A Universal Decline Law of Classical Novae. IV. V838 Her (1991): A Very Massive White Dwarf

We present a unified model of optical and ultraviolet (UV) light curves for one of the fastest classical novae, V838 Herculis (Nova Herculis 1991), and estimate its white dwarf (WD) mass. Based on an optically thick wind theory of nova outbursts, we model the optical light curves with free-free emission and the UV 1455 \AA light curves with blackbody emission. Our models of 1.35 \pm 0.02 M_\sun WD reproduce simultaneously the optical and UV 1455 \AA observations. The mass lost by the wind is \Delta M_{wind} \sim 2 \times 10^{-6} M_\sun. We provide new determinations of the reddening, E(B-V) = 0.53 \pm 0.05, and of the distance, 2.7 \pm 0.5 kpc.