伽玛暴X射线耀发能谱成分及其对火球模型的限制

发布时间：2018-01-12 01:28

本文关键词：伽玛暴X射线耀发能谱成分及其对火球模型的限制　出处：《广西大学》2014年硕士论文　论文类型：学位论文

【摘要】：伽玛暴是宇宙深处大质量的恒星演化到晚期塌缩或者两个致密天体并合产生。一般认为伽玛暴辐射来源于极端相对论性火球,但是组份、辐射机制等问题至今是个谜。本硕士论文综述伽玛暴观测和理论研究进展,重点阐述我们利用Swift卫星的观测数据研究伽玛暴能谱成分及其对火球组份限制的相关结果。 Swift卫星上的伽玛暴预警探测器(BAT)被触发后,X射线望远镜(XRT)快速转向进行观测,获取大量的X射线观测数据。明亮的X射线耀发被探测到,而且许多伽玛暴早期X射线耀发同时被BAT探测到。我们选择同时具有BAT和XRT观测的明亮X射线耀发作为样本,联合分析XRT-BAT的能谱。我们的样本包含了29个XRT-BAT有联合观测的明亮耀发的伽玛暴。我们的联合谱分析结果表明,有8个暴可以用幂律函数很好的拟合,10个可以用Band函数很好的拟合,剩余的11个可以用幂律加黑体(blackbody)辐射拟合。这说明一些暴的能谱已经演化至低能段,一些暴的峰值能量则依然在BAT能段之外或者是附近。在发现热辐射成分的11个暴X射线耀发中有8个有红移。我们基于探测到的热辐射成分,在重子火球模型框架下计算了火球参数,包括火球的光球洛伦兹因子Γph,光球层半径Rph,饱和半径R5,初始半径R0。我们发现光球辐射的Ep-LBB与从Band函数得到的Ep-LP和关系是吻合的。利用我们得到的光球洛伦兹因子,我们还发现Γph-L子BB关系也与用余辉光变曲线中的火球减速时标得到的火球初始洛伦兹因子与光度之间的关系是吻合的。结果支持伽玛暴的热辐射可能来自重子火球的光球层辐射。考虑到仅仅在少部分伽玛暴中探测到热辐射成分,而且其温度普遍比较低,我们指出伽玛暴火球的组份可能是比较多样的。对于探测到很强热辐射的伽玛暴(比如GRB090902B)可能是重子成分占主导到。如果观测到热辐射温度很低(比如我们目前探测到热辐射的样本),热辐射占总辐射非常少(-5%),这类暴的喷流有可能是中等磁化的。大部分暴没有看到热辐射,其喷流可能是高度磁化的。
[Abstract]:Gamma-ray bursts (GRBs) are the collapse of massive stars in the depths of the universe or the combination of two dense celestial bodies. It is generally believed that Gamma bursts radiate from extreme relativistic fireballs, but the components. The problem of radiation mechanism is still a mystery. This thesis reviews the progress of Gamma burst observation and theoretical research. In this paper, we study the composition of gamma-ray storm spectrum and its limitation on fireball by using the observed data of Swift satellite. The gamma-storm early warning detector on the Swift satellite was triggered and the X-ray Telescope turned quickly to observe it. A large number of X-ray observations were obtained. Bright X-ray flares were detected. Moreover, many early X-ray flares were detected by BAT simultaneously. We selected bright X-ray flares with both BAT and XRT observations as samples. The energy spectrum of XRT-BAT is analyzed jointly. Our sample contains 29 gamma bursts of bright flares observed jointly by XRT-BAT. The results of our joint spectral analysis show that. Eight bursts can be fitted well by power law function and 10 by Band function. The remaining 11 can be fitted with power law and blackbody blackbody radiation, indicating that the energy spectrum of some storms has evolved to the low energy range. The peak energy of some storms is still outside or near the BAT energy range. Eight of the 11 X-ray flares in which thermal radiation components are found are red-shifted. We are based on the detected thermal radiation components. In the framework of baryon fireball model, the parameters of fireball are calculated, including the luminous Lorentz factor 螕 phof the fireball, the radius Rphof the optical sphere layer, and the saturation radius R5. The initial radius R0. We find that the Ep-LBB of the luminous sphere radiates in agreement with the Ep-LP sum obtained from the Band function. We also find that the 螕 ph-L sub-BB relation is also consistent with the relation between the initial Lorentz factor and the luminosity obtained from the fireball deceleration time scale in the afterglow curve. The results support the possibility of thermal radiation of the gamma-ray burst. Radiation from the photospheric layer of a baryon fireball. Considering that thermal radiation is detected only in a small number of gamma-ray bursts. And the temperature is generally low. We point out that the composition of gamma-ray burst fireballs may be relatively diverse. For gamma storms that detect very strong thermal radiation (e.g. GRB0902B). It may be baryons that dominate. If the temperature of thermal radiation is observed to be very low (for example, we are currently detecting the sample of thermal radiation). Thermal radiation accounts for very little to 5% of the total radiation, and the jet of this type of storm is likely to be moderately magnetized. Most storms do not see thermal radiation, and the jet may be highly magnetized.
【学位授予单位】：广西大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P142.6;P172.3

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