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GW Librae: A unique laboratory for pulsations in an accreting white dwarf

GW Librae: A unique laboratory for pulsations in an accreting white dwarf
GW Librae: A unique laboratory for pulsations in an accreting white dwarf
Non-radial pulsations have been identified in a number of accreting white dwarfs in cataclysmic variables. These stars offer insight into the excitation of pulsation modes in atmospheres with mixed compositions of hydrogen, helium, and metals, and the response of these modes to changes in the white dwarf temperature. Among all pulsating cataclysmic variable white dwarfs, GW Librae stands out by having a well-established observational record of three independent pulsation modes that disappeared when the white dwarf temperature rose dramatically following its 2007 accretion outburst. Our analysis of Hubble Space Telescope (HST) ultraviolet spectroscopy taken in 2002, 2010, and 2011, showed that pulsations produce variations in the white dwarf effective temperature as predicted by theory. Additionally in 2013 May, we obtained new HST/Cosmic Origin Spectrograph ultraviolet observations that displayed unexpected behaviour: besides showing variability at ?275 s, which is close to the post-outburst pulsations detected with HST in 2010 and 2011, the white dwarf exhibits high-amplitude variability on an ?4.4 h time-scale. We demonstrate that this variability is produced by an increase of the temperature of a region on white dwarf covering up to ?30?per?cent of the visible white dwarf surface. We argue against a short-lived accretion episode as the explanation of such heating, and discuss this event in the context of non-radial pulsations on a rapidly rotating star.
0035-8711
3929-3938
Toloza, O.
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Gansicke, B.T.
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Hermes, J.J.
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Townsley, D.M.
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Schreiber, M.R.
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Szkody, P.
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Pala, A.
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Beuermann, K.
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Bildsten, L.
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Breedt, E.
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Cook, M.
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Godon, P.
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Henden, A.A.
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Hubeny, I.
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Knigge, C.
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Long, K.S.
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Marsh, R.R.
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De Martino, D.
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Mukadam, A.S.
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Myers, G.
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Nelson, P.
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Oksanen, A.
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Patterson, J.
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Sion, E.M.
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Zorotovic, M.
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Toloza, O.
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Gansicke, B.T.
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Hermes, J.J.
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Townsley, D.M.
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Schreiber, M.R.
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Szkody, P.
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Pala, A.
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Beuermann, K.
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Bildsten, L.
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Breedt, E.
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Cook, M.
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Godon, P.
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Henden, A.A.
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Hubeny, I.
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Knigge, C.
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Long, K.S.
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Marsh, R.R.
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De Martino, D.
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Mukadam, A.S.
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Myers, G.
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Nelson, P.
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Oksanen, A.
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Patterson, J.
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Sion, E.M.
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Zorotovic, M.
ca25d8c2-3165-4320-82c4-f6242f656d05

Toloza, O., Gansicke, B.T., Hermes, J.J., Townsley, D.M., Schreiber, M.R., Szkody, P., Pala, A., Beuermann, K., Bildsten, L., Breedt, E., Cook, M., Godon, P., Henden, A.A., Hubeny, I., Knigge, C., Long, K.S., Marsh, R.R., De Martino, D., Mukadam, A.S., Myers, G., Nelson, P., Oksanen, A., Patterson, J., Sion, E.M. and Zorotovic, M. (2016) GW Librae: A unique laboratory for pulsations in an accreting white dwarf. Monthly Notices of the Royal Astronomical Society, 459 (4), 3929-3938. (doi:10.1093/mnras/stw838).

Record type: Article

Abstract

Non-radial pulsations have been identified in a number of accreting white dwarfs in cataclysmic variables. These stars offer insight into the excitation of pulsation modes in atmospheres with mixed compositions of hydrogen, helium, and metals, and the response of these modes to changes in the white dwarf temperature. Among all pulsating cataclysmic variable white dwarfs, GW Librae stands out by having a well-established observational record of three independent pulsation modes that disappeared when the white dwarf temperature rose dramatically following its 2007 accretion outburst. Our analysis of Hubble Space Telescope (HST) ultraviolet spectroscopy taken in 2002, 2010, and 2011, showed that pulsations produce variations in the white dwarf effective temperature as predicted by theory. Additionally in 2013 May, we obtained new HST/Cosmic Origin Spectrograph ultraviolet observations that displayed unexpected behaviour: besides showing variability at ?275 s, which is close to the post-outburst pulsations detected with HST in 2010 and 2011, the white dwarf exhibits high-amplitude variability on an ?4.4 h time-scale. We demonstrate that this variability is produced by an increase of the temperature of a region on white dwarf covering up to ?30?per?cent of the visible white dwarf surface. We argue against a short-lived accretion episode as the explanation of such heating, and discuss this event in the context of non-radial pulsations on a rapidly rotating star.

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Accepted/In Press date: 8 April 2016
e-pub ahead of print date: 13 April 2016
Published date: 11 July 2016
Organisations: Astronomy Group

Identifiers

Local EPrints ID: 396287
URI: http://eprints.soton.ac.uk/id/eprint/396287
ISSN: 0035-8711
PURE UUID: a578ba0f-c9ad-4438-8ab5-e3322eb61b89

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Date deposited: 07 Jun 2016 14:18
Last modified: 16 Dec 2019 19:53

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Contributors

Author: O. Toloza
Author: B.T. Gansicke
Author: J.J. Hermes
Author: D.M. Townsley
Author: M.R. Schreiber
Author: P. Szkody
Author: A. Pala
Author: K. Beuermann
Author: L. Bildsten
Author: E. Breedt
Author: M. Cook
Author: P. Godon
Author: A.A. Henden
Author: I. Hubeny
Author: C. Knigge
Author: K.S. Long
Author: R.R. Marsh
Author: D. De Martino
Author: A.S. Mukadam
Author: G. Myers
Author: P. Nelson
Author: A. Oksanen
Author: J. Patterson
Author: E.M. Sion
Author: M. Zorotovic

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