Transcript Snímek 1 - Cosmos

Archive data mining
the Lyrids
Pavel Koten(1)
in cooperation with
(1) J. Borovička, P. Spurný, R. Štork, V. Vojáček
(2) K. Fliegel, P. Páta, S. Vítek
Astronomical Institute ASCR, Ondřejov, Czech Republic
(2) Czech Technical University, Prague, Czech Republic
(1)
Meteoroids 2016 conference, ESA/ESTEC Noordwijk, June 6-10
Lyrid meteor shower
annual meteor shower (006 LYR) with variable activity
usually peak around April 21-22 (λo ~ 31.6º)
occasionally outbursts > 100 meteors/hour
parent – C/1861 Thatcher
radiant α ~ 272º, δ ~ 33º
(Lindblad & Porubcan (1991), Arter & Williams (1997), …)
many papers – orbital evolution (enhanced activity 12years period) – but no physical structure
video observations – several campaigns
1998, 1999, 2004, 2006, …, 2014, 2015
Archive and new data
archive – analogue video, new – digital cameras (MAIA)
both – image intensifier Mullard XX1332, 50mm lens
25 and 61.15 fps
8 and 10 bits
simultaneous
campaigns
in 2014, 2015
usual processing
Atmospheric trajectory calculation
Manual measurement
and calculation
distance of measured
points from average
trajectory
22.4.2015
19:45:18 UT
April Lyrid
D = 0.02
Properties of Lyrids
1.
2.
3.
4.
beginning heights
parameter KB
light curves
deceleration => meteoroid composition
Beginning heights
73 Lyrid meteors DSH < 0.15
only complete light curves
masses: 10-4 ÷ 10-1 g
method of Hapgood et al.(1982)
increasing with increasing
photometric mass
slope: k = 3.5
explanation:
gradual ablation before
reaching of camera’s
lim. mag. (Koten et al.,2004)
Comparison with other showers
with k = 3.5
almost the same
as Quadrantids,
but few km higher
more compact than
Perseids, Taurids,
Leonids
less than Geminids
Parameter KB
One dimensional parameter – eliminates potential effect of different
zenith distance of radiant (Ceplecha, 1988)
K B  log(  B )  2.5 log( v )  0.5 log cos( zR )
Lyrids: KB = 7.0 ± 0.1
(group C2 – “regular cometary material, long period comets”)
Leonids – 6.6
Quadrantids – 7.2
Perseids – 6.8
Geminids – 7.2
Orionids – 6.8
(all using the same video systems)
Light curve shape
parameter F
(Flemming et al. 1993)
symmetrical light curves
with maximum around
the middle of luminous
trajectory
(mean F ~ 0.55)
Deceleration
18 Lyrid meteors show deceleration – 15 modeled
erosion model (Borovička et al., 2007) was applied
(grain density 3000 kg/m3, atm. model NRLMSISE-00)
Lyrid meteor 04421047 – good fit of deceleration and light curves
Deceleration II.
Lyrid 15422005 – both systems, more points for fitting
mass 7x10-3 g
grains 8x10-8 to 1,5x10-7 g
about 53 500 pcs
mass distr. index 2.0
Modeled light curves
usually smooth
light curves
without any flares
=> complete and
continues
disintegration into
the grains
Erosion heights
Erosion starts between
112 and 106 km
around 100 km majority
of meteoroids completely
disintegrated into grains
HBE around HB
higher / lower by up to
few km
Other parameters
ablation coefficient σ = 0.0015 – 0.026
erosion coefficient η = 0.025 – 0.57
mean ratio η / σ ~ 23
lower values in comparison with Draconids
(Borovička et al. 2007)
ES – energy received per unit cross-section prior start of
the erosion: from 4.3 x 105 to 5.3 x 106 J/m2
in average higher than in the case of DRA (~ 1 x 106 J/m2)
Grain distribution
From 27 000 up
to 4x106 grains
Mass distribution
index 1,8 – 2,8
(for grains)
Grain sizes
Usual sizes: 0.01 – 0.3 mm
extreme case – range 0.004 – 0.37 mm
comparison with:
- Draconids – 0.03 to 0.1 mm (LYR larger)
- Quadrantids, Geminids – 0.08 to 0.3 mm (Borovička et al.,
2010)
(LYR grains of similar sizes or smaller)
Summary
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good quality double station data on >70 Lyrids
light curves and height data – similar to QUA,
few km higher beginning, more compact that
PER, ORI
erosion model for 15 meteors
grain distribution – generally 10 to 300 μm
Thank you for your attention!
Work supported by the Grant Agency of the Czech Republic
grant no. 14-25251S