Exploration of spectra of periodic Comet 153P/Ikeya−Zhang
We present preliminary results of study of middle-resolution optical spectra of Comet 153P/Ikeya–Zhang obtained on May 5, 2002 with the help of the 2.12-m reflector of the Guillermo Haro Astrophysical Observatory. Emission lines of the molecules C₂, C₃, CN, NH₂, CO (Asundi and triplet bands), and H₂...
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Головна астрономічна обсерваторія НАН України
2005
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| Цитувати: | Exploration of spectra of periodic Comet 153P/Ikeya−Zhang / K.I. Churyumov, I.V. Lukyanyk, L.S. Chubko, V.V. Kleshchonok, A.A. Berezhnoy, V.H. Chavushyan, L. Sandoval, A. Palma // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 472-476. — Бібліогр.: 13 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859612583782252544 |
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| author | Churyumov, K.I. Lukyanyk, I.V. Chubko, L.S. Kleshchonok, V.V. Berezhnoy, A.A. Chavushyan, V.H. Sandoval, L. Palma, A. |
| author_facet | Churyumov, K.I. Lukyanyk, I.V. Chubko, L.S. Kleshchonok, V.V. Berezhnoy, A.A. Chavushyan, V.H. Sandoval, L. Palma, A. |
| citation_txt | Exploration of spectra of periodic Comet 153P/Ikeya−Zhang / K.I. Churyumov, I.V. Lukyanyk, L.S. Chubko, V.V. Kleshchonok, A.A. Berezhnoy, V.H. Chavushyan, L. Sandoval, A. Palma // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 472-476. — Бібліогр.: 13 назв. — англ. |
| collection | DSpace DC |
| container_title | Кинематика и физика небесных тел |
| description | We present preliminary results of study of middle-resolution optical spectra of Comet 153P/Ikeya–Zhang obtained on May 5, 2002 with the help of the 2.12-m reflector of the Guillermo Haro Astrophysical Observatory. Emission lines of the molecules C₂, C₃, CN, NH₂, CO (Asundi and triplet bands), and H₂O⁺ are identified in these spectra. On the basis of the intensity distribution along the slit of the spectrograph in C₂, C₃, CN emission lines we determined the velocities expansion and life times of these molecules.
|
| first_indexed | 2025-11-28T15:29:09Z |
| format | Article |
| fulltext |
EXPLORATION OF SPECTRA OF PERIODIC COMET 153P/IKEYA–ZHANG
K. I. Churyumov1, I. V. Lukyanyk1, L. S. Chubko1, V. V. Kleshchonok1,
A. A. Berezhnoy4, V. H. Chavushyan2, L. Sandoval3, A. Palma3
1Astronomical Observatory, National Taras Shevchenko University of Kyiv
3 Observatorna Str., 04053 Kyiv, Ukraine
e-mail: klim.churyumov@observ.univ.kiev.ua
2Instituto Nacional de Astrofisica, Optica y Electronica, Tonantzintla, Puebla, Mexico
3Benemerita Universidad Autonoma de Puebla, Puebla, Mexico
4Moscow State University P.K. Sternberg State Astronomical Institute, Moscow, Russia
We present preliminary results of study of middle-resolution optical spectra of Comet 153P/Ikeya–
Zhang obtained on May 5, 2002 with the help of the 2.12-m reflector of the Guillermo Haro
Astrophysical Observatory. Emission lines of the molecules C2, C3, CN, NH2, CO (Asundi and
triplet bands), and H2O+ are identified in these spectra. On the basis of the intensity distribution
along the slit of the spectrograph in C2, C3, CN emission lines we determined the velocities
expansion and life times of these molecules.
INTRODUCTION
Middle-resolution optical comet spectra obtained with long slit allow one to calculate some physical parameters
of cometary neutral atmospheres (escaping velocities of gas in coma, life time of particles, and others), to search
for new cometary emission lines, to estimate parameters of gas and dust productivity of comet nucleus, to detect
the cometary luminescence continuum of the non-solar nature, and others.
