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The binary of the pulsar PSRB1259$-$63 and the Be star LS 2883 has beenobserved at the 2010 and 2014 periastron passages in the near-infrared (NIR)bands using the IRSF/SIRIUS and SIRPOL. The light curves in the J-,H-, andKs-bands are almost identical in these periastron passages. A flare starts nolater than 10 days before periastron and the maximum brightening of about 0.1magnitude is observed 12--17 days after periastron. The rising part of thelight curve is steeper and reaches a peak slightly earlier in the Ks-band thanin the other bands, thus a characteristic track appears on the NIRcolor-magnitude diagram. The time lag between the NIR light curves indicatesthat the variation in the Be circumstellar disk first occurs in an outerregion. We propose that the initial rapid contraction followed by the gradualexpansion of the disk is evoked by the rapidly changing tidal torque aroundperiastron and the resultant change of the optically thick area causes theobserved NIR light curves.

Near-infrared Brightening around the Periastron Passages of the Gamma-ray Binary PSR B1259$-$63 /LS 2883