Optical evolution of Nova Ophiuchi 2007 = V2615 Oph

The moderately fast Nova Oph 2007 reached maximum brightness on 2007 March 28 at V = 8.52, B - V = +1.12, V - R[SUB]C[/SUB] = +0.76, V - I[SUB]C[/SUB] = +1.59 and R[SUB]C[/SUB] - I[SUB]C[/SUB] = +0.83, after fast initial rise and a pre-maximum halt lasting a week. Decline times were t[SUP]V[/SUP][SUB]2[/SUB] = 26.5, t[SUP]B[/SUP][SUB]2[/SUB] = 30, t[SUP]V[/SUP][SUB]3[/SUB] = 48.5 and t[SUP]B[/SUP][SUB]3[/SUB] = 56.5 d. The distance to the nova is d = 3.7 +/- 0.2 kpc, the height above the Galactic plane is z = 215 pc, the reddening is E(B - V) = 0.90 and the absolute magnitude at maximum is M[SUP]max[/SUP][SUB]V[/SUB] = -7.2 and M[SUP]max[/SUP][SUB]B[/SUB] = -7.0. The spectrum four days before maximum resembled a F6 supergiant, in an agreement with broad-band colours. It later developed into that of a standard `FeII'-class nova. Nine days past maximum, the expansion velocity estimated from the width of Hα emission component was ~730 km s[SUP]-1[/SUP], and the displacement from it of the principal and diffuse-enhanced absorption systems was ~650 and 1380 km s[SUP]-1[/SUP], respectively. Dust probably formed and disappeared during the period from 82 to 100 d past maximum, causing (at peak dust concentration) an extinction of ΔB = 1.8 mag and an extra ΔE(B - V) = 0.44 reddening.