Measuring the Evolution of the Most Stable Optical Clock G 117-B15A

We report our measurement of the rate of change of period with time (P) for the 215 s periodicity in the pulsating white dwarf G 117-B15 A, the most stable optical clock known. After 31 years of observations, we have finally obtained a 4 s measurement P sub(observed) = (4-27 c 0.80) x 10 super(-15)...

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Bibliographic Details
Published in:The Astrophysical journal 2005-12, Vol.634 (2), p.1311-1318
Main Authors: Kepler, S. O, Costa, J. E. S, Castanheira, B. G, Winget, D. E, Mullally, Fergal, Nather, R. E, Kilic, Mukremin, von Hippel, Ted, Mukadam, Anjum S, Sullivan, Denis J
Format: Article
Language:English
Subjects:
Astronomy
Earth, ocean, space
Exact sciences and technology
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Summary:We report our measurement of the rate of change of period with time (P) for the 215 s periodicity in the pulsating white dwarf G 117-B15 A, the most stable optical clock known. After 31 years of observations, we have finally obtained a 4 s measurement P sub(observed) = (4-27 c 0.80) x 10 super(-15) s s super(-1). Taking into account the proper-motion effect of P sub(proper) = (7.0 c 2.0) x 10 super(-16) s s super(-1), we obtain a rate of change of period with time of P = (3.57 c 0.82) x 10 super(-15) s s super(-1). This value is consistent with the cooling rate in our white dwarf models only for cores of C or C/O. With the refinement of the models, the observed rate of period change can be used to accurately measure the ratio of C/O in the core of the white dwarf.
ISSN:0004-637X
1538-4357
DOI:10.1086/497002