Farihi, J;
Fossati, L;
Wheatley, PJ;
Metzger, BD;
Mauerhan, J;
Bachman, S;
Gansicke, BT;
... Stone, N; + view all
(2018)
Magnetism, X-rays and accretion rates in WD 1145+017 and other polluted white dwarf systems.
Monthly Notices of the Royal Astronomical Society
, 474
(1)
pp. 947-960.
10.1093/mnras/stx2664.
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Abstract
This paper reports circular spectropolarimetry and X-ray observations of several polluted white dwarfs including WD 1145+017, with the aim to constrain the behaviour of disc material and instantaneous accretion rates in these evolved planetary systems. Two stars with previously observed Zeeman splitting, WD 0322–019 and WD 2105–820, are detected above 5σ and Bz > 1 kG, while WD 1145+017, WD 1929+011, and WD 2326+049 yield (null) detections below this minimum level of confidence. For these latter three stars, high-resolution spectra and atmospheric modelling are used to obtain limits on magnetic field strengths via the absence of Zeeman splitting, finding B∗ < 20 kG based on data with resolving power R ≈ 40 000. An analytical framework is presented for bulk Earth composition material falling on to the magnetic polar regions of white dwarfs, where X-rays and cyclotron radiation may contribute to accretion luminosity. This analysis is applied to X-ray data for WD 1145+017, WD 1729+371, and WD 2326+049, and the upper bound count rates are modelled with spectra for a range of plasma kT = 1–10 keV in both the magnetic and non-magnetic accretion regimes. The results for all three stars are consistent with a typical dusty white dwarf in a steady state at 108–109 g s−1. In particular, the non-magnetic limits for WD 1145+017 are found to be well below previous estimates of up to 1012 g s−1, and likely below 1010 g s−1, thus suggesting the star-disc system may be average in its evolutionary state, and only special in viewing geometry.
| Type: | Article |
|---|---|
| Title: | Magnetism, X-rays and accretion rates in WD 1145+017 and other polluted white dwarf systems |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1093/mnras/stx2664 |
| Publisher version: | http://dx.doi.org/10.1093/mnras/stx2664 |
| Language: | English |
| Additional information: | © 2017 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | Science & Technology, Physical Sciences, Astronomy & Astrophysics, circumstellar matter, stars: magnetic field, planetary systems, white dwarfs, X-rays: stars, DIGITAL SKY SURVEY, INTERSTELLAR-MEDIUM, PLANETARY DEBRIS, CHEMICAL-COMPOSITION, MINOR PLANET, DATA RELEASE, STARS, FIELDS, SEARCH, CONSTRAINTS |
| 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-pp.ucl.ac.uk/id/eprint/10044321 |
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