Probing Gamma-ray Bursts and their Progenitors with Multiwavelength Observations

宇宙伽马射线暴是宇宙中最壮观、最广为人知的现象之一。它们由来自宇宙遥远地区的短时间爆发(几秒钟到几分钟)的高能辐射组成，每天都会观察到几次这样的爆发。上世纪60年代初，美国VELA卫星首次观测到了这些天体。在过去的30年里，它们一直是天体物理学的主要谜团之一。在20世纪90年代末，S的突破性发现发现，爆发起源于典型的几十亿光年远的微弱星系。使用大型地面望远镜测量到爆发的距离，发现其中一些显然发出了惊人的能量；超过了太阳在大约100亿年的整个预计寿命中产生的总能量，但压缩到了几秒钟！尽管各种理论层出不穷，但这些令人惊叹的宇宙爆炸的终极原因仍不得而知。然而，现在看来，至少有一些爆发可能代表着黑洞在大质量恒星(“超新星”)爆炸时发出的“出生呐喊”。目前的研究表明，伽玛暴现象与宇宙中恒星形成的历史密切相关，它可以作为早期宇宙演化的一个新的探测器。大多数伽玛暴也可能产生高度准直的非常高能粒子和辐射的喷流，有效地成为天空中的巨型加速器。虽然在过去的几年里已经了解了很多东西，但关于这些非凡的宇宙爆炸背后的来源和最终的物理机制，还有更多的东西有待发现。进一步了解它们的关键在于：(1)详细观察它们在从无线电波、可见光到X射线的各种波长的余辉；(2)额外测量到这些神秘事件的距离；以及(3)更好地了解它们所处的环境和它们起源的遥远星系。这就是当前项目的主题。使用世界上最大的光学/红外望远镜(夏威夷的10米凯克望远镜和山上的大型望远镜)。为了在首次发现伽玛暴时对其进行观测并在其亮度下降时继续对其进行观测，我们还拥有世界上最先进的射电望远镜(如加利福尼亚州帕洛玛的甚大射电望远镜)，目标是建立一个足够广泛的数据库，以便对目前正在研究的数十个理论模型进行测试和筛选。该项目的资金由NSF河外天文与宇宙学计划(AST/EXC)提供。*

AST 0098676KulkarniCosmic gamma-ray bursts (GRBs) are among the most spectacular, known phenomena in the universe. They consist of short outbursts (fractions of seconds to a few minutes) of high-energy radiation originating in distant regions of the universe, There are a few such outbursts observed per day. These were first observed by the US Vela satellites in the early 1960's. They have remained one of the major mysteries of astrophysics for the past 30 years. In the late 1990's breakthrough discoveries found that the bursts originated in faint galaxies, at typical distances of several billion light years. Measurements of distances to the bursts, using large, ground-based telescopes, revealed that apparently some of them emit prodigious amounts of energy; larger than the total amount of energy produced by our Sun over its entire projected lifespan of about 10 billion years, but compressed into a few seconds! While theories abound, the ultimate cause of these amazing cosmic explosions remains unknown. However, it now seems likely that at least some bursts represent "birth cries" of black holes, produced in the explosion of massive stars ("hypernovas"). Current research suggests that the GRB phenomenon is closely related to the history of star formation in the universe, and that it can be used as a novel probe of early cosmic evolution. It is also likely that most GRBs produce highly collimated jets of very energetic particles and radiation, effectively becoming giant acceleratorsin the sky. While a lot has been learned over the past few years, much more remains to be found about the source and the ultimate physical mechanism behind these remarkable cosmic explosions. The keys to this further understanding lies in (1) detailed observations of their afterglows seen at wavelengths ranging from radio waves, through visible light and out to x-rays; (2) additional measurements of the distances to these enigmatic events; and (3) a better understanding of their environments and the distant galaxies in which they originate. This is the subject of the presentproject. Using the worlds largest optical/infrared telescopes (the 10-m Keck telescopes in Hawaii and the large telescopes at Mt. Palomar in California), and the world's premier radio telescopes (e.g., the Very Large Array in New Mexico) to observe GRBs when they are first identified and to continue to observe them as they decline in brightness, the goal is to construct a wide enough bank of data to permit testing and winnowing of the scores of theoretical models presently under study. Funding for this project was provided by the NSF program for Extragalactic Astronomy & Cosmology (AST/EXC).***