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See detailThe compositional evolution of C/2012 S1 (ISON) from ground-based high-resolution infrared spectroscopy as part of a worldwide observing campaign
Dello Russo, N.; Vervack, R. J.; Kawakita, H. et al

in Icarus (2016), 266

Volatile production rates, relative abundances, rotational temperatures, and spatial distributions in the coma were measured in C/2012 S1 (ISON) using long-slit high-dispersion (λ/Δλ ∼ 2.5 × 10[SUP]4[/SUP ... [more ▼]

Volatile production rates, relative abundances, rotational temperatures, and spatial distributions in the coma were measured in C/2012 S1 (ISON) using long-slit high-dispersion (λ/Δλ ∼ 2.5 × 10[SUP]4[/SUP]) infrared spectroscopy as part of a worldwide observing campaign. Spectra were obtained on UT 2013 October 26 and 28 with NIRSPEC at the W.M. Keck Observatory, and UT 2013 November 19 and 20 with CSHELL at the NASA IRTF. H[SUB]2[/SUB]O was detected on all dates, with production rates increasing markedly from (8.7 ± 1.5) × 10[SUP]27[/SUP] molecules s[SUP]-1[/SUP] on October 26 (R[SUB]h[/SUB] = 1.12 AU) to (3.7 ± 0.4) × 10[SUP]29[/SUP] molecules s[SUP]-1[/SUP] on November 20 (R[SUB]h[/SUB] = 0.43 AU). Short-term variability of H[SUB]2[/SUB]O production is also seen as observations on November 19 show an increase in H[SUB]2[/SUB]O production rate of nearly a factor of two over a period of about 6 h. C[SUB]2[/SUB]H[SUB]6[/SUB], CH[SUB]3[/SUB]OH and CH[SUB]4[/SUB] abundances in ISON are slightly depleted relative to H[SUB]2[/SUB]O when compared to mean values for comets measured at infrared wavelengths. On the November dates, C[SUB]2[/SUB]H[SUB]2[/SUB], HCN and OCS abundances relative to H[SUB]2[/SUB]O appear to be within the range of mean values, whereas H[SUB]2[/SUB]CO and NH[SUB]3[/SUB] were significantly enhanced. There is evidence that the abundances with respect to H[SUB]2[/SUB]O increased for some species but not others between October 28 (R[SUB]h[/SUB] = 1.07 AU) and November 19 (R[SUB]h[/SUB] = 0.46 AU). The high mixing ratios of H[SUB]2[/SUB]CO/CH[SUB]3[/SUB]OH and C[SUB]2[/SUB]H[SUB]2[/SUB]/C[SUB]2[/SUB]H[SUB]6[/SUB] on November 19, and changes in the mixing ratios of some species with respect to H[SUB]2[/SUB]O between October 28 to November 19, indicates compositional changes that may be the result of a transition from sampling radiation-processed outer layers in this dynamically new comet to sampling more pristine natal material as the outer processed layer was increasingly eroded and the thermal wave propagated into the nucleus as the comet approached perihelion for the first time. On November 19 and 20, the spatial distribution for dust appears asymmetric and enhanced in the antisolar direction, whereas spatial distributions for volatiles (excepting CN) appear symmetric with their peaks slightly offset in the sunward direction compared to the dust. Spatial distributions for H[SUB]2[/SUB]O, HCN, C[SUB]2[/SUB]H[SUB]6[/SUB], C[SUB]2[/SUB]H[SUB]2[/SUB], and H[SUB]2[/SUB]CO on November 19 show no definitive evidence for significant contributions from extended sources; however, broader spatial distributions for NH[SUB]3[/SUB] and OCS may be consistent with extended sources for these species. Abundances of HCN and C[SUB]2[/SUB]H[SUB]2[/SUB] on November 19 and 20 are insufficient to account for reported abundances of CN and C[SUB]2[/SUB] in ISON near this time. Differences in HCN and CN spatial distributions are also consistent with HCN as only a minor source of CN in ISON on November 19 as the spatial distribution of CN in the coma suggests a dominant distributed source that is correlated with dust and not volatile release. The spatial distributions for NH[SUB]3[/SUB] and NH[SUB]2[/SUB] are similar, suggesting that NH[SUB]3[/SUB] is the primary source of NH[SUB]2[/SUB] with no evidence of a significant dust source of NH[SUB]2[/SUB]; however, the higher production rates derived for NH[SUB]3[/SUB] compared to NH[SUB]2[/SUB] on November 19 and 20 remain unexplained. This suggests a more complete analysis that treats NH[SUB]2[/SUB] as a distributed source and accounts for its emission mechanism is needed for future work. [less ▲]

