Query Results from the ADS Database Retrieved 51 abstracts, starting with number 1. Total number selected: 26417. TY - Journal T1 - Characterization of preserved primitive fine-grained material from the Jupiter family comet 81P/Wild 2 -- A new link between comets and CP-IDPs A1 - Stodolna, Julien A1 - Gainsforth, Zack A1 - Butterworth, Anna L. A1 - Westphal, Andrew J. JO - Earth and Planetary Science Letters VL - 388 Y1 - 2014/2/1 SP - 367 EP - 373 UR - http://adsabs.harvard.edu/abs/2014E%26PSL.388..367S N2 - We report the presence of preserved primitive fine-grained material containing an enstatite whisker with the crystallographic characteristics of a primary condensate in a sample of the Jupiter-family comet Wild 2, returned to earth by NASA's Stardust mission. The preserved primitive material is composed of silica-rich amorphous material embedded with iron sulfides and silicates. It is in close association with a type II chondrule-like object in the track C2052,2,74 (Ogliore et al., 2012). The close association of a chondrule and a primary condensate shows they must have formed in different environments and probably met in the comet-forming region. The first observation of an enstatite whisker with properties indicating primary condensation in a comet is a new link between comets and Chondritic Porous IDPs (CP-IDPs). DO - 10.1016/j.epsl.2013.12.018 SN - 0012-821X ER - TY - Journal T1 - Comet 1P/Halley Multifluid MHD Model for the Giotto Fly-by A1 - Rubin, M. A1 - Combi, M. R. A1 - Daldorff, L. K. S. A1 - Gombosi, T. I. A1 - Hansen, K. C. A1 - Shou, Y. A1 - Tenishev, V. M. A1 - Tóth, G. A1 - van der Holst, B. A1 - Altwegg, K. JO - The Astrophysical Journal VL - 781 Y1 - 2014/2/1 SP - 86 KW - comets: individual: Halley/ magnetohydrodynamics: MHD/ methods: numerical/ plasmas/ solar wind UR - http://adsabs.harvard.edu/abs/2014ApJ...781...86R N2 - The interaction of comets with the solar wind has been the focus of many studies including numerical modeling. We compare the results of our multifluid MHD simulation of comet 1P/Halley to data obtained during the flyby of the European Space Agency's Giotto spacecraft in 1986. The model solves the full set of MHD equations for the individual fluids representing the solar wind protons, the cometary light and heavy ions, and the electrons. The mass loading, charge-exchange, dissociative ion-electron recombination, and collisional interactions between the fluids are taken into account. The computational domain spans over several million kilometers, and the close vicinity of the comet is resolved to the details of the magnetic cavity. The model is validated by comparison to the corresponding Giotto observations obtained by the Ion Mass Spectrometer, the Neutral Mass Spectrometer, the Giotto magnetometer experiment, and the Johnstone Plasma Analyzer instrument. The model shows the formation of the bow shock, the ion pile-up, and the diamagnetic cavity and is able to reproduce the observed temperature differences between the pick-up ion populations and the solar wind protons. We give an overview of the global interaction of the comet with the solar wind and then show the effects of the Lorentz force interaction between the different plasma populations. DO - 10.1088/0004-637X/781/2/86 SN - 0004-637X ER - TY - Journal T1 - Far-ultraviolet Observations of Comet C/2001 Q4 (NEAT) with FIMS/SPEAR A1 - Lim, Y.-M. A1 - Min, K.-W. A1 - Feldman, P. D. A1 - Han, W. A1 - Edelstein, J. JO - The Astrophysical Journal VL - 781 Y1 - 2014/2/1 SP - 80 KW - comets: individual: C/2001 Q4/ ultraviolet: planetary systems UR - http://adsabs.harvard.edu/abs/2014ApJ...781...80L N2 - We present the results of far-ultraviolet observations of comet C/2001 Q4 (NEAT) that were made with the Far-Ultraviolet Imaging Spectrograph on board the Korean satellite STSAT-1. The observations were conducted in two campaigns during its perihelion approach between 2004 May 8 and 15. Based on the scanning mode observations in the wavelength band of 1400-1700 Å, we have constructed an image of the comet with an angular size of 5°×5°, which corresponds to the central coma region. Several important