GW Librae

A unique laboratory for pulsations in an accreting white dwarf

O. Toloza, B. T. Gänsicke, J. J. Hermes, D. M. Townsley, M. R. Schreiber, P. Szkody, A. Pala, K. Beuermann, L. Bildsten, E. Breedt, M. Cook, P. Godon, A. A. Henden, Ivan - Hubeny, C. Knigge, K. S. Long, T. R. Marsh, D. de Martino, A. S. Mukadam, G. Myers & 5 others P. Nelson, A. Oksanen, J. Patterson, E. M. Sion, M. Zorotovic

Research output: Contribution to journalArticle

8 Citations (Scopus)

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.

Original languageEnglish (US)
Pages (from-to)3929-3938
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Volume459
Issue number4
DOIs
StatePublished - 2016

Fingerprint

Hubble Space Telescope
cataclysmic variables
outburst
temperature
accretion
ultraviolet spectrometers
stars
ultraviolet spectroscopy
helium
coverings
spectroscopy
hydrogen
heating
timescale
atmospheres
laboratory
atmosphere
metal
metals
excitation

Keywords

  • Binaries: close
  • Stars: individual: GW Librae
  • Stars: variables: general
  • White dwarfs

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Toloza, O., Gänsicke, B. T., Hermes, J. J., Townsley, D. M., Schreiber, M. R., Szkody, P., ... 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. https://doi.org/10.1093/mnras/stw838

GW Librae : A unique laboratory for pulsations in an accreting white dwarf. / Toloza, O.; Gänsicke, 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, Ivan -; Knigge, C.; Long, K. S.; Marsh, T. R.; de Martino, D.; Mukadam, A. S.; Myers, G.; Nelson, P.; Oksanen, A.; Patterson, J.; Sion, E. M.; Zorotovic, M.

In: Monthly Notices of the Royal Astronomical Society, Vol. 459, No. 4, 2016, p. 3929-3938.

Research output: Contribution to journalArticle

Toloza, O, Gänsicke, BT, Hermes, JJ, Townsley, DM, Schreiber, MR, Szkody, P, Pala, A, Beuermann, K, Bildsten, L, Breedt, E, Cook, M, Godon, P, Henden, AA, Hubeny, I, Knigge, C, Long, KS, Marsh, TR, de Martino, D, Mukadam, AS, Myers, G, Nelson, P, Oksanen, A, Patterson, J, Sion, EM & Zorotovic, M 2016, 'GW Librae: A unique laboratory for pulsations in an accreting white dwarf', Monthly Notices of the Royal Astronomical Society, vol. 459, no. 4, pp. 3929-3938. https://doi.org/10.1093/mnras/stw838
Toloza, O. ; Gänsicke, 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, Ivan - ; Knigge, C. ; Long, K. S. ; Marsh, T. R. ; de Martino, D. ; Mukadam, A. S. ; Myers, G. ; Nelson, P. ; Oksanen, A. ; Patterson, J. ; Sion, E. M. ; Zorotovic, M. / GW Librae : A unique laboratory for pulsations in an accreting white dwarf. In: Monthly Notices of the Royal Astronomical Society. 2016 ; Vol. 459, No. 4. pp. 3929-3938.
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AU - Toloza, O.

AU - Gänsicke, B. T.

AU - Hermes, J. J.

AU - Townsley, D. M.

AU - Schreiber, M. R.

AU - Szkody, P.

AU - Pala, A.

AU - Beuermann, K.

AU - Bildsten, L.

AU - Breedt, E.

AU - Cook, M.

AU - Godon, P.

AU - Henden, A. A.

AU - Hubeny, Ivan -

AU - Knigge, C.

AU - Long, K. S.

AU - Marsh, T. R.

AU - de Martino, D.

AU - Mukadam, A. S.

AU - Myers, G.

AU - Nelson, P.

AU - Oksanen, A.

AU - Patterson, J.

AU - Sion, E. M.

AU - Zorotovic, M.

PY - 2016

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N2 - 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.

AB - 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.

KW - Binaries: close

KW - Stars: individual: GW Librae

KW - Stars: variables: general

KW - White dwarfs

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