A Gaussian process model for stellar activity in 2D line profile time-series
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Date
2024-11
Publication Type
Journal Article
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yes
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Abstract
Stellar active regions like spots and faculae can distort the shapes of spectral lines, inducing variations in the radial velocities that are often orders of magnitude larger than the signals from Earth-like planets. Efforts to mitigate these activity signals have hitherto focused on either the time or the velocity (wavelength) domains. We present a physics-driven Gaussian process (GP) framework to model activity signals directly in time series of line profiles or cross-correlation functions (CCFs). Unlike existing methods that correct activity signals in line profile time series, our approach exploits the time correlation between velocity (wavelength) bins in the line profile variations, and is based on a simplified but physically motivated model for the origin of these variations. When tested on both synthetic and real data sets with signal-to-noise ratios down to ∼100, our method was able to separate the planetary signal from the activity signal, even when their periods were identical. We also conducted injection/recovery tests using two years of realistically sampled HARPS-N solar data, demonstrating the ability of the method to accurately recover a signal induced by a 1.5-Earth mass planet with a semi-amplitude of 0.3 m s-1 and a period of 33 d during high solar activity.
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published
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Journal / series
Volume
535 (1)
Pages / Article No.
634 - 646
Publisher
Oxford University Press
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Edition / version
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Date collected
Date created
Subject
line: profiles; methods: statistical; techniques: spectroscopic; Sun: activity; planets and satellites: detection
Organisational unit
09754 - Queloz, Didier / Queloz, Didier