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We report on 8.4GHz Very Long Baseline Interferometry (VLBI) observations of the type II-P supernova SN2004et in the spiral galaxy NGC 6946, made on 20 February 2005 (151 days after explosion). The Very Large Array (VLA) flux density was 1.23$pm$0.07 mJy, corresponding to an isotropic luminosity at 8.4GHz of (4.45$pm$0.3)$times10^{25}$ erg s$^{-1}$ Hz$^{-1}$ and a brightness temperature of (1.3$pm$0.3)$times10^{8}$ K. We also provide an improved source position, accurate to about 0.5 mas in each coordinate. The VLBI image shows a clear asymmetry. From model fitting of the size of the radio emission, we estimate a minimum expansion velocity of 15,700$pm$2,000 km s$^{-1}$. This velocity is more than twice the expected mean expansion velocity estimated from a synchrotron self-absorbed emission model, thus suggesting that synchrotron self-absorption is not relevant for this supernova. With the benefit of an optical spectrum obtained 12 days after explosion, we favor an emission model which consists of two hot spots on an underlying expanding shell of width comparable to that of SN 1993J.
We report new cm-wave measurements at five frequencies between 15 and 18GHz of the continuum emission from the reportedly anomalous region 4 of the nearby galaxy NGC6946. We find that the emission in this frequency range is significantly in excess of
We present a new centimeter polarimetric VLBI image of the BL Lac object 0735+178. This source exhibits one of the most pronounced curvatures observed in jets of AGNs, with two sharp apparent bends of 90 degrees within the inner 2 milliarcseconds fro
Outside the Milky Way, the most luminous H2O masers at 22 GHz, called megamasers because of their extreme luminosity with respect to the Galactic and extragalactic H2O masers associated with star formation, are mainly detected in active galactic nucl
Observations of the starburst galaxy, M82, have been made with a 20-station global VLBI array at $lambda$18cm. Maps are presented of the brightest young supernova remnants (SNR) in M82 and the wide-field mapping techniques used in making images over
Five compact radio sources, include 0420-014, 1334-127, 1504-166, 2243-123, and 2345-167, were observed at 5GHz by European VLBI (Very Long Baseline Interferometry) Network (EVN) in June, 1996. The primary purpose of this observation was to confirm t