Open Exploration of the Time Domain with the Catalina Real-Time Transient Survey

对时间域的探索--发现和研究在几秒到几年的时间尺度上变化的物体和现象--现在是天文学中最活跃和最迅速发展的领域之一，涉及从太阳系和系外行星的发现到遥远的类星体，从恒星天体物理学到宇宙学和极端相对论天体物理学的广泛和多样化的研究领域。时间域信息对于理解我们观察到的一些最有趣的现象是必不可少的；例如，我们无法从超新星的一张照片或伽马射线暴的一张快照中学到任何东西；恒星的可变性有助于我们了解它们的结构和演化；恒星的运动告诉我们银河系的结构。我们现在把宇宙及其主要组成部分作为一个动态的、不断变化的系统来研究。这一变化是由信息技术的进步促成的。多年来，大型数字巡天一直是天文学数据的主要来源。虽然它们可以被视为全景宇宙摄影，但我们现在正在进入全景宇宙摄影，信息量和质量也相应增加：多次覆盖天空的数字天气巡天，探测变化或移动的物体和现象。这一趋势将在几年后的大型天文观测望远镜(LSST)中达到顶峰，但我们已经在利用前兆观测来探索时间域天文学的科学和技术。它们已经具有巨大的发现潜力，并将帮助我们在未来更大的调查中改进我们的问题和策略。该项目是Catalina实时瞬变调查(CRTS)的继续和实质性扩展，CRTS是一项持续的、富有成效的天气观测，正在产生源源不断的天文瞬变事件，并立即向整个社区提供这些事件；它是目前唯一这样做的天空调查。它利用在搜索近地小行星和行星灾害小行星时获得的数据流，由美国国家航空航天局提供资金，并利用在软件和数据服务方面的大量现有投资。我们为后续观察和数据分析建立了广泛的合作网络。这些可观的外部资源对NSF来说是免费的，并提供了比全额资助的新调查所能完成的更大的科学投资回报。CRTS的总体科学目标是对微弱、多变的天空进行系统的探索。到目前为止，CRTS已经发现了约6,500个不同的瞬变事件和1,300万个可变源，包括各种变星、活动星系核、各种宇宙爆炸和恒星耀斑等。在至少连续两年的时间里，CRTS发布的超新星(SNE)比任何其他调查都多，包括有史以来最明亮的超新星、来自活动星系吸积盘的长期预测的超新星、数百颗矮新星和其他有趣的激变变星、白矮星周围的行星、新的x射线源、银晕中的新潮汐等等。确实有可能发现以前未知的种类。这个项目将继续这些研究，并开始一些新的研究，涉及各种开放的天文挑战。CRTS独特的开放数据政策使整个天文学社区能够分享这些发现。所有瞬时事件都以电子方式实时发布，所有数据(图像、目录等)也是公开的；它们将使广泛的档案学成为可能。CRT可能是数据共享和重复使用的一个展示窗口，这在21世纪必须成为一种标准做法。该项目将帮助整个天文学社区做出新的发现和制定新的科学战略。这是新一代科学实验的一个例子，涉及海量数据流的实时挖掘和动态后续策略。我们培养本科生、研究生和博士后，他们是未来的科学技术领袖，并为新的科学和计算开发各种教育和公共宣传材料。

Exploration of the time domain - discovery and studies of objects and phenomena changing on time scales ranging from seconds to years - is now one of the most vibrant and rapidly developing fields of astronomy, touching on a broad and diverse spectrum of research areas, from the Solar system and discoveries of exoplanets to the distant quasars, and from stellar astrophysics to cosmology and extreme relativistic astrophysics. Time domain information is essential for understanding of some of the most interesting phenomena we observe; for example, we could not learn anything from a single picture of a Supernova, or a single snapshot of a gamma-ray burst; variability of stars aids to our understanding of their structure and evolution; motions of stars tell us about the structure of our Galaxy. We now study the universe and its major constituents as a dynamical, and always changing system. This change was enabled by the progress in information technology. For many years now, large digital sky surveys have been the main sources of data in astronomy. While they can be seen as panoramic cosmic photography, we are now moving into a panoramic cosmic cinematography, with a corresponding increase in information volumes and quality: digital synoptic sky surveys which cover the sky many times, detecting objects and phenomena which change or move. This trend will culminate in the Large Synoptic Survey Telescope (LSST) years from now, but we are already exploring the science and technology of time-domain astronomy with precursor surveys. They already have a significant potential for discovery, and will help us sharpen our questions and strategies for the larger surveys in the future.This project is a continuation and substantial expansion of the Catalina Real-Time Transient Survey (CRTS), an ongoing, productive synoptic sky survey that is producing a steady stream of astronomical transient events, and making them immediately available to the entire community; it is the only current sky survey that does so. It utilizes a data stream obtained in a search for near-Earth and planetary hazard asteroids, funded by NASA, and it leverages considerable existing investments in software and data services. We have established an extensive web of collaborations for the follow-up observations and data analysis. These substantial external resources come at no cost to the NSF, and provide for much greater scientific returns on investment than what could be done with a fully funded, new survey.The overall scientific goal of CRTS is a systematic exploration of the faint, variable sky. CRTS has so far discovered ~6,500 distinct transient events, and 13 million variable sources, including a wide variety of variable stars, active galactic nuclei, various cosmic explosions, stellar flares, etc. For at least 2 years in a row, CRTS has published more Supernovae (SNe) than any other survey, including the most luminous SNe ever seen, long-predicted SNe from AGN accretion disks, hundreds of dwarf novae and other interesting cataclysmic variables, planets around white dwarfs, new counterparts of x-ray sources, new tidal streams in the Galactic halo, etc. In addition to a plenty of known types of objects and phenomena, there is a real possibility of a discovery of previously unknown kinds. This project will continue these studies, and start a number of new ones, that touch on a variety of open astronomical challenges. The unique open data policy of CRTS enables the entire astronomical community to partake in these discoveries. All transient events are published electronically in real time, and all data (images, catalogs, etc.) are also made publicly available; they will enable a broad range of archival science. CRTS may be a showcase for the data sharing and re-use, that must become a standard practice in the 21st century.This project will aid the entire astronomical community in making new discoveries and developing new scientific strategies. It is an example of a new generation of scientific experiments involving real-time mining of massive data streams, and dynamical follow-up strategies. We train undergraduate and graduate students and postdocs, the future science and technology leaders, and develop a broad variety of educational and public outreach materials, both for the new science and computation.