next previous
Up: Alpha Cygnids - a

1 Introduction

The first data about meteors from radiant near $\alpha$ Cygni come from W.F. Denning (Denning 1919). In years 1885-1918 he observed 50 meteors radiating from the close vicinity of Deneb. He did not know the activity period of the stream so he noted meteors during the whole year. It is clearly visible from his Table 2 that most of the meteors were noted during July nights. Almost all events observed this month were classified as rapid.

During the next years one can find the different parameters describing $\alpha$-Cygnids stream in the astronomical literature. Polish meteor publications were giving activity period between June 16th and July 31st. No clear maximum of activity was found (Kosinski 1990).

Photographic data are also poor. Only one possible member was captured in Dushanbe on 1961 July 12. The radiant of this event was $\alpha=304.5^\circ$, $\delta=+49.7^\circ$ and geocentric velocity $V_\infty=41.0$ km s-1 (Babadzhanov & Kramer 1965).

In the comprehensive work undertaken by Dutch Meteor Society (DMS) and North Australian Planetary Observers - Meteor Section (NAPO-MS) in years 1981-1991 and described in detail by Jenniskens (1994) one can read about weak stream called o-Cygnids. During 98 hours of effective time of observations 8 observers noted 72 possible members of that stream. From this data Jenniskens (1994) estimated the following parameters of the stream:

$\bullet$ equatorial coordinates of the radiant during the maximum of activity: $\alpha=305^\circ$   $\delta=+47^\circ$,

$\bullet$ drift of the radiant (in units $^\circ$/day): $\Delta\alpha=+0.6$   $\Delta\delta=+0.2$,

$\bullet$ maximum of activity: $\lambda_{\odot(1950.0)}=116.0^\circ\pm0.5^\circ$,

$\bullet$ population index r=2.7, where r is defined as:
r={{\Phi (m+1)}\over{\Phi (m)}}\end{displaymath} (1)


\Phi (m) = \sum^{m}_{-\infty} N(m)\end{displaymath} (2)

and N(m) is the number of meteors with magnitude m corrected for probabilities of perception given by Koschack & Rendtel (1990),

$\bullet$ Maximal Zenithal Hourly Rates (ZHRs) are equal to $2.5\pm0.8$, where ZHR is defined as:
ZHR={{N_{\rm h}\cdot r^{(6.5-LM)}}\over{{(\sin H)}^\gamma}}\end{displaymath} (3)

where $N_{\rm h}$ is the observed number of meteors per hour (corrected for clouds coverage), LM is the limiting magnitude in the field of view, H is an altitude of the radiant of the stream, and $\gamma$ is a zenith exponent factor,

$\bullet$ geocentric velocity: $V_\infty=37$ km s-1.

From the Fig. 11 in paper by Jenniskens (1994) it is clearly visible that the activity of o-Cygnids lasts from $\lambda_\odot\approx105^\circ$to $\lambda_\odot\approx127^\circ$ i.e. from around July 5th to July 27th.

next previous
Up: Alpha Cygnids - a

Copyright The European Southern Observatory (ESO)