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See detailOutgassing and chemical evolution of C/2012 S1 (ISON)
Dello Russo, Neil; Vervack, Ronald J.; Kawakita, Hideyo et al

in Bulletin of the American Astronomical Society (2015, November 01), 47

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 ~ 25,000) infrared ... [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 ~ 25,000) 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 by about a factor of 40 between October 26 (R[SUB]h[/SUB] = 1.12 AU) and November 20 (R[SUB]h[/SUB] = 0.43 AU). Short-term variability of H[SUB]2[/SUB]O was also seen as the production rate increased by nearly a factor of two during observations obtained over a period of about six hours on November 19. C[SUB]2[/SUB]H[SUB]6[/SUB], CH[SUB]3[/SUB]OH and CH[SUB]4[/SUB] abundances were slightly depleted relative to H[SUB]2[/SUB]O in ISON 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 close to the range of mean values, whereas H[SUB]2[/SUB]CO and NH[SUB]3[/SUB] were significantly enhanced. We will compare derived chemical abundances in ISON to other comets measured with infrared spectroscopy. [less ▲]

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See detailChariklo's size, shape and orientation from stellar occultations
Bérard, Diane; Sicardy, Bruno; Assafin, Marcelo et al

in Bulletin of the American Astronomical Society (2015, November 01), 47

Chariklo is the largest Centaur object known to date, and it is surrounded by dense and narrow rings (Braga-Ribas et al. Nature 508, 72, 2014). The size, shape and orientation of the central body are ... [more ▼]

Chariklo is the largest Centaur object known to date, and it is surrounded by dense and narrow rings (Braga-Ribas et al. Nature 508, 72, 2014). The size, shape and orientation of the central body are important parameters to better understand the dynamics of the rings.In that context, we have analyzed three stellar occultations by Chariklo and its main ring observed on June 3, 2013, April 29, 2014 and June 28, 2014. Elliptical limb fitting to Chariklo’s main body occultation chords has been performed, where we denote a (resp. b) the semi-major (resp. semi-minor) axis of the limb. Preliminary results indicate that Chariklo’s limb is elliptical with axes ratio b/a~0.89. We obtain a~133 km and b~119 km, providing an equivalent radius of R[SUB]equiv[/SUB]=√(ab)~126 km. The rms dispersion of the fit, about 4 km, is compatible with local topographic features on a small icy body. For comparison, an equivalent radius of R[SUB]equiv[/SUB]= 119±5 km, based on thermal data, is given by Fornasier et al, AA 518, L11, 2014, while Duffard et al. AA 568, A79, 2014 estimate a= 122 km and b= 117 km.Our results are obtained under the simplifying assumption that the main ring is circular and that its center coincides with that of Chariklo. Caveats and error bars will be discussed, and dynamical implications will be presented. In particular, rough estimations of the ring apsidal precession rates will be given, as well as constraints on Chariklo's density. [less ▲]

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See detailFive years of comet narrow band photometry and imaging with TRAPPIST
Opitom, Cyrielle ULg; Jehin, Emmanuel ULg; Manfroid, Jean ULg et al

in Bulletin of the American Astronomical Society (2015, November 01), 47

TRAPPIST is a 60-cm robotic telescope in La Silla Observatory [1] mainly dedicated to the study of exoplanets and comets. The telescope is equipped with a set of narrow band cometary filters designed by ... [more ▼]

TRAPPIST is a 60-cm robotic telescope in La Silla Observatory [1] mainly dedicated to the study of exoplanets and comets. The telescope is equipped with a set of narrow band cometary filters designed by the NASA for the Hale-Bopp observing campaign [2]. Since its installation in 2010, we gathered a high quality and homogeneous data set of more than 30 bright comets observed with narrow band filters. Some comets were only observed for a few days but others have been observed weekly during several months on both sides of perihelion. From the images, we derived OH, NH, CN, C[SUB]2[/SUB], and C[SUB]3[/SUB] production rates using a Haser [3] model in addition to the Afρ parameter as a proxy for the dust production. We computed production rates ratios and the dust color for each comet to study their composition and followed the evolution of these ratios and colors with the heliocentric distance.The TRAPPIST data set, rich of more than 10000 images obtained and reduced in an homogeneous way, allows us to address several fundamental questions such as the pristine or evolutionary origin of composition differences among comets. The evolution of comet activity with the heliocentric distance, the differences between species, and from comet to comet, will be discussed. Finally, the first results about the one year campaign on comet C/2013 US10 (Catalina) and our recent work on the re-determination of Haser scalelengths will be presented.[1] Jehin et al., The Messenger, 145, 2-6, 2011[2] Farnham et al., Icarus, 147, 180-204, 2000[3] Haser, Bulletin de l’Académie Royal des Sciences de Belgique,63, 739, 1957 [less ▲]

