THE non-thermal radio source, VRO 42.22.01 (BL Lac), shows linear polarization in both the radio1 and the optical2 regions of its spectrum. The first report of variations in the total flux density of this source included the possible detection of circularly polarized radiation in its emission at 2695 MHz (ref. 3). A recent publication4 describing extensive observations of this object at 2.8 cm and 4.5 cm has shown that the variations in its total flux density are the most rapid detected to date. BL Lac has been monitored since April 1968 at a frequency of 8 GHz (3.75 cm) as part of a programme at the University of Michigan to study the polarization of variable extra -galactic radio sources, and large variations in its linearly polarized emission have been detected.
- 1 - general ; 2 - general science & technology ; 3 - general science & technology
- 1 - sciences appliquees, technologies et medecines ; 2 - sciences biologiques et medicales ; 3 - sciences biologiques fondamentales et appliquees. psychologie ; 4 - biophysique des tissus, organes et organismes