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arXiv 1205.3259astro-ph.HE
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回退盘对中子星光谱和时间特性的影响

The influence of fallback discs on the spectral and timing properties of neutron stars

Ting Yan, Rosalba Perna, Roberto Soria

摘要:

中子星(NS)周围的回退盘被认为是超新星爆炸的预期结果。在这里,我们调查的后果,这样一个共同的结果,相关的NS人口的时间和光谱特性,使用蒙特卡罗人口合成模型。我们发现,由回退盘施加的长期扭矩可以大大影响后期的时间周期分布,但与定量的差异取决于初始自旋分布是由慢或快的自旋。对于后者,一个单峰的初始自旋分布变成双峰在以后的时间。计时年龄往往会低估年长者的真实年龄,而高估年轻者的年龄。制动指数在1.5 <~ n <~ 3的范围内聚集,对于慢生的恒星,制动指数在-0.5 <~ n <~ 5的范围内聚集,对于快生的恒星,制动指数在-0.5 <~ n <~ 5的范围内聚集,年轻的天体主要在n <~ 3的范围内发现。较大的n值(虽然不常见)是可能的,并且与NS+椎间盘系统中的扭矩转换相关。发现NS+盘系统的0.1-10 keV热光度在早期(t <~ 10^3年)通常由盘发射控制,但这比NS的热表面发射下降得更快。根据初始参数的不同,可能会有一些偶然的时期,其中一些NS从推进器阶段切换到吸积阶段,将它们的光度增加到爱丁顿极限约10^3-10^4年。

英文摘要:

Fallback discs around neutron stars (NSs) are believed to be an expected outcome of supernova explosions. Here we investigate the consequences of such a common outcome for the timing and spectral properties of the associated NS population, using Monte Carlo population synthesis models. We find that the long-term torque exerted by the fallback disc can substantially influence the late-time period distribution, but with quantitative differences which depend on whether the initial spin distribution is dominated by slow or fast pulsars. For the latter, a single-peaked initial spin distribution becomes bimodal at later times. Timing ages tend to underestimate the real age of older pulsars, and overestimate the age of younger ones. Braking indices cluster in the range 1.5 <~ n <~ 3 for slow-born pulsars, and -0.5 <~ n <~ 5 for fast-born pulsars, with the younger objects found predominantly below n <~ 3. Large values of n, while not common, are possible, and associated with torque transitions in the NS+disc system. The 0.1-10 keV thermal luminosity of the NS+disc system is found to be generally dominated by the disc emission at early times, t <~ 10^3 yr, but this declines faster than the thermal surface emission of the NS. Depending on the initial parameters, there can be occasional periods in which some NSs switch from the propeller to the accretion phase, increasing their luminosity up to the Eddington limit for ~ 10^3-10^4 years.

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