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See detailNitrogen Isotopic Ratios in Cometary NH2: Implication for 15N-fractionation in Ammonia
Shinnaka, Yoshiharu; Kawakita, Hideyo; Jehin, Emmanuel ULg et al

in Bulletin of the American Astronomical Society (2015, November 01), 47

Isotopic ratios in cometary molecules are diagnostic for the physico-chemical conditions where molecules formed and are processed, from the interstellar medium to the solar nebula. Usually temperatures at ... [more ▼]

Isotopic ratios in cometary molecules are diagnostic for the physico-chemical conditions where molecules formed and are processed, from the interstellar medium to the solar nebula. Usually temperatures at the molecular formation control the fractionation of the heavier element in molecular species, e.g., D-fractionation in water.In cometary volatiles, the [SUP]14[/SUP]N/[SUP]15[/SUP]N ratios in CN have been well observed (Manfroid et al. 2009, A&A, 503, 613, and reference therein) and is consistent with the ratio in HCN (a most probable parent of CN) measured in few comets (Bockelée-Morvan et al. 2008, ApJ, 679, L49). Those ratios are enriched compared to the proto-solar value by a factor of ~3. In contrast to those Nitriles, there are only few reports on [SUP]14[/SUP]N/[SUP]15[/SUP]N ratios in Ammonia (as Amine) (Rousselot et al. 2014, ApJ, 780, L17; Shinnaka et al. 2014, ApJ, 782, L16). Ammonia (NH[SUB]3[/SUB]) is usually the most abundant and HCN is the second most abundant N-bearing volatiles in cometary ice. Especially, recent observations of [SUP]15[/SUP]NH[SUB]2[/SUB] revealed the [SUP]14[/SUP]N/[SUP]15[/SUP]N ratios in NH[SUB]3[/SUB] are comparable to those of CN. However, from the viewpoint of theoretical work, the enrichment of [SUP]15[/SUP]N in cometary NH[SUB]3[/SUB] cannot be reproduced by current chemical network models. Information about the diversity of the [SUP]14[/SUP]N/[SUP]15[/SUP]N ratios in NH[SUB]3[/SUB] of individual comets is needed to understand the formation mechanisms/environments of NH[SUB]3[/SUB] in the early solar system.To clarify the diversity of the [SUP]14[/SUP]N/[SUP]15[/SUP]N ratios in cometary NH[SUB]3[/SUB], we determine the [SUP]14[/SUP]N/[SUP]15[/SUP]N ratios in NH[SUB]3[/SUB] for more than ten comets individually which include not only Oort cloud comets but also short period comets by using the high-resolution optical spectra of NH[SUB]2[/SUB]. These spectra were obtained with both the UVES mounted on the VLT in Chile and the HDS on the Subaru Telescope in Hawaii.The derived [SUP]14[/SUP]N/[SUP]15[/SUP]N ratios in NH[SUB]3[/SUB] for more than ten comets show high [SUP]15[/SUP]N-enrichment compared with the elemental abundances of nitrogen in the Sun by about factor of ~3 and has no large diversity depending on these dynamical properties. We discuss about the origin of the formation conditions of cometary NH[SUB]3[/SUB] and its physico-chemical evolution in the solar nebula based on our and other results.This work was supported by JSPS, 15J10864 (Y. Shinnaka). [less ▲]

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See detailReport on the ground-based observation campaign of 67P/Churyumov-Gerasimenko
Jehin, Emmanuel ULg

in Bulletin of the American Astronomical Society (2015, November 01), 47

Rosetta gets closer to the nucleus than any previous mission, and returns wonderfully detailed measurements from the heart of the comet, but at the cost of not seeing the large scale coma and tails. The ... [more ▼]