OBSERVATIONS AND DATA REDUCTION
Spectroscopic observations of Comet 153P/Ikeya–Zhang were carried out with the 2.12-m telescope of the Guille-
rmo Haro Observatory in Cananea, Sonora, Mexico, operated by the National Institute of Astrophysics, Optics,
and Electronics. The diffraction gratings of the Boller and Chivens spectrographs (long slit and CCD) with
a reciprocal dispersion of 3.5 Å per pixel and spectral resolution of 15 Å was used on May 5, 2002. The long
slit was orientated along the cometary tail. Grating with 150 l/mm was used. Log of observations of comet is
presented in Table 1. A helium-argon lamp was utilized in order to calibrate the spectra for wavelengths.
Table 1. Summary of observations of Comet 153P/Ikeya–Zhang
Starting time, UT Exposure, s Wavelengths, Å Spectral resolution, Å
May 5, 2002, 8:41 1800 3222–6440 15
May 5, 2002, 9:45 1800 3881–7169 11
One comet spectrum in the spectral region from 3222 to 6440 Å and one comet spectrum with the resolution
in the spectral region from 3881 to 7169 Å were obtained on May 5, 2002 with the slit spectrograph. The slit of
the spectrograph has a width of 2.5 arcsec and a length of 2.5 arcmin. The distance between Comet 153P/Ikeya–
Zhang and the Sun was equal to 1.14 AU, the distance between comet and the Earth was 0.42 AU on May 5,
2002. The comet passed the perihelion at 0.51 AU on March 19, 2002. All CCD spectra of 153P/Ikeya–Zhang
were processed with the help of the LONG-MIDAS and the Research System IDL computer programs allowing
for reductions of the CCD bias level, cosmic ray particles, flat fielding, and night sky contribution. Figures 1–3
show the spectra of Comet 153P/Ikeya–Zhang on May 5, 2002. With the obtained S/N ratios, it is possible to
detect emission lines stronger than 2 · 10−16 erg cm−2 s−1Å−1. The accuracy of determination of wavelengths of
well-known emission lines is 3 Å.
c© K. I.Churyumov, I. V. Lukyanyk, L. S.Chubko, V.V. Kleshchonok, A.Berezhnoy, V.H. Chavushyan, L. Sandoval, A.Palma, 2004
472
INTERPRETATION OF RESULTS OF THE INVESTIGATION
The catalogue of the spectral lines in Comet Brorsen–Metcalf [1] and the catalogue of CO optical bands [10]
were used for identification of the emission lines in the spectra of Comet 153P/Ikeya–Zhang. In the case of
the comet nucleus spectrum on May 5, 2002, 8:41 UT, we found emission lines of the following neutral radicals:
69 of C2, 15 of NH2, 3 of CN, 7 of C3, 20 of CO (Asundi, triplet, and Herman bands), 4 of CH, 2 of H2O+,
1 of CH+. For the comet coma spectrum on May 5, 2002, 8:41 UT, we found emission lines of the following
neutral radicals: 71 of C2, 15 of NH2, 5 of CN, 7 of C3, 16 of CO (Asundi and triplet bands), 5 of CH, 1 of NH,
1 of H2O+, 2 of CH+. In the case of the comet nucleus spectrum on May 5, 2002, 9:45 UT, we found emission
lines of the following neutral radicals: 73 of C2, 16 of NH2, 10 of CN, 3 of C3, 29 of CO (Asundi, triplet, and
Herman bands), 3 of CH, 3 of H2O+, 2 of CH+. The results of this investigation favour the identification of
CO triplet, CO Asundi, CO Herman bands, but the numbers do not seem to be quite large enough to rely
entirely on the argument of a small statistical probability of 17% for CO triplet, CO Asundi, and CO Herman
bands, respectively, that the presence of the observed bands is merely due to chance.
Figure 1. Energy distribution in the spectrum of Comet 153P/Ikeya–Zhang on May 5, 2002 (9:45 UT)
In order to determine some physical parameters of gaseous components of the neutral cometary atmosphere
(the gas component expansion u and the lifetime of the particles τ), we built a photometric profiles for the C2,
C3, and CN emission lines along slit. Then the obtained monochromatic profiles were processed by Shulman’s
model. Within this model the surface brightness was determined by the following formulas:
log
I(ρ, φ + π)
I(ρ, φ)
= 1.72
ρ
r0c
sin Θ0 cosφ, (1)
1
2
[ log I(ρ, φ + π)I(ρ, φ)] = const + log
[
r0k
ρ
∫ ∞
ρ
r0k
K0(y)dy
]
, (2)
where I(ρ, φ + π) and I(ρ, φ) are brightness surface of emission line along slit, ρ, φ are polar coordinates
on the picture plane with the polar axis directed to the Sun, roc = 2u2/g is characteristic scale of the spheric
symmetry region, u is expansion velocity, g denotes acceleration of molecules in the gravity field of the Sun, Θo is
an angle between the axis z and g-vector, rok = uτ is characteristic size of a coma, and K0(y) is McDonald’s
function.
