NSF Young Investigator: Binarity in Young Stars

小行星9457458 对星星形成的研究往往是出于解释太阳系形成和演化的愿望。 因此，目前星星形成的范例集中在一颗星星的产生上，这颗恒星在年轻的时候被一个气体和尘埃盘所包围，大约几百个天文单位（AU）大小，行星可能从其中形成。 然而，最近由盖兹博士和其他人对银河系金牛座和蛇夫座的星星形成区进行的调查得出的结论是，大多数（如果不是全部的话）年轻的低质量恒星都有伴星。 此外，这些双星中的大多数都是由距离小于通常假设的拱星盘的大小。 在距离我们银河系最近的星星形成地点金牛座和蛇夫座（距离= 150秒差距），一个拱星盘的角度范围预计大约是1-2弧秒。 不幸的是，由于大气中的湍流，传统成像技术的角分辨率仅限于1弧秒，比4米望远镜的理论分辨率差10-30倍。 因此，为了研究这些复杂而又普遍存在的近距离双星，将使用高分辨率的斑点成像技术。 目前的研究工作集中在研究这些近距离双星对星周盘形成和演化的影响。 星周盘的存在及其性质主要是从金牛座T星的光谱能量分布（SED）中推断出来的。 特别是，它是过度的辐射在紫外线和红外线波长已被归因于磁盘过程。 最近，越来越多的努力，在模拟的影响，导致在解释下降的SED作为行星形成的证据。 然而，近距离双星的SED到目前为止都是观测来自两个组成部分的合并光的结果。 在一种方法来回答问题的后果，密切的伴星拱盘，博士Ghez测量SED，从光学到红外波长，每个单独的组成部分，在这些密切的双星星系统使用高空间分辨率成像技术。 这将允许确定（1），有多少先前观察到的过量可以归因于与拱星盘相对的次级源的存在;（2）如果过量仍然存在，无论是两个组件还是只有一个组件显示出拱星盘的证据;以及（3），无论SED中的下降是否是由两颗具有不同视温度的恒星的存在造成的。 在第二种方法中，Ghez博士还将比较经典金牛座T星（CTTS）的星星频率，这些恒星被认为具有内部吸积盘，而弱线金牛座T星（WTTS）被认为缺乏内部吸积盘。 在他们最初的工作中，Ghez博士和她的合作者观察到了3 sigma水平的区别;在距离小于35 Au的双星中，WTTS比CTTS更常见。 这些观测结果表明，密切的同伴显着干扰磁盘吸积过程与许多金牛座T星。 这一结果是一个令人兴奋的可能性，但需要后续观测更多的金牛座T星，以获得统计意义。 这将通过（1）使用更灵敏的相机将观测到的金牛座T星的样本扩展到更多的星星形成区和更暗的系统，（2）最终使用更大的望远镜（直径5米，如凯克望远镜）进一步探测这种关系。 如果Ghez博士的假设是正确的，那么CTTS和WTTS双星星星数量的差异应该会在更小的距离上增加。 这个奖项是为了表彰一位在科学和工程领域杰出的年轻教师。 该奖项将通过为研究和教育活动提供灵活的支持来提高教师的职业生涯。 鼓励与支持研究和教育的行业和机构合作。

9457458 Ghez The study of star formation is often motivated by the desire to explain the formation and evolution of the solar system. Thus, the current paradigm for star formation is centered on the production of a single star that, at a young age, is surrounded by a disk of gas and dust, roughly a few hundred astronomical units (AUs) in size, from which planets may form. However, recent surveys, carried out by Dr. Ghez and others, of the star forming regions of Taurus and Ophiuchus in our Galaxy have led to the conclusion that most, if not all, young low mass stars have companion stars. Furthermore, the majority of these binary stars are separated by distances that are smaller than the size typically assumed for a circumstellar disk. At the distance to Taurus and Ophiuchus, the nearest sites of star formation in our Galaxy (Distance = 150 parsec), the angular extent of a circumstellar disk is expected to be roughly 1-2 seconds of arc. Unfortunately, due to turbulence in the atmosphere, the angular resolution of traditional imaging techniques is limited to 1 second of arc, a factor of 10-30 times worse than the theoretical resolution of a 4-m telescope. Thus, to study these perplexing and yet prevalent close binary stars, the high resolution imaging technique of speckle imaging will be used. The current research effort is focussed on studying the effect of these close binary stars on the formation and evolution of circumstellar disks. The presence of a circumstellar disk and its properties are primarily inferred from the measured spectral energy distribution (SED) of T Tauri stars. In particular, it is the excesses of radiation at ultra-violet and infrared wavelengths that have been attributed to disk processes. More recently, increased efforts in modeling the effects have resulted in the interpretation of dips in the SED as evidence for planetary formation. However, the SED's for close binary stars have so far been the result of observing the co mbined light from both components. In one approach to answering questions regarding the consequence of close companion stars for circumstellar disks, Dr. Ghez is measuring the SED, from optical to infrared wavelengths, of each individual component within these close binary star systems using high spatial resolution imaging techniques. This will allow a determination of (1), how much of the previously observed excess can be attributed to the presence of a secondary source as opposed to a circumstellar disk (2), if the excess remains, whether both components or only one shows evidence for a circumstellar disk and (3), whether or not the dips in the SED are created by the presence of two stars with different apparent temperatures. In a second approach, Dr. Ghez will also compare the binary star frequency of the classical T Tauri stars (CTTS), which are thought to have an inner accretion disk, with that of the weak-lined T Tauri stars (WTTS), which are thought to lack an inner accretion disk. In their initial work, Dr. Ghez and her collaborators observed a distinction at the 3 sigma level; at separations less than 35 AU binary stars are more frequent among the WTTS than the CTTS. These observations suggest that close companions significantly interfere with the disk accretion process associated with many T Tauri stars. This result is an exciting possibility but requires follow up observations of more T Tauri stars to gain statistical significance. This will be accomplished by (1), expanding the sample of observed T Tauri stars to additional star forming regions and to fainter systems with the use of a more sensitive camera and (2), eventually using larger telescopes (Diameter 5-m, such as the Keck telescope) to probe this relationship further. If Dr. Ghez' hypothesis is correct, then the difference between the CTTS and WTTS binary star populations should increase at smaller separations. This award is to recognize an outstanding young faculty member in s cience and engineering. The award will enhance the career of the faculty member by providing flexible support for research and educational activities. Cooperation with industry and institutions that support research and education is encouraged.