The meteor shower list of EDMOND, the J8-list, is based on the IAUMDC shower list and in most cases, it is the first line for each shower listed in the IAUMDC list. It is not good to assume that these first lines are the most reliable shower data, because they are the oldest reported data and should be rather replaced by more recent ones in several cases. Southern iota Aquariids (SIA#003), zeta Cassiopeiids (ZCS#444) and zeta Taurids (ZTA#226) are such cases. The misclassifications have an influence on the statistics obtained for these showers as well as on the neighboring showers, i.e. Southern delta Aquariids (SDA#005), Orionids (ORI#008) and Perseids (PER#007). The EDMOND results are accurate enough to study meteor showers, just like the orbit data of CAMS and SonotaCo net.
There are three major video meteor orbit databases: EDMOND, SonotaCo and CAMS. All three use an original meteor shower list to classify meteors with the proper meteor shower. We can find several problematic classifications in the lists and the author analyzed some specific cases by comparing SonotaCo net with CAMS (Koseki, 2018). The author has shown the overestimated numbers of several minor showers in EDMOND (Koseki, 2019b) and in this paper he explains the probable reasons for the misclassifications. Table 1 lists the statistics for the Southern iota Aquariids (SIA#003), zeta Cassiopeiids (ZCS#444) and zeta Taurids (ZTA#226), which are good examples to illustrate the problem.
2 Southern iota Aquariids (SIA#003)
Four entrees for the SIA-shower are included in the IAUMDC list (IAUMDC, version 2018 January 18: https://www.ta3.sk/IAUC22DB/MDC2007/) and the summary of these is shown in Table 2. However, the Southern iota Aquariids are one of the problematic showers (Koseki, 2016) and each of the four entrees in the IAUMDC does not show a clear distinction from the sporadic background.
Figure 1 (left) shows the radiant distribution of the SIA meteors as classified by EDMOND and Figure 1 (right) displays the active IAUMDC showers (see also Table 3 for the positions). The activity period and the center of this period are these taken for the SIA’s of EDMOND; the median values are listed in Table 1. Table 1 shows that EDMOND defines the start of the SIA activity at λʘ = 118.9° and the end at λʘ = 146.7° with the peak activity (median) at λʘ = 128.1°, the average and the standard deviation (sd) being respectively λʘ = 128.3° and sd = 3.6. We can easily see from the radiant distribution of Figure 1 (right) that the EDMOND’s SIA activity represents the SDA activity.
We can conclude that the EDMOND’s SIA meteors are misclassified SDA meteors mainly by the activity profiles (Figure 2). The SDA activity profile looks crippled by the contamination with incorrect SIA identifications. The author described the SDA activity profiles for both CAMS and SonotaCo net and these are very similar with a maximum around λʘ = 125°, but not later than λʘ = 130° as suggested by EDMOND.
Table 1 – The statistics for the SIA, ZCS and ZTA as like originally classified in EDMOND. The stream codes are followed by their total number of classified meteors.
Table 2 – All entries for the SIA, ZCS and ZTA as listed in the IAUMDC meteor shower list.
|003SIA01||339||–15.6||203.1||–6.3||34.8||131.7||Dutch Meteor Society 2001|
|003SIA02||332.9||–14.7||200.1||–3.3||30.5||129.5||0.36||–0.14||Brown et al., 2008|
|003SIA03||337.5||–13.3||198.7||–3.6||28.9||135.6||Jenniskens et al., 2017|
|444ZCS00||6.9||50.7||277.8||42.8||57.3||113.2||1.4||0.5||Segon et al., 2012|
|444ZCS01||5.9||50.5||277||43||57.4||113.1||Zoladek and Wisniewski 2012|
|444ZCS02||3.1||49.5||278.3||43.1||57.1||109||0.95||0.4||Jenniskens et al.,2016|
|444ZCS03||5.1||50.2||277.8||43||57.1||111.5||Jenniskens et al., 2017|
|226ZTA02||79.7||12.2||236.7||–10.9||60.6||203||0.8||–0.8||Molau and Rendtel, 2009|
Table 3 – IAU showers plotted in Figure 1 (right): x, y and r indicate each shower position in Figure 1 (right) in degrees.
3 Zeta Cassiopeiids (ZCS#444)
The statistics of EDMOND’s ZCS meteors given in Table 1 are quite different from the four entrees in the IAUMDC list (Table 2). EDMOND situates the main ZCS activity later than λʘ = 120, although the four entrees in the IAUMDC clearly show that it occurs around λʘ = 110.
Figure 3 shows the radiant distribution for the ZCS orbits similar to Figure 1. Figure 3 (left) is centered at the median value of EDMOND’s ZCS but the primary ZCS radiants suggested by IAUMDC list are located at the upper right of the center. Although the PER radiant is not included in Figure 3 (right) or Table 4, the concentration of radiants is mainly related to PER. Figure 3 (right) and Table 4 represent the positions of the radiants at their maximum and the PER radiant reaches its maximum much later than the limit of the ZCS-activity defined by EDMOND.
The activity profile obtained from the EDMOND ZCS orbits is curious (Figure 4). The activity is ascending after λʘ = 120°. On the other hand, the activity of the PER orbits is cut off before λʘ = 127°. When we connect the curves of ZCS and PER, the profile of PER would be natural. The PER-activity starts after λʘ = 120° and the number of PER orbits increases gradually and does not burst out after λʘ = 128° as EDMOND suggests. We find that the real ZCS activity occurs around λʘ = 110° with a small peak as shown in Figure 4.
