Near Infrared Observations of the novae V2491 Cygni and V597 Puppis

Abstract

We present results obtained from near-infrared JHK spectroscopic observations of novae V2491 Cyg and V597 Pup in the early declining phases of their 2007 and 2008 outbursts respectively. In both objects, the spectra displayed emission lines of HI, OI, HeI and NI. In V597 Pup, the HeI lines were found to strengthen rapidly with time. Based on the observed spectral characteristics, both objects are classified as He/N novae. We have investigated the possibility of V2491 Cyg being a recurrent nova as has been suggested. By studying the temporal evolution of the line widths in V2491 Cyg it appears unlikely that the binary companion is a giant star with heavy wind as in recurrent novae of the RS Oph type. Significant deviations from that of recombination case B conditions are observed in the strengths of the HI lines. This indicates that the HI lines, in both novae, are optically thick during the span of our observations. The slope of the continuum spectra in both cases was found to have a λ^-(3-3.5) dependence which deviates from a Rayleigh-Jeans spectral distribution. Both novae were detected in the post-outburst super-soft X-ray phase; V2491 Cyg being very bright in X-rays has been the target of several observations. We discuss and correlate our infrared observations with the observed X-ray properties of these novae.

arXiv comment9 pages, 7 figures, Accepted for publication in MNRAS

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• A Prediction Formula of Supersoft X-ray Phase of Classical Novae
• Identifying and Quantifying Recurrent Novae Masquerading as Classical Novae
• XMM-Newton X-ray and UV observations of the fast nova V2491 Cyg during the supersoft source phase
• Swift observations of the X-ray and UV evolution of V2491 Cyg (Nova Cyg 2008 No. 2)
• The 2010 nova outburst of the symbiotic Mira V407 Cyg
• A New Catalogue of Galactic Novae: Investigation of the MMRD relation & Spatial Distribution
• A Light Curve Analysis of 32 Recent Galactic Novae --- Distances and White Dwarf Masses
• An extensive optical study of V2491 Cyg (Nova Cyg 2008 N.2), from maximum brightness to return to quiescence
• Detection and evolution of the CO (v = 2) emission in nova V2615 Ophiuchi (2007)
• Analysis of physical processes in eruptive YSOs with near infrared spectra and multi-wavelength light curves
• The eclipsing Intermediate Polar V597 Pup (Nova Puppis 2007)
• Near Infrared studies during maximum and early decline of Nova Cephei 2014 and Nova Scorpii 2015
• A phenomenological model for the X-ray spectrum of Nova V2491 Cygni
• Nova light curves from the Solar Mass Ejection Imager (SMEI) - II. The extended catalog
• The $UBV$ Color Evolution of Classical Novae. IV. Time-Stretched $(U-B{)}_0$-$(M_B-2.5\log f_{\mathrm{s}})$ and $(V-I{)}_0$-$(M_I-2.5\log f_{\mathrm{s}})$ Color-Magnitude Diagrams of Novae in Outburst
• The $UBV$ Color Evolution of Classical Novae. III. Time-Stretched Color-Magnitude Diagram of Novae in Outburst
• Nova KT Eri 2009: Infrared studies of a very fast and small amplitude He/N nova
• Near-infrared studies of the 2010 outburst of the recurrent nova U Scorpii
• Infrared spectroscopy of the 2019 eruption of the recurrent nova V3890 Sgr: separation into equatorial and polar winds revealed
• Unresolved X-ray emission in M31 and constraints on progenitors of Classical Novae
• Optical and Near-Infrared Photometry of Nova V2362 Cyg : Rebrightening Event and Dust Formation
• Near-infrared Observations of Be/X-ray Binary Pulsar A0535+262
• Near-infrared Observations of Nova V574 Puppis (2004)