Rosetta gets closer to the nucleus than any previous mission, and returns wonderfully detailed measurements from the heart of the comet, but at the cost of not seeing the large scale coma and tails. The ground-based campaign fills in the missing part of the picture, studying the comet at about 1000 km resolution, and following how the overall activity of the comet varies. These data provide context information for Rosetta, so changes in the inner coma seen by the spacecraft can be correlated with the phenomena observable in comets. This will not only help to complete our understanding of the activity of 67P, but also to allow us to compare it with other comets that are only observed from the ground.The ground-based campaign includes observations with nearly all major facilities world-wide. In 2014 the majority of data came from the ESO VLT, as the comet was still relatively faint and in Southern skies, but as it returns to visibility from Earth in 2015 it is considerably brighter, approaching its perihelion in August, and at Northern declinations. I will present results from the 2014 campaign, including visible wavelength photometry and spectroscopy, and the latest results from 2015 observations. [less ▲]

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See detailPluto's atmosphere from stellar occultations in 2012 and 2013
Dias-Oliveira, Alex; Sicardy, Bruno; Lellouch, Emmanuel et al

in Bulletin of the American Astronomical Society (2015, November 01), 47

We present results from two Pluto stellar occultations observed on 18 July 2012 and 04 May 2013, and monitored respectively from five and six sites in South America. Both campaigns involved large ... [more ▼]

We present results from two Pluto stellar occultations observed on 18 July 2012 and 04 May 2013, and monitored respectively from five and six sites in South America. Both campaigns involved large telescopes (including the 8.2-m VLT at ESO/Paranal). The high SNR ratios and multi-chord coverage provide amoung the best Pluto atmospheric profiles ever obtained from the ground.We show that a spherically symmetric, clear (no-haze) and pure N2 atmosphere with a unique temperature profile satisfactorily fits the twelve lightcurves provided by the two events. We find, however, a small but significant increase of pressure of 6% (6-sigma level) between the two dates, with values of 2.16 ± 0.2 and 2.30 ± 0.01 μbar at the reference radius 1275 km, respectively.We provide atmospheric constrains between 1190 km and 1450 km from Pluto's center, and we determine the temperature profile with accuracy of a few km in vertical scale. Our model shows a stratosphere with strong positive gradient between 1190 km (at 36 K, 11 μbar) and r =1215 km (6.0 μbar), where a temperature maximum of 110 K is reached. Above it is a mesosphere with negative thermal gradient of -0.2 K/km up to 1,390 km (0.25 μbar), at which point, the mesosphere connects itself to a more isothermal upper branch at 81 K. This profile provides (assuming no troposphere) a Pluto surface radius of 1190 ± 5 km, consistent with preliminary values obtained by New Horizons. Currently measured CO abundances are too low to explain the negative mesospheric thermal gradient. We explore the possibility of an HCN (recently detected by ALMA) cooling. This model, however, requires largely supersaturated HCN. Zonal winds and vertical compositional variations of the atmosphere are also unable to explain the observed mesospheric trend.These events are the last useful ground-based occultations recorded before the 29 June 2015 occultation observed from Australia and New Zealand, and before the NASA's New Horizons flyby of July 2015. This work can serve as a benchmark in the New Horizons context, enabling comparisons between ground-based and space results concerning Pluto's atmospheric structure and temporal evolution. [less ▲]

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See detailHigh-Dispersion Spectroscopic Observations of Comet C/2012 S1 (ISON) with the Subaru Telescope
Shinnaka, Yoshiharu; Kawakita, Hideyo; Nagashima, Masayoshi et al

in Bulletin of the American Astronomical Society (2014, November 01), 46

Comet C/2012 S1 (ISON) was one of the Oort cloud comets and dynamically new. This comet was broken at its perihelion passage on UT 2013 November 28.1 (at Rh ~ 17 solar radius). We observed the comet C ... [more ▼]

