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dc.contributor.authorHu, J-
dc.contributor.authorWebb, JK-
dc.contributor.authorAyres, TR-
dc.contributor.authorBainbridge, MB-
dc.contributor.authorBarrow, JD-
dc.contributor.authorBarstow, MA-
dc.contributor.authorBerengut, JC-
dc.contributor.authorCarswell, RF-
dc.contributor.authorDzuba, VA-
dc.contributor.authorFlambaum, VV-
dc.contributor.authorHolberg, JB-
dc.contributor.authorLee, CC-
dc.contributor.authorPreval, SP-
dc.contributor.authorReindl, N-
dc.contributor.authorTchang-Brillet, W-ÜL-
dc.identifier.citationMonthly Notices of the Royal Astronomical Society, 2019, 485(4), pp. 5050–5058en
dc.description.abstractWhite dwarf atmospheres are subjected to gravitational potentials around $10^5$ times larger than occur on Earth. They provide a unique environment in which to search for any possible variation in fundamental physics in the presence of strong gravitational fields. However, a sufficiently strong magnetic field will alter absorption line profiles and introduce additional uncertainties in measurements of the fine structure constant. Estimating the magnetic field strength is thus essential in this context. Here we model the absorption profiles of a large number of atomic transitions in the white dwarf photosphere, including first-order Zeeman effects in the line profiles, varying the magnetic field as a free parameter. We apply the method to a high signal-to-noise, high-resolution, far-ultraviolet HST/STIS spectrum of the white dwarf G191-B2B. The method yields a sensitive upper limit on its magnetic field of $B < 2300$ Gauss at the $3\sigma$ level. Using this upper limit we find that the potential impact of quadratic Zeeman shifts on measurements of the fine structure constant in G191-B2B is 4 orders of magnitude below laboratory wavelength uncertainties.en
dc.description.sponsorshipThis research project was undertaken with the assistance of resources and services from the National Computational Infrastructure (NCI), which is supported by the Australian Government. Based on observations made with the NASA/ESA HST, obtained from the data archive at the Space Telescope Science Institute (STScI). STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. JH is grateful for a CSC Fund and a UNSW scholarship. JDB thanks the STFC for support. CCL thanks the Royal Society for a Newton International Fellowship. JKW thanks the John Templeton Foundation, the Department of Applied Mathematics and Theoretical Physics and the Institute of Astronomy Cambridge for hospitality and support, and Clare Hall Cambridge for a Visiting Fellowship. TRA thanks the STScI for its support, especially through the ASTRAL project. NR is supported by a Royal Commission 1851 research fellowship. WULTB wishes to acknowledge supports from the French CNRS–PNPS National Program and from the LabEx Plas@Par managed by the French ANR (ANR-11-IDEX-0004-02). SPP, MAB, and MBB acknowledge the support of the Leverhulme Trust. NR is supported by a Royal Commission 1851 research fellowship.en
dc.publisherOxford University Press (OUP), Royal Astronomical Societyen
dc.rightsCopyright © 2019, Oxford University Press (OUP), Royal Astronomical Society. Deposited with reference to the publisher’s open access archiving policy. (
dc.subjectatomic processesen
dc.subjectline: profilesen
dc.subjectmagnetic fieldsen
dc.subjectwhite dwarfsen
dc.titleConstraining the magnetic field on white dwarf surfaces; Zeeman effects and fine structure constant variationen
dc.typeJournal Articleen
dc.description.versionPublisher Versionen
pubs.organisational-group/Organisation/COLLEGE OF SCIENCE AND ENGINEERINGen
pubs.organisational-group/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomyen
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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