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arXiv 2008.04171astro-ph.SR
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作为微透镜源的非径向脉动星

Non-radially pulsating stars as microlensing sources

Sedighe Sajadian, Richard Ignace

摘要:

我们研究了非径向脉动(NRP)星的微透镜现象。用不同的l,m值的球谐函数来表示恒星半径和温度的脉动。研究了NRP星微透镜光变曲线与不同脉动模的关系。对于NRP星的微透镜效应,除非可以忽略有限源尺寸的影响,否则光变曲线不是放大率曲线和源星内禀光度曲线的简单乘积。从模拟的光变曲线可以得出三个主要结论。第一,对于具有$m\neq0$的模式,当观测倾角更接近于极点时,朝向观测者的恒星光度随脉动相位的变化很小。在这种情况下,高放大率的微透镜事件是彩色的,可以揭示这些源星的变化。其次,脉动模式的某些组合产生几乎退化的光度曲线(例如,(1,m)=(3,0),(5,0))。除非透镜穿过投影光源,否则由此产生的微透镜光曲线也会退化。最后,对于m=1的模式,恒星亮度中心与坐标中心不重合,投影源亮度中心在天空中以脉动相位移动。由于亮度质心的这种时间相关位移,放大峰值的时间与透镜最接近亮度中心而不是光源坐标中心的时间一致。NRP星的双星微透镜和焦散线交叉特征是彩色的。

英文摘要:

We study the microlensing of Non-Radially Pulsating (NRP) stars. Pulsations are formulated for stellar radius and temperature using spherical harmonic functions with different values of l,m. The characteristics of the microlensing light curves from NRP stars are investigated in relation to different pulsation modes. For the microlensing of NRP stars, the light curve is not a simple multiplication of the magnification curve and the intrinsic luminosity curve of the source star, unless the effect of finite source size can be ignored. Three main conclusions can be drawn from the simulated light curves. First, for modes with $m\neq0$ and when the viewing inclination is more nearly pole-on, the stellar luminosity towards the observer changes little with pulsation phase. In this case, high-magnification microlensing events are chromatic and can reveal the variability of these source stars. Second, some combinations of pulsation modes produce nearly degenerate luminosity curves (e.g., (l,m)=(3,0), (5,0)). The resulting microlensing light curves are also degenerate, unless the lens crosses the projected source. Finally, for modes involving m=1, the stellar brightness centre does not coincide with the coordinate centre, and the projected source brightness centre moves in the sky with pulsation phase. As a result of this time-dependent displacement in the brightness centroid, the time of the magnification peak coincides with the closest approach of the lens to the brightness centre as opposed to the source coordinate centre. Binary microlensing of NRP stars and in caustic-crossing features are chromatic.

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