Flux density variations of radio sources in M82 over the last 3 decades
  This paper presents the results of the 2009-2010 monitoring sessions of the
starburst galaxy M82, obtained with the Multi-Element Radio-Linked
Interferometer Network (MERLIN) at 5GHz and e-MERLIN at 6GHz. Combining several
5GHz MERLIN epochs to form a map with 33.0 uJy/bm noise level, 52 discrete
sources, mostly supernova remnants and HII regions, are identified. These
include three objects which were not detected in the 2002 5GHz MERLIN
monitoring session: supernova SN2008iz, the transient source 43.78+59.3, and a
new supernova remnant shell. Flux density variations, in the long (1981 to
2010), medium (2002 to 2010) and short (2009 to 2010) term, are investigated.
We find that flux densities of SNRs in M82 stay constant in most of the sample
(~95%). In addition, aside from SN2008iz and the well-known variable source
41.95+57.5, two sources display short and medium term variations over the
period 2009-2010. These sources being among the most compact SNR in M82, these
flux density variations could be due to changes in the circumstellar and
interstellar medium in which the shocks travel.
