During July of 1995, 1996 and 1997 CMW observers plotted on gnomonic star maps 2748 paths of meteor events. For each of them the angular velocity was estimated. We used 0-5 scale with 0 corresponding to stationary meteor, 1 to very slow event, 2 to slow, 3 to medium, 4 to fast and 5 to very fast meteor. Equatorial coordinates of the begins and ends of these events and their velocities were put into the RADIANT software (Arlt 1992). This software as an input also requires the geocentric velocity of the meteors and the daily drift of the radiant. Changing both these values we can obtain different density distributions of the probability area near suspected radiant. Choosing the best distribution (this one with smallest parameter) we are able to estimate the values of and the daily drift. The systematic errors play a role, which are difficult to handle and estimate of the accuracy of the obtained value of is difficult but the errors are at minimum km s-1. For more details see Arlt (1993).
Before analyzing our sample we decided to analyze also the meteors observed by Denning (1919). However we selected only meteors observed by him during July nights. Number of these events accounted to 20. We performed our calculation using parameters of the stream given by Jenniskens (1994) i.e. km s-1, , and . Results as probability function distribution of the presence of radiant are presented in Fig. 1. The best fit of the two dimensional Gaussian surface to the density of probability map gives coordinates of the radiant equal to and . The accuracy of this estimate is certainly low due to the small number of events observed by Denning (1919).
|Figure 1: The radiant of -Cygnids resulting from Denning's (1919) observations. Assumed parameters are: km s-1, , and . Number of the events is 20|
|Figure 2: The radiant of -Cygnids resulting from CMW visual data. Assumed parameters are: km s-1, , and . Number of the events is 2748|
|Figure 3: The radiant of -Cygnids resulting from CMW telescopic data. Used parameters are: km s-1, , and . Number of the events is 234|
Fortunately, the sample collected by CMW observers in years 1995-1997 is significantly larger. It allows us to derive a few valuable conclusions. First we calculate our sample (2748 meteors including possible members of the stream, sporadics and meteors from other showers) using parameters given by Jenniskens (1994). During calculation we remove meteors observed at a distance larger than from the radiant of the stream. The prominence of the -Cygnid radiant on the resulting picture is striking. The best fit gives coordinates of the radiant as and .Nevertheless we obtain better results i.e. a more compact shape of the radiant using geocentric velocity km s-1 and the drift of the radiant , . The resulting radiant picture for the above parameters is displayed in Fig. 2. The final coordinates of the radiant of -Cygnid stream are and , which do not differ significantly from coordinates obtained for parameters given by Jenniskens (1994).
We also used the RADIANT software for the analysis of the paths of our telescopic meteors. Our sample contains 234 meteors with known paths and velocities. The resulting density distribution from telescopic observations is displayed in Fig. 3. The best fit (with smallest value) is obtained for the following parameters: geocentric velocity km s-1, the daily drift of the radiant and . The coordinates of the center of the radiant are and . One can see that the position of the radiant obtained from telescopic observations differs from the position obtained from visual data by only . Taking into account that radii of the majority of radiants vary between and both our results are strictly consistent. It is also clear that our parameters are in very good agreement with the data of the one photographed meteor (Babadzhanov & Kramer 1965).
In years 1995-1997 the CMW observers made as many as 738 and 4546 estimates of the brightness of meteor events from -Cygnids and sporadics, respectively. The distribution of this quantity is presented in Tables 3 and 4.
Such a large amount of magnitude estimates for -Cygnids encouraged us to compute the value of the population index r defined in Eq. (1). We obtained which is a typical value among meteor streams. Jenniskens (1994) obtained a similar result with r equal to 2.7. The population index obtained from the magnitudes of our 4546 sporadics is equal to .
Also the telescopic observers estimated the magnitudes of meteor events. The magnitude distributions for 1996 and 1997 -Cygnids and sporadics are presented in Tables 5 and 6.
Knowing the value of r we can compute ZHR using the formula given in (3). According to the results of Koschack (1994) and Bellot (1995) who showed that for visual observations with radiant altitudes higher than the zenith exponent factor , we adopted .
|Figure 4: The activity profile of -Cygnids during 1995-1997. The solid line represents the fit given in Eq. (4)|
The resulting activity profile of -Cygnids in years 1995-1997 is exhibited in Fig. 4. The activity of the stream lasts from (June 30) to (July 31). It seems to be slightly wider than the result of Jenniskens (1994) who noted meteors from -Cygnid stream in interval . The accuracy of the ZHR estimates by Jenniskens (1994) was low due to the small number of his observations, therefore we prefer our result.
Our Fig. 4 one exhibits a clear maximum of activity at with . The error of this estimate is large but points in the vicinity of the maximum have smaller errors and their moments and ZHRs are with and with
The moment of the maximum and its ZHR is in very good agreement with result of Jenniskens (1994) who obtained with .
Jenniskens (1994) found also that the activity profiles of meteor streams are well represented by the following equation:
The CMW observers estimated also the angular velocity of the events. The 0-5 scale (defined in Sect. 3.1 of this paper) was used. Finally we obtained 754 estimates of the angular velocity for -Cygnids and 4339 estimates for sporadics. The velocity distribution from visual observations is presented in Tables 7-8.
We used the above distributions to find another proof for existence of the -Cygnid stream. We compared empirical velocity distributions of -Cygnids and sporadics using Kolmogorov-Smirnov and tests. We obtained that with the probability larger than 0.999 both distributions are different. Such a large probability is certainly caused by the clear enhancement of meteors with velocity 3 and 4 in -Cygnid velocity distribution. This result is also is good agreement with the value of geocentric velocity obtained from RADIANT analysis of our visual and telescopic data. The meteors with velocity km s-1 given by RADIANT software at mean distance from the radiant of the stream appear mainly with velocities 3 and 4 in 0-5 scale.
The velocity of meteor events was also estimated by our telescopic observers. They used A-F scale with A corresponding to the angular velocity /s and F to over s. Finally we obtained 41 estimates of the angular velocity for telescopic -Cygnids and 192 velocity estimates for telescopic sporadics. Both distributions are presented in Tables 9-10.
For telescopic observations the distance from the radiant is generally well defined. Usually it is worthwhile to analyze the mean angular velocity as a function of distance from the radiant. Unfortunately due to the small number of our telescopic -Cygnids which were observed in as many as 10 fields such an analysis is impossible yet.
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