Ejecta and progenitor of the low-luminosity type IIP supernova 2003Z

Context. The origin of low-luminosity type IIP supernovae is unclear: they have been proposed to originate either from massive (similar to 25 M-circle dot) or low- mass (similar to 9 M-circle dot) stars. Aims. We wish to determine parameters of the low- luminosity type IIP supernova 2003Z, to estimate a mass-loss rate of the presupernova, and to recover a progenitor mass. Methods. We compute the hydrodynamic models of the supernova to describe the light curves and the observed expansion velocities. The wind density of the presupernova is estimated using a thin shell model for the interaction with circumstellar matter. Results. We estimate an ejecta mass of 14.0 +/- 1.2 M-circle dot, an explosion energy of (2.45 +/- 0.18) x 1050 erg, a presupernova radius of 229 +/- 39 R (circle dot), and a radioactive Ni-56 amount of 0.0063 +/- 0.0006 M-circle dot. The upper limit of the wind density parameter in the presupernova vicinity is 1013 g cm(-1), and the mass lost at the red/ yellow supergiant stage is <= 0.6 M-circle dot assuming the constant mass-loss rate. The estimated progenitor mass is in the range of 14.4 - 17.4 M-circle dot. The presupernova of SN 2003Z was probably a yellow supergiant at the time of the explosion. Conclusions. The progenitor mass of SN 2003Z is lower than those of SN 1987A and SN 1999em, normal type IIP supernovae, but higher than the lower limit of stars undergoing a core collapse. We propose an observational test based on the circumstellar interaction to discriminate between the massive (similar to 25 M-circle dot) and moderate- mass (similar to 16 M-circle dot) scenarios.