  We present near-infrared and optical observations of moderately fast
FeII-class Nova Scuti 2009 (V496 Sct) covering various phases; pre-maximum,
early decline and nebular, during the first 10 months after its discovery
followed by limited observations up to 2011 April. In the initial phase the
nova spectra show prominent P Cygni profiles and later all the lines are seen
in emission. The notable feature of the near-IR spec- tra in the early decline
phase is the rare presence of the first overtone bands of carbon monoxide (CO)
in emission. The IR spectra show clear dust formation in the expand- ing ejecta
at later phase about 150 days after the peak brightness. The presence of lines
of elements with low ionization potentials like Na and Mg in the early IR
spectra and the detection of CO bands in emission and the dust formation in
V496 Sct represents a complete expected sequence in the dust formation in nova
ejecta. The light curve shows a slow rise to the maximum and a slow decline
indicating a prolonged mass loss. This is corroborated by the strengthening of
P Cygni profiles during the first 30 days. The broad and single absorption
components seen in many lines in the optical spectra at the time of discovery
are replaced by two sharper components in the spectra taken close to the
optical maximum brightness. These sharp dips seen in the P Cygni absorption
components of Fe II and H I lines during the early decline phase show
increasing outflow velocities. The onset of the nebular phase is evident from
the optical spectra in 2010 March. During the nebular phase, several emission
lines display saddle-like profiles. In the nebular stage, the observed fluxes
of [O III] and H lines are used to estimate the electron number densities and
the mass of the ejecta. The optical spectra show that the nova is evolved in
the P_fe A_o spectral sequence.
