Novel modelling of ultracompact X-ray binary evolution - stable mass transfer from white dwarfs to neutron stars
Novel modelling of ultracompact X-ray binary evolution - stable mass transfer from white dwarfs to neutron stars
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DOI：
10.1093/mnrasl/slx064
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发表时间：
2017-04
影响因子：
4.8
通讯作者：
R. Sengar;T. Tauris;N. Langer;A. Istrate
中科院分区：
文献类型：
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作者：
R. Sengar;T. Tauris;N. Langer;A. Istrate
由于轨道的引力衰减，围绕毫秒脉冲星(MSPS)运行的氦-白矮星(He-WDS)的致密双星最终将“合并”。据预测，其结果是产生长寿命的超致密X射线双星(UCXB)，在UCXB中，WD将物质转移到吸积的中子星(NS)。在这里，我们第一次给出了完整的数值计算，从他WD到NS的这种稳定的质量传递。我们已经计算了一些完整的双星演化轨迹，从LMXB之前的系统开始，并将这些演化到分离的MSP+WD系统，并进一步演化到UCXB。最小轨道周期被发现短至5.6分钟。我们跟随着随后系统的扩大，直到施主恒星在大约一个哈勃时间后成为质量约为0.005太阳的行星。我们的模型能够解释观测到的具有高氦丰度的UCXB的性质，并且我们可以在质量传输率与轨道周期的关系图中识别上升或下降分支上的这些源。
Tight binaries of helium white dwarfs (He WDs) orbiting millisecond pulsars (MSPs) will eventually "merge" due to gravitational damping of the orbit. The outcome has been predicted to be the production of long-lived ultra-compact X-ray binaries (UCXBs), in which the WD transfers material to the accreting neutron star (NS). Here we present complete numerical computations, for the first time, of such stable mass transfer from a He WD to a NS. We have calculated a number of complete binary stellar evolution tracks, starting from pre-LMXB systems, and evolved these to detached MSP+WD systems and further on to UCXBs. The minimum orbital period is found to be as short as 5.6 minutes. We followed the subsequent widening of the systems until the donor stars become planets with a mass of ~0.005 Msun after roughly a Hubble time. Our models are able to explain the properties of observed UCXBs with high helium abundances and we can identify these sources on the ascending or descending branch in a diagram displaying mass-transfer rate vs. orbital period.