Optical and Near-infrared Study of Nova V2676 Oph 2012

Abstract

We present optical spectrophotometric and near-infrared (NIR) photometric observations of the nova V2676 Oph covering the period from 2012 March 29 through 2015 May 8. The optical spectra and photometry of the nova have been taken from SMARTS and Asiago; the near-infrared photometry was obtained from SMARTS and Mt. Abu. The spectra are dominated by strong H i lines from the Balmer series, Fe ii, N i and [O i] lines in the initial days, typical of an Fe ii type nova. The measured FWHM for the Hβ and Hα lines was 800-1200 km s −1 . There was pronounced dust formation starting 90 days after the outburst. The J − K color was the largest among recent dust forming novae.

A Review of the Evolution of Classical Nova V2676 Oph: Formation of Molecules and Dust Grains

“…Just after its discovery, the emission lines were narrow, and the P-Cygni profile of Hα emission indicated a decrease in the expansion velocity of the nova outflow, from ∼750 km s −1 to ∼400 km s −1 , during days t = 2 -13 [32]. The P-Cygni absorption profile of Na I indicated an outflow velocity of 600 km s −1 at day t = 10 [46]. The emissions became progressively weaker until day t = 12 (when almost no emission lines were seen in the observed spectrum).…”

“…The distance to V2676 Oph was determined by Raj et al in 2017 [46] to be d = 6.9 -7.9 kpc (near the Galactic center), based on the absolute magnitude in the V -band at the visual-brightness maximum (M V,max = −6.5 to −6.8, as estimated from the Maximum Magnitude Rate of Decline (MMRD) relation [12] with t 2 = 60 -80 days) and a visual extinction A V = 2.9 ± 0.1, together with the apparent magnitude at the visual-brightness maximum (m V = 10.6 mag). Raj et al derived the visual extinction by using the "Balmer decrement" method and their spectroscopic observations.…”

“…Based on the estimated distance to V2676 Oph, Raj et al determined the total mass of hydrogen in the ejecta from V2676 Oph to be (0.27 -3.3)×10 −4 d 2 M ⊙ from their observations during the early-decline phase [46]. Furthermore, Raj et al recently determined the ejected mass from V2676 Oph to be ∼ 1.4×10 −5 M ⊙ based on the nebular phase spectrum of the nova [47].…”

“…Low-resolution optical spectroscopic observations were performed by several observers around the visual-brightness maximum of V2676 Oph [36,32,46]. Just after its discovery, the emission lines were narrow, and the P-Cygni profile of Hα emission indicated a decrease in the expansion velocity of the nova outflow, from ∼750 km s −1 to ∼400 km s −1 , during days t = 2 -13 [32].…”

“…The classical nova V2676 Oph is unique in that C 2 , CN, and CO molecules -and larger molecules such as polycyclic aromatic hydrocarbons (PAHs) or hydrogenated amorphous carbon (HAC) -have all been detected in the same nova. In addition, significant dust formation began ∼90 days after the nova explosion [36,51,34,46]. Dust formation is recognized in about ∼20% of classical novae [59] and usually occurs in "CO novae" that involve CO 1 white dwarfs (WDs), whereas dust formation rarely occurs in "ONe novae" involving ONe WDs [20].…”