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4 Discussion

We presented here the results of visual and telescopic observations of $\alpha$-Cygnid stream made by CMW observers in years 1995-1997. This stream is not included in the IMO List of Visual Meteor Showers (Rendtel et al. 1995) due to the lack of photographic, video and radio data confirming its presence. The only continuous (not visual) surveys are the Harvard Super Schmidt Program of the 1952-54 period and the Harvard Radar Project in the 1960's. Both have gaps in coverage due to weather or instrument irregularities. Unfortunately the $\alpha$-Cygnids seem to fall in such gaps. McCrosky & Posen (1961) presented the orbital elements of 2529 meteors photographed simultaneously from two camera stations of the Harvard Meteor Project. The mean number of meteors captured in periods January-June and August-December is 221 events per month. The number of meteors photographed in July is only 102. It is over two times smaller than in other months and certainly it is the reason of lacking the meteors from $\alpha$-Cygnid stream in that project. The similar situation occurred during the Harvard Radar Project. However recent radio results obtained by Michael Boschat from Dalhousie University in Canada (Boschat 1998) showed clear enhancement of radio echoes in days 1998 July 19-20.

Analysis of 2748 paths of meteor events observed in July 1995, 1996 and 1997 allowed us to obtain the basic properties of the stream. The geocentric velocity of the $\alpha$-Cygnid events is $V_\infty=41$ km s-1 and daily drift of the radiant $\Delta\alpha=+0.6^\circ$, $\Delta\delta=+0.2^\circ$.The coordinates of the center of the radiant of $\alpha$-Cygnid stream are $\alpha=302.5^\circ$ and $\delta=+46.3^\circ$.

We performed a similar analysis for 234 telescopic meteors plotted also by CMW observers. The parameters of the stream are in very good agreement with the results derived from visual data.

Our results are also consistent with visual observations by Denning (1919) and Jenniskens (1994) and the photographic results obtained by Babadzhanov & Kramer (1965).

From magnitude distribution of 738 $\alpha$-Cygnids we obtained the population index r equal to $2.55\pm0.14$ which is in good agreement with previously obtained value r=2.7 (Jenniskens 1994).

The velocity distributions of 754 $\alpha$-Cygnids and 4339 sporadics are different, with a probability higher than 0.999 which gives another proof for reality of the $\alpha$-Cygnid stream.

From visual observations made by CMW members during the years 1995-1997 we obtained the clear activity profile of the $\alpha$-Cygnid stream. Meteors belonging to this shower were detected from June 30 to July 31 with clear maximum near July 18 ($\lambda_\odot=116.5^\circ$). The maximal ZHRs reached the level $3.6\pm1.2$. These results are in very good agreement with results presented by Jenniskens (1994) who obtained $\lambda_{\odot{\rm (max)}}=116.0\pm0.5^\circ$ and ${ ZHR_{\rm max}}=2.5\pm0.8$.

In spite of making many photographic exposures we still have no photographic confirmation of this stream. To confirm of disprove our results further visual, telescopic and particularly video and photographic observations are clearly needed.


We would like to thank to all observers who sent us their observations. We are especially grateful to Prof. Jerzy Madej for helpful discussions, reading and commenting on the manuscript and also to Dr. Jacek Cho\l 
oniewski for many helpful hints. This work was supported by KBN grants 2 P03D 020 11 and 2 P03D 002 15 to A. Olech.

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