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dc.contributor.authorHaywood, R. D.
dc.contributor.authorMilbourne, T. W.
dc.contributor.authorSaar, S. H.
dc.contributor.authorMortier, A.
dc.contributor.authorPhillips, D.
dc.contributor.authorCharbonneau, D.
dc.contributor.authorCameron, A. Collier
dc.contributor.authorCegla, H. M.
dc.contributor.authorMeunier, N.
dc.contributor.authorIII, M. L. Palumbo
dc.identifier.citationHaywood , R D , Milbourne , T W , Saar , S H , Mortier , A , Phillips , D , Charbonneau , D , Cameron , A C , Cegla , H M , Meunier , N & III , M L P 2022 , ' Unsigned magnetic flux as a proxy for radial-velocity variations in sun-like stars ' , Astrophysical Journal , vol. 935 , no. 1 , 6 .
dc.identifier.otherPURE: 280849641
dc.identifier.otherPURE UUID: 575ba676-08b4-4739-868a-526d940553ff
dc.identifier.otherJisc: 513174
dc.identifier.otherpublisher-id: apjac7c12
dc.identifier.othermanuscript: ac7c12
dc.identifier.otherother: aas24808
dc.identifier.otherORCID: /0000-0002-8863-7828/work/117211243
dc.identifier.otherScopus: 85135988681
dc.identifier.otherWOS: 000837396900001
dc.descriptionFunding: A.C.C. acknowledges support from the Science and Technology Facilities Council (STFC) consolidated grant number ST/R000824/1.en
dc.description.abstractA major obstacle to detecting and characterizing long-period, low-mass exoplanets is the intrinsic radial-velocity (RV) variability of host stars. To better understand RV variability, we estimate disk-averaged RV variations of the Sun over its magnetic cycle, from the Fe i line observed by SDO/HMI, using a physical model for rotationally modulated magnetic activity that was previously validated against HARPS-N solar observations. We estimate the unsigned magnetic flux and show that a linear fit to it reduces the rms of RV variations by 62%, i.e., a factor of 2.6. We additionally apply the FF′ method, which predicts RV variations based on a star’s photometric variations. At cycle maximum, we find that additional processes must be at play beyond suppression of convective blueshift and velocity imbalances resulting from brightness inhomogeneities, in agreement with recent studies of RV variations. By modeling RV variations over the magnetic cycle using a linear fit to the unsigned magnetic flux, we recover injected planets at a period of ≈300 days with RV semi-amplitudes down to 0.3 m s−1. To reach 0.1 m s−1, we will need to identify and model additional phenomena that are not well traced by ∣Bˆobs∣ or FF′. This study motivates ongoing and future efforts to develop observation and analysis techniques to measure the unsigned magnetic flux at high precision in slowly rotating, relatively inactive stars like the Sun. We conclude that the unsigned magnetic flux is an excellent proxy for rotationally modulated, activity-induced RV variations, and could become key to confirming and characterizing Earth analogs.
dc.relation.ispartofAstrophysical Journalen
dc.rightsCopyright © 2022. The Author(s). Published by the American Astronomical Society. 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.en
dc.subjectSolar cycleen
dc.subjectActive sunen
dc.subjectQuiet sunen
dc.subjectSolar faculaeen
dc.subjectExoplanet detection methodsen
dc.subjectRadial velocityen
dc.subjectAstronomy data analysisen
dc.subjectQB Astronomyen
dc.subjectQC Physicsen
dc.titleUnsigned magnetic flux as a proxy for radial-velocity variations in sun-like starsen
dc.typeJournal articleen
dc.contributor.sponsorScience & Technology Facilities Councilen
dc.description.versionPublisher PDFen
dc.contributor.institutionUniversity of St Andrews. School of Physics and Astronomyen
dc.contributor.institutionUniversity of St Andrews. St Andrews Centre for Exoplanet Scienceen
dc.description.statusPeer revieweden

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