We present the spectroscopic and photometric observations on the Be/X-ray binary RX~J0440.9+4431 from 2001 to 2014. The short-term and long-term variability of the H$α$ line profile indicates that one-armed global oscillations existed in the circumstellar disk. Several positive and negative correlations between the $V$-band brightness and the H$α$ intensity \textbf{were} found from the long-term photometric and spectroscopic observations. We suggest that the monotonic increase of the $V$-band brightness and the H$α$ brightness between our 2005-2007 observations might be the result of a continuous mass ejection from the central Be star, while the negative correlation in 2007-2010 should be caused by the cessation of mass loss from the Be star just before the decline in $V$-band brightness began (around our 2007 observations). With the extension of the ejection material, the largest circumstellar disk during the last two decades has been observed in our 2010 observations with an equivalent width of $\sim$$-12.88$ Å, which corresponds to a circumstellar disk with a size of 12.9 times the radius of the central Be star. Three consecutive X-ray outbursts peaking around MJD 55293, 55444, and 55591 might be connected with the largest circumstellar disk around the Be star. We also use the orbital motion of the neutron star as a probe to constrain the structure of the circumstellar disk and estimate the eccentricity of the binary system to be $\ge$ 0.4. After three years of the H$α$ intensity decline after the X-ray outbursts, a new circumstellar disk was being formed around the Be star after our 2013 observations.
Discovery of an X-ray Emitting Contact Binary System 2MASS J11201034$-$2201340
我们报告了一个新发现的接触双星2 MASS J11201034 $-$ 2201340的轨道调制、模型解和X射线性质。我们在{ \it Fermi Gamma-ray Space Telescope}探测到的不明天体中寻找可能的$γ$射线毫秒双星的X射线对应物时，偶然发现了这个位于误差椭圆之外的X射线点源。然后使用档案数据库识别X射线源的光学对应物（与$γ$射线源无关）。皇家空间遥感中心的长期调查发现了一个精确的信号，周期为$P=0.28876208(56)$天。鹿林天文台的射电望远镜进行的后续观测揭示了该物体的双星性质。利用存档的多波段测量的光度数据，我们构建的光谱能量分布，这是很好地拟合的K2 V光谱模板。用Wilson-Devinney程序拟合的结果表明，2 MASS J11201034-2201340是一个短周期A型接触双星，质量较大的部分有一个冷点。X射线发射首先在\swift \观察中发现，然后通过\xmm \观察进一步确认和表征。X射线谱可用幂律或热韧致辐射来描述。不幸的是，我们不能观察到明显的X射线轨道调制。最后，根据光谱能量分布，估计该系统距离地球690 pc，计算的X射线强度为$(0.7-1.5)\times 10^{30}$ erg s $^{-1}$，在预期的发射接触双星的X射线范围内。
Extremely fast orbital decay of the black hole X-ray binary Nova Muscae 1991
本文介绍了用8. 2 m-VLT望远镜上的X-射手摄谱仪对黑洞X射线双星Nova Muscae 1991进行的新的中等分辨率光谱观测。这些观测使我们能够测量次级恒星与该系统中的黑洞的下合时间，与以前的测量结果一起，产生$\dot P=-20.7\pm12.7$ ms yr $^{-1}$的轨道周期衰减（$-24.5\pm15.1$ $μ$ s per orbital cycle）。这比以前在其他黑洞X射线双星A0620-00和XTE J1118+480中测量到的速度要快得多。没有标准的黑洞X射线双星演化模型能够解释这种极快的轨道衰变。按照这个速度，第二颗恒星将在大约270万年后到达事件视界（由史瓦西半径约32公里给出）。这一结果对黑洞X射线双星的演化和寿命具有重要意义。
