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1.
Absolute spectrophotometry of the coma of Comet Kohoutek 1973f during post-perihelion period has been presented for seven nights in January 1984. Moderately wide range of heliocentric distance (0.436–0.799 AU) covered during observations allowed us to study the flux variation of emission bands with heliocentric distance. The emission features of CN, CH, C2, C3, and NaI have been identified in this comet. The abundances of CN and C2 have been estimated and the production rates of CN, C2 and C3 have been derived. Production rates of CN and C2 seem to vary as r
–0.33 and r
–3.50 respectively. The continuum of the comet became more and more redder as the heliocentric distance of the comet increased and phase angle decreased. 相似文献
2.
Emission fluxes of CN, C2 and C3 species observed in the coma of some comets are analysed in the framework of Haser model. CN, C2 and C3 production rates are determined using recently derived fluorescence efficiencies and dependence of CN, C2 and C3 production rates on the heliocentric distance is studied. Evidence for a burst type activity around January 15, 1974 in the post-perihelion period of comet Kohoutek (1973f) is observed. 相似文献
3.
Tetsuo Yamamoto 《Earth, Moon, and Planets》1981,24(4):453-463
The formation of cometary CN, C2 and C3 radicals is investigated in a photochemical reaction scheme. From an analysis of the observed brightness profiles of these radicals, it is shown that CN is formed as a primary product in the photolysis of its parent molecules, whereas C2 and C3 are formed via two-step photodissociation of their parents. We suggest that major parent of C2 is different species from those of CN and C3 on the basis of the difference of the variation with heliocentric distance of the sublimation rate of the parents of these radicals. Parent molecules and reaction schemes for the formation of these radicals are discussed. 相似文献
4.
Amaury A. De Almeida 《Earth, Moon, and Planets》1991,53(3):205-216
Emission fluxes of CN, C2 and C3 carbon-bearing molecular species observed in the coma of comets Rudnicki (1967II), Ikeya-Seki (1968I), Whitaker-Thomas (1968V), and Honda (1968VI) are analysed in the framework of Haser model. CN, C3 and C3 production rates are determined using recently derived fluorescence efficiencies. The dependence of CN, C2 and C3 production rates on the heliocentric distance and the possible correlations among these radicals is studied. It is shown that comets Ikeya-Seki (1968I) and Honda (1968VI) have the same mean color indices (B-V) and (U-B). 相似文献
5.
P. D. Singh K. Sinha B. M. Tripathi Heloisa M. B. Roberty 《Earth, Moon, and Planets》1989,47(3):231-239
Post-perihelion observed emission fluxes at 388 nm (CN) and 516 nm (C2) of the coma of comets Austin (1982g) and Bradfield (1980t) are analysed in the framework of the Haser model. Ratios of Haser model CN and C2 parent production rates with expansion velocity show that each comet behaves normally. For comet Austin (1982g), the Q
CN/v and Q
c2/v values decrease with increase of heliocentric distance of comet. For an assumed %; activity of the total spherical surface area of the nucleus, the water vaporization theory coupled with derived water production rates from the International Ultraviolet Explorer H and OH flux data yields a nuclear diameter of about 6 km for comet Austin (1982g). For comet Bradfield (1980t), the derived nuclear diameter is expected to be of about 1 km. In each comet, the dust mass production rates as well as ratio of dust-to-gas mass production rates decrease with increase of heliocentric distance of comet. 相似文献
6.
Spectral scans of Comet Bradfield (1987s) at heliocentric distance of 1.539 AU have been observed spectrophotometrically. The column densities and production rates of C2 and CN have been derived. 相似文献
7.
The results of the photoelectric photometry with the narrowband CN, C3, C2 and Blue Continuum (BC) IHW interference filters are presented. Observations were carried out with a set of diaphragms of different effective radii. On the base of the Haser model the production rates of the radicals have been obtained. The CN and C2 molecules scale lengths (3.4 × 105 km and 8.5 × 104 km respectively for 1.0 AU heliocentric distance) have been also derived. The dust continuum spectrum is negligibly low in comparison with the molecular one, which stay in agreement with the results of other observations of comet Okazaki-Levy-Rudenko. 相似文献
8.
