Properties, evolution and morpho-kinematical modelling of the very fast nova V2672 Oph (Nova Oph 2009), a clone of U Sco

Nova Oph 2009 (V2672 Oph) reached maximum brightness V = 11.35 on 2009 August 16.5. With observed t(2)(V) = 2.3 and t(3)(V) = 4.2 d decline times, it is one of the fastest known novae, being rivalled only by V1500 Cyg (1975) and V838 Her (1991) among classical novae, and U Sco among the recurrent ones. The line of sight to the nova passes within a few degrees of the Galactic Centre. The reddening of V2672 Oph is E(B - V) = 1.6 +/- 0.1, and its distance d similar to 19 kpc places it on the other side of the Galactic Centre at a galactocentric distance larger than the solar one. The lack of an infrared counterpart for the progenitor excludes the donor star from being a cool giant like in RS Oph or T CrB. With close similarity to U Sco, V2672 Oph displayed a photometric plateau phase, a He/N spectrum classification, extreme expansion velocities and triple peaked emission-line profiles during advanced decline. The full width at zero intensity of H alpha was 12 000 km s-1 at maximum, and declined linearly in time with a slope very similar to that observed in U Sco. The properties displayed by V2672 Oph lead us to infer a mass of its white dwarf close to the Chandrasekhar limit and a possible final fate as a Type Ia supernova. Morpho-kinematical modelling of the evolution of the H alpha profile suggests that the overall structure of the ejecta is that of a prolate system with polar blobs and an equatorial ring. The density in the prolate system appeared to decline faster than that in the other components. V2672 Oph is seen pole-on, with an inclination of 0 degrees +/- 6 degrees and an expansion velocity of the polar blobs of 4800+900(-800) km s-1. On the basis of its remarkable similarity to U Sco, we suspect this nova may be a recurrent. Given the southern declination, the faintness at maximum, the extremely rapid decline and its close proximity to the ecliptic, it is quite possible that previous outbursts of V2672 Oph have been missed.