A CCD search for the dust trail of the Draconid parent comet 21P/Giacobini-Zinner

Introduction: Meteor streams occur when the Earth happen to enter a small portion of cometary dust trails. Hence we had rare chance to investigate the cometary dust trails during the meteoric streams. Infrared Astronomical Satellite (IRAS) discovered the thermal radiation from the particles in the dust trails, and it provided the unique way to obtain a synoptic view of wide-spread cometary debris [1]. Using the infrared images, it is possible to establish the intimate dynamical model of dust trails [2]. State-of-the-art technologies of data analysis and observing system have opened up the new opportunities to investigate the dust trails from the ground; Ishiguro et al. succeeded to detect the scattered sunlight by the dust trail particles of 22P/Kopff using the ground-based telescope with optical CCD camera [3]. The time comes to study the dust trails at any time with inexpensive astronomical instruments. The Draconids show periodic activities, and they produced twice spectacular meteor storms in 1933 and 1946. Their parent comet is 21P/Giacobini-Zinner, which is thought to be unusual in the chemical composition [4]. It belongs to the group of “depleted” comets characterized by low abundances of carbon in the gas phase. It is likely that organics may be in the dust phase. Observations: We searched a faint scattered light from meteoroids of 21P/Giacobini-Zinner using UH 2.24-m telescope and Kiso 1.05-m Schmidt telescope. The instruments consist of 8kCCD camera with R-band filter (UH88 run) and 2K CCD camera with R-filter (Kiso run). Observations were carried out at UH88 on 2004 May 23 and at Kiso between 2005 May 2 and 14. The perihelion passage of this comet is on 2005 July 2. Both UH88 and Kiso data were obtained under the photometric condition. Results: Size of the dust particles can be identified by beta, the ratio of solar radiation pressure to gravity. No significant enhancement of the brightness on the line of beta<10 (assuming the spherical particles with mass density of 1.0 g/cc, the diameter is larger than 1mm grains). In this presentation we discuss the reasons of our negative results.