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Charles E. Woodward

IR Study of Nova V2468 Cyg from Early Decline to the Coronal Phase
Raj, A.; Ashok, N. M.; Rudy, Richard J.; Russell, Ray W.; Lynch, David K.; Woodward, Charles E.; Sitko, Michael; and 4 coauthors, The Astronomical Journal

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We present infrared spectroscopic and photometric observations of the nova V2468 Cyg covering the period from 2008 March 13 to 2008 November 11. The JHK spectra of the object were taken from the Mt. Abu Infrared Observatory using the Near-Infrared Imager/Spectrometer. Spectra from 0.8 to 5.2 μm that were obtained using the NASA Infrared Telescope Facility and the SPEX instrument are also presented. The spectra are dominated by strong H I lines from the Brackett and Paschen series and Fe II, O I, and C I lines in the initial days, typical of an Fe II type nova. The lines were broader in the period immediately after outburst, with measured FWHMs of 1800-2300 km s-1 for the Paβ and Brγ lines. These values narrowed to 1500-1600 km s-1 by 12 days from the outburst. The spectra showed prominent He i lines at 1.0830 and 2.0581 μm together with H i and O i emission features after 36 days from the 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 infrared wavelengths. We also note a short lived emission line of Fe II at 2.0888 μm, which was present between 2008 April 9 and 2008 May 9. 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 × 10-6 e-5M ⊙ .