Quadrantids 2016: observations of a short pre-maximum peak

The Quadrantid meteoroid stream is known to show variations between annual returns as well as signs of mass sorting along the cross section. Only a little modelling of the stream has been published. For 2016, a possible short flux enhancement a few hours before the main peak of the shower was announced. Here we present results obtained from two independent optical observation samples. The data strongly support the presence of the predicted feature at solar longitude 282.884 deg+-0.010 deg showing an increase by about 50 percent of the visual ZHR and about 25 percent of the video meteor flux compared to the neighbouring values. The width of the peak is of the order of 30 minutes. The population index profile indicates that the meteoroids are not different in size distribution form the surrounding stream. A similar narrow increase by about 50 percent is found in radio forward scatter data at solar longitude 282.748 deg +-0.010 deg. This is 0.14 deg or 3.4 hours earlier than the peak of the optical meteors and may be explained as a mass sorting effect in this part of the stream.