Predicting radial-velocity jitter induced by stellar oscillations based on Kepler data

Abstract

Radial-velocity jitter due to intrinsic stellar variability introduces challenges when characterizing exoplanet systems, particularly when studying small (sub-Neptune-sized) planets orbiting solar-type stars. In this Letter we predicted for dwarfs and giants the jitter due to stellar oscillations, which in velocity have much larger amplitudes than noise introduced by granulation. We then fitted the jitter in terms of the following sets of stellar parameters: (1) Luminosity, mass, and effective temperature: the fit returns precisions (i.e., standard deviations of fractional residuals) of 17.9% and 27.1% for dwarfs and giants, respectively. (2) Luminosity, effective temperature, and surface gravity: The precisions are the same as using the previous parameter set.(3) Surface gravity and effective temperature: we obtain a precision of 22.6% for dwarfs and 27.1% for giants. (4): Luminosity and effective temperature: the precision is 47.8% for dwarfs and 27.5% for giants. Our method will be valuable for anticipating the radial-velocity stellar noise level of exoplanet host stars to be found by the T E SS and PL ATO space missions, and thus can be useful for their follow-up spectroscopic observations. We provide publicly available code (https://github.com/Jieyu126/Jitter) to set a prior for the jitter term as a component when modeling the Keplerian orbits of the exoplanets.

A Hot Saturn Orbiting an Oscillating Late Subgiant Discovered by TESS

“…We placed a strong Gaussian prior on the mean stellar density using the value derived from asteroseismology ( Table 2) and weak priors on the linear and quadratic limb-darkening coefficients, derived from the closest I-band grid points in Claret & Bloemen (2011), with a width of 0.6 for both coefficients. We also adopted a prior for the radial-velocity jitter from granulation and oscillations of 2.5±1.5 m s −1 , following Yu et al (2018;see also Tayar et al 2018), and a 1/e prior on the eccentricity to account for the linear bias introduced by sampling in e cos ω and e sin ω (Eastman et al 2013). Independent zero-point offsets and stellar jitter values for each of the five instruments that provided radial velocities.…”

The effects of granulation and supergranulation on Earth-mass planet detectability in the habitable zone around F6-K4 stars

“…There are other scaling laws, for example byYu et al (2018), but they are not very different. Because the oscillations are strongly averaged in this work, this choice is not critical.…”

$\texttt{pySYD}$: Automated measurements of global asteroseismic parameters

“…pySYD is adapted from the framework of the IDL-based SYD pipeline (Huber et al, 2009; hereafter referred to as SYD), which has been used frequently to measure asteroseismic parameters for Kepler stars and has been extensively tested against other closed-source tools on Kepler data Verner et al, 2011). Papers based on asteroseismic parameters measured using the SYD pipeline include Huber et al (2011), Bastien et al (2013, Chaplin et al (2014), Serenelli et al (2017), andYu et al (2018). pySYD was developed using the same well-tested methodology, but has improved functionality including automated background model selection and parallel processing as well as improved flexibility through a user-friendly interface, while still maintaining its speed and efficiency.…”