A. A. De Almeida 《Earth, Moon, and Planets》1992,56(1):61-74
Emission fluxes of CN, C2 and C3 carbon-bearing molecular species observed in the coma of comets Bennett (1969i 1970II), West (1975n 1976VI), P Halley (1982i), Hartley-Good (19851) and Bradfield (1987s) are analysed in the framework of Haser model. CN, C2 and C3 production rates are determined using recently derived fluorescence efficiencies. The dependence of CN, C2 and C3 production rates on the heliocentric distance and the possible correlations among these radicals is studied and briefly discussed. 相似文献
9.
P. S. Goraya B. S. Rautela B. B. Sanwal S. K. Gupta H. K. Duggal J. S. Malhi 《Earth, Moon, and Planets》1989,45(1):17-27
Spectral scans of the head of periodic Comet Halley (1982i) have been presented and analysed in detail in the optical region (3200–7000 Å); for ten nights during pre-perihelion period. Emission features due to NH, CN, CH, C3, and C2 molecules have been identified. The behaviour of the variation of different emission lines strength as a function of heliocentric distance has been investigated. It is found that the comet exhibits night-to-night variation of brightness. The abundances and production rates of CN and C2 species have also been derived. 相似文献
10.
The variations in production rates for Comet 46P/Wirtanen for the species H2O and the parents of C2 and CN are examined from the point of view of a variety of commonly used scale lengths. The calculations are carried out as a function of heliocentric distance. It is shown that, by using a common set of scale lengths, the results of various investigators can be brought into acceptable accord. The resulting production rates of H2O and the parents of C2 and CN versus heliocentric distance are recalculated and plotted versus the heliocentric distance rH. The curves show reasonable agreement with a slope of ∼rH−4. The water production rate near perihelion of 46P/Wirtanen is close to . 相似文献
11.
Interference filter photometry was taken of Comet Encke on June 14, 1974 (1.07 AU heliocentric distance, postperihelion) at the CTIO (Cerro Tololo Interamerican Observatory) 150-cm reflector. Production rates were calculated of 4.1 × 1023 mol sec?1 of CN, 5.3 × 1023 mol sec?1 of C3, and 4.3 × 1024 mol sec?1 of C2. These are about three times smaller than at comparable heliocentric distance preperihelion, assuming a value of 100 for the ratio H2O/ (C2 + C3 + CN). An upper limit was placed on the production of nonvolatiles at about one-third that of volatiles in mass by assuming a bulk density of 1 g cm?3, a particle geometric albedo of 0.1, and a phase function of 0.2. 相似文献
12.
A. A. de Almeida 《Earth, Moon, and Planets》1993,60(1):69-79
Emission fluxes of CN, G2 and C3 carbon-bearing molecular species observed in the spectra of the nuclear fragment A and D of comet West (1976VI) are analysed in the framework of Haser's two-component model with radial outflow symmetry. Gas production rates have been derived and their ratios obtained. We find these vary as Q
r
n
(where 1.0r2.6 is the heliocentric distance in AU) with photometric parametern = -4.11 (CN), -2.68 (C2), -1.89 (C3) andQ
x
/Q
y
r
n
withn = 2.22 (C3/CN), 1.42 (C2/CN), -0.79 (C2/C3). The gas-to-dust ratio, dust production rates in arbitrary units, total number of dust particles in the field of view and an effective radius Reff 2.0 km for the principal nuclear fragmentA is also estimated. 相似文献
13.
The variation with heliocentric distance of the production rates of various species in Comet West (1975n=1976 VI) is explained with a cometary model consisting of a CO2-dominated nucleus plus a halo of icy grains of H2O or clathrate hydrate. We conclude that the parents of CN and C3 are released primarily from the nucleus but that the parent of C2 is released primarily from the halo of icy grains. 相似文献
14.
