Supernova 2000cb: high-energy version of SN 1987A

¹ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching, Germany
e-mail: utrobin@itep.ru
² Institute of Theoretical and Experimental Physics, B. Cheremushkinskaya St. 25, 117218 Moscow, Russia
³ Institute of Astronomy of Russian Academy of Sciences, Pyatnitskaya St. 48, 119017 Moscow, Russia

Received: 26 April 2011
Accepted: 6 July 2011

Abstract

Context. Among type IIP supernovae there are a few events that resemble the well-studied supernova 1987A produced by the blue supergiant in the Large Magellanic Cloud.

Aims. We study a peculiar supernova 2000cb and compare it with the supernova 1987A.

Methods. We carried out hydrodynamic simulations of the supernova in an extended parameter space to describe its light curve and spectroscopic data. The hydrogen Hα and Hβ lines are modeled using a time-dependent approach.

Results. We constructed the hydrodynamic model by fitting the photometric and spectroscopic observations. We infer a presupernova radius of 35  ±  14   R_⊙, an ejecta mass of 22.3  ±  1   M_⊙, an explosion energy of (4.4 ± 0.3)  ×  10⁵¹ erg, and a radioactive ⁵⁶Ni mass of 0.083  ±  0.039   M_⊙. The estimated progenitor mass on the main sequence lies in the range of 24 − 28   M_⊙. The early Hα profile on Day 7 is consistent with the density distribution found from hydrodynamic modeling, while the Hα line on Day 40 indicates an extended ⁵⁶Ni mixing up to a velocity of 8400 km s^-1. We emphasize that the dome-like light curves of both supernova 2000cb and supernova 1987A are entirely powered by radioactive decay. This is unlike normal type IIP supernovae, the plateau of which is dominated by the internal energy deposited after the shock wave propagation through the presupernova. We find signatures of the explosion asymmetry in the photospheric and nebular spectra.

Conclusions. The explosion energy of supernova 2000cb is higher by a factor of three compared to supernova 1987A, which poses a serious problem for explosion mechanisms of type IIP supernovae.