Comet C/2012 S1 (ISON) was one of the Oort cloud comets and dynamically new. This comet was broken at its perihelion passage on UT 2013 November 28.1 (at Rh ~ 17 solar radius). We observed the comet C/2012 S1 (ISON) on UT 2013 November 15 with the High Dispersion Spectrograph (HDS) mounted on the Subaru Telescope atop Mauna Kea, Hawaii. Its heliocentric and geocentric distances were 0.601 and 0.898 AU, respectively. We selected the slit size of 0”.5 x 9”.0 on the sky to achieve the spectral resolution of R = 72,000 from 550 to 830 nm. The total exposure time of comet C/2012 S1 (ISON) was 1200 seconds. We detected many emission lines caused from radicals (e.g., CN, C2, NH2), ions (H2O+), atoms ([OI] and Na I) and also many unidentified lines in the spectra. We report the (1) the ortho-to-para abundance ratios (OPRs) of water and ammonia estimated from the high-dispersion spectra of H2O+ and NH2, (2) the green-to-red line ratio of forbidden oxygen emissions, (3) the isotopic ratios of C2 (the carbon isotopic ratio from Swan band) and CN (the carbon and nitrogen isotopic ratios from red band), (4) the sodium-to-continuum ratio of comet C/2012 S1 (ISON). </PRE></BODY></HTML> [less ▲]

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See detailThe TRAPPIST comet survey in 2014
Jehin, Emmanuel ULg; Opitom, Cyrielle ULg; Manfroid, Jean ULg et al

in Bulletin of the American Astronomical Society (2014, November 01), 46

TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) is a 60-cm robotic telescope that has been installed in June 2010 at the ESO La Silla Observatory [1]. Operated from Liège (Belgium) it is ... [more ▼]

TRAPPIST (TRAnsiting Planets and PlanetesImals Small Telescope) is a 60-cm robotic telescope that has been installed in June 2010 at the ESO La Silla Observatory [1]. Operated from Liège (Belgium) it is devoted to the detection and characterisation of exoplanets and to the study of comets and other small bodies in the Solar System. A set of narrowband cometary filters designed by the NASA for the Hale-Bopp Observing Campaign [2] is permanently mounted on the telescope along with classic Johnson-Cousins filters. We describe here the hardware and the goals of the project. For relatively bright comets (V < 12) we measure several times a week the gaseous production rates (using a Haser model) and the spatial distribution of several species among which OH, NH, CN, C2 and C3 as well as ions like CO+. The dust production rates (Afrho) and color of the dust aredetermined through four dust continuum bands from the UV to the red (UC, BC, GC, RC filters). We will present the dust and gas production rates of the brightest comets observed in 2014: C/2012 K1 (PANSTARRS), C/2014 E2 (Jacques), C/2013 A1 (Siding Springs) and C/2013 V5 (Oukaimeden). Each of these comets have been observed at least once a week for several weeks to several months. Light curves with respect to the heliocentric distance will be presented and discussed. [1] Jehin et al., The Messenger, 145, 2-6, 2011.[2] Farnham et al., Icarus, 147, 180-204, 2000. [less ▲]

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See detailTRAPPIST monitoring of comet C/2013 A1 (Siding Spring)
Opitom, Cyrielle ULg; Jehin, Emmanuel ULg; Manfroid, Jean ULg et al

in Bulletin of the American Astronomical Society (2014, November 01), 46

C/2013 A1 (Siding Spring) is a long period comet discovered by Robert H McNaught at Siding Spring Observatory in Australia on January 3, 2013 at 7.2 au from the Sun. This comet will make a close encounter ... [more ▼]

C/2013 A1 (Siding Spring) is a long period comet discovered by Robert H McNaught at Siding Spring Observatory in Australia on January 3, 2013 at 7.2 au from the Sun. This comet will make a close encounter with Mars on October 19, 2014. At this occasion the comet will be extensively observed both from Earth and from several orbiters around Mars.On September 20, 2013 when the comet was around 5 au from the Sun, we started a monitoring with the TRAPPIST robotic telescope installed at La Silla observatory [1]. A set of narrowband cometary filters designed by the NASA for the Hale-Bopp Observing Campaign [2] is permanently mounted on the telescope along with classic Johnson-Cousins B, V, Rc, and Ic filters.We observed the comet continuously at least once a week from September 20, 2013 to April 6, 2014 with broad band filters. We then recovered the comet on May 20. At this time we could detect the gas and started the observations with narrow band filters until early November, covering the close approach to Mars and the perihelion passage.We present here our first results about comet Siding Springs. From the images in the broad band filters and in the dust continuum filters we derived A(θ)fρ values [3] and studied the evolution of the comet activity with the heliocentric distance from September 20, 2013 to early November 2014. We could also detect gas since May 20, 2014. We thus derived gas production rates using a Haser model [4]. We present the evolution of gas production rates and gas production rates ratios with the heliocentric distance.Finally, we discuss the dust and gas coma morphology. [less ▲]

