标题： 在LMXB XBT 0748-676浸入过程中的ADC渐进覆盖 显示英文标题

标题： Progressive Covering of the ADC during Dipping in the LMXB XBT 0748-676

摘要： 我们报告了对1993年5月7日 dipping LMXB 源 XBT 0748-676 的 ASCA 观测结果，并提出了对此源中 dipping 的光谱演化的新的解释。我们表明，在多个强度波段中的非 dip 和 dip 光谱可以使用相同的物理模型进行良好拟合，我们之前已证明该模型能很好地解释几个 dipping 源，该模型包括中子星的点源黑体辐射，加上吸积盘冕（ADC）的扩展康普顿化辐射，在 dipping 过程中 ADC 逐渐被遮挡。找到的最佳拟合值为 kT_bb = 1.99 +/- 0.16 keV 和幂律光子指数 Gamma = 1.70 +/- 0.16。低于 1 keV 的强过量部分可以通过 ~0.65 keV 处的高斯线进行良好拟合。在 dipping 中，通过允许其被与扩展连续谱相同的逐步遮挡因子遮挡，获得了良好的拟合，这提供了强有力的证据，表明该线起源于 ADC。通过使用我们的两组分模型，我们表明未吸收的成分是康普顿化辐射的未遮挡部分，在 1 - 10 keV 波段，我们不需要引入显著的电子散射来解释 dipping。 显示英文摘要

摘要： We report results of analysis of the ASCA observation of 1993, May 7th of the dipping LMXB source XBT 0748-676, and propose a new explanation of the spectral evolution in dipping in this source. We show that the non-dip and dip spectra in several intensity bands are well fitted using the same physical model that we have previously shown gives good explanations of several dipping sources, consisting of point source blackbody emission from the neutron star, plus extended Comptonised emission from the accretion disk corona (ADC), with progressive covering of the ADC during dipping. Best fit values of kT_bb = 1.99 +/- 0.16 keV and power law photon index Gamma = 1.70 +/- 0.16 are found. The strong excess below 1 keV was well fitted by a Gaussian line at ~0.65 keV. In dipping, good fits were obtained by allowing it to be covered by the same progressive covering factor as the extended continuum emission, providing strong evidence that the line originates in the ADC. By using our two-component model we show that the unabsorbed component is the uncovered fraction of the Comptonised emission, and in the band 1 - 10 keV, we do not need to invoke substantial electron scattering to explain dipping.