An Extremely Hot Pulsating Pre-White Dwarf from OGLE

Abstract

We show that the blue 18.3-minute variable object discovered in the Galactic disk by the OGLE-III survey and named OGLE-GD-WD-0001 is a pulsating pre-white dwarf of PG 1159 spectral type. With an effective temperature of about 160,000 K it is among the hottest known pulsators being located close to the blue edge of the GW Virginis instability strip. The long-term OGLE observations indicate that the object has a positive period change rate of about $5 \times 10^{-10}$ $s~s^{-1}$ and thus already contracts. There are no traces of a planetary nebula around this star.