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M.P. Rupen, V. Dhawan, A.J. Mioduszewski (NRAO)
We report radio observations by the VLA, MERLIN, and the VLBA, of the unusual variable star V445 Puppis. Optical data indicate an initial outburst sometime between 27 September and 24 November 2000; by contrast, while observations in January 2001 showed no radio emission to well below 1\,mJy, a chance observation on 9 September 2001 showed a strong (5--20\,mJy) radio source. The subsequent radio evolution has been quite complicated, with several rapidly-evolving outbursts over the following month. While the emission is clearly synchrotron, it is often optically thick at frequencies as high as 22\,GHz, suggesting either substantial free-free absorption due to ionized gas, or an extremely small source subject to synchrotron self-absorption. The radio emission probably originates either in accretion onto a compact companion hidden by a thick dust shell (seen through optical extinction and infrared emission), or in an asymmetric, clumpy shock at the boundary between the current and previous ejecta. The rapid evolution of both the radio emission and the radio absorption favors the former explanation. We are in the process of reducing MERLIN and VLBA target-of-opportunity observations which may settle the issue.
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