Optical evolution of Nova Ophiuchi 2007 = V2615 Oph

TL;DR

This paper presents detailed optical observations of Nova Ophiuchi 2007, analyzing its brightness evolution, spectral features, dust formation, and deriving key physical parameters like distance, reddening, and velocity.

Contribution

It provides a comprehensive optical evolution study of Nova Ophiuchi 2007, including spectral analysis, dust formation evidence, and physical parameter estimation, which enhances understanding of nova behavior.

Findings

Maximum brightness at V=8.52 on March 28, 2007

Dust formation caused significant extinction and reddening between 82-100 days post-maximum

Expansion velocity from Hα line was approximately 730 km/s

Abstract

The moderately fast Nova Oph 2007 reached maximum brightness on March 28, 2007 at V=8.52, B-V=+1.12, V-Rc=+0.76, V-Ic=+1.59 and Rc-Ic=+0.83, after fast initial rise and a pre-maximum halt lasting a week. Decline times were t(V,2)=26.5, t(B,2)=30, t(V,3)=48.5 and t(B,3)=56.5 days. The distance to the nova is d=3.7 kpc, the height above the galactic plane z=215 pc, the reddening E(B-V)=0.90 and the absolute magnitude at maximum M(V,max)=-7.2 and M(B,max)=-7.0. The spectrum four days before maximum resembled a F6 super-giant, in agreement with broad-band colors. It later developed into that of a standard 'FeII'-class nova. Nine days past maximum, the expansion velocity estimated from the width of H$\alpha$ emission component was 730 km/s, and the displacement from it of the principal and diffuse enhanced absorption systems were 650 and 1380 km/s, respectively. Dust probably formed and disappeared during the period from 82 to 100 days past maximum, causing (at peak dust concentration) an extinction of Delta B=1.8 mag and an extra Delta E(B-V)=0.44 reddening.