Astron. Astrophys. Suppl. Ser. 135, 291-297

Alpha Cygnids - a possible July minor meteor shower

A. Olech^1,2 -  M. Gajos^1,2 - M. Jurek²

Send offprint request: Arkadiusz Olech,
e-mail: olech@sirius.astrouw.edu.pl

1 - Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
2 - Comets and Meteors Workshop, ul. Sokolicz 3/59, 01-508 Warszawa, Poland

Received June 23; accepted November 6, 1998

Abstract:

We present a comprehensive study of a possible $\alpha$-Cygnid meteor shower. Based on visual and telescopic observations made by Polish observers we estimate basic parameters of the stream. Activity of $\alpha$-Cygnids lasts from around June 30 to July 31 with clear maximum near July 18 (solar longitude $\lambda_\odot=116.5^\circ$). Maximal Zenithal Hourly Rates (ZHRs) are equal to $3.6\pm1.2$. The structure of the radiant analyzed by RADIANT software is most compact for geocentric velocity of the events equal to 41 km s^-1, and for the drift of the radiant (in units $^\circ$/day) equal to $\Delta\alpha=+0.6$ $\Delta\delta=+0.2$. Center of the radiant for the moment of maximum is $\alpha=302.5^\circ$$\delta=+46.3^\circ$. We derive population index r equal to $2.55\pm0.14$ from magnitude distribution of 738 possible members of the stream. Comparing the velocity distributions of 754 possible $\alpha$-Cygnids and 4339 sporadic events by $\chi^2$ and Kolmogorov-Smirnov tests we conclude that both distributions are different with a probability very close to 1.0.

Telescopic observations strictly confirm the results obtained from visual observations. The smallest values of $\chi^2$ parameter were obtained for the geocentric velocity equal to 40 km s^-1 and for the drift of the radiant (in units $^\circ$/day) equal to $\Delta\alpha=+0.6$ $\Delta\delta=+0.2$. The center of the radiant for moment of maximum is $\alpha=304.9^\circ$$\delta=+46.2^\circ$.

In spite of making many photographic exposures we still have no photographic or video confirmation of the existence of this stream.

Key words: meteoroids, meteors -- interplanetary medium