Gamma ray burst astrophysics

在20世纪60年代末发现伽马射线暴之后的大约30年里，伽马射线暴一直是天文学最大的谜团之一。20世纪90年代末，伽马射线暴的位置最终被定位到了足够精确的位置，以搜索X射线和光学余辉，并确定它们起源的星系。2004年，NASA的SWIFT天文台发射升空，该天文台在伽马射线暴发生时自动定位，并在90秒内旋转，使其光学/紫外线望远镜和X射线望远镜在爆发后几分钟内捕捉到余辉。我们现在知道，长伽马射线爆发(持续时间超过2秒)发生在结束大质量恒星生命的超新星爆炸中，而短伽马射线爆发很可能来自中子星双星的合并。爆炸和随后的余辉的物理问题是激烈争论的话题。SWIFT与地面望远镜和其他空间天文台一起，正在提供关于伽马射线暴及其余辉的丰富数据。SWIFT上的光学/紫外线望远镜(UVOT)是在麻省理工学院设计和建造的，我们拥有一个在SWIFT天文台发挥主要作用的操作团队，分析从SWIFT传来的伽马射线暴数据。这个项目是为了让一名博士生与我们的操作团队一起研究伽马射线暴，并利用大量的UVOT数据来加深我们对这些现象爆炸的物理学的理解：它们是如何提供能量的，相对论冲击波如何将其能量储存到周围的介质中，伽马射线爆发发生的环境，前驱恒星可能是什么，伽马射线暴告诉我们关于恒星和星系形成的宇宙历史。学生将研究伽马射线和光学能量学之间的相关性，建立在我们最近发现的余辉亮度和褪色速度之间的相关性(Oates，Page等人)。2012年，MNRAS 426，L26)。学生还将体验伽马射线爆发的实时调查和跟踪，从SWIFT探测到的爆发的最初几分钟开始，有机会详细研究学生值班时发生的任何异常爆发。学生将对这些爆炸的物理原理有一个一线的了解，并为提高这种理解做出贡献。

For around 30 years after their discovery in the late 1960s, gamma-ray bursts were one of astronomy's biggest mysteries. The locations of gamma ray bursts were finally localised with enough precision to search for X-ray and optical afterglows, and identify the galaxies in which they originate, in the late 1990s. In 2004, NASA's Swift observatory was launched, which localises gamma ray bursts autonomously as they are happening, and slews within 90 seconds to bring its Optical/UV Telescope and X-ray Telescope to capture the afterglow within a few minutes of the burst. We now know that long gamma-ray bursts (with durations longer than 2 seconds) occur in the hypernova explosions that end the lives of massive stars, and that the short gamma-ray bursts are likely to come from the merging of neutron star binaries. The physics of the explosion and subsequent afterglow are hot topics of debate. Swift, together with ground based telescopes and other space observatories, are providing a wealth of data on gamma ray bursts and their afterglows. The Optical/Ultraviolet Telescope (UVOT) onboard Swift was designed and constructed at MSSL, and we host an operations team which plays a major role in the Swift observatory, analysing the gamma-ray burst data as it comes down from Swift.This project is for a PhD student to work alongside our operations team in studying gamma-ray bursts and to utilise the large body of UVOT data to further our understanding of the physics of these phenomenal explosions: how they are powered, how the relativistic blastwave deposits its energy into the surrounding medium, the environments in which gamma-ray bursts occur, what the progenitor stars could be, and what gamma-ray bursts tell us about the cosmic history of star and galaxy formation. The student will examine correlations between the gamma-ray and optical energetics, building on the correlation we recently found between the brightness of the afterglow and the speed with which it fades (Oates, Page et al. 2012, MNRAS 426, L26). The student will also experience real-time investigation and follow up of gamma-ray bursts, starting within the first few minutes of a burst being detected with Swift, with the opportunity to study in detail any exceptional bursts that go off when the student is on duty.The student will develop a front-line understanding of the physics of these explosions, and contribute to improving this understanding.