Parameters of type IIP SN 2012A and clumpiness effects

Abstract

Context. The explosion energy and the ejecta mass of a type IIP supernova (SN IIP) derived from hydrodynamic simulations are principal parameters of the explosion theory. Few SNe IIP have been studied by hydrodynamic modeling so far, however. Some doubts exist about the reliability of the derived SN IIP parameters. Aims. We studied the well-observed type IIP SN 2012A with hydrodynamic modeling. We examined its early spectra for ejecta clumpiness. We also explored other observational effects of clumpiness. Methods. We determined the supernova parameters by means of standard hydrodynamic modeling. We used the early hydrogen Hα and Hβ lines as clumpiness diagnostics. We used a modified hydrodynamic code to study the clumpiness effect in the light curve and expansion kinematics. Results. We found that SN 20012A is the result of the explosion of a red supergiant with a radius of 715 ± 100 R⊙. The explosion energy is (5.25 ± 0.6) × 1050 erg, the ejecta mass is 13.1 ± 0.7 M⊙, and the total 56Ni mass is 0.012 ± 0.002 M⊙. The estimated mass of a progenitor, a main-sequence star, is 15 ± 1 M⊙. The Hα and Hβ lines in early spectra indicate that outer ejecta are clumpy. Hydrodynamic simulations show that the clumpiness modifies the early light curve and increases the maximum velocity of the outer layers. Conclusions. The pre-SN 2012A was a normal red supergiant with the progenitor mass of ≈ 15 M⊙. The outer layers of ejecta indicate the clumpy structure. The clumpiness of the external layers can increase the maximum expansion velocity.