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See detailStudy of the Forbidden Oxygen Lines in Comets at Different Heliocentric and Nucleocentric Distances
Decock, Alice ULg; Rousselot, P.; Jehin, Emmanuel ULg et al

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

Oxygen is an important element in the chemistry of the solar system objects given its abundance and its presence in many molecules including H2O 80% of cometary ices). The analysis of oxygen atoms in ... [more ▼]

Oxygen is an important element in the chemistry of the solar system objects given its abundance and its presence in many molecules including H2O 80% of cometary ices). The analysis of oxygen atoms in comets can provide information not only on the comets themselves but also on the solar system. These atoms have been analyzed using the 3 forbidden oxygen lines [OI] observed in emission in the optical region at 5577.339 Å (the green line), 6300.304 Å and 6363.776 Å (the red lines) (Swings, 1962). Our analysis is based on a sample of 12 comets of various origins. The observing material is made of 53 high signal-to-noise spectra obtained with the high-resolution UVES spectrograph at the ESO VLT from 2002 to 2012 (Manfroid et al, 2009). After noticing that the green line is blended with one C2 line, we built synthetic spectra of C2 for each observing circumstances and we subtracted its contribution to the cometary spectra in order to ensure the decontamination of the 5577 Å line. Then, we measured the intensity of the 3 [OI] lines at different heliocentric distances. By comparing the green to red lines ratio (G/R) with the Bhardwaj & Raghuram (2012) effective excitation rates, we found that H2O is the main parent molecule when the comet is observed at 1 au. When the comet is located beyond 2.5 au from the Sun, CO2 also contributes to the production of oxygen. Studying forbidden oxygen lines could be a new way to estimate the abundances of CO2 in comets, a very difficult task from the ground (Decock et al. 2013). In order to estimate the effect of the quenching on our results, we analyzed the evolution of the G/R ratio at different nucleocentric distances. For nearby comets, we divided the extended 2D spectrum into several zones in order to analyze the oxygen lines as close as possible to the nucleus (down to ~10 km for the closest comets). Their analysis will allow us to study the link of the oxygen lines with the nucleocentric distance. We found a clear variation of the G/R ratio close to the comet nucleus that is in agreement with a contribution from CO2 as predicted by Raghuram & Bhardwaj (2013). [less ▲]

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See detailThe May 4, 2013 Stellar Occultation by Pluto and Implications for Pluto's Atmosphere
Olkin, Catherine B.; Young, L. A.; Borncamp, D. et al

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

On May 4 2013, Pluto passed in front of a 14 star and the shadow was well observed from multiple occultation groups. This paper presents results from the three light curves observed at Las Cumbres ... [more ▼]

On May 4 2013, Pluto passed in front of a 14 star and the shadow was well observed from multiple occultation groups. This paper presents results from the three light curves observed at Las Cumbres Observatory Global Telescope Network (LCOGT) from their Cerro Tololo site. The three LCOGT telescopes have 1.0 m apertures and used identical frame-transfer cameras. The cameras currently have a 2 second readout time therefore autonomous observations were scheduled with different exposure times to give good time resolution of the event. We will present results of this occultation and compare occultation results from 1988 to 2013 with volatile transport models. [less ▲]

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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 detailA Search For 15NH2 Emission Lines In Comets
Rousselot, Philippe; Pirali, O.; Jehin, Emmanuel ULg et al

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

The determination of nitrogen isotopic ratios in solar system objects is important for a good understanding of their origin. The measurements of [SUB]14[/SUB]N/[SUB]15[/SUB]N isotopic ratio done so far in ... [more ▼]

