Exoplanets & Exomoons

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

By Keith Cowing
April 27, 2022
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Impact of Correlated Noise on the Mass Precision of Earth-analog Planets in Radial Velocity Surveys
Histograms of RV SNR for measurements of Earth-mass planets for proposed RV survey architectures and various noise models for the effects of stellar variability on RV measurements. Each column shows a different telescope architecture, as described in Section 2 and Figure 1. Diagrams for each telescope architecture are repeated in the top right of each histogram for easy reference. Histograms are colored according to the assumptions for how stellar variability affects the RV measurements: correlated noise (“corr” in red/pink), white noise (labeled as “iid”) in blue, and no additional noise due to stellar variability (“ideal”) plotted for just the top row in black/grey. The vertical dashed red line indicates where planet mass measurements will have a precision of 10% or better. The exact percentage of planets above this threshold is given in red and blue in the bottom right, corresponding to the correlated and white noise models, respectively. We also include in parentheses the percentage of planets with mass SNR > 5 (20% mass precision). These data were generated using the default survey duration of 10 years and instrumental precision 5 cm s−1 . Note that the percentage of planets with mass measurement SNR > 10 in the “ideal” scenario (shown in the black/grey histograms) is 100% for every architecture, meaning that the labels also indicate the reduction expected by including the specified noise source

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 (National Academies of Sciences, Engineering, and Medicine 2018) 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. (2021) simulated such 10-year 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 (SNR) 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 SNR, reducing the SNR 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 years doubles the number of Earth-analogs with mass SNR > 10, and reaching this threshold for any Earth-analog orbiting a star > 0.76 M⊙ in a 10-year survey would require an increase in number of observations per star from that in Newman et al. (2021).

Jacob K. Luhn, Eric B. Ford, Zhao Guo, Christian Gilbertson, Patrick Newman, Peter Plavchan, Jennifer A. Burt, Johanna Teske, Arvind F. Gupta

Comments: 30 pages, 9 figures, accepted in AJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Instrumentation and Methods for Astrophysics (astro-ph.IM)
Cite as: arXiv:2204.12512 [astro-ph.EP] (or arXiv:2204.12512v1 [astro-ph.EP] for this version)
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Submission history
From: Jacob Luhn
[v1] Tue, 26 Apr 2022 18:00:05 UTC (6,211 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