OGLE 2008-BLG-290: an accurate measurement of the limb darkening of a galactic bulge K Giant spatially resolved by microlensing
OGLE 2008-BLG-290: an accurate measurement of the limb darkening of a galactic bulge K Giant spatially resolved by microlensing
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OGLE 2008-BLG-290：通过微透镜空间解析的银河核球K巨星边缘变暗的精确测量
DOI：
10.1051/0004-6361/201014053
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发表时间：
2010
影响因子：
6.5
通讯作者：
Fouqué P
中科院分区：
文献类型：
--
作者：
Fouqué P
引力微透镜不仅是发现遥远系外行星的一个成功工具，而且它还可以表征透镜事件中涉及的透镜和源星。AimsIn高放大率事件，透镜焦散可能跨越源盘，这允许确定源的角大小和测量其临边暗化。所得到的光变曲线不同于特征Paczyoski点光源曲线。接近峰值的光变曲线的确切形状取决于光源的临边暗化。密集的光度覆盖范围允许测量各自的边缘变暗coefficients.ResultsIn的微透镜事件OGLE 2008-BLG-290的情况下，K巨星源星星达到峰值放大率约100。十三台不同的望远镜在八个不同的光度波段覆盖了这一事件。随后的光变曲线分析产生的线性边缘变暗系数的来源在六个光度带的测量。最好的测量系数导致源的有效温度约为4700 K的估计。然而，从颜色星等图的光度估计有利于较冷的温度为4200±100 K。结论由于边缘变暗测量，至少在CTIO/SMARTS 2和波段，是最准确的获得，上述分歧需要理解。提出了一个解决办法，这可能适用于以前的事件，这种差异也出现了。
ContextNot only is gravitational microlensing a successful tool for discovering distant exoplanets, but it also enables characterization of the lens and source stars involved in the lensing event.AimsIn high-magnification events, the lens caustic may cross over the source disk, which allows determination of the angular size of the source and measurement of its limb darkening.MethodsWhen such extended-source effects appear close to maximum magnification, the resulting light curve differs from the characteristic Paczyński point-source curve. The exact shape of the light curve close to the peak depends on the limb darkening of the source. Dense photometric coverage permits measurement of the respective limb-darkening coefficients.ResultsIn the case of the microlensing event OGLE 2008-BLG-290, the K giant source star reached a peak magnification at about 100. Thirteen different telescopes have covered this event in eight different photometric bands. Subsequent light-curve analysis yielded measurements of linear limb-darkening coefficients of the source in six photometric bands. The best-measured coefficients lead to an estimate of the source effective temperature of about 4700K. However, the photometric estimate from colour-magnitude diagrams favours a cooler temperature of 4200±100 K.ConclusionsBecause the limb-darkening measurements, at least in the CTIO/SMARTS2- and-bands, are among the most accurate obtained, the above disagreement needs to be understood. A solution is proposed, which may apply to previous events where such a discrepancy also appeared.