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arXiv 0704.2874astro-ph
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4U 0115+63来自RXTE和INTEGRAL数据:脉冲轮廓和回旋加速器线能量

4U 0115+63 from RXTE and INTEGRAL Data: Pulse Profile and Cyclotron Line Energy

S. S. Tsygankov, A. A. Lutovinov, E. M. Churazov, R. A. Sunyaev

摘要:

利用RXTE和INTEGRAL天文台对4U 0115+63在宽X射线(3-100 keV)能区的观测资料,分析了其在1999年和2004年的强烈爆发过程。回旋共振吸收线的基波能量接近来自源的X射线通量的最大值(亮度范围为5x 10 ^{37} -2x 10 ^{38} erg/s),约为11 keV。当脉冲星的光度低于~ 5 × 10 ^{37} erg/s时,基波的能量急剧地向高能量方向移动,最高可达~16 keV。在假设的偶极磁场配置,这种变化的回旋谐波能量对应的发射区域的高度减少约2公里,而其他光谱参数,特别是,截止能量,基本上保持不变。在光度约为7 × 10 ^{37} erg/s时,在光谱中可以清楚地看到四个几乎等距的回旋线谐波。这表明,要么发射起源的区域是紧凑的,要么从吸积柱的不同(高度)段的出射光谱是均匀的。我们已经发现了显着的脉冲轮廓的变化与能量,光度和时间。特别是,我们表明,从脉冲到脉冲的轮廓变化不会减少到一个简单的调制的吸积率指定的外部条件。

英文摘要:

We analyze the observations of the transient X-ray pulsar 4U 0115+63 with the RXTE and INTEGRAL observatories in a wide X-ray (3-100 keV) energy band during its intense outbursts in 1999 and 2004. The energy of the fundamental harmonic of the cyclotron resonance absorption line near the maximum of the X-ray flux from the source (luminosity range 5x10^{37} - 2x10^{38} erg/s) is ~11 keV. When the pulsar luminosity falls below ~5x10^{37} erg/s, the energy of the fundamental harmonic is displaced sharply toward the high energies, up to ~16 keV. Under the assumption of a dipole magnetic field configuration, this change in cyclotron harmonic energy corresponds to a decrease in the height of the emitting region by ~2 km, while other spectral parameters, in particular, the cutoff energy, remain essentially constant. At a luminosity ~7x10^{37} erg/s, four almost equidistant cyclotron line harmonics are clearly seen in the spectrum. This suggests that either the region where the emission originates is compact or the emergent spectrum from different (in height) segments of the accretion column is uniform. We have found significant pulse profile variations with energy, luminosity, and time. In particular, we show that the profile variations from pulse to pulse are not reduced to a simple modulation of the accretion rate specified by external conditions.

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