The origin of CN radicals in comets is not completely understood so far. We present a study of CN and HCN production rates and CN Haser scale lengths showing that: (1) at heliocentric distances larger than 3 AU, CN radicals could be entirely produced by HCN photolysis; (2) closer to the Sun, for a fraction of comets CN production rates are higher than HCN ones whereas (3) in the others, CN distribution cannot be explained by the HCN photolysis although CN and HCN production rates seem to be similar. Thus, when the comets are closer than 3 AU to the Sun, an additional process to the HCN photolysis seems to be required to explain the CN density in some comets.The photolysis of HC3N or C2N2 could explain the CN origin. But the HC3N production rate is probably too low to reproduce CN density profile, even if uncertainties on its photolysis leave the place for all possible conclusions. The presence of C2N2 in comets is a reliable hypothesis to explain the CN origin; thus, its detection is a challenging issue. Since C2N2 is very difficult to detect from ground-based observations, only in situ measurements or space observations could determine the contribution of this compound in the CN origin.Another hypothesis is a direct production of CN radicals by the photo- or thermal degradation of complex refractory organic compounds present on cometary grains. This process could explain the spatial profile of CN inside jets and the discrepancy noted in the isotopic ratio 14N/15N between CN and HCN. Laboratory studies of the thermal and UV-induced degradation of solid nitrogenated compounds are required to model and validate this hypothesis. 相似文献
15.
We present spectrophotometric studies of comet Hartley-Good (1985l) in the spectral region 3200–7000 Å. The emission features of molecules CN, CH, C2, and C3 are observed. The variation of the emission strength of different species has been studied as a function of heliocentric distance. The abundances (N) and production rates (Q) of the molecules are also estimated. 相似文献
16.
One-dimensional radial models of the chemistry in cometary comae have been constructed for heliocentric distances ranging from 2 to 0.125 AU. The coma's opacity to solar radiation is included and photolytic reaction rates are calculated. A parent volatile mixture similar to that found in interstellar molecular clouds is assumed. Profiles through the coma of number density and column density are presented for H2O, OH, O, CN, C2, C3, CH, and NH2. Whole-coma abundances are presented for NH2, CH, C2, C3, CN, OH, CO+, H2O+, CH+, N2+, and CO2+. 相似文献
17.
Millimeter wavelength emission from the “parent” molecules HCN, CO, and CH3CN, the latter in both its ground and ν8 = 1 excited vibrational states, was sought from Comet Bradfield (1978c) during March 1978 after comet perihelion, when the heliocentric distance was between 0.45 and 0.55 AU. No lines were detected, and upper limits on the molecular column densities (averaged over the antenna beam) and production rates, Q are estimated. The upper limits on Q for HCN, CH3CN (ν8 = 0), and CH3CN (ν8 = 1) are less than the production rates inferred from the millimeter-wave detection of these species in Comet Kohoutek (1973f). The CO upper limit on Q is comparable to that inferred from a detection of Comet West (1975n) in the rocket uv. It seems likely that the total gas production rate of Comet Bradfield (1978c) was relatively low. 相似文献
18.
Column density profiles for CN, C3, C2 and NH have been determined from a long-slit CCD spectrum of periodic comet P/Schaumasse (1992x). Comparisons of these profiles with Haser models indicate that the ratios of the CN, C3 and C2 production rates are typical for a short-period comet. Although the scale lengths for NH and its parent species are uncertain, the results indicate that the production rate for NH is much greater than for either C2 or CN. 相似文献
19.
The results of the photometric observations of comet C/2009 P1 (Garradd) performed at the 60-cm Zeiss-600 telescope of the Terskol observatory have been analyzed. During the observations, the comet was at the heliocentric and geocentric distances of 1.7 and 2.0 AU, respectively. The CCD images of the comet were obtained in the standard narrowband interference filters suggested by the International research program for comet Hale-Bopp and correspondingly designated the “Hale-Bopp (HB) set.” These filters were designed to isolate the BC (λ4450/67 Å), GC (λ5260/56 Å) and RC (λ7128/58 Å) continua and the emission bands of C2 (λ5141/118 Å), CN (λ3870/62 Å), and C3 (λ4062/62 Å). From the photometric data, the dust production rate of the comet and its color index and color excess were determined. The concentration of C2, CN, and C3 molecules and their production rates along the line of sight were estimated. The obtained results show that the physical parameters of the comet are close to the mean characteristics typical of the dynamically new comets. 相似文献
20.
Preliminary results of a spectrum scanner study of Comet Kohoutek (1973f) are reported. Ratios of band sequence fluxes and their variations with solar distance have been determined for three sequences of C2, and two sequences of CN from observations obtained on eleven dates. The λ4050 feature of C3 was visible on two dates, and CH (λ4300) detectable once. 相似文献