Ultraviolet spectrophotometry of comet Giacobini-Zinner during the ICE encounter

McFadden, L. A.; A’Hearn, Michael F.; Feldman, P. D.; Böhnhardt, H.; Rahe, J.; Festou, M. C.; Brandt, John C.; Maran, S. P.; Niedner, M. B.; Smith, Andrew M.; Schleicher, D. G.

doi:10.1016/0019-1035(87)90109-6

Cited by 25 publications

(23 citation statements)

References 26 publications

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“…In view of the different methods adopted by Hanner et al (1992), we consider the agreement good. The continuum emissions at A = 4845 A before perihe lion were due to dust particles of equivalent radius a = 4.5 μm and for the post-perihelion period (Schleicher et al 1987;McFadden et al 1987) the continuum was due to dust particles of effective radius a = 3.5 pm. A similar conclusion was drawn by Hanner et al (1992) who re ported that the infrared emission was due to micron-sized absorbing grains for a dust release rate qd = 105 g/s.…”

Section: Resultsmentioning

confidence: 99%

Dust colors, dust release rates, and dust-to-gas ratios in the comae of six comets

Sanzovo

Singh

Huebner³

1996

Astron. Astrophys. Suppl. Ser.

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Abstract. -In an attempt to find correlations between properties of comets, we determine the dust colors, dust release rates, and dust-to-gas mass ratios in the comae of Comets Bowell (1980 b = 1982 I), Bradfield (1979Bradfield ( 1 = 1979, Brorsen-Metcalf (1989 o = 1989, Giacobini-Zinner (1984 e = 1985, Levy (1990 c = 1990, and Stephan-Oterma (1980 g = 1980 X) using a uniform and systematic analysis of the continuum fluxes measured at optical wavelengths. We assume that the continuum fluxes observed in these comets are from light scattered by micrometer-sized dust particles. The color of the dust is blue, relative to the Sun, in Comets Bradfield (1979 X) and Brorsen-Metcalf (1989 X); both comets have a low dust-to-gas mass ratio (χ < 10%). Comets Giacobini-Zinner (1985 X III) and Stephan-Oterma (1980 X) have an intermediate dust-to-gas mass ratio (10% < χ < 40%), whereas Comets Levy (1990 XX) and Bowell (1982 I) have a high dust-to-gas mass ratio (χ > 40%). The continuum flux from dust particles in comets with intermediate to high dust-to-gas mass ratios is in general red, relative to the Sun. However, the color changes to blue in these comets when the dust-to-gas mass ratios are low relative to their peak values.

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Section: Resultsmentioning

confidence: 99%

Dust colors, dust release rates, and dust-to-gas ratios in the comae of six comets

Sanzovo

Singh

Huebner³

1996

Astron. Astrophys. Suppl. Ser.

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“…Water had never been directly detected in GZ, although its presence has been inferred from UV and radio observations of OH (McFadden et al 1987, Schleicher et al 1987, Gérard et al 1988. These previous studies of OH demonstrated conclusively that H 2 O is the dominant volatile constituent in GZ, a property that GZ probably shares with all other comets.…”

Section: H 2 Omentioning

confidence: 99%

“…However, their CO production rate of 4.2 × 10 27 molecules s −1 is ∼6 times larger than our 3σ upper limit from late October and ∼4 times larger than the 3σ upper limit derived from radio observations in later October (Biver et al 1999c). We searched unsuccessfully for CO Fourth Positive Group emission in a UV spectrum taken five days postperihelion during the 1985 IUE observations of GZ (see McFadden et al 1987) and derive Q CO ≤ 2 × 10 27 molecules s −1 (3σ ) at r = 1.03 AU. If we use the Mumma et al value for Q CO and our value for Q H 2 O , then CO/H 2 O ∼ 14-21%, which is very high for a short-period comet.…”

Section: Comentioning

confidence: 99%

“…Interest in this comet was especially heightened in 1985 when the Third International Sun-Earth Explorer (ISEE-3) was retargeted and renamed the International Comet Explorer, or ICE, to fly through the tail of GZ at a distance of ∼7800 km from the nucleus. 1 In support of the flyby mission, an intensive observational campaign was mounted to observe GZ at ultraviolet (UV; McFadden et al 1987), optical (Cochran andBarker 1987, Schleicher et al 1987), infrared (IR; Telesco et. al.…”

Section: Introductionmentioning

confidence: 99%

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An Infrared Investigation of Volatiles in Comet 21P/Giacobini–Zinner

