Kepler K2 observations of the intermediate polar FO Aquarii

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Date
2016-04-20
Authors
Kennedy, Mark R.
Garnavich, Peter M.
Breedt, E.
Marsh, T. R.
Gänsicke, B. T.
Steeghs, D.
Szkody, P.
Dai, Z.
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Oxford University Press
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Abstract
We present photometry of the intermediate polar FO Aquarii (FO Aqr) obtained as part of the K2 mission using the Kepler space telescope. The amplitude spectrum of the data confirms the orbital period of 4.8508(4) h, and the shape of the light curve is consistent with the outer edge of the accretion disc being eclipsed when folded on this period. The average flux of FO Aqr changed during the observations, suggesting a change in the mass accretion rate. There is no evidence in the amplitude spectrum of a longer period that would suggest disc precession. The amplitude spectrum also shows the white dwarf spin period of 1254.3401(4) s, the beat period of 1351.329(2) s, and 31 other spin and orbital harmonics. The detected period is longer than the last reported period of 1254.284(16) s, suggesting that FO Aqr is now spinning down, and has a positive P. There is no detectable variation in the spin period over the course of the K2 observations, but the phase of the spin cycle is correlated with the system brightness. We also find that the amplitude of the beat signal is correlated with the system brightness.
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Accretion , Accretion discs , Magnetic fields – eclipses , Novae Cataclysmic variables , White dwarfs
Citation
Kennedy, M. R., Garnavich, P., Breedt, E., Marsh, T. R., Gänsicke, B. T., Steeghs, D., Szkody, P. and Dai, Z. (2016) 'Kepler K2 observations of the intermediate polar FO Aquarii', Monthly Notices of the Royal Astronomical Society, 459(4), pp. 3622-3628. doi:10.1093/mnras/stw834
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This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society, © 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.