Searching for long period pulsations in He-rich subdwarfs

热亚矮星是氦核燃烧的恒星，它们失去了富含h的包层。虽然大多数热亚矮星显示出几乎纯氢的大气，但这些恒星中有一小部分显示出混合的氢/氦表面组成。这些恒星预计将在氦核闪光后立即处于快速阶段，在此阶段，引力沉降尚未使大气变成纯氢。在这个阶段，它们预计会经历氦核亚闪，预计会驱动脉动。由氦核闪光驱动的恒星脉动的确认将是对氦亚闪光本身存在的第一次直接确认。我们利用Calar Alto天文台的BUSCA仪器进行了四个晚上的观测，对14个H/He混合大气的热亚矮星的恒星振荡进行了特别搜索。

Hot subdwarf stars are He-core burning stars that have lost their H-rich envelopes. While most hot subdwarfs show almost pure H atmospheres, a small fraction of these stars show a mixed H/He surface composition. These stars are expected to be in a fast stage immediately after the He-core flash, where gravitational settling did not turn the atmosphere H-pure yet. During this phase they are expected to undergo He-core subflashes, which are predicted to drive pulsations. The confirmation of stellar pulsations driven by the He-core flash would be the first direct confirmation of the existence of the He-subflashes themselves. We granted four nights of observing time with the BUSCA instrument at the Calar Alto observatory to pursue an ad hoc search of stellar oscillations in 14 hot subdwarfs with mixed H/He atmospheres.