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空间硬X射线调制望远镜 总被引:5,自引:0,他引:5
用宇宙作为物理实验室,探索在地球上无法企及的条件下,例如极早期宇宙或黑洞视界附近强引力场中的物理规律,已成为新世纪物理学和天文学共同的前沿课题;空间天文观测是其中一个最重要的研究途径.自主研制和发放空间硬X射线调制望远镜(HXMT),实现中国空间天文卫星零的突破,是中国<"十一·五"空间科学发展规划>的目标之一.HXMT将实现宽波段X射线(1-250 keV)巡天,其中在硬X射线波段具有世界最高灵敏度和空间分辨率,发现大批被尘埃遮挡的超大质量黑洞和未知类型天体,探测宇宙硬X射线背景辐射;HXMT还将通过对黑洞和其他高能天体宽波段X射线时变和能谱的观测,研究致密天体极端物理条件下的动力学和辐射过程.基于成像技术创新提出HXMT项目迄今已有15年,能不能抓住技术创新所提供的科学机遇仍然是一个严重的挑战. 相似文献
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The structures of optically-thick accretion discs with radial advection have been investigated by the iteration and integration algorithms. The advective cooling term changes mostly the inner part of disc solution, and even results in an optically-thick advection-dominated accretion flow (ADAF). Three distinct branches-the outer Shakura-Sunyaev disc (SSD), the inner ADAF and the middle transition layer-are found for a super-Eddington disc. The SSD-ADAF transition radius can be estimated as 18(\dot{M}/\dot{M}E)RG where RG is the Schwarzschild radius, \dot{M} is the mass accretion rate and \dot{M}E is the Eddington accretion rate. SSD solutions calculated with the iteration and integration methods are identical, while ADAF solutions obtained by these two methods differ greatly. Detailed algorithms and their differences have been analysed. The iteration algorithm is not self-consistent, since it implies that the dimensionless advection factor ξ is invariant, but in the inner ADAF region the variation of ξ is not negligible. The integration algorithm is always effective for the whole region of an optically-thick disc if the accretion rate is no smaller than 10-4\dot{M}E. For optically-thin discs, the validity of these two algorithms is different. We suggest that the integration method be employed to calculate the global solution of a disc model without assuming ξ to be a constant. We also discuss its application to the emergent continuum spectrum in order to explain observational facts. 相似文献
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