基于Insight-HXMT和Fermi-LAT对微类星体观测的联合分析研究

Microquasars are a class of accreting black hole or neutron star X-ray binaries with relativistic and spatially extended jet. Similar to the extragalactic accreting supermassive black holes like blazars, gamma rays may be generated within the jet or through the interaction between the jet and the surrounding environment. However, Fermi-LAT observations revealed that blazars are the main extragalactic gamma-ray source, but microquasars are not the main Galactic gamma-ray source. In addition, gamma-ray emissions of the only two gamma-ray microquasars, Cyg X-1 and Cyg X-3, occur in different X-ray states or state transitions. This project intends to conduct a joint analysis of the microquasars observed by Insight-HXMT and Fermi-LAT. Through: (1) enlarge the gamma-ray microquasar sample; (2) understanding the similarities and differences between the gamma-ray emission of Cyg X-1 and Cyg X-3 more deeply, we aim to answer when microquasars produce gamma rays. The survey and pointing observation modes of Insight-HXMT can result in X-ray data with wider energy bands, high temporal resolution, good energy resolution and high statistics, which is beneficial to the fine study of X-ray radiation of microquasars. By examining the correlation of gamma rays with X-rays in the three energy bands of Insight-HXMT (especially that >50 keV), the generation time of gamma rays can be better constrained.

微类星体是一类吸积黑洞/中子星X射线双星系统。与河外超大质量吸积黑洞耀变体类似，伽马射线可产生于其所具有的相对论性喷流内部或者喷流与周围环境的作用 。然而Fermi-LAT观测发现，耀变体是主要的河外伽玛源，微类星体却非主要的河内伽玛源。且目前仅有的两个伽玛微类星体Cyg X-1和Cyg X-3的伽玛辐射还发生在不同的X射线态或态转化期 。本项目拟对HXMT和Fermi-LAT所观测的微类星体开展联合分析，通过: (1) 增加伽玛微类星体样本，(2) 更深入理解Cyg X-1和Cyg X-3伽玛辐射的异同，解决微类星体何时产生伽玛射线这一问题。利用HXMT巡天和定点观测两种模式获得的宽能段、高时间分辨率、良好能量分辨率、高统计性和高频次观测数据对微类体的X射线辐射进行精细研究。通过考察伽玛射线与HXMT三个能段 (特别是大于50keV) 辐射的相关性，更精确地限定伽玛射线的产生时间。

本项目首先利用慧眼和费米卫星数据对伽马射线微类星体候选体的观测开展了联合分析研究，以期理解微类星体何时产生伽马射线辐射。在分析微类星体的伽马射线和X射线光变的相关过程中，发展了利用慧眼数据的低能光变为模版搜寻高能光变信号的交叉相关分析方法。本项目未发现除已知的Cyg X-1和Cyg X-3之外的新的伽马射线微类星体样本；对这两个已知伽马射线微类星体的细致研究也未发现伽马射线和X射线辐射有显著相关性。随后，我们将该方法改进后应用到吸积脉冲星高能脉冲的搜寻上并获得更突出的优势和结果。本项目首先将该方法应用到了对超亮X射线脉冲星RX J0209.6−7427的研究上，探测到了超过180 keV的脉冲辐射，这是迄今为止从X射线脉冲星探测到的最高能量脉冲，并且证明了它的超亮辐射是内禀的。最后，本项目还对多个慧眼观测的X射线吸积脉冲星进行了详细的研究，获得了丰富的结果。