---
author:
- 'Victor P. Utrobin'
date: 'Received 21 July 2006 / accepted 22 August 2006'
title: An optimal hydrodynamic model for the normal Type IIP supernova 1999em
---

Introduction
============

The supernova (SN) 1999em was discovered by the Lick Observatory Supernova Search on October 29.44 UT in the nearly face-on SBc galaxy NGC 1637 (Li [@li99]). Detected shortly after the explosion at an unfiltered magnitude of $\sim 13.5$, SN 1999em was bright enough to be observed well both photometrically and spectroscopically for more than 500 days (Hamuy et al. [@hpm01]; Leonard et al. [@lfg02]; Elmhamdi et al. [@edc03]). SN 1999em was the first Type II-plateau supernova (SN IIP) detected at both X-ray and radio wavelengths, being the least radio luminous and one of the least X-ray luminous SNe (Pooley et al. [@plf02]). The X-ray data indicated the interaction between SN ejecta and a pre-SN wind with a low mass-loss rate of $\sim 2 \times 10^{-6}
   M_{\sun}\,yr^{-1}$. Leonard et al. ([@lfab01]) presented the first spectropolarimetry of SN IIP based on the optical observations of SN 1999em during $\sim 160$ days after SN discovery. The weak continuum polarization increasing from $p \approx 0.2\%$ on day 7 to $p \approx 0.5\%$ in 