The Missing Link? Discovery of Pulsations in the Nitrogen-rich PG 1159 Star PG 1144+005

Up to 98% of all single stars will eventually become white dwarfs—stars that link the history and future evolution Galaxy, whose previous is engraved in their interiors. Those interiors can be studied using asteroseismology, utilizing stellar pulsations as seismic waves. The pulsational instability strips DA DB dwarf are pure, allowing for important generalization interior structure represents dwarfs. This not case hottest pulsating dwarfs, GW Vir stars: only about 50% dwarfs this domain pulsate. Several explanations impurity strip have been proposed, based on different elemental abundances, metallicity, helium content. Surprisingly, there a dichotomy rich nitrogen, which by itself cannot cause pulsation driving, pulsate—the exception being nitrogen-rich nonpulsator PG 1144+005. Here, we report discovery 1144+005 new observations. We identified four frequency regions: 40, 55, 97, 112 day−1 with low variable amplitudes 3–6 mmag therefore confirm nitrogen dichotomy. As trace element revealing occurrence very late thermal pulse (VLTP) hot stars, speculate it VLTP provides required make pulsator.