The physical parameters for neutral gaseous molecules C2 (5165 Å), C3 (4050 Å), and CN (4200 Å), namely,
velocity of expansion and lifetime of molecules, are given in Table 2.
One can see from Table 2 that real velocities of expansion of the C2, C3, and CN molecules in the coma
of Comet 153P/Ikeya–Zhang diverse noticeably from velocity of expansion for gas, determined by Delsemme’s
formula which gives the values of expansion velocities [6].
Important feature of optical spectra of Comet 153P/Ikeya–Zhang is the presence of weak CO Asundi, triplet,
and Herman bands. In spectral region between 3880 and 6440 Å, 5 Asundi, 7 triplet, and 3 Herman bands were
473
Figure 2. Energy distribution in the spectrum of Comet 153P/Ikeya–Zhang on May 5, 2002 (8:41 UT)
Figure 3. Spectrum of Comet 153P/Ikeya–Zhang on May 5, 2002 (9:45 UT)
Table 2. Physical parameters of neutral gaseous cometary components of C2, C3, and CN
Species Velocity, m s−1 Lifetime, 106 s
C2 (5165 Å) 200.6 3.08
C3 (4050 Å) 166 0.075
CN (4200 Å) 157 0.06
474
detected at 8:41 UT on May 5, 2002. At the same time only 3 Asundi, 6 triplet, and 1 Herman bands were
detected in coma. This means that a high particle density is required for formation of these emission bands.
Besides, 3 Asundi, 7 triplet, and 2 Herman bands were detected near the comet nucleus at 9:45 UT. From
15 bands observed at 8:41 UT, only 7 bands were detected at 9:45 UT. So, intensity of CO optical bands can be
changed significantly during tens of minutes. To explain this result, we can assume a short lifetime of CO parent
molecule (about 2 · 103 s or less). For analysis of relative intensities of CO optical bands, their Franck–Condon
factors were compared. The complete results of Franck–Condon factors calculations are presented in [4]. At given
vibrational level of upper electronic state, Franck–Condon factors have maxima for 6–0, 7–1, 8–1, 9–1, 10–2, 11–
2, 12–2, 13–2, 14–3, 15–3, 16–3 transitions of Asundi system and for 2–0, 3–0, 4–0, 5–0, 6–0, 7–0, 8–1, 9–1, 10–1,
11–1, 12–2, 13–2, 14–2, 15–3 transitions of triplet system. At given vibrational level of upper electronic state,
all transitions with maximal Franck–Condon factors values were observed in Comet 153P/Ikeya–Zhang. This
means that relative intensities of observed CO transitions correspond to their Franck–Condon factors values.
There is only one exception for transitions from a′3 ∑+, state with v′ = 16. Franck–Condon factor is maximal
for 16–3 transition but only 16–4 and 16–5 transitions were detected. Probably, Franck–Condon factors can not
be calculated with accuracy good enough for such high vibrational levels.
From our observations, it is possible to determine that the existence of CO optical bands leads mainly to
formation of CO molecules at low vibrational states (v′′ = 0−3) of a3Π state. In [13] the vibrational temperature
(4500 K) for CO a3Π molecules formed during CO+
2 dissociative recombination and (a′ − a), (d − a), (e − a)
cascade emission is estimated. This value correspond to a high relative population of only low vibrational levels
(v′′ = 0 − 3). So, our results are in good agreement with experimental data.
Knowing relative intensities of electronic-vibrational transitions and their Franck–Condon factors, it is possi-
ble to determine relative populations of vibrational levels of upper electronic state. In Comet 153P/Ikeya–Zhang,
the population of vibrational levels of CO molecules at a′3Σ+ and d3Δ states is not under thermal equilibrium
because even high vibrational levels are high populated. This is in agreement with experimental data [13].
In this work the intensities of 6–0, 7–0, 8–0, 9–0 Asundi, 2–0, 3–0, 4–0 triplet transitions, and 2–0, 3–0 Herman
transitions were strong.
