Probing Gamma-ray Bursts and their Progenitors with Multiwavelength Observations

宇宙伽马射线暴（GRBs）是宇宙中已知的最壮观的现象之一。它们由源自宇宙遥远区域的高能辐射的短爆发（几秒到几分钟）组成。每天都能观测到一些这样的爆发。美国船帆号卫星在20世纪60年代早期首次观测到这些现象。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年代末的突破性发现发现，这些爆发起源于昏暗的星系，通常距离几十亿光年。利用大型地面望远镜测量到爆发的距离，发现其中一些爆发显然会释放出惊人的能量；比我们的太阳在其大约100亿年的整个预计寿命中产生的总能量还要大，但被压缩到几秒钟内！虽然有很多理论，但这些惊人的宇宙爆炸的最终原因仍然未知。然而，现在看来，至少有一些爆发很可能是黑洞的“诞生之声”，是由大质量恒星（“超超新星”）爆炸产生的。目前的研究表明，GRB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新探针。还有一种可能是，大多数伽马射线暴会产生高度准直的高能粒子和辐射射流，有效地成为天空中的巨型加速器。虽然在过去的几年里我们已经了解了很多，但关于这些非凡的宇宙爆炸背后的来源和最终物理机制，还有更多的东西有待发现。进一步理解的关键在于：(1)在从无线电波到可见光再到x射线的波长范围内对它们的余辉进行详细观察；(2)对这些神秘事件的距离的额外测量；(3)更好地了解它们的环境和它们起源的遥远星系。这就是本项目的主题。使用世界上最大的光学/红外望远镜(十米级在夏威夷凯克望远镜和大型望远镜。在加州帕洛),和世界首屈一指的射电望远镜(例如,甚大阵在新墨西哥州)观察伽马射线爆时首次发现并继续观察他们的亮度下降,我们的目标是构建一个足够宽的银行数据,允许检测和筛选的分数理论模型目前正在研究。本项目由美国国家科学基金会星系外天文学和宇宙学项目（AST/EXC）资助

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).***