关于Oumuamua的纵横比：不规则表面特性的较小细长形状
On the aspect ratio of Oumuamua: less elongated shape for irregular surface properties
摘要：
Oumuamua观测到的光变曲线中的大亮度变化可能与其形状有关，即，与其最长轴和最短轴之间的比率（纵横比）有关。几种方法发现Oumuamua的长宽比异常细长。此外，自旋轴方向必须几乎垂直于观察者，以获得这样一个极端的光变曲线，这是不可能的配置。然而，星际Oumuamua可能有不同的表面性质比我们知道在我们的太阳系。因此，在这项工作中，我们扩大了参数空间的表面性质超出了小行星状模型，并研究其对Oumuamua的光变曲线的影响。我们计算了四种模型从旋转椭球体的反射：朗伯反射，镜面反射，单散射漫射和后向散射。然后，我们计算的概率，以获得一个光变曲线比大于观察到的，作为对象的长宽比的函数，假设一个同位旋取向分布。我们发现Oumuamua的伸长率是不太极端的朗伯和镜面反射模型。因此，对于那些模型，观察到Oumuamua的光变曲线比的概率在其未知的自旋轴方向上更大。我们的结论是，不同的表面反射特性可能会建议Oumuamua的极端形状的替代品，减轻需要复杂的地层情况下，极端的反射变化，或非自然的起源。虽然这里建议的模型是理想的椭球形状和理想反射的方法，结果强调的重要性，表面特性的衍生的纵横比。
英文摘要：
The large brightness variation in the observed lightcurve of Oumuamua is probably related to its shape, i.e., to the ratio between its longest axis and its shortest axis (aspect ratio). Several approaches found the aspect ratio of Oumuamua to be unusually elongated. Moreover, the spin axis orientation has to be almost perpendicular to the observer in order to obtain such an extreme lightcurve, a configuration which is unlikely. However, interstellar Oumuamua may have different surface properties than we know in our solar system. Therefore, in this work we widen the parameter space for surface properties beyond the asteroid-like models and study its effect on the lightcurve of Oumuamua. We calculate reflection from a rotating ellipsoidal object for four models: Lambertian reflection, specular reflection, single scattering diffusive and backscatter. We then calculate the probability to obtain a lightcurve ratio larger than the observed, as a function of the object aspect ratio, assuming an isotopic spin orientation distribution. We find the elongation of Oumuamua to be less extreme for the Lambertian and specular reflection models. Consequently, the probability to observe the lightcurve ratio of Oumuamua given its unknown spin axis orientation is larger for those models. We conclude that different surface reflection properties may suggest alternatives to the extreme shape of Oumuamua, relieving the need for complicated formation scenario, extreme albedo variation, or unnatural origin. Although the models suggested here are for ideal ellipsoidal shape and ideal reflection method, the results emphasize the importance of surface properties for the derived aspect ratio.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
