Impact of Correlated Noise on the Mass Precision of Earth-analog Planets in Radial Velocity Surveys

Abstract

Characterizing the masses and orbits of near-Earth-mass planets is crucial for interpreting observations from future direct imaging missions (e.g., HabEx, LUVOIR). Therefore, the Exoplanet Science Strategy report recommended further research so future extremely precise radial velocity surveys could contribute to the discovery and/or characterization of near-Earth-mass planets in the habitable zones of nearby stars prior to the launch of these future imaging missions. Newman et al. (2023) simulated such 10 yr surveys under various telescope architectures, demonstrating they can precisely measure the masses of potentially habitable Earth-mass planets in the absence of stellar variability. Here, we investigate the effect of stellar variability on the signal-to-noise ratio (S/N) of the planet mass measurements in these simulations. We find that correlated noise due to active regions has the largest effect on the observed mass S/N, reducing the S/N by a factor of ∼5.5 relative to the no-variability scenario; granulation reduces by a factor of ∼3, while p-mode oscillations has little impact on the proposed survey strategies. We show that in the presence of correlated noise, 5 cm s−1 instrumental precision offers little improvement over 10 cm s−1 precision, highlighting the need to mitigate astrophysical variability. With our noise models, extending the survey to 15 yr doubles the number of Earth-analogs with mass S/N > 10, and reaching this threshold for any Earth-analog orbiting a star >0.76 M ⊙ in a 10 yr survey would require an increase in the number of observations per star from that in Newman et al. (2023).

Fishing for Planets: A Comparative Analysis of EPRV Survey Performance in the Presence of Correlated Noise

“…For oscillations, we adopt the GP kernel described by Luhn et al (2023) and based on work by Pereira et al (2019) and Guo et al (2022), which takes the form…”

“…4 2 11 2 . We also adopt the following two-component granulation kernel from Luhn et al (2023) and Guo et al (2022):…”

“…In this regime, RV uncertainties are dominated by correlated noise from intrinsic stellar variability, which has been identified as the largest remaining hurdle for RV detection of Earth-like exoplanets (Crass et al 2021). We expect our ability to mitigate these correlated noise contributions and extract exoplanet-induced signals to be greatly impacted by the enacted observing scheme (Dumusque et al 2011;Hall et al 2018;Chaplin et al 2019;Luhn et al 2023). Indeed, recent studies on the scheduling of RV observations to confirm and characterize transiting systems (Burt et al 2018;Cloutier et al 2018;Cabona et al 2021), as well as for large-scale planet searches (Luhn et al 2023), have shown that the choice of observing strategy will impact survey efficacy in the presence of correlated noise.…”

“…We expect our ability to mitigate these correlated noise contributions and extract exoplanet-induced signals to be greatly impacted by the enacted observing scheme (Dumusque et al 2011;Hall et al 2018;Chaplin et al 2019;Luhn et al 2023). Indeed, recent studies on the scheduling of RV observations to confirm and characterize transiting systems (Burt et al 2018;Cloutier et al 2018;Cabona et al 2021), as well as for large-scale planet searches (Luhn et al 2023), have shown that the choice of observing strategy will impact survey efficacy in the presence of correlated noise. To identify an optimal strategy for Earthanalog searches, a sizeable parameter space of survey strategies may need to be explored.…”

Dynamics of Photospheric Magnetic Flux Distribution and Variations in Solar RVs: A Study Using HARPS-N Solar and SDO Observations

“…Major efforts are currently underway toward achieving extreme precision RV (EPRV) of centimeters per second needed to detect Earth-size planets around Sun-like stars (Newman et al 2023) (see also NASA EPRV Working group final report, Crass et al 2021). However, it is also well recognized that convective flows and magnetic activity in the photospheres of host stars cause RV fluctuations, known as astrophysical noise or jitter, much larger than the wobble signals caused by the orbital motion of a planet (Boisse et al 2011;Luhn et al 2023). The RV contributions from stellar surface magnetic fields are intimately related to one of the fundamental effects in magnetohydrodynamics (MHD), viz.…”