标题： 高超声速恒星 SDSS J090745.0+024507 是一颗短周期变星 显示英文标题

标题： The Hypervelocity Star SDSS J090745.0+024507 is a Short-Period Variable

摘要： 我们展示了高精度光度测量的超高速星SDSS J090745.0+024507（HVS），该星在银河系参考框架中的径向速度为v=709 km/s，因此很可能已被从银河系中心的超大质量黑洞弹射出去。 我们的数据是在两个晚上使用MMT 6.5米望远镜获得的，并通过在四个晚上使用FLWO 1.2米望远镜得到的较低精度的光度测量加以补充。 高精度光度测量表明HVS是一种短周期、低振幅的变星，周期P=0.2-2天，振幅A=2-10%。 结合已知的有效温度T_eff ~ 10,500 K（光谱类型B9），这种变化性表明HVS是缓慢脉动B型主序星类别的一员，从而解决了之前报道的关于恒星亮度和距离的双重退化问题。 HVS的日心距离为71千秒差距，年龄约为0.35亿年。 从银河系中心弹射的时间< 1亿年，因此OS的存在构成了大约0.1亿年前中央超大质量黑洞附近年轻恒星群体的观测证据。 可能HVS曾是双星系统的一员，被中央黑洞潮汐瓦解；我们讨论了对其伴星轨道性质的限制。 ``` 显示英文摘要

摘要： We present high-precision photometry of the hypervelocity star SDSS J090745.0+024507 (HVS), which has a Galactic rest-frame radial velocity of v=709 km/s, and so has likely been ejected from the supermassive black hole in the Galactic center. Our data were obtained on two nights using the MMT 6.5m telescope, and is supplemented by lower precision photometry obtained on four nights using the FLWO 1.2m telescope. The high-precision photometry indicates that the HVS is a short-period, low-amplitude variable, with period P=0.2-2 days and amplitude A = 2-10%. Together with the known effective temperature of T_eff ~ 10,500 K (spectral type B9), this variability implies that the HVS is a member of the class of slowly pulsating B-type main sequence stars, thus resolving the previously-reported two-fold degeneracy in the luminosity and distance of the star. The HVS has a heliocentric distance of 71 kpc, and an age of ~0.35 Gyr. The time of ejection from the center of the Galaxy is < 100 Myr, and thus the existence of the OS constitutes observational evidence of a population of young stars in the proximity of the central supermassive black hole ~0.1 Gyr ago. It is possible that the HVS was a member of a binary that was tidally disrupted by the central black hole; we discuss constraints on the properties of the companion's orbit.