We present infrared spectroscopic and photometric observations of the nova V2468 Cyg covering the period from 2008 March 13 till 2008 November 11. The JHK spectra of the object have been taken from the Mount Abu Infrared Observatory using the Near-In
frared Imager/Spectrometer. Spectra from 0.8-5.2 micron are also presented that were obtained using the NASA Infrared Telescope Facility and the SPEX instrument. The spectra are dominated by strong H I lines from the Brackett and Paschen series, Fe II, OI and CI lines in the initial days, typical of an Fe II type nova. The lines were broader in the period immediately after outburst with measured FWHM of 1800-2300 km/s for the Pa-beta and Br-gamma lines. These values narrowed to 1500-1600 km/s by 12 days from outburst. The spectra showed prominent He I lines at 1.0830 and 2.0581 micron together with H I and O I emission features after 36 days from outburst. Our IR observations show the comparatively broad emission lines, the rapid development of the spectrum to higher ionization, the early appearance of coronal lines, and the absence of dust emission, all features that indicate the hybrid nature of the nova. This is perhaps the most extensively observed example of a probable Fe IIb type nova at the infrared wavelengths. We also notice a short lived emission line of Fe II at 2.0888 micron which was present between April 9, 2008 to May 9, 2008. No dust emission is seen from the nova ejecta. We have also estimated the range for the ejecta mass in V2468 Cyg to be 3 x 10^{-6} - 10^{-5} Msun.
We present near-infrared spectroscopic and photometric observations of the nova KT Eridani taken during the first 100 days following its discovery in 2009 November. The JHK spectra of the object have been taken from the Mount Abu Infrared Observatory
using the Near-Infrared Imager/Spectrometer. The spectra, typical of the He/N class novae, show strong He I emission lines together with H I and O I emission features. The H I, Pa-beta and Br-gamma spectral lines and the He I line at 2.0581 micron show broad wings with a relatively narrow central component. The broad wings extend to 1900 km/s while the central component has FWHM of 2100 km/s. The V and near-infrared JHK light curves show an additional small amplitude outburst near 40 days after optical maximum. The distance to the nova d = 6.3 +/- 0.1 kpc is derived using the MMRD relation and the estimated value of t2 = 5.7 +/- 0.3 days. The small value of t2 places KT Eri in the class of very fast novae. Using the value of the distance to the nova d, we estimate the height of the nova to be z = 3.3 +/- 0.1 kpc below the galactic plane. We have also calculated the upper limit for the ejecta mass for KT Eri to be in the range 2.4-7.4 x 10^(-5) Msun. Kinematic evidence is presented from the shape of the line profiles for a possible bipolar flow. We analyze the temporal evolution of the continuum and also discuss the possibility of KT Eri being a recurrent nova.
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 observation
s 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.