The determination of nitrogen isotopic ratios in solar system objects is important for a good understanding of their origin. The measurements of [SUB]14[/SUB]N/[SUB]15[/SUB]N isotopic ratio done so far in various solar system objects and molecules have revealed a great diversity (from 50 to 441), all of them, except Jupiter, being enriched in [SUB]15[/SUB]N compared to the protosolar nebula. Different explanations have been proposed to explain this enrichement. One of them suggests that these differences reflect the different interstellar N reservoirs from which N-bearing molecules are originating (Hily-Blant et al., 2013). These authors, from observations of H[SUB]13[/SUB]CN and HC[SUB]15[/SUB]N in two prestellar cores, suggest that the molecules carrying the nitrile- (-CN) functional group would be more enriched in [SUB]15[/SUB]N than the molecules carrying the amine (-NH) functional group. Comets are interesting targets to test this theory because they contain both HCN and NH[SUP]3[/SUP] molecules. So far the [SUB]14[/SUB]N/[SUB]15[/SUB]N ratio has only been measured in CN (Arpigny et al., 2003; Manfroid et al., 2009) and HCN (Bockelée-Morvan et al., 2005, 2008) in comets, leading for both species to [SUB]14[/SUB]N/[SUB]15[/SUB]N ≈ 150. Our work aimed at measuring the [SUB]14[/SUB]N/[SUB]15[/SUB]N isotopic ratio in NH[SUP]2[/SUP], which comes from NH[SUP]3[/SUP]. We have determined accurately the wavelengths of [SUB]15[/SUB]NH[SUP]2[/SUP] emission lines with the AILES beamline spectrometer at synchrotron SOLEIL by Fourier transform spectroscopy. The analysis of this spectrum has permitted to extract the [SUB]15[/SUB]NH[SUP]2[/SUP] emission lines wavelengths and to search for [SUB]15[/SUB]NH[SUP]2[/SUP] cometary emission lines. Thanks to a collection of spectra of 12 different comets obtained from 2002 to 2011 with the UVES spectrometer at the VLT ESO 8-m telescope (Manfroid et al., 2009), it has been possible to search for [SUB]15[/SUB]NH[SUP]2[/SUP] emission lines with a high sensitivity. We will present the results obtained from these data. Arpigny et al., Science, 301, 1522-1525, 2003 Bockelée-Morvan et al., in Comets II, ed. M. C. Festou, H. U. Keller, & H. A. Weaver (Tucson: Univ. Arizona Press), 391-423, 2005 Bockelée-Morvan et al., ApJ, 679, L49-L52, 2008 Hily-Blant et al., Icarus 223, 582-590, 2013 Manfroid et al., A&A, 503, 613-624, 2009 [less ▲]

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See detailA Search For 15NH2 Lines In Comet C/2002 T7 (LINEAR)
Rousselot, Philippe; Pirali, O.; Jehin, Emmanuel ULg et al

in Bulletin of the American Astronomical Society (2012), 44

The determination of isotopic ratios in comets is of primary importance for a good understanding of their origin and the formation of solar system. The [SUP]14[/SUP]N/[SUP]15[/SUP]N ratio is an ... [more ▼]

The determination of isotopic ratios in comets is of primary importance for a good understanding of their origin and the formation of solar system. The [SUP]14[/SUP]N/[SUP]15[/SUP]N ratio is an interesting tracer, because of its variability among various solar system bodies. So far it has only been measured in bright comets through optical observations of the CN radical (Arpigny et al., 2003; Manfroid et al., 2009) and millimeter observations of HCN (Bockelée-Morvan et al., 2005, 2008). The measurements give for both species the same non-terrestrial isotopic composition ([SUP]14[/SUP]N/[SUP]15[/SUP]N≈150 in comets versus 272 in the Earth atmosphere), but HCN and CN are minor species. In order to get a determination of this ratio in another molecule we have searched for [SUP]15[/SUP]NH[SUB]2[/SUB] lines in a high-resolution and high signal-to-noise ratio spectrum of comet C/2002 T7 (LINEAR) obtained with the UVES spectrometer at the VLT ESO 8-m telescope (Hutsemékers et al., 2008). This work is based on a new laboratory experiment conducted with the AILES beamline spectrometer at synchrotron SOLEIL to determine the [SUP]15[/SUP]NH[SUB]2[/SUB] wavelengths by Fourier transform spectroscopy. We will present the first results obtained from these data, which have allowed to search for the first time [SUP]15[/SUP]NH[SUB]2[/SUB] emission lines in a comet. References: Arpigny et al., 2003, Science, 301, 1522 Bockelée-Morvan et al.,2005, in Comets II, ed. M. C. Festou, H. U. Keller, & H. A. Weaver (Tucson: Univ. Arizona Press), 391 Bockelée-Morvan et al., 2008, ApJ, 679, L49 Hutsemékers et al., 2008, A&A 490, L31 Manfroid et al., 2009, A&A 503, 613 [less ▲]

