Precision Timing of the Periodic Radio Flares from Ultracool Dwarf Stars

该项目将利用阿雷西博射电望远镜观测到的射电耀斑的精确计时来探测超冷矮星（ucd）的内部结构和磁性。ucd是跨越恒星-行星边界的不寻常物体。这一组包括质量最低的恒星和褐矮星，ucd的温度在1600-2700 K之间。像许多气态巨行星和褐矮星一样，这些相对较冷的物体被认为有尘埃云，并可能通过旋转、对流和导电流体（也被称为“磁发电机”）产生磁场。在无线电波长处观察到短期周期性爆发，在某些情况下，它们的周期随着时间的推移而缩短，有时非常突然。PI计划分析显示这些突然下降的数据，以测试有关这些物体的模型。内部结构，也可适用于棕矮星和巨型气体行星的建模。该项目计划招收本科女生和少数族裔学生，并为他们提供结构良好的机会，以获得等离子体物理学、天体物理学、观测技术、先进数据分析和仪器方面的经验。计划中的ucd射电探测为测量低质量恒星的场强、拓扑结构和稳定性提供了一种直接手段。PI的初步工作表明，两个ucd的燃烧周期一直在稳步减少，并且相隔几个月观察到相跃。每次跳跃后，周期明显缩短。这项工作将测试它是否可以用恒星的微分旋转来解释，就像其他主序星上的太阳黑子一样。

This award is to probe the internal structures and magnetic properties of ultracool dwarfs (UCDs) using precise timing of radio flares observed with the Arecibo radio telescope. UCDs are unusual objects which straddle the star-planet boundary. This group includes the lowest mass stars and brown dwarfs, and UCDs have temperatures ranging from about 1600-2700 K. Like many gas-giant planets and brown dwarfs, these relatively cool objects are thought to have dust clouds, and may generate magnetic fields through a rotating, convecting and electrically conducting fluid (also known as a 'magnetic dynamo'). Short-term periodic outbursts are observed at radio wavelengths, and in some cases their period decreases over time, sometimes very abruptly. The PI plans to analyze data showing these abrupt decreases in order to test models about the objects? interior structure, and also may be applicable to brown dwarfs and giant gas planets modeling. The PI plans to involve undergraduate female and underrepresented minority students, and provide them with well-structured opportunities to gain experience with plasma physics, astrophysics, observational techniques, advanced data analysis and instrumentation.The planned radio detection of the UCDs provides a direct means to measure the field strength, topology and stability of low mass stars. Preliminary work by the PI shows that flaring period of two UCDs have been steadily decreasing, and that phase jumps have been observed a few months apart. After each jump, the period shortens significantly. This work will test whether it can be explained by differential rotation of the stars, in a manner analogous to sunspots in other main sequence stars.