstruction of total and spectral solar irradiance from 1974 to 2013 based on KPVT, SoHO/MDI and SDO/HMI observations
• Magnitudes and Timescales of Total Solar Irradiance Variability
• Towards a long-term record of solar total and spectral irradiance
• Magnetic cycles at different ages of stars
• Astrometric Confirmation and Preliminary Orbital Parameters of the Young Exoplanet 51 Eridani b with the Gemini Planet Imager
• The Gemini Planet Imager Exoplanet Survey: Dynamical Mass of the Exoplanet beta Pictoris b from Combined Direct Imaging and Astrometry
• Using the Sun to estimate Earth-like planets detection capabilities. III. Impact of spots and plages on astrometric detection
• Overview of the SIM PlanetQuest Light (SIM-Lite) mission concept
• Spotting Stellar Activity Cycles in Gaia Astrometry
• Astrometric jitter of the sun as a star
• Predictions of Astrometric Jitter for Sun-like Stars. II. Dependence on Inclination, Metallicity, and Active-Region Nesting
• Astrometric effects of solar-like magnetic activity in late-type stars and their relevance for the detection of extrasolar planets
• Predictions of astrometric jitter for Sun-like stars. I. The model and its application to the Sun as seen from the ecliptic

Cited by in corpus (6)

• Small-scale dynamo in cool main sequence stars. II. The effect of metallicity
• Astrometric Gravitational-Wave Detection via Stellar Interferometry
• Closeby Habitable Exoplanet Survey (CHES). I. Astrometric Noise and Planetary Detection Efficiency due to Stellar Spots and Faculae
• Predictions of Astrometric Jitter for Sun-like Stars. III. Fast Rotators
• A Dataset for Exploring Stellar Activity in Astrometric Measurements from SDO Images of the Sun
• Astrometric exoplanet detection survives solar-like stellar contamination