dc.contributor.author Callingham, J. R. dc.contributor.author Gaensler, B. M. dc.contributor.author Zanardo, G. dc.contributor.author Staveley-Smith, L. dc.contributor.author Hancock, P. J. dc.contributor.author Hurley-Walker, N. dc.contributor.author Bell, M. E. dc.contributor.author Dwarakanath, K. S. dc.contributor.author Franzen, T. M. O. dc.contributor.author Hindson, L. dc.contributor.author Johnston-Hollitt, M. dc.contributor.author Kapinska, A. dc.contributor.author For, B. Q. dc.contributor.author Lenc, E. dc.contributor.author McKingley, B. dc.contributor.author Offringa, A. R. dc.contributor.author Procopio, P. dc.contributor.author Wayth, R. B. dc.contributor.author Wu, C. dc.contributor.author Zheng, Q. dc.date.accessioned 2017-06-14T16:04:13Z dc.date.available 2017-06-14T16:04:13Z dc.date.issued 2016-10-11 dc.identifier.citation Callingham , J R , Gaensler , B M , Zanardo , G , Staveley-Smith , L , Hancock , P J , Hurley-Walker , N , Bell , M E , Dwarakanath , K S , Franzen , T M O , Hindson , L , Johnston-Hollitt , M , Kapinska , A , For , B Q , Lenc , E , McKingley , B , Offringa , A R , Procopio , P , Wayth , R B , Wu , C & Zheng , Q 2016 , ' Low Radio Frequency Observations and Spectral Modelling of the Remnant of Supernova 1987A ' , Monthly Notices of the Royal Astronomical Society , vol. 462 , no. 1 , pp. 290-297 . https://doi.org/10.1093/mnras/stw1489 dc.identifier.issn 1365-2966 dc.identifier.other PURE: 10291597 dc.identifier.other PURE UUID: bbd3105c-5056-4fcc-91a0-ab96bd175e4d dc.identifier.other ArXiv: http://arxiv.org/abs/1606.05974v1 dc.identifier.other Scopus: 84988728364 dc.identifier.uri http://hdl.handle.net/2299/18335 dc.description This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. ©: 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. dc.description.abstract We present Murchison Widefield Array observations of the supernova remnant (SNR) 1987A between 72 and 230 MHz, representing the lowest frequency observations of the source to date. This large lever arm in frequency space constrains the properties of the circumstellar medium created by the progenitor of SNR 1987A when it was in its red supergiant phase. As of late-2013, the radio spectrum of SNR 1987A between 72 MHz and 8.64 GHz does not show any deviation from a non-thermal power-law with a spectral index of $-0.74 \pm 0.02$. This spectral index is consistent with that derived at higher frequencies, beneath 100 GHz, and with a shock in its adiabatic phase. A spectral turnover due to free-free absorption by the circumstellar medium has to occur below 72 MHz, which places upper limits on the optical depth of $\leq$ 0.1 at a reference frequency of 72 MHz, emission measure of $\lesssim$ 13,000 cm$^{-6}$ pc, and an electron density of $\lesssim$ 110 cm$^{-3}$. This upper limit on the electron density is consistent with the detection of prompt radio emission and models of the X-ray emission from the supernova. The electron density upper limit implies that some hydrodynamic simulations derived a red supergiant mass loss rate that is too high, or a wind velocity that is too low. The mass loss rate of $\sim 5 \times 10^{-6}$ $M_{\odot}$ yr$^{-1}$ and wind velocity of 10 km s$^{-1}$ obtained from optical observations are consistent with our upper limits, predicting a current turnover frequency due to free-free absorption between 5 and 60 MHz. en dc.format.extent 8 dc.language.iso eng dc.relation.ispartof Monthly Notices of the Royal Astronomical Society dc.rights Open dc.subject supernovae: indiviual: SN 1987A dc.subject ISM: supernova remnants dc.subject radio continuum: general dc.title Low Radio Frequency Observations and Spectral Modelling of the Remnant of Supernova 1987A en dc.contributor.institution School of Physics, Astronomy and Mathematics dc.description.status Peer reviewed dc.description.versiontype Final Published version dcterms.dateAccepted 2016-10-11 rioxxterms.version VoR rioxxterms.versionofrecord https://doi.org/10.1093/mnras/stw1489 rioxxterms.type Journal Article/Review herts.preservation.rarelyaccessed true herts.rights.accesstype Open
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