Detection of Circular Polarization in M81*

We report the detection of circular polarization in the compact radio jet ofthe nearby spiral galaxy M81 (M81*). The observations were made with the VeryLarge Array at 4.8 and 8.4 GHz and circular polarization was detected at bothfrequencies. We estimate a value of $m_{c}=0.54\pm0.06\pm0.07%$ at 8.4 GHz and$m_{c}=0.27\pm0.06\pm0.07%$ at 4.8 GHz for the fractional circularpolarization. The errors are separated into statistical and systematic terms.The spectrum of the circular polarization is possibly inverted which would beunusual for AGN. We also detected no linear polarization in M81* at a level of0.1% implying that the source has a very high circular-to-linear polarizationratio as found so far only in Sgr A*, the central radio source in our Galaxy.This further supports the idea that M81* is a scaled-up version of Sgr A* andsuggests that the polarization properties are intrinsic to the two sources andare not caused by a foreground screen in the Galaxy.Comment: 9 pages, 1 figure, accepted for publication in ApJ Letter