Jonathan Braithwaite

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We investigate the 50-year old hypothesis that the magnetic fields of the Ap stars are stable equilibria that have survived in these stars since their formation. With numerical simulations we find that stable magnetic field configurations indeed appear to exist under the conditions in the radiative interior of a star. Confirming a hypothesis by Prendergast(More)
We review the current state of knowledge of magnetic fields inside stars, concentrating on recent developments concerning magnetic fields in stably stratified (zones of) stars, leaving out convective dynamo theories and observations of convective envelopes. We include the observational properties of A, B and O-type main-sequence stars, which have radiative(More)
We present numerical models of hydromagnetic instabilities under the conditions prevailing in a stably stratified, non-convective stellar interior, and compare them with previous results of analytic work on instabilities in purely toroidal fields. We confirm that an m = 1 mode ('kink') is the dominant instability in a toroidal field in which the field(More)
Interpretation of imagery requires contrast between the object being sought and its background. A technique is described for increasing the contrast of selected objects based on their spectral reflectance or emittance characteristics, and two applications are discussed. Means for implementing this technique with an optical-mechanical scanner, multielement(More)
An arbitrary initial magnetic field in an A star evolves into a stable equilibrium. Simulations are presented of the formation of non-axisymmetric equilibria consisting of twisted flux tubes meandering under the surface of the star, and analytic arguments are given relating the stability and form of these equilibria. These results may help to explain(More)
A detailed study spanning approximately a year has been conducted on the Type Ib supernova 2007Y. Imaging was obtained from X-ray to radio wavelengths, and a comprehensive set of multi-band (w2m2w1u ′ g ′ r ′ i ′ U BV Y JHK s) light curves and optical spectroscopy is presented. A virtually complete bolometric light curve is derived, from which we infer a 56(More)
  • Iam G Wili, Weitkamr, +4 authors Bqdansky
  • 2011
No evidence for a violation of time-reversal (T) invariance has been found in a study of the inverse reactions Mg'4+d~~Mg"+ p using approximately 10-MeV deuterons and 15-MeV protons. In order to reduce systematic uncertainties, the reactions were compared by measuring, as a function of incident energy, the ratio of differential cross sections at angles(More)
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