Multisite campaign on the open cluster M67 – II. Evidence for solar-like oscillations in red giant stars
Multisite campaign on the open cluster M67 – II. Evidence for solar-like oscillations in red giant stars
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DOI：
10.1111/j.1365-2966.2007.11585.x
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发表时间：
2007-02
影响因子：
4.8
通讯作者：
D. Stello;D. Stello;D. Stello;H. Bruntt;H. Bruntt;H. Bruntt;H. Kjeldsen;T. Bedding;T. Arentoft;T. Arentoft;R. Gilliland;J. Nuspl;S.-L. Kim;Y. B. Kang;J. Koo;J. Lee;C. Sterken;C.‐U. Lee;H. R. Jensen;A. Jacob;R. Szabó;R. Szabó;S. Frandsen;Z. Csubry;Z. Dind;M. Bouzid;T. Dall;L. Kiss
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文献类型：
--
作者：
D. Stello;D. Stello;D. Stello;H. Bruntt;H. Bruntt;H. Bruntt;H. Kjeldsen;T. Bedding;T. Arentoft;T. Arentoft;R. Gilliland;J. Nuspl;S.-L. Kim;Y. B. Kang;J. Koo;J. Lee;C. Sterken;C.‐U. Lee;H. R. Jensen;A. Jacob;R. Szabó;R. Szabó;S. Frandsen;Z. Csubry;Z. Dind;M. Bouzid;T. Dall;L. Kiss
测量星系团中一组恒星的类太阳振荡，有望更严格地测试恒星结构和演化，而不仅仅是对单场恒星进行参数拟合。追求这些前景的最雄心勃勃的尝试是吉利兰等人。(1993)将疏散星团M67(NGC 2682)中的11颗关闭恒星作为目标，但振荡幅度太小(<；20微马格)，无法获得明确的探测。如Gillland等人。(1993)我们的目标也是探测M67中类似太阳的振荡，但我们的目标是红巨星，预期振幅在50-500微马格之间，周期为1-8小时。我们分析了我们最近发表的光度测量，这些测量是在一个为期六周的多地点活动中使用世界上的九个望远镜获得的。观测结果与模拟结果以及恒星振荡的估计性质进行了比较。对于单个地点，傅里叶光谱中的噪声水平低至27微毫克，而综合数据达到19微毫克，这使得这是一组红巨星的最佳光度时间序列。这些数据使我们能够用一组均匀的恒星对标度关系(用于估计频率和幅度)进行第一次测试。探测到的超额能量与恒星振荡的预期信号在频率范围和幅度上都是一致的。然而，我们的结果受到明显的高水平非白噪声的限制，这些噪声不能明显地与恒星信号分开。
Measuring solar-like oscillations in an ensemble of stars i n a cluster, holds promise for testing stellar structure and evolution more stringently than just fitting parameters to single field stars. The most ambitious attempt to pursue these prospects was by Gilliland et al. (1993) who targeted 11 turn-off stars in the open cluster M67 (NGC 2682), but the oscillation amplitudes were too small (< 20µmag) to obtain unambiguous detections. Like Gilliland et al. (1993) we also aim at detecting solar-like oscillations in M67, but we target red giant stars with expected amplitudes in the range 50‐500µmag and periods of 1 to 8 hours. We analyse our recently published photometry measurements, obtained during a six-week multisite campaign using nine telescopes around the world. The observations are compared with simulations and with estimated properties of the stellar oscillations. Noise le vels in the Fourier spectra as low as 27µmag are obtained for single sites, while the combined data reach 19µmag, making this the best photometric time series of an ensemble of red giant stars. These data enable us to make the first test of the scaling relations (used to estimate frequency and amplitude) with an homogeneous ensemble of stars. The detected excess power is consistent with the expected signal from stellar oscillations, both in terms of its frequ ency range and amplitude. However, our results are limited by apparent high levels of non-white noise, which cannot be clearly separated from the stellar signal.