Lily L. Zhao, Yale UniversityFollow
Debra A. Fischer, Yale UniversityFollow
Eric B. Ford, The Pennsylvania State UniversityFollow
Alex Wise, The Pennsylvania State University
Michaël Cretignier, University of Geneva
Suzanne Aigrain, University of OxfordFollow
Oscar Barragan, University of OxfordFollow
Megan Bedell, Flatiron Institute, Simons Foundation
Lars A. Buchhave, Technical University of DenmarkFollow
João D. Camacho, Universidade do Porto
Heather M. Cegla, University of WarwickFollow
Jessi Cisewski-Kehe, University of Wisconsin-Madison
Andrew Collier Cameron, University of St Andrews
Zoe L. de Beurs, Massachusetts Institute of Technology
Sally Dodson-Robinson, University of Delaware
Xavier Dumusque, University of GenevaFollow
João P. Faria, Universidade do Porto
Christian Gilbertson, The Pennsylvania State University
Charlotte Haley, Argonne National Laboratory
Justin Harrell, University of Delaware
David W. Hogg, New York University
Parker Holzer, Yale University
Ancy Anna John, University of St Andrews
Baptiste Klein, University of Oxford
Marina Lafarga, University of Warwick
Florian Lienhard, University of Cambridge
Vinesh Maguire-Rajpaul, University of Cambridge
Annelies Mortier, University of Cambridge
Belinda Nicholson, University of Oxford
Michael L. Palumbo III, The Pennsylvania State University
Victor Ramirez Delgado, University of Delaware
Christopher J. Shallue, Harvard-Smithsonian Center for Astrophysics
Andrew Vanderburg, Massachusetts Institute of TechnologyFollow
Pedro T. P. Viana, Universidade do Porto
Jinglin Zhao, The Pennsylvania State University
Norbert Zicher, University of Oxford
Samuel H. C. Cabot, Yale UniversityFollow
Gregory W. Henry, Tennessee State UniversityFollow
Rachael M. Roettenbacher, Yale UniversityFollow
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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 Extreme-precision Spectrograph (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 radial-velocity (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.