EXPRES. I. HD 3651 as an Ideal RV Benchmark

Brewer, John M.; Fischer, Debra A.; Blackman, Ryan; Davis, Allen B.; Laughlin, Gregory; Ong, J. M. Joel; Petersburg, Ryan R.; Szymkowiak, Andrew E.; Zhao, Lily; Henry, Gregory W.; Llama, Joe

doi:10.3847/1538-3881/ab99c9

Cited by 31 publications

(30 citation statements)

References 30 publications

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“…Successful exo-Earth discovery therefore requires both more sophisticated models of stellar variability and the improved RV precision, long-term stability, and dense observational sampling from a next-generation spectrograph (Wright & Robertson 2017) such as the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO; Pepe et al 2013Pepe et al , 2021Damasso et al 2020;Suárez Mascareño et al 2020), NEID (Allen et al 2018), EXtreme PREcision Spectrometer (EXPRES; Jurgenson et al 2016;Blackman et al 2020;Brewer et al 2020;Petersburg et al 2020), HARPS3 (Thompson et al 2016), or GMT Consortium Large Earth Finder (G-CLEF; Szentgyorgyi et al 2014).…”

Section: Discussionmentioning

confidence: 99%

Detection Limits of Low-mass, Long-period Exoplanets Using Gaussian Processes Applied to HARPS-N Solar Radial Velocities

Langellier

Milbourne

Phillips

et al. 2021

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Radial velocity (RV) searches for Earth-mass exoplanets in the habitable zone around Sun-like stars are limited by the effects of stellar variability on the host star. In particular, suppression of convective blueshift and brightness inhomogeneities due to photospheric faculae/plage and starspots are the dominant contribution to the variability of such stellar RVs. Gaussian process (GP) regression is a powerful tool for statistically modeling these quasi-periodic variations. We investigate the limits of this technique using 800 days of RVs from the solar telescope on the High Accuracy Radial velocity Planet Searcher for the Northern hemisphere (HARPS-N) spectrograph. These data provide a well-sampled time series of stellar RV variations. Into this data set, we inject Keplerian signals with periods between 100 and 500 days and amplitudes between 0.6 and 2.4 m s −1 . We use GP regression to fit the resulting RVs and determine the statistical significance of recovered periods and amplitudes. We then generate synthetic RVs with the same covariance properties as the solar data to determine a lower bound on the observational baseline necessary to detect low-mass planets in Venus-like orbits around a Sun-like star. Our simulations show that discovering planets with a larger mass (∼0.5 m s −1 ) using current-generation spectrographs and GP regression will require more than 12 yr of densely sampled RV observations. Furthermore, even with a perfect model of stellar variability, discovering a true exo-Venus (∼0.1 m s −1 ) with current instruments would take over 15 yr. Therefore, next-generation spectrographs and better models of stellar variability are required for detection of such planets.

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Section: Discussionmentioning

confidence: 99%

Detection Limits of Low-mass, Long-period Exoplanets Using Gaussian Processes Applied to HARPS-N Solar Radial Velocities

Langellier

Milbourne

Phillips

et al. 2021

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“…Two or three consecutive exposures, separated only by read-out time, are obtained for each target star per night to improve the nightly-binned precision (Brewer et al 2020). The on-sky, analytical single-measurement precision for exposures with a SNR of 250 (per pixel at λ=550 nm) is about 0.3 m s −1 (Petersburg et al 2020).…”

Section: Spectroscopic Data From Expresmentioning

confidence: 99%

“…The four ESSP stars, as described in Table 1, are being observed as part of the EXPRES 100 Earths survey (Brewer et al 2020). The targets range in activity level, as predicted by log R HK values.…”

Section: Targetsmentioning

confidence: 99%

“…With the new generation of extreme-precision spectrographs, sub-meter-per-second radial velocity (RV) measurement precision has become achievable (Pepe et al 2013;Schwab et al 2016;Jurgenson et al 2016;Blackman et al 2020;Petersburg et al 2020;Suárez Mascareño et al 2020;Brewer et al 2020;Pepe et al 2021). Photospheric velocities from stellar variability and activity features are now the dominant source of RV scatter.…”

Section: Introductionmentioning

confidence: 99%

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The EXPRES Stellar Signals Project II. State of the Field in Disentangling Photospheric Velocities

Zhao,

Fischer,

Ford

et al. 2022

Preprint

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Measured spectral shifts due to intrinsic stellar variability (e.g., pulsations, granulation) and activity (e.g., spots, plages) are the largest source of error for extreme precision radial velocity (EPRV) exoplanet detection. Several methods are designed to disentangle stellar signals from true center-of-mass shifts due to planets. The EXPRES Stellar Signals Project (ESSP) presents a self-consistent comparison of 22 different methods tested on the same extreme-precision spectroscopic data from EXPRES. Methods derived new activity indicators, constructed models for mapping an indicator to the needed RV correction, or separated out shape-and shift-driven RV components. Since no ground truth is known when using real data, relative method performance is assessed using the total and nightly scatter of returned RVs and agreement between the results of different methods. Nearly all submitted methods return a lower RV RMS than classic linear decorrelation, but no method is yet consistently reducing the RV RMS to sub-meter-per-second levels. There is a concerning lack of agreement between the RVs returned by different methods. These results suggest that continued progress in this field necessitates increased interpretability of methods, high-cadence data to capture stellar signals at all timescales, and continued tests like the ESSP using consistent data sets with more advanced metrics for method performance. Future comparisons should make use of various well-characterized data sets-such as solar data or data with known injected planetary and/or stellar signals-to better understand method performance and whether planetary signals are preserved.

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“…EXPRES is an ultra-stable optical spectrograph recently commissioned at the Lowell Discovery Telescope (Levine et al 2012). It is designed for extreme-precision RV surveys (see Jurgenson et al 2016;Blackman et al 2020;Brewer et al 2020;Petersburg et al 2020, for details about the instrument specifications and reduction pipeline) and also has the capacity for atmospheric characterization (see, for example, the recent study of ultra-hot Jupiter MASCARA-2b by Hoeijmakers et al 2020). One transit of TOI-1518b was observed on the night of 2020 August 2, involving 41 ∼300 s exposures.…”

Section: Expres Spectroscopymentioning

confidence: 99%