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Unsigned magnetic flux proxy from solar optical intensity spectra
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Lienhard, F., Mortier, A., Cegla, H. M., Cameron, A. Collier, Klein, B. and Watson, C. A. (2023) Unsigned magnetic flux proxy from solar optical intensity spectra. Monthly Notices of the Royal Astronomical Society, 522 (4). pp. 5862-5878. doi:10.1093/mnras/stad1343 ISSN 1365-2966.
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Official URL: https://doi.org/10.1093/mnras/stad1343
Abstract
The photospheric unsigned magnetic flux has been shown to be highly correlated with radial velocity (RV) variations caused by solar surface activity. This activity indicator is therefore a prime candidate to unlock the potential of RV surveys to discover Earth twins orbiting Sun-like stars. We show for the first time how a precise proxy of the unsigned magnetic flux ( ΔαB2 ) can be obtained from Sun-as-a-star intensity spectra by harnessing the magnetic information contained in over 4000 absorption lines in the wavelength range from 380 to 690 nm. This novel activity proxy can thus be obtained from the same spectra from which RVs are routinely extracted. We derived ΔαB2 from 500 randomly selected spectra from the HARPS-N public solar data set, which spans from 2015 to 2018. We compared our estimates with the unsigned magnetic flux values from the Solar Dynamics Observatory (SDO) finding excellent agreement (median absolute deviation: 4.9 per cent). The extracted indicator ΔαB2 correlates with SDO’s unsigned magnetic flux estimates on the solar rotational timescale (Pearson correlation coefficient 0.67) and on the three-year timescale of our data set (correlation coefficient 0.91). We find correlations of ΔαB2 with the HARPS-N solar RV variations of 0.49 on the rotational timescale and 0.78 on the three-year timescale. The Pearson correlation of ΔαB2 with the RVs is found to be greater than the correlation of the classical activity indicators with the RVs. For solar-type stars, ΔαB2 therefore represents the best simultaneous activity proxy known to date.
Item Type: | Journal Article | |||||||||||||||
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Subjects: | Q Science > QB Astronomy | |||||||||||||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | |||||||||||||||
SWORD Depositor: | Library Publications Router | |||||||||||||||
Library of Congress Subject Headings (LCSH): | Stars -- Magnetic fields, Stellar activity , Solar granulation | |||||||||||||||
Journal or Publication Title: | Monthly Notices of the Royal Astronomical Society | |||||||||||||||
Publisher: | Oxford University Press (OUP) | |||||||||||||||
ISSN: | 1365-2966 | |||||||||||||||
Official Date: | July 2023 | |||||||||||||||
Dates: |
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Volume: | 522 | |||||||||||||||
Number: | 4 | |||||||||||||||
Page Range: | pp. 5862-5878 | |||||||||||||||
DOI: | 10.1093/mnras/stad1343 | |||||||||||||||
Status: | Peer Reviewed | |||||||||||||||
Publication Status: | Published | |||||||||||||||
Reuse Statement (publisher, data, author rights): | This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society. All rights reserved. | |||||||||||||||
Access rights to Published version: | Open Access (Creative Commons) | |||||||||||||||
Copyright Holders: | © 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society | |||||||||||||||
Date of first compliant deposit: | 21 July 2023 | |||||||||||||||
Date of first compliant Open Access: | 24 July 2023 | |||||||||||||||
RIOXX Funder/Project Grant: |
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