Low-resolution spectrum of comet C/2004 Q2 (Machholz)
We analysed the spectroscopic data for comet C/2004 Q2 (Machholz), obtained on the Zeiss-600 telescope in Andrushivka Astronomical Observatory on January 29, 2005. The observed spectrum covers a wavelength range 3600-9200 Å with a spectral resolution of 6.2 Å. The molecular-line features of C₂, C₃,...
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irk-123456789-1193942017-06-07T03:05:45Z Low-resolution spectrum of comet C/2004 Q2 (Machholz) Shubina, O. Korsun, P. Ivashchenko, Yu. We analysed the spectroscopic data for comet C/2004 Q2 (Machholz), obtained on the Zeiss-600 telescope in Andrushivka Astronomical Observatory on January 29, 2005. The observed spectrum covers a wavelength range 3600-9200 Å with a spectral resolution of 6.2 Å. The molecular-line features of C₂, C₃, CN, NH₂, CH, H₂O⁺, and CH⁺ were found in the spectrum. 2012 Article Low-resolution spectrum of comet C/2004 Q2 (Machholz) / O. Shubina, P. Korsun, Yu. Ivashchenko // Advances in Astronomy and Space Physics. — 2012. — Т. 2., вип. 2. — С. 173-176. — Бібліогр.: 17 назв. — англ. 2227-1481 http://dspace.nbuv.gov.ua/handle/123456789/119394 en Advances in Astronomy and Space Physics Головна астрономічна обсерваторія НАН України |
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We analysed the spectroscopic data for comet C/2004 Q2 (Machholz), obtained on the Zeiss-600 telescope in Andrushivka Astronomical Observatory on January 29, 2005. The observed spectrum covers a wavelength range 3600-9200 Å with a spectral resolution of 6.2 Å. The molecular-line features of C₂, C₃, CN, NH₂, CH, H₂O⁺, and CH⁺ were found in the spectrum. |
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Article |
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Shubina, O. Korsun, P. Ivashchenko, Yu. |
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Shubina, O. Korsun, P. Ivashchenko, Yu. Low-resolution spectrum of comet C/2004 Q2 (Machholz) Advances in Astronomy and Space Physics |
| author_facet |
Shubina, O. Korsun, P. Ivashchenko, Yu. |
| author_sort |
Shubina, O. |
| title |
Low-resolution spectrum of comet C/2004 Q2 (Machholz) |
| title_short |
Low-resolution spectrum of comet C/2004 Q2 (Machholz) |
| title_full |
Low-resolution spectrum of comet C/2004 Q2 (Machholz) |
| title_fullStr |
Low-resolution spectrum of comet C/2004 Q2 (Machholz) |
| title_full_unstemmed |
Low-resolution spectrum of comet C/2004 Q2 (Machholz) |
| title_sort |
low-resolution spectrum of comet c/2004 q2 (machholz) |
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Головна астрономічна обсерваторія НАН України |
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2012 |
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http://dspace.nbuv.gov.ua/handle/123456789/119394 |
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Low-resolution spectrum of comet C/2004 Q2 (Machholz) / O. Shubina, P. Korsun, Yu. Ivashchenko // Advances in Astronomy and Space Physics. — 2012. — Т. 2., вип. 2. — С. 173-176. — Бібліогр.: 17 назв. — англ. |
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Advances in Astronomy and Space Physics |
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AT shubinao lowresolutionspectrumofcometc2004q2machholz AT korsunp lowresolutionspectrumofcometc2004q2machholz AT ivashchenkoyu lowresolutionspectrumofcometc2004q2machholz |
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Low-resolution spectrum of comet C/2004 Q2 (Machholz)
O. Shubina1∗, P.Korsun2, Yu. Ivashchenko3
Advances in Astronomy and Space Physics, 2, 173-176 (2012)
© O. Shubina, P.Korsun, Yu. Ivashchenko, 2012
1Faculty of Physics, Taras Shevchenko National University of Kyiv, Glushkova ave. 4, Kyiv, Ukraine
2Main Astronomical Observatory of the National Academy of Sciences of Ukraine, Zabolotnoho 27, 03680, Kyiv, Ukraine
3Andrushivka Astronomical Observatory, Andrushivka, Ukraine
We analysed the spectroscopic data for comet C/2004Q2 (Machholz), obtained on the Zeiss�600 telescope in
Andrushivka Astronomical Observatory on January 29, 2005. The observed spectrum covers a wavelength range
3600�9200Å with a spectral resolution of 6.2Å. The molecular-line features of C2, C3, CN, NH2, CH, H2O+, and
CH+ were found in the spectrum.
