KOEN C., O'DONOGHUE D., KILKENNY D., STOBIE R.S. and SAFFER R.A.
Abstract (from CDS):
We report the discovery of short-period oscillations in the sdB stars EC 05217-3914 and KUV 0442+1416, establishing them as members of the EC 14026 stars, a recently discovered class of sdB pulsators. The pulsation periods and atmospheric parameters for both stars are determined. The results are: periods of 218, 216 and 213 s, Teff = 31 300±250 K and log g= 5.76 ± 0.06 for EC 05217-3914; periods of 231, 216 and 184 s, Teff = 30 900 ± 400 K and log g= 5.72±0.1 for KUV 0442+1416. Considerable substructure in the periods is apparent in both stars when several nights of data are combined. KUV 0442+1416 is significantly reddened. The evolutionary status of the 13 well-studied EC 14026 stars is examined. All stars except PG 1605+072 appear to be core He burning. The positions of the pulsators and the apparently constant stars are plotted in the log g-Teff plane. Apparently constant stars mingle with the pulsators so that there is no well-defined instability strip. This poses a significant challenge to the Fe driving mechanism of Charpinet et al. Five out of the 13 pulsators are obvious binaries.