  We present results obtained from an extensive near-infrared spectroscopic and
photometric observations of the Be/X-ray binary A0535+262/HDE 245770 at
different phases of its ~111 day orbital period. This observation campaign is a
part of the monitoring programme of selective Be/X-ray binary systems aimed at
understanding the X-ray and near-IR properties at different orbital phases,
especially during the periastron passage of the neutron star. The near-IR
observations were carried out using the 1.2 m telescope at Mt. Abu IR
observatory. Though the source was relatively faint for spectroscopic
observations with 1.2 m telescope, we monitored the source during the 2011
February--March giant outburst to primarily investigate whether any drastic
changes in the near-IR JHK spectra take place at the periastron passage.
Changes of such a striking nature were expected to be detectable in our
spectra. Photometric observations of the Be star show a gradual and systematic
fading in the JHK light curves since the onset of the X-ray outburst that could
suggest a mild evacuation/truncation of the circumstellar disc of the Be
companion. Near-IR spectroscopy of the object shows that the JHK spectra are
dominated by the emission lines of hydrogen Brackett and Paschen series and HeI
lines at 1.0830, 1.7002 and 2.0585 micron. The presence of all hydrogen
emission lines in the JHK spectra, along with the absence of any significant
change in the continuum of the Be companion during X-ray quiescent and X-ray
outburst phases suggest that the near-IR line emitting regions of the disc are
not significantly affected during the X-ray outburst.