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See detailComet 29P/Schwassmann-Wachmann Observed with the Herschel Space Observatory: Detection of Water Vapour and Dust Far-IR Thermal Emission
Bockelee-Morvan, Dominique; Biver, N.; Crovisier, J. et al

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

The distant comet 29P/Schwassmann-Wachmann was observed with the HIFI, PACS and SPIRE instruments aboard the Herschel Space Observatory, as part of the guaranteed time key programme "Water and related ... [more ▼]

The distant comet 29P/Schwassmann-Wachmann was observed with the HIFI, PACS and SPIRE instruments aboard the Herschel Space Observatory, as part of the guaranteed time key programme "Water and related chemistry in the Solar System" (KP-GT HssO). Supporting observations of the 230 GHz CO line were carried out with the IRAM 30-m telescope. The HIFI observations of the 557 GHz H2O line were performed on 19.05 April 2010, about 2 days after a major outburst, and on 11.02 May 2010, when 29P was in a more quiescent phase. H2O was detected on both dates with a production rate corresponding to about 1/10th the CO production, assuming near-nucleus production. The H2O line shape is consistent with release of water vapour from icy grains. PACS and SPIRE imaging data from 70 to 500 micrometers were acquired mid-June 2010 when the comet was in a quiescent phase. The continuum emission detected in the 70-μm and 160-μm PACS images is weakly extended with respect to the PSF, suggesting a major contribution from the nucleus or from slowly moving large grains. [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 detailThe 3/4 July 2010 Pluto Stellar-Occultation Observations
Pasachoff, Jay M; Elliot, J. L.; Souza, S. P. et al

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

Continuing our monitoring of Pluto's atmospheric temperature and pressure, previously shown by us to be increasing (Elliot et al., Nature 424, 165, 2003; Pasachoff et al., AJ 129, 1718, 2005) and ... [more ▼]

Continuing our monitoring of Pluto's atmospheric temperature and pressure, previously shown by us to be increasing (Elliot et al., Nature 424, 165, 2003; Pasachoff et al., AJ 129, 1718, 2005) and subsequently found by us to be leveling off (Elliot et al., AJ 134, 1, 2007), we report on a stellar occultation by Pluto of UCAC2 mag=15.3, observed from South America and Africa on 4 July 2010 UT. Success was achieved with a 0.45 m at Cerro Calan using one of our POETS (Portable Occultation, Eclipse, and Transit System; Souza et al. PASP 118, 1550, 2006), a 1.0 SMARTS (Small and Medium Aperture Research Telescope System) at Cerro Tololo, four 0.6 m telescopes of PROMPT (Panchromatic Robotic Optical Monitoring and Polarimetry Telescopes) on Cerro Tololo, and TRAPPIST's (TRansiting Planets and Planetesimals Small Telescope) 0.6-m telescope on La Silla in Chile; the 0.35 m telescope of U. Ponta Grossa, Brazil; and the 0.75-m ATOM (Automatic Telescope for Optical Monitoring), Namibia, using POETS. Winds prevented opening the 6.5 m Magellan/Clay telescope on Las Campanas, Chile, with its own frame-transfer camera, and clouds obscured the 1.9 m telescope at Sutherland, South Africa, which had POETS. With shadow velocity 23.6 km/s, it was a rapid event: maximum occultation <2 minutes. The observations were supported in part by grants NNX08AO50G to Williams College and NNX10AB27G to MIT from NASA's Planetary Astronomy Division, and NNH08AI17I to USNO for astrometry. Student participation was supported in part by NASA's Massachusetts Space Grant and NSF's REU. Japan's government donated U. Chile's Cerro Calan Goto telescope. PROMPT observations were made possible by the Robert Martin Ayers Science Fund. TRAPPIST is a project driven by the University of Liège, in close collaboration with the Observatory of Geneva, supported by the Belgian Fund for Scientific Research and the Swiss National Science Foundation. [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 detailHigh-dispersion Spectroscopic Observations Of 8P/Tuttle With VLT/CRIRES
Kobayashi, Hitomi; Bockelee-Morvan, D.; Dello Russo, N. et al