Weaver¹,

Chin

Bockelée‐Morvan

et al. 1999

Icarus

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We obtained high resolution (λ/δλ ∼ 10,000-20,000) infrared (IR) spectra of Comet 21P/Giacobini-Zinner (GZ) at five different wavelengths between 1.9 and 5.0 µm during 25-29 October 1998 using CSHELL at the NASA Infrared Telescope Facility (IRTF) on Mauna Kea. We also obtained a moderate resolution (λ/δλ ∼ 680) spectrum covering the wavelength range from 3.082 to 3.720 µm on 29 October 1998 using CGS4 at the United Kingdom Infrared Telescope (UKIRT) on Mauna Kea. Five rovibrational lines in three different vibrational bands of H 2 O were detected in the CSHELL spectra. Assuming that the rotational temperature was ∼50 K, we derive a H 2 O production rate of ∼2-3 × 10 28 molecules s −1 , which is ∼2 times smaller than the value derived from nearly simultaneous radio observations of OH. After continuum subtraction, the CGS4 spectrum displays significant excess flux that we attribute mainly to CH 3 OH fluorescence, and we derive that the CH 3 OH production rate was ∼2.7 × 10 26 molecules s −1 . The corresponding CH 3 OH/H 2 O relative abundance is ∼0.9-1.4%, which falls within the range of values observed in other comets, albeit at the low end. The CGS4 spectrum also has significant excess flux near 3.43 µm that is not explained by our CH 3 OH fluorescence model; a similar feature has been observed in several other comets, but its origin remains a mystery. We did not detect any excess emission near 3.28 µm, where some comets show a feature that may be associated with polycyclic aromatic hydrocarbons. We also searched for emissions from C 2 H 6 , CO, HCN, C 2 H 2 , and H 2 CO but did not detect any of these molecules. The 3σ upper limits for the abundances relative to H 2 O are 0.05-0.08% for C 2 H 6 , 2-3% for CO, 0.2-0.3% for HCN, 0.3-0.4% for C 2 H 2 , and 0.5-0.8% for H 2 CO, assuming that all species are parent molecules and that their rotational temperature in the coma is 50 K. C 2 H 6 is depleted by a factor of ∼15 or more compared to its relative abundance in Comets Hale-Bopp VOLATILES IN COMET 21P/GZ 483 (C/1995 O1) and Hyakutake (C/1996 B2); this depletion is similar to that observed for C 2 and C 3 from optical observations of GZ (A'Hearn et al. 1995) and suggests that the formation of volatile carbon-chain molecules was inhibited in GZ. We are unable to find any clear correlation between the C 2 H 6 and the C 2 and C 3 abundances in a sample of nine other comets, assuming that the residual emission near 3.35 µm in moderate resolution spectra of seven of the comets provides an accurate indicator of the C 2 H 6 abundance. However, this latter assumption is questionable and highlights the need to obtain high spectral resolution data in order to make accurate abundance measurements of C 2 H 6 .

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“…This comet, during its 1985 apparition, also showed the peculiarity of peaking in gas production a full month before perihelion (McFadden et al 1987), yet the visual light curve did not decline until after perihelion. Photometry in the 1−20 µm range by Hanner et al (1992) confirmed that the visual light curve did not follow either the water production rate (which peaked ∼30 days pre-perihelion) or the scattering and emitting cross section of dust in the inner coma.…”

Section: Introductionmentioning

confidence: 99%

Behaviour of Comet 21P/Giacobini-Zinner during the 1998 perihelion

Lara¹,

Licandro²,

Oscoz³

et al. 2003

A&A

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Abstract. Comet 21P/Giacobini-Zinner was observed from Nov. 8 to Dec. 10, 1998. Pre-and post-perihelion CCD images of the gas (CN, C 2 ) and dust (green and red continua) coma were obtained with the 82 cm IAC-80 telescope at Teide Observatory (Canary Islands, Spain). For v p = 0.85r −0.5 H and v d = 1.19 km s −1 (i.e. characteristic of HCN being the CN parent species), the CN column density profiles are best reproduced with parent and daughter lifetimes of the order of 19 300 and 256 000 s. An equally good reproduction of the observed profiles is achieved by considering that a mixture of nitrogen compounds expanding at v p = 1 km s −1 and with a lifetime of 19 000 s produces CN with an ejection velocity of v d = 2.5 km s −1 and a lifetime of 174 000 s. Fitting the observed CN profiles with variable velocities and lifetimes, the results indicate that the nature of the CN precursor in comet 21P/Giacobini-Zinner is still unclear, ruling out HCN as the only precursor and favouring a mixture of nitrogen compounds. Regarding C 2 , the derived lifetimes are 35 000 and 62 000 s, if the parent and daughter velocities are fixed at ∼1 km s −1 . Gas production rates derived by means of the Vectorial modeling with the mentioned above lifetimes and velocities indicate that (i) the comet activity decreases with decreasing r H (i.e. peak activity is not reached at the perihelion), and (ii) as already known, the comet is typically depleted in C 2 with a log Q C 2 Q CN ≈ −0.4. The azimuthally averaged surface brightness profiles of the continuum images are well fitted with m ≥ 1 in a log B − log ρ representation at projected radial distances (ρ) larger than 1000 km. The continuum light scattered from the dust in the coma of comet Giacobini-Zinner is redder than the Sun light on every date from Nov. 8 to 24, regardless the cometocentric distance. On Nov. 25, there is a sudden change in the dust color, being considerably bluer than the Sun, whereas on Dec. 7 and 8, the dust became much redder than it was before. These color variations do not seem to be related to sudden variations (relative minimum or maximum) in the cometary activity. The gas-to-dust mass ratio is ∼1, but affected by a large uncertainty (about a factor of 2) since the comet was not simultaneously imaged in the OH band, and the H 2 O production rate has been considered from other measurements taken some weeks before ours.

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Ultraviolet spectrophotometry of comet Giacobini-Zinner during the ICE encounter

Cited by 25 publications

References 26 publications

Dust colors, dust release rates, and dust-to-gas ratios in the comae of six comets

Dust colors, dust release rates, and dust-to-gas ratios in the comae of six comets

An Infrared Investigation of Volatiles in Comet 21P/Giacobini–Zinner

Behaviour of Comet 21P/Giacobini-Zinner during the 1998 perihelion

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