A theoretical light curve for the 1999 outburst of U Scorpii is presented in order to obtain various physical parameters of the recurrent nova .
Our U Sco model consists of a very massive white dwarf ( WD ) with an accretion disk and a lobe-filling , slightly evolved , main-sequence star ( MS ) .
The model includes a reflection effect by the companion and the accretion disk together with a shadowing effect on the companion by the accretion disk .
The early visual light curve ( with a linear phase of t \sim 1 - 15 days after maximum ) is well reproduced by a thermonuclear runaway model on a very massive WD close to the Chandrasekhar limit ( M _ { WD } = 1.37 \pm 0.01 ~ { } M _ { \odot } ) , in which optically thick winds blowing from the WD play a key role in determining the nova duration .
The ensuing plateau phase ( t \sim 15 - 30 days ) is also reproduced by the combination of a slightly irradiated MS and a fully irradiated flaring-up disk with a radius \sim 1.4 times the Roche lobe size .
The cooling phase ( t \sim 30 - 40 days ) is consistent with a low hydrogen content X \approx 0.05 of the envelope for the 1.37 M _ { \odot } WD .
The best fit parameters are the WD mass M _ { WD } \sim 1.37 ~ { } M _ { \odot } , the companion mass M _ { MS } \sim 1.5 M _ { \odot } ( 0.8 - 2.0 M _ { \odot } is acceptable ) , the inclination angle of the orbit i \sim 80 \arcdeg , and the flaring-up edge , the vertical height of which is \sim 0.30 times the accretion disk radius .
The duration of the strong wind phase ( t \sim 0 - 17 days ) is very consistent with the BeppoSAX supersoft X-ray detection at t \sim 19 - 20 days because supersoft X-rays are self-absorbed by the massive wind .
The envelope mass at the peak is estimated to be \sim 3 \times 10 ^ { -6 } M _ { \odot } , which is indicating an average mass accretion rate \sim 2.5 \times 10 ^ { -7 } M _ { \odot } yr ^ { -1 } during the quiescent phase between 1987 and 1999 .
These quantities are exactly the same as those predicted in a new progenitor model of Type Ia supernovae .