Exploring Young Brown Dwarfs

在过去的五年里，我们已经在太阳附近和恒星形成区域发现了大量的亚恒星天体。事实上，棕矮星似乎和恒星一样普遍。然而，对它们的起源和早期演化几乎没有观测限制。对年轻褐矮星的研究为它们的形成机制提供了有价值的线索。这个项目探索恒星形成区域的褐矮星的物理特性，并将它们与研究得更好的主序前恒星进行比较，以阐明它们的起源。该计划采用了许多研究金牛座T星的方法，包括(1)寻找年轻的亚恒星物体周围的盘的热红外辐射，(2)光学光谱来获得它们的吸积光度和质量吸积率，(3)散射光和盘的热发射建模，(4)观测x射线发射，作为活动的指标，(5)测量基于光学光度变化的旋转周期。这个项目的结果将有助于区分棕矮星的不同形成场景，如云破碎、原恒星盘不稳定、新生多系统的弹射，以及年轻的亚恒星物体是否经历了类似金牛座T星的阶段

AST-0205130PI JayawardhanaThe past five years have seen the identification of a large number of sub-stellar objects in the solar neighborhood and in star-forming regions. Indeed, it appears that brown dwarfs maybe as common as stars. However, there are few observational constraints on their origin and early evolution. Studies of young brown dwarfs provide valuable clues to their formationmechanism(s). This program explores the physical properties of brown dwarfs in star-forming regions and compare them to the much better studied pre-main sequence stars, in order to shed light on their origin. The program employs many of the methods developed in the study of T Tauri stars, and includes (1) a search for thermal infrared emission from disks around young sub-stellar objects, (2) optical spectroscopy to derive their accretion luminosities and mass accretion rates, (3) modeling of scattered light and thermal emission of disks, (4) observations of X-ray emission, as an indicator of activity, and (5) measurements of rotation periods based on photometric variability in the optical. The results of this program will help distinguish among different formation scenarios for brown dwarfs, such as cloud fragmentation, protostellar disk instability, and ejection from newborn multiple systems, whether young sub-stellar objects undergo a T Tauri-like phase.***