Figure 4. The wavelet transform of the sda radiant region using a Mexican Hat probe 3° wide. Constraints on the two dimensions, not shown, are defined by VG of 40.4±4.9 kms-1 and A0 of 130° ± 15°.

The sda is used to introduce the methodology used for the exploration of each shower region. This shower, the strongest detected by amor, shows many interesting features whose visibility is enhanced by the shower's high meteor rate and relatively low measurement uncertainties. The wavelet transform of the sda radiant region, using a Mexican Hat probe of size a = 3°, is shown in Figure 4. Radiant positions are reduced to A0 = 125°, this leads to a clear (daily motion corrected) maxima at (A - A0,/?) = (210.2°,-7.2°) which changes very slightly to (210.2°, —7.8°) if only the central activity period (A0 G [120°, 130°]) is used, reflecting perhaps a small unaccounted for radiant instability or drift. A cut-off in this image at 5% of the maximum coefficient is found to remove all surrounding background. For all meteors appearing in the selected radiant region over the central shower activity period a 2 kms-1 wide sliding window in VG is moved from 20 kms-1 to 60 kms-1 to produce the profile shown in Figure 5. This profile, representing the combination of shower and background meteoroid speeds, is fitted well by a Gaussian defined by VG = 40.4 kms-1 and ay = 4.9 kms-1. Shower meteoroids are arbitrarily selected to have speeds within la of the mean and occurring within the selected radiant region over the period A0 e [115°, 145°]. Table 1 lists the definitions used for the other showers found in Section 2 (a 2a VG cut-off is used in the case of the 77 Aquarids due to its relatively large speed measurement uncertainty); the radiant centres in each case are reduced to the central mean solar longitude listed.

Was this article helpful?

0 0

Post a comment