Wickramasinghe, DT;
Farihi, J;
Tout, CA;
Ferrario, L;
Stancliffe, RJ;
(2010)
Does GD 356 have a terrestrial planetary companion?
Monthly Notices of the Royal Astronomical Society
, 404
(4)
pp. 1984-1991.
10.1111/j.1365-2966.2010.16417.x.
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Abstract
GD 356 is unique among magnetic white dwarfs because it shows Zeeman-split Balmer lines in pure emission. The lines originate from a region of nearly uniform field strength (δB/B≈ 0.1) that covers 10 per cent of the stellar surface in which there is a temperature inversion. The energy source that heats the photosphere remains a mystery but it is likely to be associated with the presence of a companion. Based on current models, we use archival Spitzer Infrared Array Camera (IRAC) observations to place a new and stringent upper limit of 12 MJ for the mass of such a companion. In the light of this result and the recent discovery of a 115-min photometric period for GD 356, we exclude previous models that invoke accretion and revisit the unipolar inductor model that has been proposed for this system. In this model, a highly conducting planet with a metallic core orbits the magnetic white dwarf and, as it cuts through field lines, a current is set flowing between the two bodies. This current dissipates in the photosphere of the white dwarf and causes a temperature inversion. Such a planet is unlikely to have survived both the red and asymptotic giant branch phases of evolution so we argue that it may have formed from the circumstellar disc of a disrupted He or CO core during a rare merger of two white dwarfs. GD 356 would then be a white dwarf counterpart of the millisecond binary pulsar PSR 1257+12 which is known to host a planetary system.
Type: | Article |
---|---|
Title: | Does GD 356 have a terrestrial planetary companion? |
Open access status: | An open access version is available from UCL Discovery |
DOI: | 10.1111/j.1365-2966.2010.16417.x |
Publisher version: | http://dx.doi.org/10.1111/j.1365-2966.2010.16417.x |
Language: | English |
Additional information: | This article has been accepted for publication in the Monthly Notices of the Royal Astronomical Society ©: 2010 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. |
Keywords: | planetary systems, white dwarfs |
UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
URI: | https://discovery.ucl.ac.uk/id/eprint/1477426 |
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