Open AccessMeasuring the Evolution of the Most Stable Optical Clock G 117‐B15A
Author(s) -
S. O. Kepler,
J. E. S. Costa,
B. G. Castanheira,
D. E. Winget,
Fergal Mullally,
R. E. Nather,
Mukremin Kilic,
Ted von Hippel,
Anjum S. Mukadam,
D. J. Sullivan
Publication year - 2005
Publication title -
the astrophysical journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.376
H-Index - 489
eISSN - 1538-4357
pISSN - 0004-637X
DOI - 10.1086/497002
Subject(s) - white dwarf , core (optical fiber) , white (mutation) , period (music) , physics , measure (data warehouse) , adaptation (eye) , astrophysics , geodesy , mathematics , optics , biology , geology , computer science , genetics , acoustics , stars , database , gene
We report our measurement of the rate of change of period with time dP/dt forthe 215 s periodicity in the pulsating white dwarf G 117-B15A, the most stableoptical clock known. After 31 years of observations, we have finally obtained a4 sigma measurement dP/dt_observed = (4.27 +/- 0.80) x 10^{-15} s/s. Takinginto account the proper-motion effect of dP/dt_pm = (7.0 +/- 2.0) x 10^{-16}s/s, we obtain a rate of change of period with time of dP/dt = (3.57 +/- 0.82)x 10^{-15} s/s. This value is consistent with the cooling rate in our whitedwarf models only for cores of C or C/O. With the refinement of the models, theobserved rate of period change can be used to accurately measure the ratio ofC/O in the core of the white dwarf.Comment: 22 pages, 4 figure
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