  Type IIP supernova progenitors are often surrounded by dense circumstellar
media that may result from mass-loss enhancement of the progenitors shortly
before their explosions. Previous light-curve studies suggest that the
mass-loss rates are enhanced up to ~ 0.1 Msun/yr, assuming a constant wind
velocity. However, density of circumstellar media at the immediate stellar
vicinity can be much higher than previously inferred for a given mass-loss rate
if wind acceleration is taken into account. We show that the wind acceleration
has a huge impact when we estimate mass-loss rates from early light curves of
Type IIP supernovae by taking SN 2013fs as an example. We perform numerical
calculations of the interaction between supernova ejecta and circumstellar
media with a constant mass-loss rate but with a beta-law wind velocity profile.
We find that the mass-loss rate of the progenitor of SN 2013fs shortly before
the explosion, which was inferred to be ~ 0.1 Msun/yr with a constant wind
velocity of 10 km/s by a previous light-curve modeling, can be as low as ~ 1e-3
Msun/yr with the same terminal wind velocity of 10 km/s but with a wind
velocity profile with beta ~ 5. In both cases, the mass of the circumstellar
medium is similar (~ 0.5 Msun). Therefore, the beginning of the progenitor's
mass-loss enhancement in our interpretation is ~ 100 years before the
explosion, not several years. Our result indicates that the immediate dense
environment of Type II supernova progenitors may be significantly influenced by
wind acceleration.