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See detailThe evolving chemical composition of C/2012 S1 ISON as it approached the Sun
Dello Russo, N.; Vervack, R.; Weaver, H. et al

in Muinonen, Karri (Ed.) Asteroids, Comets, Meteors 2014 (2014, July 01)

Shortly after its discovery by Vitali Nevski and Artyom Novichonok on September 21, 2012, the orbit of C/2012 S1 ISON was determined, indicating a perihelion passage very close to the Sun (0.012 au) in ... [more ▼]

Shortly after its discovery by Vitali Nevski and Artyom Novichonok on September 21, 2012, the orbit of C/2012 S1 ISON was determined, indicating a perihelion passage very close to the Sun (0.012 au) in late November 2013. Initial observations suggested that ISON could be quite bright with a long period of favorable observing conditions leading up to perihelion, followed by a close post-perihelion approach to the Earth (0.42 au) in December 2013. Comet ISON thus became the first sungrazing comet discovered early enough to be studied for many months prior to perihelion, through its close solar passage, and potentially after perihelion. This spurred a worldwide campaign to coordinate observations of ISON from numerous facilities covering a broad spectral range. We report volatile abundances in comet ISON as determined from high-resolution (R ˜ 25,000) infrared spectroscopy. Our strategy was to use the NIRSPEC spectrometer at the 10-m Keck observatory and the CSHELL spectrometer on the 3-m IRTF telescope. We proposed to use NIRSPEC when the comet was fainter but still available during darktime (October through early November 2013 pre-perihelion, and January 2014 post-perihelion), and CSHELL when the comet was brighter and closer to the Sun, but only available during daytime. Although observations on many dates were lost owing to poor weather, and the disruption of the comet near perihelion prevented any post-perihelion observations, successful observations were obtained with NIRSPEC on October 26 (R_h= 1.12 au, Δ = 1.38 au) and October 28 (R_h = 1.08 au, Δ = 1.32 au), and CSHELL on November 19 (R_h = 0.46 au, Δ = 0.86 au) and November 20 (R_h = 0.43 au, Δ = 0.86 au). All dates are specified in UT. The primary results from these observations are as follows. (1) The overall volatile productivity as measured by the H_2O production rate increased from ˜ 10^{28} molec/s on October 26 and 28 to ˜ 3-4×10^{29} molec/s on November 19/20. (2) The volatile production rate was increasing rapidly as ISON approached perihelion, and we investigate whether statistically significant variations in volatile production rates are seen on November 19 between UT 17:15 to 23:00. (3) The relative abundances of some measured volatiles with respect to water remained constant during this time period (e.g., C_2H_6 and CH_3OH), whereas others increased significantly from late October to November 19/20 (e.g., C_2H_2, NH_2, NH_3). (4) Comparison of the measured spatial distributions within the coma of ISON on November 19 show differences that suggest some species are released from extended sources in the coma as well as ices in the nucleus. (5) C_2H_6, CH_3OH and CH_4 appear slightly depleted relative to H_2O in ISON compared to other comets. C_2H_2, HCN, and OCS abundances appear to be in the typical range on November 19, although C_2H_2 abundances appeared depleted in October. Abundances of H_2CO, NH_2, and NH_3 in November were significantly enhanced compared to other comets, with NH_3 abundances being the highest measured to date in any comet. This contrasts with measured abundances and upper limits for NH_2 and NH_3 in late October, which are closer to the typical values seen in comets. [less ▲]

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See detailHigh-dispersion spectroscopic observations of comet C/2013 R1 (Lovejoy) with the Subaru Telescope on 2013 November 15
Shinnaka, Y.; Kawakita, H.; Nagashima, M. et al

in Muinonen, Karri (Ed.) Asteroids, Comets, Meteors - Book of Abstracts (2014, July 01)

Comet C/2013 R1 (Lovejoy) probably originates from the Oort Cloud. Comet Lovejoy provided us with great opportunities to investigate the chemical composition of the comet thanks to its brightness and ... [more ▼]

