Exploring & Exploiting the Dynamic Optical Sky

几千年来，人类已经注意到“新星”在夜空中出现和消失。由于传感器、计算和算法的进步，天文学家现在能够发现夜空中数以百万计的变化。这些天体的范围从近地小行星到宇宙中爆炸死亡的恒星。这个充满活力的“时域天文学”领域现在正在解决基本的科学问题，如宇宙中元素的起源，以及在识别引力波或中微子中明亮的奇异天文事件和提供对恒星的独特见解方面发挥关键作用。时域天文学是维拉鲁宾天文台的四大科学支柱之一，该天文台是美国国家科学基金会在未来十年中优先考虑的地面天文台。兹威基瞬变设施（ZTF）正在为包括学生在内的天文学界做好准备，使他们成为鲁宾天文台的熟练使用者。ZTF-II建立在ZTF-I的成功基础上，ZTF-I于2018年3月开始调查操作，并在过去一年中负责全球50%的超新星发现，以及实时警报流和数十亿天体目录发布的大量其他发现。该奖项通过ZTF与多信使天体物理学的强烈相关性推进了“宇宙大想法之窗”的目标。ZTF-II是一种最先进的时域测量，在帕洛玛48英寸塞缪尔·奥辛·施密特望远镜上使用了一个47平方度的视场相机。它每两个晚上在g和r波段进行一次公众观测，覆盖可见的北方天空（赤纬在-30度以上），亮度约为20.5等。每个ZTF观测都由图像差分管道处理，该管道为所有点源瞬态事件的5西格玛检测生成实时警报，每晚总计数十万个警报。这些警报包含发现图像的缩略图、参考图像和两者之间的差异，以及30天的光照曲线历史记录，以及各种元数据，例如真假分数、最近的PS1源的详细信息和管道参数。所有亮度超过18.5等的超新星的每日光谱分类都是通过机器人光谱仪获得的，并通过瞬态名称服务器公布。每个ZTF观测也由一个点扩展函数测光管道处理，该管道产生一个覆盖所有已识别源的单一历元目录。这些数据被存档在IPAC，用于创建ZTF数据发布中所有检测到的物体的光曲线——在ZTF- ii中，这些数据将从2021年开始以2个月的周期发布。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

For millennia, human beings have noticed "new stars" appearing and disappearing in the night sky. Thanks to advances in sensors, computation and algorithms astronomers are now able to discover millions of changes in the night sky. The objects range from near-earth asteroids to explosive stellar deaths across the Universe. This vibrant field of “time-domain astronomy” is now addressing fundamental scientific questions such as the origin of the elements in the Universe, as well as playing a critical role in identifying exotic astronomical events which are bright in gravitational waves or neutrinos and providing unique insights into stars. Time-domain astronomy is one of the four scientific pillars of the Vera Rubin Observatory, the NSF’s high priority ground-based observatory for the next decade. The Zwicky Transient Facility (ZTF) is preparing the astronomy community including students to become adept users of the Rubin Observatory. ZTF-II builds on the success of ZTF-I which began survey operations in March 2018 and has been responsible for 50% of global supernova discoveries over the past year, along with a slew of other discoveries from both the real-time alert stream and the multi-billion object catalog releases. This award advances the goals of the Windows on the Universe Big Idea via ZTF’s strong relevance to Multi-Messenger Astrophysics.ZTF-II is a state-of-the art time-domain survey employing a 47 square degrees field-of-view camera on the Palomar 48-inch Samuel Oschin Schmidt telescope. It operates a public survey covering the visible northern sky (declination above -30 degrees) every 2 nights in g- and r-bands to about 20.5 magnitude. Each ZTF observation is processed by an image differencing pipeline which generates real-time alerts for all 5-sigma detections of point-source transient events, amounting to several hundred thousand alerts per night. These alerts contain thumbnail images of the discovery image, a reference image, and the difference between the two, as well as a 30-day light curve history, and various metadata, such as a real-bogus score, details of the nearest PS1 source, and pipeline parameters. Daily spectral classifications of all supernovae brighter than 18.5 mag are obtained using a robotic spectrometer and announced via the Transient Name Server. Each ZTF observation is also processed by a Point Spread Function photometry pipeline which produces a single epoch catalog covering all identified sources. These are archived at IPAC and used to create light-curves for all detected objects in ZTF data releases - in ZTF-II, these will be released on a 2-month cycle starting in 2021.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.