Some peculiarities of
cometary light curves as new
criterions for physical mechanism
of outburst activity of comets
V.S.Filonenko
Astronomical Institute of Kharkov National University, Kharkov, Ukraine
K.I.Churyumov
Astronomical Observatory of Kiev National University, Kiev, Ukraine
1. Introduction
The cometary brightness outburst activity was studied more than 150
years, but its physical mechanism is not known until now. More than ten
different physical mechanisms of brightness outbursts were proposed. But
no mechanism can explain all phenomena in full, which observe during
brightness
outbursts.
Therefore
the
theoretical
and
observational
investigations of peculiarities of cometary brightness outburst activity are
topically until now.
In result of long-term study of the photometrical behavior and
outburst activity of comets the authors had revealed the new observational
peculiarities of brightness outbursts, which are presented below.
2. Peculiarity of the outbursts
distribution on heliocentric
distances
The short-period comets give unique opportunity to study the evolution
of their brightness during several appearances.
We compiled the light curves of one of such comets – the comet
10P/Tempel 2 during three appearances 1967, 1983 and 1988 years (Fig. 1).
As can see on Figure 1, brightness outbursts of this comet were
occurred at the same heliocentric distances during the several comet’s
appearances. Later, M.R.Kidger (Earth, Moon, and Planets, 1993, V. 63, pp.
179-185) had found the similar peculiarity of outburst activity of comet
P/Metcalf-Brewington.
Fig. 1. The light curves of comet 10P/Tempel 2
during three different appearances.
Next we have studied the distribution of 180 brightness outbursts of
129 comets, which observed during 1847-1975, on the heliocentric distance
(Fig 2).
Fig. 2. The distribution of 180 brightness outbursts
on the heliocentric distances
As can see, this distribution has narrow sharp maximums of outbursts
frequency on the certain heliocentric distances. The narrow deep minimums
part these maximums.
The use the Pirson’s Kolmogorov’s and von Mises’s statistical
criterions (they had been used to all distribution as a whole and to each
maximum locally) shown that found structure of distribution is statistically
significant with probability more than 0.97.
Thus we shown that brightness outbursts of comets occur with greater
probability on the same heliocentric distances.
3. Quasi-periodicity of cometary
outburst activity
On the basis of visual estimations of integrated brightness obtained
from ICQ archive we compiled light curves of 27 comets. In result of study
of this light curves we have revealed about 280 brightness outbursts of these
comets.
We have found that the brightness outbursts of these comets occur
with mean frequency ν = 1.03 ± 0.09 outbursts per week. This frequency
correspond to mean period Т = 6d.8 ± 0d.6. Since 4Т = 27d.2, consequently
the found quasi-periodicity of outburst activity is a new evidence of
correlation between brightness outbursts of comets and
recurring
corpuscular streams and sector structure of interplanetary magnetic field.
However, taking into
account
the
view
of
dependence between outbursts
amplitude and their frequency
(Fig. 3), we may affirm that
only
outbursts
of
small
amplitude (≤ 0.8) are result of
the influence of solar activity.
The big amplitude outbursts
Fig. 3. The dependence between amplitude
and frequency of outbursts.
A is amplitude, ν is frequency,
R is correlation coefficient.
have apparently some another
trigger mechanism.
This can explain, in particular,
discrepant results of investigations of
relation between brightness outbursts
and solar activity: the big amplitude
outbursts can do not show correlation
with indexes of solar activity.
4. Changing of a power low
exponent: a new peculiarity
Usually the change of comet’s brightness with heliocentric distance
corresponds to the well-known formula
m 1 = H 0 + 5 log ∆ + 2 . 5 n log r .
(1)
As is well known, n (the power low exponent which determines how
the comet’s brightness varies with heliocentric distance) may spasmodically
change its own value.
We compiled the light curves of comets C/2001 A2 (LINEAR),
C/2002 F1 (Utsunomiya) and 19P/Borrelly in appearance 2001-2002 years
(Fig. 4, 5, 6).
Fig. 4. The light curves of comet C/2001 A2 (LINEAR).
1-observations, 2-line correspond to (1),
3-also, but n varies.
Fig. 5. The light curves of comet C/2002 F1 (Utsunomiya).
1-observations, 2-line correspond to (1),
3-also, but n varies.
Fig.6. The light curves of comet 19P Borrelly.
1-observations, 2-line correspond to (1),
3-also, but n varies.
As can see on these figures, the moments of break of the straight line,
which corresponds to (1), coincide with the moments of brightness
outbursts.
This is a new peculiarity of the comet’s photometrical behavior.
What here is cause but what here is consequence - the change of value
n provokes the brightness outburst or vice versa the outburst brings to vary
of value n? This question demands apparently the additional investigation.
Precision position of comets
depending on brightness outbursts
During Aug. 1-5, 2001 the BVR CCD observations of comet C/2001
A2 (LINEAR) had been obtained at the 70-cm reflector of Astronomical
Institute of Kharkov National University.
These observations fall on the period of the small brightness outburst
(amplitude is about 0.m5).
CCD Light curve
13.0
We found a correlation
Magnitude
13.1
between the light curve and
13.2
13.3
the brightness of central near
13.4
13.5
1
2
3
4
5
6
7
nuclear area and the curve of
August, 2001
change value (O-C) – the
O-C
deviations
17.0
of
position
of
O-C,(")
16.5
comet from ephemeris places
16.0
15.5
15.0
(Fig 7).
14.5
1
2
3
4
5
6
7
August, 2001
Fig.7. The CCD light curve of comet C/2001 A2 (above) and
curve of values (O-C) (below). Solid line - R band, dotted line - V band.
The increase of the values of
(O-C) in the moment of maximum of
outburst, possibly, was a result of the
displacement
of
cometary
photometrical center in result of the
redistribution of brightness image,
which
had
been
cometary activity.
provoked
by
A
reddening
of
comet’s central area after
outburst
which
well
visible on the Fig. 8 and
that is a result probably
of dispersion of dust
ejection
also.
Fig. 8. Color index V-R of central
near nucleus area of comet
C/2001 A2.
confirms
this
Conclusions
As had been shown in this
talk, authors had found the next
new peculiarities of cometary
outburst activity:
1. The brightness outbursts of
different comets or during
different appearances of
periodic comets occur on
the
same
distance
heliocentric
2. The
brightness
outburst
activity of comets shows a
quasi-periodicity with mean
d
d
period T = 6. 8 ± 0. 6.
3. The moments of the sharp
changes of the power low
exponent n coincide with the
comet’s brightness outbursts
4. The values (O-C) are increasing
during the brightness outbursts
of comets
These
peculiarities
of
brightness outburst activity must be
taken
into
mechanism
account
when
of
cometary
the
outburst activity is developing.
a