Comet C/2013 R1 (Lovejoy) probably originates from the Oort Cloud. Comet Lovejoy provided us with great opportunities to investigate the chemical composition of the comet thanks to its brightness and elongation angle from October 2013 to March 2014. We observed comet C/2013 R1 (Lovejoy) on 2013 November 15 UT using the High Dispersion Spectrograph (HDS) mounted on the Subaru Telescope on Mauna Kea. Its heliocentric and geocentric distances were 1.066 and 0.412 au, respectively. The obtained spectra cover the wavelength region from 360 to 830 nm with the resolving power of R = λ/Δλ = 72,000 for the slit size of 0''.5 × 9''.0 (360-520 nm) and 0''.5 × 9''.0 (550-830 nm) on the sky. Exposure time was 130 minutes in total (100 minutes for shorter and 30 minutes for longer wavelength regions). We could identify many species such as the radicals (CN, CH, C_{3}, C_{2}, NH_{2}, etc.), ions (CH^{+}, H_{2}O^{+}), and atoms ([OI] and NaI) in the spectra and many unidentified lines were also detected. Here we discuss the chemical reaction in cometary coma and the origin of icy materials of comet C/2013 R1 (Lovejoy), based on the high-dispersion spectra in the optical wavelength regions. We present (1) the ortho-to-para abundance ratios (OPRs) of water and ammonia inferred from the high-dispersion spectra of H_{2}O^{+} and NH_{2}, (2) the green-to-red line ratio of forbidden oxygen emissions, (3) the nitrogen and the carbon isotopic ratios of CN, and (4) spatial distributions of radicals, atoms, and dust continuum in the inner coma. [less ▲]

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See detailComet C/2012 S1 (Ison)
Dello Russo, N.; Vervack, R. J.; Kawakita, H. et al

in Central Bureau Electronic Telegrams (2013), 3686

CBET 3686 available at Central Bureau for Astronomical Telegrams.

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See detailHyper-volatiles in Comet C/2010 G2 (Hill)
Kawakita, Hideyo; Dello Russo, N.; Vervack, R. J. J. et al

in Bulletin of the American Astronomical Society (2013, October 01), 45

We performed high-dispersion near-infrared spectroscopic observations of comet C/2010 G2 (Hill) at 2.5 AU from the Sun using NIRSPEC (R ~ 2.5x10^4) at the Keck II telescope on UT 2012 Jan 9 and 10. The ... [more ▼]

We performed high-dispersion near-infrared spectroscopic observations of comet C/2010 G2 (Hill) at 2.5 AU from the Sun using NIRSPEC (R ~ 2.5x10^4) at the Keck II telescope on UT 2012 Jan 9 and 10. The comet had been in outburst. Over the two nights of our observations, prominent emission lines of CH4 and C2H6 along with weaker emission lines of H2O, HCN, CH3OH and CO were detected. The gas production rate of CO was comparable to that of H2O. The mixing ratios of CO, HCN, CH4, C2H6, and CH3OH with respect to H2O are higher than those for normal comets by a factor of five or more. Hyper-volatile species such as CO and CH4 were enriched in the coma of comet Hill suggesting that the sublimation of these hyper-volatiles could sustain the outburst of the comet. Based on a comparison with optical observations, some fraction of water in the inner coma existed as icy grains. Those icy ice grains were likely ejected from nucleus by the sublimation of hyper-volatiles. [less ▲]

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See detailEPOXI: Comet 103P/Hartley 2 Observations from a Worldwide Campaign
Meech, K. J.; A'Hearn, M. F.; Adams, J. A. et al

in Astrophysical Journal (2011), 734(Letters), 11-9

Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales, at different wavelengths and using techniques that are impossible ... [more ▼]

Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales, at different wavelengths and using techniques that are impossible with an in situ flyby. We report here such observations in support of the EPOXI spacecraft flyby of comet 103P/Hartley 2. The nucleus is small and dark, and exhibited a very rapidly changing rotation period. Prior to the onset of activity, the period was ~16.4 hr. Starting in 2010 August the period changed from 16.6 hr to near 19 hr in December. With respect to dust composition, most volatiles and carbon and nitrogen isotope ratios, the comet is similar to other Jupiter-family comets. What is unusual is the dominance of CO[SUB]2[/SUB]-driven activity near perihelion, which likely persists out to aphelion. Near perihelion the comet nucleus was surrounded by a large halo of water-ice grains that contributed significantly to the total water production. [less ▲]

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See detailOPRs of Ammonia versus 14N/15N Ratios in CN in 15 Comets
Shinnaka, Yoshiharu; Kawakita, H.; Kobayashi, H. et al

in Bulletin of the American Astronomical Society (2010, October 01), 42

The solar system was formed from interstellar matter 4.6 Gyrs ago and comets are considered as remnants of icy planetesimals formed in the early solar system. One of interesting primordial characters of ... [more ▼]

