Radio evolution of supernova SN 2008iz in M 82
2016
We report on multi-frequency Very Large Array (VLA) and
Very Long Baseline Interferometry(VLBI) radio observations for a monitoring campaign of
supernovaSN 2008iz in the nearby
irregular galaxyM 82. We fit two models to the data, a simple time power-law, S ât?, and a simplified Weiler model, yielding decline indices of ? =-1.22 ± 0.07 (days 100-1500) and-1.41 ± 0.02 (days 76-2167), respectively. The late-time radio light-curve evolution shows flux-density flares at ?970 and ?1400 days that are a factor of ?2 and ?4 higher than the expected flux, respectively. The later flare, except for being brighter, does not show signs of decline at least from results examined so far (2014 January 23; day 2167). We derive the
spectral index, ?, S â?? for frequencies 1.4 to 43 GHz for SN 2008iz during the period from 430 to 2167 days after the
supernovaexplosion. The value of ? shows no signs of evolution and remains steep â‰-1 throughout the period, unlike that of SN 1993J, which started flattening at day 970. From the 4.8 and 8.4 GHz VLBI images, the
supernovaexpansion is seen to start with a shell-like structure that becomes increasingly more asymmetric, then breaks up in the later epochs, with bright structures dominating the southern part of the ring. This structural evolution differs significantly from SN 1993J, which remains circularly symmetric over 4000 days after the explosion. The VLBI 4.8 and 8.4 GHz images are used to derive a deceleration index, m, for SN 2008iz, of 0.86 ± 0.02, and the average expansion velocity between days 73 and 1400 as (12.1 ± 0.2) × 103 km s-1. From the energy equipartition between magnetic field and particles, we estimate the minimum total energy in
relativistic particlesand the magnetic fields during the
supernovaexpansion and also find the magnetic field
amplification factorfor SN 2008iz to be in the range of 55-400.
Keywords:
-
Correction
-
Source
-
Cite
-
Save
45
References
13
Citations
NaN
KQI