in Bulletin of the American Astronomical Society (2008, September 01), 40

We present near-infrared observations of organic molecules in comet 8P/Tuttle. Comet 8P/Tuttle is a Halley-type comet and its last perihelion was in early January 2008. Our observations were carried out ... [more ▼]

We present near-infrared observations of organic molecules in comet 8P/Tuttle. Comet 8P/Tuttle is a Halley-type comet and its last perihelion was in early January 2008. Our observations were carried out on January 28 and February 4 using CRIRES (CRyogenic high-resolution InfraRed Echelle Spectrograph) at the Very Large Telescope (VLT). We used a 0.2" slit which provided a spectral resolving power of 80,000. We detected H[SUB]2[/SUB]O, OH, HCN, C[SUB]2[/SUB]H[SUB]2[/SUB] on Jan 28, and H[SUB]2[/SUB]O, OH, CH[SUB]4[/SUB], C[SUB]2[/SUB]H[SUB]6[/SUB], and CH[SUB]3[/SUB]OH on Feb 4. We find that 8P/Tuttle is depleted in HCN, C[SUB]2[/SUB]H[SUB]2[/SUB] and C[SUB]2[/SUB]H[SUB]6[/SUB] relative to H[SUB]2[/SUB]O compared with most other Oort cloud comets studied to date. Perhaps these depletions suggest that 8P/Tuttle formed in a different region from most Oort cloud comets, but it is also possible that the depletions are caused by repeated passages through the inner solar system. [less ▲]

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See detailAnomalous 14N/15N ratio in comets 122P/1995 S1 (de Vico) and 153P/2002 C1 (Ikeya-Zhang)
Arpigny, Claude ULg; Cochran, A. L.; Jehin, Emmanuel ULg et al

in Bulletin of the American Astronomical Society (2003, May 01), 35

High-resolution (R 60,000) spectra of the Halley-type comet 122P/1995 S1 de Vico (Period 74 years) and the ``intermediate-period" comet 153P/2002 C1 Ikeya-Zhang (P 370 yr) were obtained with the 2DCoude ... [more ▼]

High-resolution (R 60,000) spectra of the Halley-type comet 122P/1995 S1 de Vico (Period 74 years) and the ``intermediate-period" comet 153P/2002 C1 Ikeya-Zhang (P 370 yr) were obtained with the 2DCoude spectrograph at the 2.7-m Harlan J. Smith telescope of the McDonald Observatory. These comets were within 1 AU from the Sun (0.66 and 0.92 AU, respectively). The spectra display CN (0,0) bands indicating an anomalous [SUP]14[/SUP]N/[SUP]15[/SUP]N isotope ratio, in the sense that it is close to half the value in Earth's atmosphere (the so-called ``Solar system value") and about half that obtained in comet Hale-Bopp from sub-millimeter measurements on HCN, generally believed to be the main parent of CN. Similar conclusions had been reached for C/1995 O1 (Hale-Bopp), an ``old long-period", and for C/2000 WM1 (LINEAR), a ``young long-period" comet. As suggested by Arpigny et al. (2003), this apparent abundance anomaly points towards the existence of other unknown parent(s) of CN, with an even higher [SUP]15[/SUP]N excess. Organic compounds like those found in interplanetary dust particles (IDPs) are good candidates. The similarity between comets of different dynamical ages is pointed out. 1 Research Director FNRS (Belgium) 2 Research Associate FNRS (Belgium) [less ▲]

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