The solar system was formed from interstellar matter 4.6 Gyrs ago and comets are considered as remnants of icy planetesimals formed in the early solar system. One of interesting primordial characters of cometary ice is an ortho-to-para abundance ratio (OPR) of molecules such as H2O, NH3, etc. The OPR probably indicates the molecular formation temperatures in the solar nebula or in the pre-solar molecular cloud. We determined the OPRs of ammonia by using the high dispersion optical spectra of NH2 in 15 comets: C/1995 O1 (Hale-Bopp), C/1999 S4 (LINEAR), C/2001 A2 (LINEAR), C/2000 WM1 (LINEAR), 153P/Ikeya-Zhang, C/2002 V1 (NEAT), C/2002 X5 (Kudo-Fujikawa), C/2002 Y1 (Juels-Holvorcem), C/2001 Q4 (NEAT), C/2002 T7 (LINEAR), C/2003 K4 (LINEAR), 8P/Tuttle, 88P/Howell, 9P/Tempel 1, and 73P-B and -C/Schwassmann-Wachmann 3. The observations were mainly carried out by the Ultraviolet and Visual Echelle Spectrograph (UVES) mounted on the Very Large Telescope (VLT) in Chile. Other telescopes/instruments were also used in some cases. The OPRs of ammonia are determined from OPRs of NH2 (0,9,0) ro-vibronic band around 600 nm. Although absorption lines (by the telluric atmosphere) and cometary C2 emission lines blended affected to NH2 emission lines in this region, we removed them in our analysis. The determined OPRs of ammonia clustered around 30K but not in the cases of 73P-B and -C. This situation is very similar to that of 14N/15N ratios in CN (i.e., 73P-B and -C are quite peculiar relative to other comets). We discuss about the relationship between the OPRs of ammonia and 14N/15N ratios in CN in these 15 comets. Our results indicate the formation of materials at relatively higher temperatures for 73P-B and -C than other comets. [less ▲]

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See detailHigh-dispersion infrared spectroscopic observations of comet 8P/Tuttle with VLT/CRIRES
Kobayashi, H.; Bockelée-Morvan, D.; Kawakita, H. et al

in Astronomy and Astrophysics (2010), 509

We report on the composition of the Halley-family comet (HFC) 8P/Tuttle investigated with high-dispersion near-infrared spectroscopic observations. The observations were carried out at the ESO VLT (Very ... [more ▼]

We report on the composition of the Halley-family comet (HFC) 8P/Tuttle investigated with high-dispersion near-infrared spectroscopic observations. The observations were carried out at the ESO VLT (Very Large Telescope) with the CRIRES instrument as part of a multi-wavelength observation campaign of 8P/Tuttle performed in late January and early February 2008. Radar observations suggested that 8P/Tuttle is a contact binary, and it was proposed that these components might be heterogeneous in chemistry. We determined mixing ratios of organic volatiles with respect to H[SUB]2[/SUB]O and found that mixing ratios were consistent with previous near infrared spectroscopic observations obtained in late December 2007 and in late January 2008. It has been suggested that because 8P/Tuttle is a contact binary, it might be chemically heterogeneous. However, we find no evidence for chemical heterogeneity within the nucleus of 8P/Tuttle. We also compared the mixing ratios of organic molecules in 8P/Tuttle with those of both other HFCs and long period comets (LPCs) and found that HCN, C[SUB]2[/SUB]H[SUB]2[/SUB], and C[SUB]2[/SUB]H[SUB]6[/SUB] are depleted whereas CH[SUB]4[/SUB] and CH[SUB]3[/SUB]OH have normal abundances. This may indicate that 8P/Tuttle was formed in a different region of the early solar nebula than other HFCs and LPCs. We estimated the conversion efficiency from C[SUB]2[/SUB]H[SUB]2[/SUB] to C[SUB]2[/SUB]H[SUB]6[/SUB] by hydrogen addition reactions on cold grains by employing the C[SUB]2[/SUB]H[SUB]6[/SUB]/(C[SUB]2[/SUB]H[SUB]6[/SUB]+C[SUB]2[/SUB]H[SUB]2[/SUB]) ratio. The C[SUB]2[/SUB]H[SUB]6[/SUB]/(C[SUB]2[/SUB]H[SUB]6[/SUB]+C[SUB]2[/SUB]H[SUB]2[/SUB]) ratio in 8P/Tuttle is consistent with the ratios found in other HFCs and LPCs within the error bars. We also discuss the source of C[SUB]2[/SUB] and CN based on our observations and conclude that the abundances of C[SUB]2[/SUB]H[SUB]2[/SUB] and C[SUB]2[/SUB]H[SUB]6[/SUB] are insufficient to explain the C[SUB]2[/SUB] abundances in comet 8P/Tuttle and that the abundance of HCN is insufficient to explain the CN abundances in the comet, so at least one additional parent is needed for each species, as pointed out in previous study. Based on observations collected at the European Southern Observatory, Paranal, Chile (ESO Prog. 080.C-0615 and 280.C-5053).We regret to note the death of Dr. J. -M. Zucconi in 2009 May. [less ▲]