Key words: comet, spectrum, emissions
introduction
Comet C/2004Q2 (Machholz) was discovered by
Donald Machholz on August 27, 2004 as an object
of 11 magnitude [6]. The comet was at a heliocen-
tric distance of 2.47AU and at a geocentric distance
of 2.16AU at the moment of the observation. The
eccentricity of its orbit is 0.999473 and the original
barycentric value of 1/a is +0.000404. The origi-
nal value suggests that this is probably not a �new�
comet from the Oort cloud [14]. The comet passed
its perihelion on January 24.9127, 2005 at the helio-
centric distance of 1.2AU. Comet C/2004Q2 (Mach-
holz) was clearly visible to the naked eye and had
brightened to about 3.5m around perihelion passage.
H.Kobayashi and H.Kawakita [10] performed
high-dispersion spectroscopic observations of comet
C/2004Q2 (Machholz) in the near-infrared spectral
region. They detected emission lines of H2O, HCN,
C2H2, NH3, C2H4, C2H6, CH3OH and H2CO in the
cometary spectra and determined the mixing ratios
of the detected volatiles relative to water. The au-
thors also found that C/2004Q2 was formed in the
region where the initial abundance of C2H2 was de-
pleted and the conversion e�ciency from C2H2 to
C2H6 was comparable with other comets.
In another paper H.Kobayashi and H.Kawakita
[8] analysed the infrared spectral region. Their re-
sults indicated that the cometary molecules (at least,
water and methane) in C/2004 Q2might be pro-
cessed under higher temperature conditions than
typical Oort Cloud comets (∼30K), probably in the
region closer to the proto-Sun. Alternatively, the
materials in C/2004 Q2 might be processed at the
epoch di�erent from that the other comets.
H.Kawakita and M. J.Mumma [9] presented �u-
orescence excitation models for ammonia and NH2
in comets. They provide quantitative g-factors for
four values of the rotational temperature in the range
typical for cometary comae, and present its values at
perihelion of 1AU. Then they applied their models
to spectra of C/2004Q2 (Machholz) obtained in the
near-infrared spectral region, and derived the mixing
ratio of ammonia relative to water. They claimed
that the ammonia is the main parent molecule for
the NH2 radical.
E. Picazzio et al. [16] performed analysis of the
spectra of comets 9P/Tempel 1, 37P/Forbes, and
C/2004 Q2 (Machholz) in the optical spectral region.
The gas component expansion u and the lifetime of
the particles in the comae of these comets are calcu-
lated. Using the Shulman's model they derived the
gas component expansion and the lifetime of the par-
ticles for the observed species in the comae of these
comets. The spectra of the comets show evidence
for a luminescent cometary continuum which may be
connected to the luminescence of organic component
of the cometary dust particles.
observations and reduction
We observed the comet C/2004Q2 (Machholz)
with the Zeiss�600 telescope at Andrushivka As-
tronomical Observatory (A50). The observations
were made on January 29, 2005, when the comet
moved near its perihelion. The spectra were
recorded with the UAGS spectrograph equipped
with the 325 gmm−1 di�raction grating and attached
to the Cassegrain focus of the telescope. The two-
dimensional spectrograms were recorded on the S1C-
017AP CCD chip with a thermo-electric cooling sys-
tem. The dimension of the used CCD is 1024×1024
pixels with a pixel size of 16×16µm that is equival
to 0.46×0.46 arcsec at the sky plane.
∗belkalenaastronom@gmail.com
173
Advances in Astronomy and Space Physics O. Shubina, P.Korsun, Yu. Ivashchenko
Table 1: The journal of the observations of the comet C/2004Q2 (January 29, 2005).
Object Angle of grating, deg Start time (UT) Exp., seconds Air mass
C/2004 Q2 29.25 19:57:53 300 1.169
C/2004 Q2 29.25 20:02:56 300 1.177
C/2004 Q2 29.25 20:08:00 300 1.185
C/2004 Q2 29.25 20:15:42 300 1.198
C/2004 Q2 29.25 20:20:46 300 1.206
C/2004 Q2 31.50 20:32:47 300 1.228
C/2004 Q2 31.50 20:37:51 300 1.237
C/2004 Q2 31.50 20:42:54 300 1.247
C/2004 Q2 31.50 20:47:58 300 1.257
HD26630 31.50 21:00:47 300 1.081
HD26630 29.25 19:43:12 300 1.081
A slit with the dimensions of 8×0.3mm is equiva-
lent to 78123.6×2929.6 km at the coma of the comet.
