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We present the spectroscopic and photometric observations on the Be/X-raybinary RX~J0440.9+4431 from 2001 to 2014. The short-term and long-termvariability of the H$\alpha$ line profile indicates that one-armed globaloscillations existed in the circumstellar disk. Several positive and negativecorrelations between the $V$-band brightness and the H$\alpha$ intensity\textbf{were} found from the long-term photometric and spectroscopicobservations. We suggest that the monotonic increase of the $V$-band brightnessand the H$\alpha$ brightness between our 2005-2007 observations might be theresult of a continuous mass ejection from the central Be star, while thenegative correlation in 2007-2010 should be caused by the cessation of massloss 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 inour 2010 observations with an equivalent width of $\sim$$-12.88$ \AA, whichcorresponds to a circumstellar disk with a size of 12.9 times the radius of thecentral Be star. Three consecutive X-ray outbursts peaking around MJD 55293,55444, and 55591 might be connected with the largest circumstellar disk aroundthe Be star. We also use the orbital motion of the neutron star as a probe toconstrain the structure of the circumstellar disk and estimate the eccentricityof the binary system to be $\ge$ 0.4. After three years of the H$\alpha$intensity decline after the X-ray outbursts, a new circumstellar disk was beingformed around the Be star after our 2013 observations.

Long-term Optical Studies of the Be/X-ray Binary RX J0440.9+4431/LS V+44 17