The light curve of supernova 1987A: The structure of the presupernova and radioactive nickel mixing

Abstract

Abstract-We have studied the influence of the presupernova structure and the degree of 56 Ni mixing on the bolometric light curve of SN 1987A in terms of radiation hydrodynamics in the one-group approximation by abandoning LTE and by taking into account nonthermal ionization and the contribution of spectral lines to its opacity. Our study shows that moderate 56 Ni mixing at velocities ≤2500 km scan explain the observed light curve if the density of the outer layers of the presupernova exceeds the value obtained in the evolutionary model of a single nonrotating star severalfold. Abandoning LTE and allowing for nonthermal ionization when solving the equation of state and calculating the mean opacities and the thermal emission coefficient leads to a significant difference between the gas temperature and the radiation temperature in the optically thin layers of the supernova envelope. We demonstrate the fundamental role of the contribution of spectral lines to the opacity in an expanding envelope and of the accurate description of radiative transfer in reproducing the observed shape of the bolometric light curve. We have found that disregarding the contribution of spectral lines to the opacity introduces an error of ∼20% into the explosion energy, and that a similar error is possible when determining the mass of the ejected matter. The resonant scattering of radiation in numerous lines accelerates the outer layers to velocities of ≈36 000 km s −1 ; this additional acceleration affects the outer layers with a mass of ≈10 −6 M . Proper calculations of the supernova luminosity require that not only the delay effects, but also the limb-darkening effects be taken into account.

Optical observations of type-IIP supernova 2004dj: Evidence for asymmetry of the 56Ni ejecta

“…The density is described by the exponential distribution ρ = ρ 0 exp(−v/v 0 ) with ρ 0 ∝ t −3 . The exponential law is fairly good for the bulk of the inner envelope where the power index |d ln ρ/d ln v| gradually increases outwards (e.g., Utrobin 2004). The parameters ρ 0 and v 0 are determined by M and E. We adopt as above M = 13 M ⊙ and E = 10 51 erg.…”

High mass of the type IIP supernova 2004et inferred from hydrodynamic modeling

“…Utrobin (2007) found that both this one-group approach and the multi-group approach of Baklanov et al (2005) measured similar ejecta mass and explosion energy for SN 1999em. The basic equations and details of the input physics, including calculations of mean opacities, are described in Utrobin (2004). The present version of the code includes additionally Compton cooling and heating.…”

“…The modeling of the SN explosion is performed using the spherically-symmetric hydrodynamic code with one-group radiation transfer (Utrobin 2004(Utrobin , 2007, which has been applied previously to other SNe IIP. Utrobin (2007) found that both this one-group approach and the multi-group approach of Baklanov et al (2005) measured similar ejecta mass and explosion energy for SN 1999em.…”

Asymmetry in the Outburst of Sn 1987a Detected Using Light Echo Spectroscopy

“…Fine structure in the Hα line (the "Bochum event") at 20-100 days after the explosion as well as redshifted emission lines at more than 150 days after explosion provides strong evidence for radial mixing of heavy elements into the upper envelope (Hanuschik & Dachs 1987;Phillips & Heathcote 1989;Spyromilio et al 1990). Updated models of the bolometric light curve at early epochs also require radial mixing of 56 Ni (Shigeyama & Nomoto 1990;Utrobin 2004). Direct Hubble Space Telescope (HST) imaging by Wang et al (2002) showed an elongated remnant ejecta, claimed to be bipolar and showing evidence for a jet-induced explosion.…”