Please use this identifier to cite or link to this item: http://hdl.handle.net/2381/44368
 Title: Constraining the magnetic field on white dwarf surfaces; Zeeman effects and fine structure constant variation Authors: Hu, JWebb, JKAyres, TRBainbridge, MBBarrow, JDBarstow, MABerengut, JCCarswell, RFDzuba, VAFlambaum, VVHolberg, JBLee, CCPreval, SPReindl, NTchang-Brillet, W-ÜL First Published: 30-Mar-2019 Publisher: Oxford University Press (OUP), Royal Astronomical Society Citation: Monthly Notices of the Royal Astronomical Society, 2019, 485(4), pp. 5050–5058 Abstract: White 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. DOI Link: 10.1093/mnras/stz739 eISSN: 1365-2966 Links: https://academic.oup.com/mnras/article/485/4/5050/5420839http://hdl.handle.net/2381/44368 Version: Publisher Version Status: Peer-reviewed Type: Journal Article Rights: Copyright © 2019, Oxford University Press (OUP), Royal Astronomical Society. Deposited with reference to the publisher’s open access archiving policy. (http://www.rioxx.net/licenses/all-rights-reserved) Appears in Collections: Published Articles, Dept. of Physics and Astronomy

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