Near-infrared observations of nova V574 Puppis (2004)

We present results obtained from extensive near-infrared spectroscopic and photometric observations of nova V574 Pup during its 2004 outburst. The observations were obtained over 4 months, starting from 2004 November 25 (4 d after the nova outburst) to 2005 March 20. The near-infrared JHK light curve is presented -it shows no evidence of the fact that dust formation has occurred during our observations. In the early decline phase, the JHK spectra of the nova are dominated by emission lines of hydrogen Brackett and Paschen series, O(I), C(I) and He(I). We also detect the fairly uncommon Fe(II) line at 1.6872 mu m in the early part of our observations. The strengths of the He I lines at 1.0830 and 2.0585 mu m are found to become very strong towards the end of the observations indicating a progression towards higher excitation conditions in the nova ejecta. The width of the emission lines does not show any significant change during the course of our observations. The slope of the continuum spectrum was found to have a lambda(-2.75) dependence in the early stages which gradually becomes flatter with time and changes to a free-free spectral dependence towards the later stages. Recombination analysis of the HI lines shows deviations from case B conditions during the initial stages. However, towards the end of our observations, the line strengths are well simulated with case B model values with electron density n(e) = 109(-10) cm(-3) and a temperature equal to 10(4)K. Based on our distance estimate to the nova of 5.5 kpc and the observed free-free continuum emission in the later part of the observations, we estimate the ionized mass of the ejecta to be between 10(-5) and 10(-6)M(circle dot).