ajThe Astronomical JournalAJAstron. J.0004-62561538-3881The American Astronomical Societyajac517610.3847/1538-3881/ac5176ac5176AAS35667350The Solar System, Exoplanets, and AstrobiologyThe EXPRES Stellar Signals Project II. State of the Field in Disentangling Photospheric Velocities0000-0002-3852-3590ZhaoLily L.1236lzhao@flatironinstitute.org0000-0003-2221-0861FischerDebra A.10000-0001-6545-639XFordEric B.3456370000-0002-5013-5769WiseAlex3370000-0002-2207-0750CretignierMichaël7380000-0003-1453-0574AigrainSuzanne8390000-0003-0563-0493BarraganOscar8390000-0001-9907-7742BedellMegan2360000-0003-1605-5666BuchhaveLars A.9390000-0001-5121-5560CamachoJoão D.1011400000-0001-8934-7315CeglaHeather M.1213410000-0002-9656-2272Cisewski-KeheJessi140000-0002-8863-7828Collier CameronAndrew15420000-0002-7564-6047de BeursZoe L.1617430000-0002-8796-4974Dodson-RobinsonSally1819440000-0002-9332-2011DumusqueXavier7380000-0002-6728-244XFariaJoão P.1011400000-0002-1743-3684GilbertsonChristian345370000-0003-3996-773XHaleyCharlotte20440000-0001-8936-6276HarrellJustin18440000-0003-2866-9403HoggDavid W.2212223360000-0001-8936-6276HolzerParker240000-0002-1715-6939JohnAncy Anna15420000-0003-0637-5236KleinBaptiste8390000-0002-8815-9416LafargaMarina12410000-0003-4047-0771LienhardFlorian250000-0001-7576-6703Maguire-RajpaulVinesh25390000-0001-7254-4363MortierAnnelies25260000-0003-1360-4404NicholsonBelinda8390000-0002-4677-8796PalumboMichael L.III3370000-0001-8183-459XRamirez DelgadoVictor18440000-0002-7585-9974ShallueChristopher J.27430000-0001-7246-5438VanderburgAndrew2829430000-0003-1572-8531VianaPedro T. P.1040110000-0001-5290-2952ZhaoJinglin3370000-0001-6143-2905ZicherNorbert8390000-0001-9749-6150CabotSamuel H. C.10000-0003-4155-8513HenryGregory W.300000-0002-9288-3482RoettenbacherRachael M.1310000-0002-9873-1471BrewerJohn M.320000-0003-4450-0368LlamaJoe330000-0003-2168-0191PetersburgRyan R.340000-0002-4974-687XSzymkowiakAndrew E.1 Department of Astronomy, Yale University, 52 Hillhouse Avenue, New Haven, CT 06511, USA; lzhao@flatironinstitute.org Center for Computational Astrophysics, Flatiron Institute, Simons Foundation, 162 Fifth Avenue, New York, NY 10010, USA Department of Astronomy & Astrophysics, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA, 16802, USA Center for Exoplanets and Habitable Worlds, 525 Davey Laboratory, The Pennsylvania State University, University Park, PA, 16802, USA Institute for Computational & Data Sciences, The Pennsylvania State University, University Park, PA, 16802, USA Institute for Advanced Sciences, 1 Einstein Drive, Princeton, NJ 08540, USA Astronomy Department of the University of Geneva, 51 Chemin de Pegasi 51, 1290 Versoix, Switzerland Sub-department of Astrophysics, Department of Physics, University of Oxford, Oxford OX1 3RH, UK DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 328, DK-2800 Kgs. Lyngby, Denmark Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762, Porto, Portugal Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK Centre for Exoplanets and Habitability, University of Warwick, Coventry CV4 7AL, UK Department of Statistics, University of Wisconsin-Madison, 1300 University Avenue, Madison, WI 53706, USA University of St Andrews, Centre for Exoplanet Science, SUPA, School of Physics & Astronomy, North Haugh, St Andrews KY16 9SS, UK Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, 54-918, Cambridge, MA 02139, USA Department of Astronomy, University of Texas at Austin, 2515 Speedway, Austin, Texas 78712, USA Department of Physics and Astronomy, University of Delaware, 217 Sharp Lab, Newark, DE 19716, USA Bartol Research Institute, Sharp Lab, 104 The Green, Newark, DE, 19716, USA Mathematics and Computer Science Division, Argonne National Laboratory, Lemont, IL, USA Center for Cosmology and Particle Physics, Department of Physics, New York University, 726 Broadway, New York, NY 10003, USA Center for Data Science, New York University, 60 Fifth Avenue, New York, NY 10011, USA Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany Department of Statistics and Data Science, Yale University, 24 Hillhouse Avenue, New Haven, CT 06511, USA Astrophysics Group, Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE, UK Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK Center for Astrophysics—Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53706, USA Center of Excellence in Information Systems, Tennessee State University, Nashville, TN 37209, USA Yale Center for Astronomy and Astrophysics, Yale University, 46 Hillhouse Avenue, New Haven, CT 06511, USA San Francisco State University University, 1600 Holloway Avenue, San Francisco, CA 94132, USA Lowell Observatory, 1400 W. Mars Hill Road, Flagstaff, AZ 86001, USA Department of Physics, Yale University, 217 Prospect Street, New Haven, CT 06511, USA

CCA Team

PennState Team

Geneva Team

OxBridGen Team

Porto Team

Warwick Team

St. Andrews Team

ML_EPRVs Team

Sidera Team

014202215032022150320221634171261020211912022251202225012022© 2022. The Author(s). Published by the American Astronomical Society.2022 Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.Abstract

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.

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