多伦多{ \em{BRITE} }卫星对沃尔夫-拉叶星EZ CMa的长时间不间断测光观测揭示了一个非常快的拱点运动
Long uninterrupted photometric observations of the Wolf-Rayet star EZ CMa by the Toronto {\em{BRITE}} satellite reveal a very fast apsidal motion
摘要：
上下文沃尔夫-拉叶星EZ CMa的变率已经被记录了将近半个世纪，并且确定了$\sim$ 3.7天的明显周期。然而，所有试图证明它是一个双星的尝试都失败了，因为它的光度、光谱和偏振变化在几个轨道周期内并不一致。目标。在这封信中，我们表明，缺乏连贯性的变化，可以解释一个非常快速的拱点运动的双轨道。方法.我们测量了多伦多{ \emph{BRITE} }卫星最近发表的异常长的光度学光变曲线中的极小值。拱线运动和系统偏心率是由这些极小值之间的时间间隔长度确定的，这些极小值在其持续时间上交替，遵循与拱线运动明显相关的模式。这些极小值叠加在激波区发射的亮度增强上，激波区发射的亮度增强发生在近星点阶段。结果我们确定轨道周期$P_{a}=3.63\, $ d和拱点运动周期$U\simeq 100\, $ d，它们共同产生平均恒星周期$P_{s}=3.77\,$ d。发现偏心率接近0.1。在观察期间，近心点后退的速率发生显著变化，在观察期开始时确定为$-16^\circ\,\mathrm{P}^{-1}_a$，在观察期结束时确定为$-10^\circ\,\mathrm{P}^{-1}_a$。结论.我们证明，通过引入一个快速拱线运动，基本的光度变化是很好的解释。EZ CMa的二元性质现在已经建立。这可能意味着其他明显的单沃尔夫-拉叶星发射硬X射线，类似于EZ CMa，也是双星。
英文摘要：
Context. The variability of the Wolf-Rayet star EZ CMa has been documented for close to half a century, and a clear periodicity of $\sim$3.7 days is established. However, all attempts to prove that it is a binary have failed because the photometric, spectroscopic, and polarimetric variations are not coherent over more than a few orbital cycles. Aims. In this letter we show that the lack of coherence in the variability can be explained with a very rapid apsidal motion in a binary orbit.} Methods. We measured the times of minima in a recently published exceptionally long photometric light curve obtained by the Toronto {\emph{BRITE}} satellite. The apsidal motion and the system eccentricity are determined from the length of the time intervals between these minima, which alternate in their duration, following a pattern that is clearly associated with apsidal motion. These minima are superposed on brightness enhancements of the emission from a shock zone, which occur at about the times of periastron phases. Results. We determine the orbital periodicity, $P_{a}=3.63\, $d, and the period of the apsidal motion, $U\simeq 100\, $d, which together yield an average sidereal period of $P_{s}=3.77\,$d. The eccentricity is found to be close to 0.1. The rate of periapsis retreat changes significantly over the period of observation and is determined to be $-16^\circ\,\mathrm{P}^{-1}_a$ at the beginning of the observing period and $-10^\circ\,\mathrm{P}^{-1}_a$ at the end. Conclusions. We demonstrate that by introducing a fast apsidal motion, the basic photometric variability is very well explained. The binary nature of EZ CMa is now established. This might imply that other apparently single Wolf-Rayet stars that emit hard X-rays, similar to EZ CMa, are also binaries.
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。