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See detailRevisit to Nuclear Spin Temperature of Ammonia in Comets
Shinnaka, Yoshiharu; Jehin, Emmanuel ULg; Manfroid, Jean ULg et al

in Bulletin of the American Astronomical Society (2009, September 01), 41

Comets had formed from dust and icy materials in the solar nebula 4.6 Gyrs ago. The cometary materials are considered as the most pristine in the solar system and both dust grains and icy materials in ... [more ▼]

Comets had formed from dust and icy materials in the solar nebula 4.6 Gyrs ago. The cometary materials are considered as the most pristine in the solar system and both dust grains and icy materials in comets have been used to investigate the formation conditions of the solar system. One of interesting primordial characters is a nuclear spin temperature (related to an ortho-to-para ratio; OPR) of cometary molecules such as H2O, NH3, etc. The nuclear spin temperatures probably reflect the molecular formation temperatures in the solar nebula (or in the presolar molecular cloud). In this work, we analyzed high dispersion optical spectra of C/2001 Q4 (NEAT), C/2000 WM1 (LINEAR), 88P/Howell, fragments B and C of 73P/Schwassmann-Wachmann 3 and 8P/Tuttle. Our observations were performed by the Ultraviolet and Visual Echelle Spectrograph (UVES) mounted on the Very Large Telescope (VLT) in Chile and the High Dispersion Spectrograph (HDS) mounted on the Subaru telescope in Hawaii. We determined nuclear spin temperatures of NH3 in five comets based on optical spectra of NH2. The nuclear spin temperatures of NH3 can be obtained from OPRs of NH2. We used the (0,9,0) ro-vibronic band at 610nm in this work. Absorption lines (by the telluric atmosphere) and cometary C2 emission lines blended with NH2 emission lines were also taken into account in our analysis. These lines have never been considered in previous studies. The origin of icy materials in the five comets will be discussed based on these results. [less ▲]

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See detailA Multi-Wavelength Simultaneous Study of the Composition of the Halley Family Comet 8P/Tuttle
Jehin, Emmanuel ULg; Bockelée-Morvan, Dominique; Dello Russo, N. et al

in Earth, Moon, and Planets (2009), 105

We report on simultaneous optical and infrared observations of the Halley Family comet 8P/Tuttle performed with the ESO Very Large Telescope. Such multi-wavelength and coordinated observations are a good ... [more ▼]

We report on simultaneous optical and infrared observations of the Halley Family comet 8P/Tuttle performed with the ESO Very Large Telescope. Such multi-wavelength and coordinated observations are a good example of what can be done to support space missions. From high resolution optical spectroscopy of the CN (0,0) 388 nm and NH[SUB]2[/SUB] (0,9,0) 610 nm bands using UVES at UT2 we determined [SUP]12[/SUP]C/[SUP]13[/SUP]C = 90 ± 10 and [SUP]14[/SUP]N/[SUP]15[/SUP]N = 150 ± 20 in CN and we derived a nuclear spin temperature of NH[SUB]3[/SUB] of 29 ± 1 K. These values are similar to those found in Oort-Cloud and Jupiter Family comets. From low resolution long slit spectroscopy with FORS1 at UT2 we determined the CN, C[SUB]3[/SUB] and C[SUB]2[/SUB] production rates and the parent and daughter scale lengths up to 5.2 10[SUP]5[/SUP] km tailward. From high resolution IR spectroscopy with CRIRES at UT1 we measured simultaneously the production rates and mixing ratios of H[SUB]2[/SUB]O, HCN, C[SUB]2[/SUB]H[SUB]2[/SUB], CH[SUB]4[/SUB], C[SUB]2[/SUB]H[SUB]6[/SUB], and CH[SUB]3[/SUB]OH. [less ▲]

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See detailA Multi-Wavelength Simultaneous Study of the Composition of the Halley-Family Comet 8P/Tuttle at the VLT
Bockelée-Morvan, Dominique; Dello Russo, N.; Jehin, Emmanuel ULg et al

in LPI contribution 1405 (2008)

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