Table 4 – IAU showers plotted in Figure 3 (right).
4 Zeta Taurids (ZTA#226)
Figure 6 shows the radiant distribution of ZCS orbits similar to Figure 1. Only one ZTA radiant (ZTA0) is shown in Table 5, although three ZTA orbits are listed in the IAUMDC list but these are very different from each other (Table 2). Figure 6 (right) suggests that the ZTA radiant is very near to the ORI radiant. The author reminds that the meteor activity during the early Orionid activity is very complex (Figure 23b of Koseki, 2018). It is very difficult to distinguish nu Eridanids (NUE#337), September omicron Orionids (SOO#479), the early Orionids (ORI#008) and sporadics. The confusion with ZTAs in the IAUMDC list seems to be influenced by these circumstances. EDMOND’s ZTA activity is much affected by the Orionids and its profile (Figure 5) shows the peak activity about 10 degrees later in solar longitude compared with ZTA0 in Table 2.
Table 5 – IAU showers drawn in Figure 6 (right).
Table 6 – The statistics of SDA: the first line (_J8_SDA) shows the EDMOND results and the lower lines the SonotaCo net results. The numbers of identified SDA meteors are_J8_SDA=1211 and _J5_sdA=2486.
Table 7 – The comparison of the statistics of EDMOND with SonotaCo net. The total numbers for each shower are as follows _J8_CAP=2096, _J5_Cap=1077, _J8_ETA=1372, _J5_etA=2755, _J8_LEO=1743, _J5_Leo=3946.
The author showed the problems in the meteor shower definition in CAMS and SonotaCo net (Koseki, 2018). December alpha Draconids (DAD#334) of SonotaCo net are defined too large and, Southern Taurids (STA#002) and Northern Taurids (NTA#017) of CAMS are divided into too many sub showers.
Former days, a photographic meteor was often classified differently; one wrote it as a shower meteor and another as a sporadic. It resulted therefore in unreliable statistics for meteor showers and in some cases a false meteor shower was stated. Nowadays, the abundant video meteor data could mislead a researcher to ‘invent’ non-existing new showers.
EDMOND defined the SIA, ZCS and ZTA showers incorrectly and, therefore, the statistics for these showers are not suitable to be used as representative references (comparing Table 1 with Table 2). These are conglomerates of some other showers and neighboring strong showers.
It is natural that the statistics of a neighboring shower might be distorted. The statistics of the SDA shower are shown in Table 6 compared to SonotaCo net’s results. The median values of the solar longitude differ by 5.1 degrees and the right ascension by 4.6, although the orbital elements are in good agreement except for the node. The timing of the observations and the radiant position are an important reference for the observers and this discrepancy cannot be disregarded.
These problems in the statistics are not caused by the observational inaccuracy. We compare the statistics of slow and fast meteor showers alpha Capricornids (CAP#001) and Leonids (LEO#013) following Koseki, 2019b in addition to the eta Aquariids (ETA#031), which has the highest SD value (Koseki, 2019a). Table 7 clearly shows that the EDMOND results fit SonotaCo’s, although the velocities of EDMOND are slightly lower than SonotaCo’s. The author concluded that SonotaCo net data are accurate enough compared with CAMS.
We can use the three databases i.e. EDMOND, SonotaCo net and CAMS as sufficient statistically accurate.
The problems discussed above are not peculiar to EDMOND but databases have these problems commonly including the IAUMDC meteor shower list. We should be careful to use the results of the classification. It is noteworthy to note that the first lines of each IAUMDC meteor showers are not always representative.
EDMOND (https://fmph.uniba.sk/microsites/daa/daa/veda-a-vyskum/meteory/edmond/) includes: BOAM (Base des Observateurs Amateurs de Meteores, France), CEMeNt (Central European Meteor Network, cross-border network of Czech and Slovak amateur observers), CMN (Croatian Meteor Network or HrvatskaMeteorskaMreza, Croatia), FMA (Fachgruppe Meteorastronomie, Switzerland), HMN (HungarianMeteor Network or Magyar Hullocsillagok Egyesulet, Hungary), IMO VMN (IMO Video Meteor Network), MeteorsUA (Ukraine), IMTN (Italian amateur observers in Italian Meteor and TLE Network, Italy), NEMETODE (Network for Meteor Triangulation and Orbit Determination, United Kingdom), PFN (Polish Fireball Network or Pracownia Komet i Meteorow, PkiM, Poland), Stjerneskud (Danish all-sky fireball cameras network, Denmark), SVMN (Slovak Video Meteor Network, Slovakia), UKMON (UK Meteor Observation Network, United Kingdom).
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Koseki M. (2018). “Different definitions make a meteor shower distorted. The views from SonotaCo net and CAMS”. WGN, Journal of the International Meteor Organization, 46, 119–135.
Koseki M. (2019a). “Showers of the IAU Meteor Data Center in the video data of SonotaCo: a simple and clear criterion for grading meteor showers”. WGN, Journal of the International Meteor Organization, 47, 7–17.
Koseki M. (2019b), “EDMOND and SonotaCo net”. eMetN, 4, 220–224.