Space Grant Consortium - University of Wisconsin - Green Bay

detected earlier than other types of SNe (Stockdale, et al., 2009). This phenomenon can be
observed when comparing a type IIb SN (Figure 1) with other type II SNe (Figure 2).
Fig. 1.— Light Curve for SN 2008ax.
Fig. 2.— Light Curve for SN 1995N (Chandra,
et al., 2009).
The radio analysis method involves measuring the intensities of radio emission at certain
wavelengths from the blastwave of the SN. The intensity of the wavelength directly corresponds
to the material shed by the SN, the circumstellar material (CSM). The CSM will
absorb certain wavelengths of radio emission as continuum absorption in contrast to an optical
absorption line spectrum, where each wavelength represents certain energy and materials
(such as hydrogen or oxygen). Thus, the emission observed by the radio telescope does not
indicate which materials are present in the CSM, but can be used to measure the density
of the CSM. Then comparing when the radio emission is observed relative to the initial
blast, and assuming the speed of the blastwave and the CSM ejected the approximate time
a material ejected before the SN can be calculated. This knowledge is called the mass-loss
history. Knowing how the CSM was formed in the SN leads to knowledge of the life and
death processes of the SN. This knowledge can then be used to determine characteristics and
properties of type IIb SNe. The radio emission created is formed when the blastwave, due
to the massive amount of energy it contains, accelerates and the electrons in the CSM to
relativistic speeds and heating them from ∼10,000 K to ∼10,000,000 K. The blastwave itself
also creates a strong magnetic field that traps the excited relativistic particles and causes
them to emit radiation called synchrotron radiation (Figure 3). This radiation is detected
by radio observations, which in turn depict the density make up of the CSM.
The CSM is often considered to be “fog-like” in nature, because the “fog” particles (free
electrons in a cloud of ionized hydrogen) obscure radio radiation. This “fog of particles” is
2