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Magnetically gated accretion in an accreting 'non-magnetic' white dwarf

Magnetically gated accretion in an accreting 'non-magnetic' white dwarf
Magnetically gated accretion in an accreting 'non-magnetic' white dwarf
White dwarfs are often found in binary systems with orbital periods ranging from tens of minutes to hours in which they can accrete gas from their companion stars. In about 15% of these binaries, the magnetic field of the white dwarf is strong enough ($\geq 10^6$ Gauss) to channel the accreted matter along field lines onto the magnetic poles. The remaining systems are referred to as "non-magnetic", since to date there has been no evidence that they have a dynamically significant magnetic field. Here we report an analysis of archival optical observations of the "non-magnetic" accreting white dwarf in the binary system MV Lyrae (hereafter MV Lyr), whose lightcurve displayed quasi-periodic bursts of $\approx 30$ minutes duration every $\approx 2$ hours. The observations indicate the presence of an unstable magnetically-regulated accretion mode, revealing the existence of magnetically gated accretion, where disk material builds up around the magnetospheric boundary (at the co-rotation radius) and then accretes onto the white dwarf, producing bursts powered by the release of gravitational potential energy. We infer a surface magnetic field strength for the white dwarf in MV Lyr between $2 \times 10^4 \leq B \leq 10^5$ Gauss, too low to be detectable by other current methods. Our discovery provides a new way of studying the strength and evolution of magnetic fields in accreting white dwarfs and extends the connections between accretion onto white dwarfs, young stellar objects and neutron stars, for which similar magnetically gated accretion cysles have been identified.
astro-ph.SR, astro-ph.HE
0028-0836
210-213
Scaringi, S.
88701970-a1b9-41fe-bf55-886716ee3374
Macarone, T.J.
9580a85e-bd54-4a56-8ab5-b6668d165304
D'Angelo, C.
e6b94611-e6bb-4e02-9116-69d406f7550c
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Groot, P.J.
6e5c3d50-c4a7-4f4b-a136-c5f85080f7c1
Scaringi, S.
88701970-a1b9-41fe-bf55-886716ee3374
Macarone, T.J.
9580a85e-bd54-4a56-8ab5-b6668d165304
D'Angelo, C.
e6b94611-e6bb-4e02-9116-69d406f7550c
Knigge, C.
ac320eec-631a-426e-b2db-717c8bf7857e
Groot, P.J.
6e5c3d50-c4a7-4f4b-a136-c5f85080f7c1

Scaringi, S., Macarone, T.J., D'Angelo, C., Knigge, C. and Groot, P.J. (2017) Magnetically gated accretion in an accreting 'non-magnetic' white dwarf. Nature, 552, 210-213. (doi:10.1038/nature24653).

Record type: Article

Abstract

White dwarfs are often found in binary systems with orbital periods ranging from tens of minutes to hours in which they can accrete gas from their companion stars. In about 15% of these binaries, the magnetic field of the white dwarf is strong enough ($\geq 10^6$ Gauss) to channel the accreted matter along field lines onto the magnetic poles. The remaining systems are referred to as "non-magnetic", since to date there has been no evidence that they have a dynamically significant magnetic field. Here we report an analysis of archival optical observations of the "non-magnetic" accreting white dwarf in the binary system MV Lyrae (hereafter MV Lyr), whose lightcurve displayed quasi-periodic bursts of $\approx 30$ minutes duration every $\approx 2$ hours. The observations indicate the presence of an unstable magnetically-regulated accretion mode, revealing the existence of magnetically gated accretion, where disk material builds up around the magnetospheric boundary (at the co-rotation radius) and then accretes onto the white dwarf, producing bursts powered by the release of gravitational potential energy. We infer a surface magnetic field strength for the white dwarf in MV Lyr between $2 \times 10^4 \leq B \leq 10^5$ Gauss, too low to be detectable by other current methods. Our discovery provides a new way of studying the strength and evolution of magnetic fields in accreting white dwarfs and extends the connections between accretion onto white dwarfs, young stellar objects and neutron stars, for which similar magnetically gated accretion cysles have been identified.

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Magnetically gated accretion in an accreting - Accepted Manuscript
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Accepted/In Press date: 16 October 2017
e-pub ahead of print date: 13 December 2017
Published date: 14 December 2017
Additional Information: 7 pages, 4 figures. Accepted in Nature 29/1/18 - Author Knigge confirmed Arxiv record 1712.04949 is Accepted manuscript.
Keywords: astro-ph.SR, astro-ph.HE

Identifiers

Local EPrints ID: 417517
URI: http://eprints.soton.ac.uk/id/eprint/417517
ISSN: 0028-0836
PURE UUID: c31e0e52-4800-490a-8c16-61c41b57294d

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Date deposited: 01 Feb 2018 17:31
Last modified: 26 Nov 2021 05:27

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Contributors

Author: S. Scaringi
Author: T.J. Macarone
Author: C. D'Angelo
Author: C. Knigge
Author: P.J. Groot

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