At given vibrational level of upper electronic state intensities of electronic-vibrational transitions are pro-
portional to their Franck–Condon factors. There are eight couples of observed transitions from the same upper
vibrational level. The comparison between intensities of observed transitions and their Franck–Condon factors
shows good agreement.
The first detection of CO bands in optical spectrum of Comet Bradfield 1980t is described in [5], where
dissociative recombination of CO+
2 or HCO+ is considered as a possible mechanism of origin of these bands.
It is also noted that the reactions of dissociative recombination require high electron densities. Fluorescence
mechanism can not explain observed intensities of CO Asundi and triplet bands because the excitation rates are
too low [11]. CO Asundi and triplet bands were observed in comets Bradfield 1980t in 1981, Scorichenko–George
in 1990, WM1 (LINEAR) in 2001 and 2002, and 153P/Ikeya–Zhang in 2002. All these years correspond to high
solar activity periods. For all comets, these bands were detected near the nucleus. This can be explained by
formation of CO parent molecule in regions near the nucleus where there are high particle densities and high
electron concentrations. It is proposed in [5] that an unusual event like outburst can be a reason of CO Asundi
and triplet bands formation. During periods of high solar activity the flash and outburst activity of comets is
increasing, this correlation supports an outburst hypothesis from [5].
For explanation of CO Asundi and triplet bands intensities in Comet Bradfield 1980t, about 3 · 1030– 3 · 1032
parent positive ions are required [5]. During these calculations it was assumed that the rate coefficient of
dissociative recombination was about 10−7 cm3 s−1 and the mean electron densities were 103– 105 cm−3. We can
make this estimation more carefully because experimental results on CO+
2 and HCO+ are available now. Rate
constant of CO+
2 recombination is about 3 · 10−7 cm3 s−1. In the recombination the 3Π3/2 CO+
2 ground state
with thermal electrons there is enough energy to populate CO (a′3Σ+, v′ < 11), CO (d3Δ, v′ < 6), and
CO (e3Σ+, v′ < 3). The yields of CO molecules in these states during CO+
2 recombination are 0.13, 0.081,
and 0.017, respectively [13]. These experimental results are in agreement with our observations because Herman
bands (e3Σ+–a3Π transition) were much weaker than Asundi and triplet bands in Comet 153P/Ikeya–Zhang.
CO+
2 recombination can not explain origin of high excited vibrational levels of a′3Σ+ and d3Δ states. HCO+
must be refused as a parent CO molecule because HCO+ recombination can produce only Asundi bands with
v′ < 3 [13]. The HOC+ recombination is more exoergic process, and it can give rise to emissions from CO (a′,
v′ < 17), CO (d, v′ < 13), CO (e, v′ < 10). During HCO+ recombination Asundi, triplet, and Herman bands
were observed [13]. This parent molecule can explain all CO observed bands except for 15–3 triplet band. For
formation of 15–3 triplet band, another parent molecule or high speed electrons are required. HCO+ ion was
not detected in comets yet, which means that the concentration of this ion is too low. So, CO+
2 is the best
candidate for CO parent molecule. Formation of high excited vibrational levels of a′3Σ+ and d3Δ states can
475
be explained by CO+
2 dissociative recombination with energetic electrons. The mean electron temperature in
pile-up region of Comet Halley is 20 000 K [8], such values of electron temperature is enough for formation of
all observed CO bands in Comet 153P/Ikeya–Zhang.
For theoretical estimation of CO production rate during CO+
2 dissociative recombination, we must estimate
the integral
Ntheor = 4πμk
∫
[CO+
2 ][e]dr, (3)
where μ is the absolute yield of CO molecules at given electronic state, k is the rate constant, [CO+
2 ] is
the concentration of CO+
2 ions, [e] is the electron concentration, and r is the distance from the comet nucleus.
