Back to Volume
Paper: Abell 43 and PG 0122+200: a Look at the Beginning and at the End of the PG 1159 Instability Strip
Volume: 372, 15th European Workshop on White Dwarfs
Page: 641
Authors: Vauclair, G.; Solheim, J.-E.; Fu, J.-N.; Chevreton, M.; Dolez, N.; O'Brien, M.S.; Mukadam, A.S.; Kim, S.-L.; Park, B.-G.; Handler, G.; Medupe, R.; Wood, M.; Gonzalez Perez, J.; Hashimoto, O.; Kinugasa, K.; Taguchi, H.; Kambe, E.; Dobrovolskas, V.; Provencal, J.L.; Dreizler, S.; Schuh, S.; Leibowitz, E.M.; Lipkin, Y.; Zhang, X.-B.; Paparo, M.; Szeidl, B.; Viraghalmy, G.; Zsuffa, D.
Abstract: While Abell 43 is entering the PG 1159 instability strip, in fact as an "hybrid-PG 1159" nucleus of a planetary nebula, PG 0122+200 presently defines its red edge. So these two stars define the limits of the instability strip along the evolutionary sequence from the planetary nebula nuclei to the pre-white dwarf PG 1159 stars. We describe the new observations that have been obtained recently on these two extreme PG 1159 pulsators. Abell 43, the second discovered "hybrid-PG 1159" pulsator after HS 2324+3944, is a multi-periodic low amplitude pulsator with the longest period observed so far in PG 1159 pulsators. As it shows amplitude variations, follow-up observations are needed to obtain a sufficient number of frequencies to start an asteroseismological analysis. We summarize the status of the presently available data. On PG 0122+200, new observations were obtained in 2001 and 2002. Together with previous data, they allow us to detect 23 frequencies, including seven triplets and two single frequencies. We interpret the triplets as = 1 modes split by rotation and confirm an average rotation period of 1.55 days. From the up-dated average period spacing of 22.9 s, we derive a mass of 0.59 - 0.02M, in better agreement with the spectroscopically derived mass than from previous estimates, and a luminosity log(L/L) = 1.3 - 0.5. The uncertainty on the luminosity is dominated by the poorly determined surface gravity. We discuss the impact of that new mass determination on the predicted neutrino luminosity.
Back to Volume