To study the most part of the optical spectral re-
gion we made expositions at two rotation positions
of the grating relative to the incident beam. Blue
and red sections of the spectrum were recorded �xing
the grating at the angles equal to 29.25◦ and 31.5◦,
respectively. The journal of observations is given in
Table 1.
An incandescent lamp spectrum was taken in or-
der to account for di�erent sensitivities of the CCD's
pixels. The wavelength calibration was made by �t-
ting a polynomial function of the second degree to
the observations of the Ne-Ar-N+
2 lamp. The spectral
response of the used telescope-instrument con�gura-
tion and the spectral dependence on the atmospheric
extinction were obtained from the spectrophotomet-
ric standard star HD26630 exposures [11].
The available dark current was removed from the
observed spectra subtracting the dark current frames
obtained under the same conditions as for the ob-
served objects. For the frames, related to each po-
sition of the grating, the median was calculated at
each pixel across a set of 2D images. This allowed to
�lter the cosmic ray events and to increase the signal-
to-noise ratio of the spectra. The one-dimensional
spectra were formed by summing along the spatial
dimension with no attempt to preserve the spatial
information. Finally, the composite spectrum was
formed joining the blue and red one-dimensional sec-
tions. This composite spectrum covers the wave-
length range of 3600-9200Å with a resolution of
about 6.2Å.
The �ux of the comet was derived from the fol-
lowing formula:
Fc (λ) = Fst (λ)
Ic (λ)
Ist (λ)
p−∆M (λ) ,
where Fc and Fst are the absolute �uxes of the comet
and the standard star, respectively; Ic and Ist are the
measured data for the comet and the standard star;
p (λ) is the spectral transparency of the Earth atmo-
sphere; ∆M is the di�erence between the air masses
of the comet and the standard.
To identify the cometary emissions the available
continuum was removed. It was estimated using a
scaled solar spectrum which was convolved with the
observed spectroscopic resolution and corrected for
the reddening e�ect.
results and conclusions
In order to identify the observed emission features
we calculated the theoretical spectra of molecules
that had been already recorded in the cometary
spectra. The intensities of individual rotation lines
were calculated assuming the thermodynamic equi-
librium. In this particular case, vibration and ro-
tation energy levels are populated according to the
Boltzmann distribution and determined by rota-
tional and vibrational temperatures. It is under-
stood that the thermodynamic equilibrium is not re-
alised in a cometary coma and the population of the
energetic levels is caused by the absorption and re-
emission of solar quanta. Nevertheless, the thermo-
dynamic equilibrium approach is successfully applied
so far for the identi�cation of molecular emissions in
cometary spectra and in this particular case the val-
ues of the temperatures are considered as parameters
that are used to �t the observed spectrum with the
highest possible accuracy [1, 2].
Using this technique we found the molecular emis-
sions of C2, C3, CN, NH2, CH, H2O+, and CH+
in the optical spectral region of comet C/2004Q2
(Machholz).
CN: The most prominent features in C/2004Q2
spectrum are due to the CN emission transitions.
The ∆v=0 and ∆v=+1 vibration bands of the vio-
let system of CN attributed to the electronic transi-
tion B2Σ+�X2Σ+ were detected in the blue region
of the spectrum. This identi�cation was done with
the LIFBASE programme package [13] developed for
calculation of the electronic spectra of some diatomic
174
Advances in Astronomy and Space Physics O. Shubina, P.Korsun, Yu. Ivashchenko
molecules. In the red section of the spectrum we de-
tected some features, which we assigned to the elec-
tronic transition A2Π�X2Σ+, the so called red sys-
tem of CN, with ∆v = +4, ∆v = +2, and ∆v = +1.
Our detections of the CN emissions are shown in
Fig. 1 (violet system) and in Fig. 2 (red system).
C2: We found �ve vibrational band systems of
C2 (∆v = −2, ∆v = −1, ∆v = 0, ∆v = +1, and
∆v = +2), belonging to the electronic transition
d3Πg-a3Πu, the so called the Swan system. For this
purpose the theoretical spectrum was calculated us-
ing the line list derived from the laboratory measure-
ments made by Phillips and Davis [15]. Obviously
taking into account the moderate spectral resolution
the rotational structure can be only partly resolved
and we can detect groups of rotational lines and
vibrational band heads of the vibrational band se-
quences. Our detection of the Swan system is shown
in Fig. 1. Also we found two vibrational bands in
the red part of the spectrum, ∆v = +2 and ∆v, be-
longing to the electronic transition a3Πu�x1Πg, the
so called the Phillips system [17]. The identi�cations
are shown in Fig. 2.
