IALP   13078
INSTITUTO DE ASTROFISICA LA PLATA
Unidad Ejecutora - UE
artículos
Título:
Measuring the Evolutionary Rate of Cooling of ZZ Ceti
Autor/es:
A. S. MUKADAM; A. BISCHOFF-KIM; O. FRASER; A. H. CÓRSICO; M. H. MONTGOMERY; S. O. KEPLER; A. D. ROMERO; D. E. WINGET; J. J. HERMES; RIECKEN, T. S.; KRONBERG, M. E; WINGET, K. I.; FALCON, ROSS E.; CHANDLER, D. W.; KUEHNE, J. W.; SULLIVAN, D. J.; REAVES, D.; VON HIPPEL, T.; MULLALLY, F.; SHIPMAN, H.; THOMPSON, S. E.; SILVESTRI, N. M.; HYNES, R. I.
Revista:
ASTROPHYSICAL JOURNAL
Editorial:
IOP PUBLISHING LTD
Referencias:
Lugar: Londres; Año: 2013 vol. 771 p. 17 - 28
ISSN:
0004-637X
Resumen:
We have finally measured the evolutionary rate of cooling of the
pulsating hydrogen atmosphere (DA) white dwarf ZZ Ceti (Ross 548), as
reflected by the drift rate of the 213.13260694 s period. Using 41 yr of
time-series photometry from 1970 November to 2012 January, we determine
the rate of change of this period with time to be dP/dt = (5.2 ±
1.4) × 1015 s s1 employing the
O C method and (5.45 ± 0.79) ×
1015 s s1 using a direct nonlinear
least squares fit to the entire lightcurve. We adopt the dP/dt obtained
from the nonlinear least squares program as our final determination, but
augment the corresponding uncertainty to a more realistic value,
ultimately arriving at the measurement of dP/dt = (5.5 ± 1.0)
× 1015 s s1. After correcting
for proper motion, the evolutionary rate of cooling of ZZ Ceti is
computed to be (3.3 ± 1.1) × 1015 s
s1. This value is consistent within uncertainties with
the measurement of (4.19 ± 0.73) × 1015 s
s1 for another similar pulsating DA white dwarf, G
117-B15A. Measuring the cooling rate of ZZ Ceti helps us refine our
stellar structure and evolutionary models, as cooling depends mainly on
the core composition and stellar mass. Calibrating white dwarf cooling
curves with this measurement will reduce the theoretical uncertainties
involved in white dwarf cosmochronometry. Should the 213.13 s period be
trapped in the hydrogen envelope, then our determination of its drift
rate compared to the expected evolutionary rate suggests an additional
source of stellar cooling. Attributing the excess cooling to the
emission of axions imposes a constraint on the mass of the hypothetical
axion particle.