A&A 466, 729–735 (2007) Astronomy DOI: 10.1051/0004-6361:20066838 & c ESO 2007 Astrophysics Optical observations of enhanced activity of the 2005 Draconid meteor shower P. Koten, J. Borovicka,ˇ P. Spurný, and R. Štork Astronomical Institute of the Academy of Sciences, Ondrejovˇ Observatory, Fricovaˇ 298, 25165 Ondrejov,ˇ Czech Republic e-mail: [email protected] Received 29 November 2006 / Accepted 11 January 2007 ABSTRACT Context. The enhanced activity of the Draconid meteor shower was observed on October 8, 2005 using video and photographic cameras. Aims. The aim of this paper is to use a higher than usual number of recorded meteors to look at some physical properties of the Draconid meteoroids, to describe the activity profile, and to infer meteor orbits. Methods. Video data on meteors are used for the determination of the meteor shower activity. Double station data provide precise beginning heights of the meteors as well as their radiants and orbits. Beginning heights and light curves of all meteors are used for investigation of meteoroid properties. Results. Only the descending branch of the enhanced activity was observed between 17:30 and 19 UT. The mass distribution index is similar to the 1998 return. Beginning heights of the Draconid meteors are several kilometres higher in comparison with other meteors of similar velocity. Light curves are nearly symmetrical, with a slight preference of early maxima. Both results are consistent with the very fragile nature of Draconid meteoroids. Key words. meteors, meteoroids – comets: individual: 21P/Giacobini-Zinner 1. Introduction which additionally included smaller particles, identified that the 2005 outburst was caused by the material released during the The Draconid or Giacobinid meteor shower is a minor periodic 1946 perihelion passage of the parent comet. meteor shower, which sometimes produces brief but spectacu- In this paper we report the results of the double-station video lar meteor storms. Such storms occurred twice during last cen- experiment, which was carried out in the Czech Republic during tury, in 1933 and 1946 (e.g., Jacchia et al. 1950). Lower activ- the time of the Draconid meteor shower activity. Despite vari- ity was observed in 1952 (Davies & Lovell 1955), whereas in able weather conditions, the enhanced activity was detected and 1985 and 1998 the shower produced moderate meteor rates (Arlt simultaneous data on some of the Draconid meteors recorded. 1998). The shower is active between October 6th and 10th, with Due to later sunset in Central Europe only the descending branch a maximum occurring between October 8th and 9th. The activ- of the activity curve was probably observed. Clouds did not al- ity of the meteor shower depends on the position of the parent low us to precisely determine if the peak still occurred before the / comet 21P Giacobini-Zinner on its orbit. observation started or was already observed. In 2005 the parent comet returned to perihelion in July, We discuss here the activity profile, mass distribution, radi- but it was not clear whether it would influence activity of the ants and orbits, beginning heights, and light curves of meteors. Draconids that year. According to the modeling of the Draconids The second paper (Borovickaˇ et al. 2007) is devoted to detailed (http://www.imcee.fr/, J. Vaubaillon), no storm was ex- study of atmospheric deceleration we detected for the meteors pected to happen in October 2005. Nevertheless an enhancement and also to Draconid spectra. due to the proximity of the comet to perihelion was not possible to exclude. Thus the observers were encouraged to look for some signs of higher activity of this shower. 2. Instrumentation, observation, data processing Campbell-Brown et al. (2006) reported the Draconid out- The double-station video observations were carried out on the ◦ burst, which occurred around the solar longitude λ = 195.42 base Ondrejovˇ – Trebíˇ cˇ during three consecutive nights between corresponding to 16.1 UT, October 8, 2005. Between 14.5 UT October 6th and 9th, 2005. Both stations are separated by the and at least 18 UT, the CMOR radar detected meteor activity distance of 109.3 km, and the azimuth of the second station significantly above the sporadic background at multiple frequen- is 314.3◦ (azimuth of south = 0◦). Each station was equipped cies. The equivalent hourly binned zenithal