CH: The emission features of the A2∆-X2Π sys-
tem of the CH molecule are con�dently identi�ed in
the blue region. They belong to the ∆v = 0 vibra-
tional band. For this identi�cation we also used the
LIFBASE package [13]. These features are marked in
Fig. 1.
CH+: Besides the neutral molecule CH, we de-
tected three weak emissions originated from the
A1Π-X1Σ+ electronic transition of the CH+ ion.
They belong to the heads of the P-, Q-, and R-
branches of the (0-0) vibrational band. The the-
oretical spectrum was calculated using the data of
Douglas and Herzberg [3] and our identi�cations are
presented in Fig. 1.
C3: In the violet region of C/2004Q2 (Machholz)
spectrum we easily recognised the �uorescence bands
of C3. The corresponding electronic transition is
1Πu-1Σ+
g . We found a most of the features which
Gausset et al. [5] reported for comet Ikeya (1963a).
The results of the this identi�cation are marked in
Fig. 1.
H2O
+
: It worth to note that the H2O+ bands
turned out to be su�ciently strong in the investi-
gated spectrum. The identi�ed features belong to
the (5-0), (6-0), (7-0), and (8-0) bands and appear
along the spectrum [12]. The identi�cations are pre-
sented in Fig. 1, 2.
NH2: The numerous weak emissions of NH2 are
dispersed along the observed spectrum. The spec-
trum of NH2 is irregular and belongs to electronic
transition A2A1-X2B1. In order to identify these
features we used the results of the laboratory mea-
surements of Dressler and Ramsay [4] and Huet et
al. [7]. The comparison between the calculated
spectrum of the NH2 molecule and the observed
C/2004Q2 spectrum resulted in the identi�cation of
the emissions of this molecule belonging to the (15-
0), (13-0), (12-0), (11-0), (10-0), (9-0), (8-0), (7-0),
(6-0), (5-0), and (3-0) vibrational bands. The iden-
ti�ed features are presented in Fig. 1, 2.
A lot of the OH atmospheric emissions are de-
tected in our spectrum, but we did not indicate them
in Fig. 1 and in Fig. 2.
references
[1] ArpignyC. 1972, in Comets: Scienti�c Data and Mis-
sions, eds.: KuiperG.P. & RoemerE., University of Ari-
zona Press, 84
[2] ArpignyC. 1976, NASA Special Publication, 393, 797
[3] DouglasA. E. & HerzbergG. 1942, Canadian Journal of
Research, 20, 71
[4] DresslerK. & RamsayD.A. 1959, Royal Society of Lon-
don Philosophical Transactions Series A, 251, 553
[5] Gausset L., HerzbergG., LagerqvistA. & RosenB. 1965,
ApJ, 142, 45
[6] GreenD.W.E. 2004, IAU Circular, 8394, 2
[7] HuetT.R., Hadj Bachir I., BolvinH. et al. 1996, A&A,
311, 343
[8] KawakitaH. & KobayashiH. 2009, ApJ, 693, 388
[9] KawakitaH. & MummaJ. 2011, ApJ, 727, 91
[10] KobayashiH. & KawakitaH. 2009, ApJ, 703, 121
[11] Le Borgne J.-F., BruzualG., PellóR. et al. 2003, A&A,
402, 433
[12] LewH. 1976, Canadian Journal of Physics, 54, 2028
[13] Luque J. & CrosleyD.R. 1999, LIFBASE: Database and
Spectral Simulation Program (version 1.5), SRI Interna-
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[14] MarsdenB. 2004, Minor Planet Electronic Circular,
2004-U31
[15] Phillips J.G. & Davis S. P. 1968, `Berkeley Analyses of
Molecular Spectra', Berkeley: University of California
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[16] Picazzio E., Churyumov K. I., Chubko L. S. et al. 2009,
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175
Advances in Astronomy and Space Physics O. Shubina, P.Korsun, Yu. Ivashchenko
Fig. 1: Emissions in comet C/2004Q2 (Machholz) spectrum (blue part).
Fig. 2: Emissions in comet C/2004Q2 (Machholz) spectrum (red part).
176
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