Planets around evolved binary systems

在观测到的3000多个白矮星加主序星（WDMS）系统中，目前已知的共包络后双星（pceb）有200多个。这种后共包络双星（pceb）不仅本身就是令人兴奋的天体，而且它们周围还可能有行星。迄今为止，少数PCEB系统提供了行星存在的证据，尽管它们的动态演化非常剧烈。目前，研究最多，因此最确定的例子是NN Ser，它的日食时间变化可以用一个行星系统的存在来解释，这个行星系统由两个大质量的类木行星组成，大约有7和2 MJup，分别在3和5 AU的距离上绕着它们的宿主双星运行。然而，目前还不清楚这些行星是如何形成的。原则上，这些围绕pceb运行的行星可以与双星一起形成，即第一代（FG）行星，也可以在CE阶段之后形成，即第二代（SG）行星。在这里，我们将用包括n体相互作用在内的三维流体动力学模拟来研究这两种情况。

From the more than 3000 observed white dwarf plus main-sequence (WDMS) systems, by now more than 200 post common envelope binaries (PCEBs) are known. Such post-common-envelope binaries (PCEBs) are not only exciting objects by themselves but could also harbour planets around them. To date, a handfull of PCEB systems have provided evidence for the presence of planets, despite their violent dynamical evolution. Currently, the most studied and hence most certain case is NN Ser, whose eclipse-timing variations can be explained by the presence of a planetary system consisting of two massive Jovian planets with roughly 7 and 2 MJup, orbiting their hosting binary at distances of 3 and 5 AU, respectively. Yet it is unclear how those planets are formed. In principle, such planets orbiting PCEBs can either form together with the binary, i.e. as first generation (FG) planets, or can be formed after the CE phase, as second generation (SG) planets. Here we will study both scenarios with three dimensional hydrodynamical simulations including N-body interaction.