New Models of M Dwarf Stars

该奖项是根据2009年《美国复苏和再投资法案》(公法111-5)资助的。达特茅斯学院的布莱恩·查博耶将对M矮星的结构进行理论研究，M矮星是像太阳一样未演化的恒星，但质量不到太阳的一半。一段时间以来的观测表明，理论模型不能正确预测食双星系统中发现的M矮星的质量-半径关系。观测到的半径系统地大于理论模型预测的半径(约10%)。最近的研究表明，这是由于这些快速旋转的恒星中磁场活动的增加，这些恒星与它们的同伴被潮汐锁定在一起。这项研究将集中在建立新的M矮星模型上，通过批判性地检查对流的处理并纳入磁场的影响来建立以前的努力。磁场的物理将以唯象的方式包含在恒星结构方程中，并将研究各种拓扑和场强的场的影响。查博耶博士还将探索对流的各种处理方法对低质量恒星的结构和观测特性的影响。这部分工作将纳入最近对流的流体力学计算的结果。最后，他将批判性地检查在将模型与观测值进行比较时所使用的颜色有效温度转换，以得出改进的定标。M矮星是银河系中最常见的恒星类型。最近，天文学家们意识到，围绕其他恒星运行的首批地球质量的行星很可能出现在M矮星附近。在这项研究中产生的模型将向普通天文学社区提供。本科生和研究生将广泛参与这项研究的各个方面。这将包括对一年级本科生的指导，他们将通过达特茅斯学院女性参与科学项目的赞助来参与这一项目。该项目旨在鼓励更多的达特茅斯女性通过早期接触实践研究经验、榜样和指导，在科学、数学或工程领域追求职业生涯。大四的本科生也将被聘为研究助理。查博耶博士还将继续与当地的K-8学校和位于佛蒙特州诺里奇的孟德希尔科学博物馆合作，与年轻学习者和广大公众讨论这项研究。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Dr. Brian Chaboyer of Dartmouth College will undertake a theoretical investigation of the structure of M dwarfs, which are unevolved stars like the Sun but with less than half its mass. Observations have indicated for some time that theoretical models are unable to correctly predict the mass-radius relation for M dwarfs found in eclipsing binary systems. The observed radii are found to be systematically larger (by about 10%) than that predicted by theoretical models. Recent work has suggested that this is due to increased magnetic activity in these rapidly rotating stars which are tidally locked to their companions. The research will center on the construction of new models of M dwarfs, building upon previous efforts by critically examining the treatment of convection and incorporating the effects of magnetic fields. The physics of the magnetic fields will be included within the stellar structure equations in a phenomenological fashion and the impact of fields of various topologies and field strengths will be studied. Dr. Chaboyer will also explore the effects that various treatments of convection have on the structure and observed properties of low mass stars. This part of the work will incorporate results from recent hydrodynamical calculations of convection. Finally, he will critically examine the color-effective temperature transformations which are used when comparing the models to observations in order to derive an improved calibration.M dwarf stars are the most common type of star in the Milky Way galaxy. Recently, astronomers have realized that the first Earth-mass planets around other stars are likely to be found around M dwarfs. The models generated in this study will be made available to general astronomical community. There will be extensive involvement of both undergraduate and graduate students in all aspects of this research. This will include mentoring of first year undergraduate students who will work on this project through the auspices of the Women in Science Project at Dartmouth College. This program is designed to encourage more Dartmouth women to pursue a career in science, math or engineering through early exposure to hands-on research experiences, role modeling and mentoring. Upper-year undergraduates will also be employed as research assistants. Dr. Chaboyer will also continue his involvement with local K-8 schools and the Monteshire Museum of Science located in Norwich, Vermont, to discuss this research with young learners and the public at large.