ADC源2A 1822-371的新星历：30年以上稳定轨道周期导数
New ephemeris of the ADC source 2A 1822-371: a stable orbital-period derivative over 30 years
摘要：
我们报告的日食到达时间的低质量X射线双星和X射线脉冲星2A 1822-371的时间进行使用所有可用的观测的正比计数器阵列上的罗西X射线定时探测器，XMM-牛顿pn，和钱德拉。这些观察跨越了1996年至2008年。结合这些日食到达时间的测量与那些已经提供的涵盖期间从1977年至1996年，我们得到一个有效的轨道解决方案超过三十年。相对于恒定轨道周期模型计算的时间延迟显示出明显的抛物线趋势，这意味着该源中的轨道周期以$\dot P_orb = 1.50(7) \times 10^{-10}$ s/s的速率随时间不断增加。这比由磁制动和引力辐射驱动的保守质量传递所预期的大3个数量级。从系统的角动量守恒出发，我们发现要解释轨道周期导数的高正值，质量转移速率必须不小于3倍于中子星的爱丁顿极限，这表明质量转移必须是部分非保守的。假设中子星在爱丁顿极限处吸积，我们找到了一个一致的解，其中至少70%的转移质量必须从系统中排出。
英文摘要：
We report on a timing of the eclipse arrival times of the low mass X-ray binary and X-ray pulsar 2A 1822-371 performed using all available observations of the Proportional Counter Array on board the Rossi X-ray Timing Explorer, XMM-Newton pn, and Chandra. These observations span the years from 1996 to 2008. Combining these eclipse arrival time measurements with those already available covering the period from 1977 to 1996, we obtain an orbital solution valid for more than thirty years. The time delays calculated with respect to a constant orbital period model show a clear parabolic trend, implying that the orbital period in this source constantly increases with time at a rate $\dot P_orb = 1.50(7) \times 10^{-10}$ s/s. This is 3 orders of magnitude larger than what is expected from conservative mass transfer driven by magnetic braking and gravitational radiation. From the conservation of the angular momentum of the system we find that to explain the high and positive value of the orbital period derivative the mass transfer rate must not be less than 3 times the Eddington limit for a neutron star, suggesting that the mass transfer has to be partially non-conservative. With the hypothesis that the neutron star accretes at the Eddington limit we find a consistent solution in which at least 70% of the transferred mass has to be expelled from the system.
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