Near-infrared studies during maximum and early decline of Nova Cephei 2014 and Nova Scorpii 2015

Abstract

We present multi-epoch near-infrared photo-spectroscopic observations of Nova Cephei 2014 and Nova Scorpii 2015, discovered in outburst on 2014 March 8.79 UT and 2015 February 11.84 UT respectively. Nova Cep 2014 shows the conventional NIR characteristics of a Fe II class nova characterized by strong CI, HI and O I lines, whereas Nova Sco 2015 is shown to belong to the He/N class with strong He I, HI and OI emission lines. The highlight of the results consists in demonstrating that Nova Sco 2015 is a symbiotic system containing a giant secondary. Leaving aside the T CrB class of recurrent novae, all of which have giant donors, Nova Sco 2015 is shown to be only the third classical nova to be found with a giant secondary. The evidence for the symbiotic nature is three-fold; first is the presence of a strong decelerative shock accompanying the passage of the nova's ejecta through the giant's wind, second is the Hα excess seen from the system and third is the spectral energy distribution of the secondary in quiescence typical of a cool late type giant. The evolution of the strength and shape of the emission line profiles shows that the ejecta velocity follows a power law decay with time (t −1.13±0.17 ). A Case B recombination analysis of the H I Brackett lines shows that these lines are affected by optical depth effects for both the novae. Using this analysis we make estimates for both the novae of the emission measure n 2 e L, the electron density n e and the mass of the ejecta.

The Peculiar Multiwavelength Evolution Of V1535 Sco

“…The nova was originally given the designation PNV J1703260-3504140, then known as Nova Sco 2015, and eventually given the official designation V1535 Sco. Srivastava et al (2015) also noted that narrowing of the H-line profiles in the infrared indicated the presence of a deceleration shock, and estimated the total mass ejected to be between 4.5 × 10 −6 and 2.6 × 10…”

“…The combination of rapid fading and a possible bright near-infrared counterpart indicated that the companion star could be an M giant, in which case the nova could be embedded in the wind from a giant companion (Walter 2015). Srivastava et al (2015) later argued that the companion could be a K giant based on pre-eruption 2MASS photometry of a likely counterpart (2MASS J17032617-3504178). Spectroscopic observations indicated it was a He/N type nova (Walter 2015;Srivastava et al 2015).…”

“…Srivastava et al (2015) later argued that the companion could be a K giant based on pre-eruption 2MASS photometry of a likely counterpart (2MASS J17032617-3504178). Spectroscopic observations indicated it was a He/N type nova (Walter 2015;Srivastava et al 2015). Early X-ray and radio observations indicated the presence of strong shocks in the ejecta, which was further evidence that the ejecta were expanding into a dense medium.…”

Nova Ophiuchus 2017 as a Probe of 13C Nucleosynthesis and Carbon Monoxide Formation and Destruction in Classical Novae

“…The fit to the first of the 12 CO bands, i.e., the 2-0 band with its band head at 2.2935 μm, is undermined by the presence of a neutral carbon line at 2.2906 μm. This CI 2.2906 μm line is routinely seen in the spectra of Fe II novae at similar strength (amplitude) as the CI 2.1023 μm line or at lesser strength than the blend of Srivastava et al 2015), both of which are marked in Figure 1. A strong CI 2.2906 μm feature seriously affects the fit of the 2-0 band as seen in the cases of V2274 Cyg (Rudy et al 2003), V705 Cas (Evans et al 1996), and V2165 Oph (Das et al 2009).…”

Rise and fall of the dust shell of the classical nova V339 Delphini

“…6) between 15.8 and 36.8 d after outburst before dust formation set in. The analysis was along similar lines as for Nova Cep 2014 (Srivastava et al 2015). Fig.…”