The Remnant of Supernova 1993J in M81

A “movie” showing the development of the supernova 1993J remnant in M81

for the one-year period of September 1993 to September 1994. These images

were taken in the radio light; the first four at 3.6 cm wavelength, the

last one at 6 cm.

References:

NRAO press release on this radio film of the SN 1993J remnant
Expansion of SN 1993J

Marcaide, J.M., Alberdi, A., Ros, E., Diamond, P., Shapiro, I.I.,

Guirado, J.C., Jones, D.L., Krichbaum, T.P., Mantovani,

F., Preston, R.A., Rius, A., Schilizzi, R.T., Trigilio, C., Whitney,

A.R., Witzel, A.

Science, 270, 1475-1478 (1995)

Abstract:

A sequence of images from very long baseline interferometry shows that the

young radio supernova SN 1993J is expanding with circular symmetry. However,

the circularly symmetric images show emission asymmetries. A scenario in which

freely expanding supernova ejecta shock mostly isotropic circumstellar material

is strongly favored. The sequence of images constitutes the first ”movie” of

a radio supernova.

The supernova remnant at 6.3 cm, September 1994.

Reference:

Discovery of Shell-like Radio-Structure in SN1993J

Marcaide, J.M., Alberdi, A., Ros, E., Diamond, P.J.,

Schmidt, B., Shapiro, I.I., Baath, Davis, R.J., de Bruyn, G.,

Elósegui, P., Guirado, J.C., Jones, D.L., Krichbaum, T.P.,

Mantovani, F., Preston, R.A., Ratner, M.I., Rius, A., Rogers, A.E.E.,

Schilizzi, R.T., Trigilio, C., Whitney, A.R., Witzel, A., Zensus, J.A.

Nature, 373, 44-45 (1995)

Abstract:

SUPERNOVA explosions are poorly understood, partly because of difficulties

in modelling them theoretically(1), and partly because there have been no

supernovae observed in our Galaxy since the invention of the telescope.

But the recent discovery(2) of supernova SN1993J in the nearby galaxy M81

offers an opportunity to investigate the evolution of the remnant, and its

interaction with the surrounding interstellar medium, at high resolution.

Here we present radio observations of SN1993J, made using

very-long-baseline interferometry, which show the development of a shell

structure. This 8-month-old radio shell is the youngest ever discovered in

a supernova. The data suggest that the supernova explosion and the

expanding shell of the remnant have nearly spherical symmetry, with small

deviations where some parts of the shell are brighter than others. If these

deviations arise because of variations in the density of the shell, this

may reconcile earlier reports of symmetric radio emission(3) with the

observed optical asymmetry(4,5), as the density variations could easily

cause the latter. We infer that the radio emission is generated at the

interface(6-9), where the surrounding gas is shocked by the ejecta.