The Broadband Spectrum of MXB 1728–34 Observed by BeppoSAX
The Broadband Spectrum of MXB 1728–34 Observed by BeppoSAX
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DOI：
10.1086/317029
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发表时间：
2000-05
期刊：
影响因子：
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通讯作者：
T. di Salvo;R. Iaria;L. Burderi;N. Robba
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文献类型：
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作者：
T. di Salvo;R. Iaria;L. Burderi;N. Robba
我们报告BeppoSAX卫星观测到的爆发环礁源MXB 1728-34（4U 1728-34）的宽带（0.1-100千电子伏）光谱分析结果。在该观察期间出现了三次爆发。爆发期间的光谱可以用温度为~ 2keV的黑体拟合。如果我们对观测到的色温和有效温度之间的差异进行校正，黑体发射区的半径与中子星星的半径是相容的。根据爆发，我们还估计到源的距离约为5.1千秒差距。MXB 1728-34在BeppoSAX号卫星观测期间处于相当软的状态。持久光谱很好地拟合由软黑体发射和康普顿化光谱组成的连续体。我们把软分量解释为来自吸积盘的辐射。考虑到~1.7的光谱硬化因子（由于电子散射，其修改了盘发射的黑体光谱），我们估计内盘半径为Rin ~ 20 km，其中i是倾角。康普顿化的成分可能起源于一个球形日冕，温度约为10 keV，光学深度约为5，围绕着中子星星。在光谱中观察到~6.7 keV的宽高斯发射线，可能是在电离日冕或盘的内部发射的。另一条发射线位于~1.66 keV。没有检测到具有高统计意义的反射分量，这可能是因为在源的这种状态下日冕的温度较低。如果铁的发射线是由康普顿化光谱被吸积盘反射而引起的，那么它需要一个电离盘（约280 °）和一个约0.2（单位为2π）的立体角，从日冕上看，反射器对着它。
We report on the results of a broadband (0.1-100 keV) spectral analysis of the bursting atoll source MXB 1728-34 (4U 1728-34) observed by the BeppoSAX satellite. Three bursts were present during this observation. The spectrum during the bursts can be fitted by a blackbody with a temperature of ~2 keV. The radius of the blackbody emitting region is compatible with the radius of the neutron star if we correct for the difference between the observed color temperature and the effective temperature. From the bursts we also estimate a distance to the source of ~5.1 kpc. MXB 1728-34 was in a rather soft state during the BeppoSAX observation. The persistent spectrum is well fitted by a continuum consisting of a soft blackbody emission and a Comptonized spectrum. We interpreted the soft component as the emission from the accretion disk. Taking into account a spectral hardening factor of ~1.7 (because of electron scattering which modifies the blackbody spectrum emitted by the disk), we estimated that the inner disk radius is Rin ~ 20 km, where i is the inclination angle. The Comptonized component could originate in a spherical corona, with temperature ~10 keV and optical depth ~5, surrounding the neutron star. A broad Gaussian emission line at ~6.7 keV is observed in the spectrum, probably emitted in the ionized corona or in the inner part of the disk. Another emission line is present at ~1.66 keV. No reflection component is detected with high statistical significance, probably because of the low temperature of the corona in this state of the source. If the iron emission line is caused by reflection of the Comptonized spectrum by the accretion disk, it requires a ionized disk (ξ ~ 280) and a solid angle of ~0.2 (in units of 2π) subtended by the reflector as seen from the corona.