Let us assume that [CO+
2 ] ∼ r−2, [e] ∼ r−2 at r > r0 and [CO+
2 ] ∼ r−2, [e] ∼ r−2 at r < r0, where r0 ∼ 3 · 108 cm
is the distance between the nucleus and the contact surface. Let us suppose that CO+
2 and electron densities
in Comet 153P/Ikeya–Zhang are the same as in Comet Halley during VEGA flybies. Extrapolating values of
CO+
2 [7] and electron [12] densities from 2 · 104 km to the contact surface, we can derive that [CO+
2 ] ∼ 103 cm−3
and [e] ∼ 2 · 105 cm−3 at r0 = 3 · 108 cm. Knowing CO absolute yields during CO+
2 recombination, it is possible
to estimate the formation rate of CO molecules at a′3Σ+, d3Δ, and e3Σ+ electronic states as 4 · 1027, 3 · 1027,
and 5 · 1026 mol s−1, respectively.
CONCLUSIONS
On the basis of the intensity distribution along the slit of the spectrograph in C2, C3, CN emission lines we
determined the velocities of expansion (v) and life times (τ) of these molecules: for C2 (5165 Å) [201 m s−1,
3.08 · 106 s]; for C3 (4050 Å) [166 m s−1, 0.075 · 106 s], and for CN (4200 Å) [157 m s−1, 0.06 · 106 s].
Acknowledgements. Authors K. I. Churyumov, I. V. Lukyanyk, and V. V. Kleshchonok thank to the Fun-
damental Research State Fund of the Ministry of Ukraine for Education and Science (grant 2002) for support
of our research in cometary physics area.
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|
| id | nasplib_isofts_kiev_ua-123456789-79701 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 0233-7665 |
| language | English |
| last_indexed | 2025-11-28T15:29:09Z |
| publishDate | 2005 |
| publisher | Головна астрономічна обсерваторія НАН України |
| record_format | dspace |
| spelling | Churyumov, K.I. Lukyanyk, I.V. Chubko, L.S. Kleshchonok, V.V. Berezhnoy, A.A. Chavushyan, V.H. Sandoval, L. Palma, A. 2015-04-03T19:47:33Z 2015-04-03T19:47:33Z 2005 Exploration of spectra of periodic Comet 153P/Ikeya−Zhang / K.I. Churyumov, I.V. Lukyanyk, L.S. Chubko, V.V. Kleshchonok, A.A. Berezhnoy, V.H. Chavushyan, L. Sandoval, A. Palma // Кинематика и физика небесных тел. — 2005. — Т. 21, № 5-додаток. — С. 472-476. — Бібліогр.: 13 назв. — англ. 0233-7665 https://nasplib.isofts.kiev.ua/handle/123456789/79701 We present preliminary results of study of middle-resolution optical spectra of Comet 153P/Ikeya–Zhang obtained on May 5, 2002 with the help of the 2.12-m reflector of the Guillermo Haro Astrophysical Observatory. Emission lines of the molecules C₂, C₃, CN, NH₂, CO (Asundi and triplet bands), and H₂O⁺ are identified in these spectra. On the basis of the intensity distribution along the slit of the spectrograph in C₂, C₃, CN emission lines we determined the velocities expansion and life times of these molecules. Authors K. I. Churyumov, I. V. Lukyanyk, and V. V. Kleshchonok thank to the Fundamental Research State Fund of the Ministry of Ukraine for Education and Science (grant 2002) for support of our research in cometary physics area. en Головна астрономічна обсерваторія НАН України Кинематика и физика небесных тел MS5: Dynamics and Physics of Solar System Bodies Exploration of spectra of periodic Comet 153P/Ikeya−Zhang Article published earlier |
| spellingShingle | Exploration of spectra of periodic Comet 153P/Ikeya−Zhang Churyumov, K.I. Lukyanyk, I.V. Chubko, L.S. Kleshchonok, V.V. Berezhnoy, A.A. Chavushyan, V.H. Sandoval, L. Palma, A. MS5: Dynamics and Physics of Solar System Bodies |
| title | Exploration of spectra of periodic Comet 153P/Ikeya−Zhang |
| title_full | Exploration of spectra of periodic Comet 153P/Ikeya−Zhang |
| title_fullStr | Exploration of spectra of periodic Comet 153P/Ikeya−Zhang |
| title_full_unstemmed | Exploration of spectra of periodic Comet 153P/Ikeya−Zhang |
| title_short | Exploration of spectra of periodic Comet 153P/Ikeya−Zhang |
| title_sort | exploration of spectra of periodic comet 153p/ikeya−zhang |
| topic | MS5: Dynamics and Physics of Solar System Bodies |
| topic_facet | MS5: Dynamics and Physics of Solar System Bodies |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/79701 |
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