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arXiv 0705.1249astro-ph
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IGR J17254-3257，一颗新的爆发中子星

IGR J17254-3257, a new bursting neutron star

J. Chenevez, M. Falanga, E. Kuulkers, R. Walter, L. Bildsten, S. Brandt, N. Lund, T. Oosterbroek, J. Zurita Heras

备注：
4 pages, 4 figures, 1 table; accepted for publication in A&A Letters. 1 reference (Cooper & Narayan, 2007) corrected
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摘要：

当研究从富氢爆发区到纯氦爆发区以及从氦燃烧到碳燃烧的转变时，研究从低光度源发出的具有长达几十分钟的衰变时间的罕见长爆发的观测特性是很重要的。IGR J17254-3257是最近发现的X射线爆发，其中只有两个爆发被记录：一个普通的短I型X射线爆发和一个15分钟长的爆发。其距离上限估计约为14.5千秒差距。利用同期的INTEGRAL和XMM-牛顿数据获得的0.3-100 keV能量带持续发射的宽带光谱表明，在8 kpc的正则距离处，辐射热通量为1.1 × 10 ^-10 erg/cm 2/s，对应于0.1-100 keV之间的光度约为8.4 × 10^35 erg/s，这意味着每年的平均吸积率约为7 × 10 ^-11太阳质量。IGR J17254-3257的低X射线持续光度似乎表明该源可能处于低吸积速率状态，通常与X射线范围内的硬光谱相关。核燃烧状态可能介于纯He和混合H/He燃烧之间。长爆发是厚He层积累的结果，而短爆发是在稍低的吸积速率下由过早的H触发的He燃烧爆发。

英文摘要：

The study of the observational properties of uncommonly long bursts from low luminosity sources with extended decay times up to several tens of minutes is important when investigating the transition from a hydrogen-rich bursting regime to a pure helium regime and from helium burning to carbon burning as predicted by current burst theories. IGR J17254-3257 is a recently discovered X-ray burster of which only two bursts have been recorded: an ordinary short type I X-ray burst, and a 15 min long burst. An upper limit to its distance is estimated to about 14.5 kpc. The broad-band spectrum of the persistent emission in the 0.3-100 keV energy band obtained using contemporaneous INTEGRAL and XMM-Newton data indicates a bolometric flux of 1.1x10^-10 erg/cm2/s corresponding, at the canonical distance of 8 kpc, to a luminosity about 8.4x10^35 erg/s between 0.1-100 keV, which translates to a mean accretion rate of about 7x10^-11 solar masses per year. The low X-ray persistent luminosity of IGR J17254-3257 seems to indicate the source may be in a state of low accretion rate usually associated with a hard spectrum in the X-ray range. The nuclear burning regime may be intermediate between pure He and mixed H/He burning. The long burst is the result of the accumulation of a thick He layer, while the short one is a prematurate H-triggered He burning burst at a slightly lower accretion rate.

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