Space Grant Consortium - University of Wisconsin - Green Bay

Results
Only five confirmed Type IIb supernovae have been measured using radio and X-ray techniques:
SN 1993J, SN 2001ig, SN 2001gd, SN 2008ax, and SN 2008bo. Below, we present the results
of the analysis of SN 1993J, SN 2008ax, and SN 2001ig.
SN 1993J in NGC 3031
SN1993J is one of the most well observed supernovae with over 680 observations taken over the
course of thousands of days. Figure 2 shows the radio flux density of SN1993J versus time since
the explosion; the x-axis represents the log time since the explosion occurred (measured in days),
and the y-axis represents the electromagnetic flux density of the source (measured in milli-
Janskys). Each colored line represents a different frequency band of data as seen in Figure 1.
The data seems to fit the parameterized model very well up until around day 3000. After that,
the data points sharply tend downward representing a sudden and dramatic decrease in radio flux
intensity. This might have been caused by a sudden change in the mass loss rate of the star. The
data fitting shows that there has to be a significant synchrotron self-absorption component to the
evolution of SN 1993J in addition to free-free absorption.
Figure 2: Radio light curve of SN 1993J in NGC 3031
As a side note, the work done by Stockdale et al. (2007) shows that SN 2001gd follows a similar
decay pattern to SN 1993J early in its evolution. It was determined from the fitting of the curve
that a significant synchrotron self-absorption component had to be present in SN 2001gd.
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