Near-infrared spectroscopic and photometric evolution of nova V476 Scuti - a nova that formed optically thin dust

R. K. Das1*, D. P. K. Banerjee2, N. M. Ashok2 and Soumen Mondal1
1Astrophysics and Cosmology Department, S N Bose National Centre for Basic Sciences, Salt Lake, Kolkata 700 098, India
2Astronomy and Astrophysics Division, Physical Research Laboratory, Ahmedabad - 380 009,Gujarat, India

Received: 07 March 2013 | Accepted: 12 July 2013

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Abstract

We present results of near-infrared (near-IR) JHK (1.07 - 2.5 μm) spectroscopic and photometric observations of Nova V476 Scuti (V476 Sct) which was discovered in outburst in 2005 September. The near-IR observations of the nova presents the evolution of the post-maxima spectra and near-IR light curve. The spectra of V476 Sct, observed on 9 di erent epochs, show prominent lines due to HI, OI, CI and NI. Based on the IR spectral signatures we independently identify it as a Fe II type of nova, consistent with the same classification obtained from optical spectra. A detailed identification of the observed spectral lines is presented.

The near-IR JHK light curve extending for a period of about 59 days after outburst clearly shows the formation of a optically thin dust shell, a phenomenon which is not commonly observed in novae. By fitting black body curves to the spectral energy distributions (SEDs) the temperatures of the dust shell on di erent epochs have been estimated. Dust formation in V476 Sct is consistent with the presence of lines of elements with low-ionization potential like Na and Mg in the early spectra which had earlier been suggested by us to be potential indicators of dust formation at a later phase in a nova’s development.



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Keywords : infrared: stars – line: identification – stars: novae, cataclysmic variables – stars: individual: V476 Sct – techniques: spectroscopic – techniques: photometric