We present multi-epoch photometric and spectroscopic near-infrared observations of the Be star X Persei in the JHK bands covering the wavelength range 1.08-2.35 μm. Combining results from our earlier studies with the present observations, it is shown that the equivalent widths and line fluxes of the prominent H I and He I lines anti-correlate with the strength of the adjacent continuum. That is, during the span of the observations, the JHK broadband fluxes increase while the emission equivalent width values of the H I and He I lines decrease (the lines under consideration being the Paschen and Brackett lines of hydrogen and the 1.7002 μm and 2.058 μm lines of helium). Such an anti-correlation effect is not commonly observed in Be stars in the optical; in the infrared, this may possibly be the first reported case of such behavior. We examine different mechanisms that could possibly cause it and suggest that it could originate due to a radiatively warped, precessing circumstellar disk. It is also shown that during the course of our studies, X Per evolved to an unprecedented state of high near-IR brightness with J, H, K magnitudes of 5.20, 5.05, and 4.84, respectively.
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机译：我们介绍了Be Star X Persei在覆盖波长范围1.08-2.35μm的JHK波段中的多时代光度和光谱近红外观测结果。结合我们以前的研究结果和当前的观察结果，可以看出，突出的H I和He I线的等效宽度和线通量与相邻连续谱的强度反相关。也就是说，在观测的跨度期间，JHK宽带通量增加，而HI和He I线的发射当量宽度值减小（所考虑的线是氢气的Paschen和Brackett线以及1.7002μm和2.058μm线氦气。在光学中的Be星中通常不会观察到这种抗相关作用。在红外线中，这可能是此类行为的首次报道。我们研究了可能导致它的不同机制，并提出它可能是由于辐射扭曲，旋进的星际盘引起的。还表明，在我们的研究过程中，X Per演变为前所未有的高近红外亮度状态，其J，H，K大小分别为5.20、5.05和4.84。
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