Four epochs of VLBA/HSA observations of SN 2001em

SN 2001em is a peculiar supernova (SN) which has been reclassified from Type Ib/c to IIn. We deduced the limits for its proper motion as well as the expansion velocity by analysing four epochs of VLBI observations. Our 2 sigma upper limit of its proper motion is (23,000 30,000) km s(-1) and for the expansion velocity is 9000 km s(-1) with 95% confidence. Thus we confirm the analysis of Bietenholz & Bartel that this was not a jet-driven gamma my burst event. The supernova is unresolved 6 years after the explosion. We find no evidence for the existence of a jet. These values suggest interaction of the SN ejecta with a dense circumstellar medium. VLA observations of the flux density over 4 years of observations show a power law decay.