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Subtle flickering in Cepheids: Kepler and MOST

Published online by Cambridge University Press:  18 February 2014

Nancy Remage Evans ,
Robert Szabó ,
Laszlo Szabados ,
Aliz Derekas ,
Jaymie M. Matthews ,
Chris Cameron  and
the MOST Team
Nancy Remage Evans
Affiliation:
SAO, MS 4, 60 Garden St., Cambridge, MA 02138, USA email: [email protected]
Robert Szabó
Affiliation:
MTA CSFK Konkoly Thege Miklos ut 15-17, H-1121 BudapestHungary
Laszlo Szabados
Affiliation:
MTA CSFK Konkoly Thege Miklos ut 15-17, H-1121 BudapestHungary
Aliz Derekas
Affiliation:
MTA CSFK Konkoly Thege Miklos ut 15-17, H-1121 BudapestHungary
Jaymie M. Matthews
Affiliation:
Dept. of Physics and Astronomy, Univ. of British Columbia, Vancouver, BC, Canada
Chris Cameron
Affiliation:
Dept. of Physics and Astronomy, Univ. of British Columbia, Vancouver, BC, Canada
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Abstract

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Fundamental mode classical Cepheids have light curves which repeat accurately enough that we can watch them evolve (change period). The new level of accuracy and quantity of data with the Kepler and MOST satellites probes this further. An intriguing result was found in the long time-series of Kepler data for V1154 Cyg the one classical Cepheid (fundamental mode, P = 4.9 d) in the field, which has short term changes in period (≃20 minutes), correlated for ≃10 cycles (period jitter). To follow this up, we obtained a month long series of observations of the fundamental mode Cepheid RT Aur and the first overtone pulsator SZ Tau. RT Aur shows the traditional strict repetition of the light curve, with the Fourier amplitude ratio R1/R2 remaining nearly constant. The light curve of SZ Tau, on the other hand, fluctuates in amplitude ratio at the level of approximately 50%. Furthermore prewhitening the RT Aur data with 10 frequencies reduces the Fourier spectrum to noise. For SZ Tau, considerable power is left after this prewhitening in a complicated variety of frequencies.

Keywords

stars: variables: CepheidspulsationKeplerMOST satellite photometry
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 9 , Symposium S301: Precision Asteroseismology , August 2013 , pp. 55 - 58
Copyright
Copyright © International Astronomical Union 2014 

References

Derekas, A., Szabó, Gy. M., Berdnikov, L., et al. 2012, MNRAS, 425, 1312Google Scholar
Matthews, J. M., Kuschnig, R., Guenther, D. B., et al. 2004, Nature, 430, 51Google Scholar
Szabados, L. 1983, Ap&SS, 96, 185Google Scholar
Walker, G., Matthews, J. M., Kuschnig, R., et al. 2003, PASP, 115, 1023Google Scholar