On the chemical nature and orbit of meteoroids from the omicron draconid stream

Abstract

The omicron Draconids were first observed by Denning in the 19th Century [1]. The activity was, however, modest, with a zenithal hourly rate (ZHR) of about 10–12. Denning [2] also reported observations in 1929 but in neither case was an orbit given, only a radiant position (RA ~271º, Dec. ~60º). However, for a considerable time after Denning’s observations, no records of any activity exist. Whether this is due to a lack of observers at the pertinent time (early July and thus close to the longest day and also close to the activity period of the delta Aquariids and observers may have preferred to study those) or an intrinsic lack of activity from the Omicron Draconids is not clear. The next record appears to be by Cook et al. [3] reporting on the work of the Harvard Meteor Project in the 1950s. In that paper they also suggested that the formation of the stream was associated with the disintegration of the nucleus of comet C/1919 Q2 Metcalf. In fact, our team recorded in 2008 a mag. -18 omicron Draconid fireball which was linked to this comet [4]. Here we present the analysis of a doublestation omicron-Draconid fireball recorded in the framework of our continuous fireball monitoring and spectroscopic campaigns in July 2007. The unique spectrum obtained for a member of this stream has provides helpful information about the chemical nature of meteoroids in the omicron-Draconid stream.