hourly rate (ZHR) with two videocameras, which were connected to the 2nd gen- during the peak of the activity was higher than 150. The en- eration image intensifiers. At the Ondrejovˇ observatory, the di- hancement, although not as strong as that found in the radar data, rect camera equipped with a Mullard XX1332 intensifier and was also observed by visual observers located in Asia, Europe, a Jupiter 2/85 mm lens provided a field-of-view of 32◦. The sec- and North America. The visual observations provided ZHR ond camera, connected to the Dedal-41 intensifier with an Arsat of 40. Refined numerical simulation of the Draconid shower, 1.4/50 mm lens and spectral grating with 600 grooves/mm Article published by EDP Sciences and available at http://www.aanda.org or http://dx.doi.org/10.1051/0004-6361:20066838 730 P. Koten et al.: Optical observations of enhanced activity of the 2005 Draconid meteor shower Table 1. Atmospheric trajectories and physical properties of Draconid video meteors. αG and δG are coordinates of the geocentric radiant, vG geocentric velocity, Mmax absolute maximum brightness, mphot photometric mass, HB beginning height, KB parameter according to Ceplecha (1988), HE terminal height, cos(z) cosine of the zenith distance of the radiant, and F parameter describing the meteor light curve shape. All meteors were observed in the night of October 8/9, 2005. ∗ Meteor Time αG δG (vG) Mmax mphot HB KB HE cos(z) F [UT] [◦][◦][kms−1] [mag] [g] [km] [km] 05A08030 18:55:02 264.0 ± 1.0 55.2 ± 0.6 20.9 ± 0.6 3.6 0.006 100.5 6.76 92.0 0.87 0.40 05A08054 20:33:13 263.2 ± 0.3 55.26 ± 0.08 21.0 ± 0.2 1.9 0.03 101.8 6.70 88.7 0.74 0.52 05A08057 20:39:31 264.5 ± 0.3 55.2 ± 0.2 21.0 ± 0.2 2.0 0.05 105.2 6.47 87.3 0.74 0.46 05A08078 21:59:01 261.1 ± 0.5 55.67 ± 0.09 21.0 ± 0.3 2.5 0.04 102.6 6.70 88.6 0.61 0.64 05A08096 22:56:44 264.3 ± 2.8 55.8 ± 0.7 21.0 ± 0.5 3.7 0.012 102.0 6.76 92.9 0.55 0.24 05A08128 00:13:22 262.7 ± 0.2 55.28 ± 0.16 20.9 ± 0.5 3.5 0.016 104.0 6.66 91.0 0.44 0.31 ∗ −1 Computed on the assumption of v∞ = 23.57 km s . Table 2. Heliocentric orbits (J2000.0) of the Draconid video meteors. DSH is the orbital similarity criterion computed according to Southworth & Hawkins (1967). The orbit of the comet 21P/Giacobini-Zinner (2005) provided by the JPL Horizons program was used as the reference orbit. ◦ ◦ ◦ Meteor a [AU] eq[AU] ω [ ] Ω [ ] i [ ] DSH 05A08030 3.7 ± 0.5 0.73 ± 0.04 0.9965 ± 0.0006 173.8 ± 0.7 195.517 31.5 ± 0.7 0.05 05A08054 3.7 ± 0.2 0.73 ± 0.013 0.9960 ± 0.0002 173.3 ± 0.2 195.585 31.6 ± 0.3 0.05 05A08057 3.8 ± 0.2 0.739 ± 0.014 0.9968 ± 0.0001 174.2 ± 0.2 195.589 31.6 ± 0.3 0.04 05A08078 3.4 ± 0.2 0.71 ± 0.02 0.9948 ± 0.0003 171.9 ± 0.3 195.643 31.9 ± 0.4 0.04 05A08096 3.6 ± 0.4 0.72 ± 0.03 0.9968 ± 0.0015 174 ± 2 195.683 31.8 ± 0.6 0.03 05A08128 3.5 ± 0.3 0.72 ± 0.02 0.9957 ± 0.0001 172.9 ± 0.2 195.736 31.5 ± 0.5 0.05 Comet 3.526 0.706 1.038 172.535 195.423 31.811 – was used for meteor spectroscopy. Both cameras on the sec- 3. Recorded data ond station were coupled to Dedal-41 intensifiers. The first one, equipped with an Arsat 1.4/50 mm lens, provided a field-of-view ◦ The detection software MetRec has relatively large tolerance in of 28 in diameter. The second one connected with a Zenitar the shower assignment and identified 12 video meteors observed 2.8/16 mm lens served as a wide-field system with a field-of- from both stations as possible Draconid shower members. More view of about 85◦. In addition to the video observations, one precise measurement and reduction of these records confirmed 7 bright Draconid meteor was also recorded by three all-sky pho- of them as real Draconids. One of them was recorded only in the tographic cameras of the Czech part of the European fireball net- zero order of the spectral camera and by the wide-field camera. work (see Spurný et al. 2007 for network description). Unfortunately, the small angle of planes resulted in a big trajec- The recorded video data were stored on S-VHS video tapes. tory uncertainty and this meteor was finally excluded from the These tapes were searched using automatic meteor detection sample. Atmospheric trajectories and physical properties of the software MetRec (Molau 1999). Meteor records were digital- six remaining double station Draconid meteors are summarized × ized with resolution 25 images per second and 768 576 pixels.