Bibcode
Mukadam, A. S.; Kepler, S. O.; Winget, D. E.; Nather, R. E.; Kilic, M.; Mullally, F.; von Hippel, T.; Kleinman, S. J.; Nitta, A.; Guzik, J. A.; Bradley, P. A.; Matthews, J.; Sekiguchi, K.; Sullivan, D. J.; Sullivan, T.; Shobbrook, R. R.; Birch, P.; Jiang, X. J.; Xu, D. W.; Joshi, S.; Ashoka, B. N.; Ibbetson, P.; Leibowitz, E.; Ofek, E. O.; Meištas, E. G.; Janulis, R.; Ališauskas, D.; Kalytis, R.; Handler, G.; Kilkenny, D.; O'Donoghue, D.; Kurtz, D. W.; Müller, M.; Moskalik, P.; Ogoza, W.; Zoa, S.; Krzesiński, J.; Johannessen, F.; Gonzalez-Perez, J. M.; Solheim, J.-E.; Silvotti, R.; Bernabei, S.; Vauclair, G.; Dolez, N.; Fu, J. N.; Chevreton, M.; Manteiga, M.; Suárez, O.; Ulla, A.; Cunha, M. S.; Metcalfe, T. S.; Kanaan, A.; Fraga, L.; Costa, A. F. M.; Giovannini, O.; Fontaine, G.; Bergeron, P.; O'Brien, M. S.; Sanwal, D.; Wood, M. A.; Ahrens, T. J.; Silvestri, N.; Klumpe, E. W.; Kawaler, S. D.; Riddle, R.; Reed, M. D.; Watson, T. K.
Referencia bibliográfica
Baltic Astronomy, v.12, p.71-103.
Advertised on:
0
2003
Número de citas
6
Número de citas referidas
3
Descripción
We report our analysis of the stability of pulsation periods in the DAV
star (pulsating hydrogen atmosphere white dwarf) ZZ Ceti, also called R
548. Based on observations that span 31 years, we conclude that the
period 213.132605 s observed in ZZ Ceti drifts at a rate
dP/dt<=(5.5+/-1.9)times 10-15 s/s, after correcting for
proper motion. Our results are consistent with previous Pdot values for
this mode and an improvement over them due to the larger time-base. The
characteristic stability timescale implied for the pulsation period is
mid P/Pdot mid >=1.2 Gyr, comparable to the theoretical cooling
timescale for the star. Our current stability limit for the period
213.132605 s is only slightly less than the present measurement for G
117-B15A for the period 215.2 s, another DAV, establishing this mode in
ZZ Ceti as the second most stable optical clock known, more stable than
atomic clocks and most pulsars. Constraining the cooling rate of ZZ
Ceti aids theoretical evolutionary models and white dwarf
cosmochronology. The drift rate of this clock is small enough that
reflex motion caused by any orbital planets is detectable within limits;
our dot {P} constraint places limits on the mass and/or distance of any
orbital companions.