NSF Young Investigator: Binarity in Young Stars

NSF 青年研究员：年轻恒星中的二元性

• 批准号: 9457458
• 负责人: Andrea Ghez
• 金额: $ 31.25万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1994
• 资助国家: 美国
• 起止时间: 1994-08-01 至 2000-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9457458&HistoricalAwards=false
• 关键词: NSF; Young; Investigator; Binarity; Stars

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.

9457458盖兹：恒星形成的研究往往是出于解释太阳系的形成和演化的愿望。因此，目前恒星形成的模式是以单个恒星的产生为中心的，在年轻的时候，它被气体和尘埃组成的圆盘包围，大约有几百个天文单位(AU)大小，行星可能由此形成。然而，盖兹博士和其他人最近对银河系中金牛座和蛇夫座的恒星形成区进行了调查，得出的结论是，即使不是全部，也是大多数年轻的低质量恒星都有伴星。此外，这些双星中的大多数相隔的距离比通常假设的星周圆盘的大小要小。在距离我们银河系最近的恒星形成地点金牛座和蛇夫座的距离(距离=150秒)处，恒星周盘的角度范围预计大约为1-2秒弧度。不幸的是，由于大气中的湍流，传统成像技术的角分辨率被限制在1弧秒，比4米望远镜的理论分辨率差10-30倍。因此，为了研究这些令人困惑而又普遍存在的近双星，将使用散斑成像的高分辨率成像技术。目前的研究工作集中在研究这些近距离双星对恒星周盘的形成和演化的影响。TTauri恒星的光谱能量分布(SED)主要是由测量得到的TTauri恒星的光谱能量分布(SED)推断的。特别是，被归因于盘过程的是紫外线和红外波长的过量辐射。最近，在模拟影响方面的更多努力导致了对SED下降的解释，认为这是行星形成的证据。然而，到目前为止，近距离双星的SED是观察到来自这两个组成部分的联合光的结果。盖兹博士用高空间分辨率成像技术测量了这些近距离双星系统中每个独立成分的SED，从光学波长到红外波长，这是一种回答近伴星对星盘影响的方法。这将允许确定(1)，以前观察到的过剩有多少可以归因于次级源的存在，而不是星周盘；(2)如果剩余的过剩，无论是两个分量还是只有一个显示出星周盘的证据，以及(3)SED的下降是否由两个视在温度不同的恒星的存在造成的。在第二种方法中，盖兹博士还将比较经典T-Tauri星(CTT)和弱线T-Tauri星(WTT)的双星频率。经典T-Tauri星被认为具有内吸积盘，而弱线T-Tauri星被认为没有内吸积盘。在最初的工作中，盖兹博士和她的合作者在3西格玛水平上观察到了一个区别：在间隔小于35AU时，WTT双星比CTT双星更常见。这些观测表明，亲密的伴星显著干扰了与许多T金牛座恒星相关的盘吸积过程。这一结果是一个令人兴奋的可能性，但需要对更多的T金牛座恒星进行后续观测才能获得统计意义。这将通过(1)利用更灵敏的相机将观测到的T-Tauri恒星的样本扩大到更多的恒星形成区域和更暗的系统，以及(2)最终使用更大的望远镜(直径5米，如凯克望远镜)来进一步探测这种关系。如果盖兹博士的假设是正确的，那么在较小的距离下，CTTS和WTTS双星群体之间的差异应该会增加。这一奖项是为了表彰S理工科一位杰出的年轻教员。该奖项将通过为研究和教育活动提供灵活的支持来促进教师的职业生涯。鼓励与支持研究和教育的行业和机构合作。