Energy dependence of a low frequency QPO in GRS 1915+105
Energy dependence of a low frequency QPO in GRS 1915+105
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DOI：
10.1051/0004-6361:20020218
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发表时间：
2002-02
影响因子：
6.5
通讯作者：
J. Rodriguez;P. Durouchoux;I. Mirabel;Y. Ueda;M. Tagger;K. Yamaoka
中科院分区：
文献类型：
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作者：
J. Rodriguez;P. Durouchoux;I. Mirabel;Y. Ueda;M. Tagger;K. Yamaoka
我们分析了一组三个RXTE目标的机会观测银河系微类星体GRS 1915+105，观察2000年4月，在多波长的运动。在三个观测期间，一个强大的，可变的低频（2 - 9 Hz）准周期振荡（以下简称QPO），通常被称为无处不在的QPO，检测到连同其第一谐波。我们研究了这两个特征的光谱性质，结果表明：1）它们的频率变化与软X射线通量（2.5keV）有较好的相关性，从而有利于QPO在吸积盘中的位置：2）QPO对硬X射线的影响更大，通常被认为是软光子在日冕中的逆康普顿散射的特征; 3）基波及其谐波的行为方式不同：基波的功率随着能量的增加而增加，直到40 keV，而谐波的功率随着能量的增加而增加，直到10 keV。这里给出的结果可以在吸积-抛射不稳定性的背景下得到解释，吸积-抛射不稳定性可以表现为位于盘的最内边缘和共旋半径之间的旋转螺旋或热点。谐波的存在可能是不稳定性的非线性行为的特征。基频的高能量（>40 keV）降低将有利于这样一种解释，即在高能量下的大部分或所有准周期调制不是来自通常假设的康普顿化日冕，而是来自光学厚盘中的热点。
We analyze a set of three RXTE Target of Opportunity observations of the Galactic microquasar GRS 1915+105, observed on April 2000, during a multi-wavelength campaign. During the three observations, a strong, variable low frequency (2 9 Hz) quasi periodic oscillation (hereafter QPO), often referred to as the ubiquitous QPO, is detected together with its rst harmonic. We study the spectral properties of both features, and show that: 1) their frequency variations are better correlated with the soft X-ray flux (2 5k eV), favoring thus the location of the QPO in the accretion disk; 2) the QPO aects more the hard X-rays, usually taken as the signature of an inverse Compton scattering of the soft photons in a corona; 3) the fundamental and its harmonic do not behave in the same manner: the fundamental sees its power increase with the energy up to 40 keV, whereas the harmonic increases up to10 keV. The results presented here could nd an explanation in the context of the Accretion-Ejection Instability, which could appear as a rotating spiral or hot point located in the disk, between its innermost edge and the co-rotation radius. The presence of the harmonic could then be a signature of the non-linear behavior of the instability. The high-energy (>40 keV) decrease of the fundamental would favor an interpretation where most or all of the quasi-periodic modulation at high energies comes not from the comptonized corona as usually assumed, but from a hot point in the optically thick disk.