fluorescence emission lines were detected including S I multiplets at 1429 and 1479 Å, C I multiplets at 1561 and 1657 Å, and the CO A1Pi-X1Sigma+ Fourth Positive system; we have estimated the production rates of the corresponding species from the fluxes of these emission lines. The estimated production rate of CO was Q CO = (2.65 ± 0.63) × 1028 s--1, which is 6.2%-7.4% of the water production rate and is consistent with earlier predictions. The average carbon production rate was estimated to be QC = ~1.59 × 1028 s--1, which is ~60% of the CO production rate. However, the observed carbon profile was steeper than that predicted using the two-component Haser model in the inner coma region, while it was consistent with the model in the outer region. The average sulfur production rate was QS = (4.03±1.03) × 1027 s--1, which corresponds to ~1% of the water production rate. DO - 10.1088/0004-637X/781/2/80 SN - 0004-637X ER - TY - Journal T1 - Meteor showers on Earth from sungrazing comets A1 - Sekhar, A. A1 - Asher, D. J. JO - Monthly Notices of the Royal Astronomical Society VL - 437 Y1 - 2014/1/1 SP - L71 EP - L75 KW - celestial mechanics/ comets: general/ comets: individual: C/2012 S1 (ISON)/ comets: individual: C/1680 V1 (Newton's comet)/ meteorites/ meteors/ meteoroids UR - http://adsabs.harvard.edu/abs/2014MNRAS.437L..71S N2 - Sungrazing comets have always captured a lot of interest and curiosity among the general public as well as scientists since ancient times. The perihelion passage of comet C/2012 S1 (ISON) at the end of this year (on 2013 November 28) is an eagerly awaited event. In this work, we do a mathematical study to check whether meteoroids ejected from this comet during its journey around the Sun can produce spectacular meteor phenomena on Earth. Our calculations show that although the orbital elements of this comet are much more favourable than for most sungrazers to have its descending node near the Earth's orbit, even ejection velocities as high as 1 km s-1 do not induce sufficient nodal dispersion to bring meteoroids to Earth intersection during present times. A similar result applies to Newton's comet C/1680 V1 which has surprisingly similar orbital elements, although it is known to be a distinct comet from C/2012 S1. Our analysis also shows that for meteoroids ejected from all known sungrazing groups during recent epochs, only the Marsden family (with required ejection velocities of some hundreds of m s-1) can produce meteor phenomena during present times. In a broader sense, we indicate why we do not observe visually brilliant meteor showers from frequently observed sungrazers. DO - 10.1093/mnrasl/slt143 C1 - eprint: arXiv:1310.3171 SN - 0035-8711 ER - TY - Journal T1 - Resonant behavior of comet Halley and the Orionid stream A1 - Sekhar, A. A1 - Asher, D. J. JO - Meteoritics and Planetary Science VL - 49 Y1 - 2014/1/1 SP - 52 EP - 62 UR - http://adsabs.harvard.edu/abs/2014M%26PS...49...52S N2 - Comet 1P/Halley has the unique distinction of having a very comprehensive set of observational records for almost every perihelion passage from 240 B.C. This has helped to constrain theoretical models pertaining to its orbital evolution. Many previous works have shown the active role of mean motion resonances (MMR) in the evolution of various meteoroid streams. Here, we look at how various resonances, especially the 1:6 and 2:13 MMR with Jupiter, affect comet 1P/Halley and thereby enhance the chances of meteoroid particles getting trapped in resonance, leading to meteor outbursts in some particular years. Comet Halley itself librated in the 2:13 resonance from 240 B.C. to 1700 A.D. and in the 1:6 resonance from 1404 B.C. to 690 B.C., while stream particles can survive for time scales of the order of 10,000 yr and 1,000 yr in the 1:6 and 2:13 resonances, respectively. This determines the long-term dynamical evolution and stream structure, influencing the occurrence of Orionid outbursts. Specifically, we are able to correlate the occurrence of enhanced meteor phenomena seen between 1436-1440, 1933-1938, and 2006-2010 with the 1:6 resonance and meteor outbursts in 1916 and 1993 with the 2:13 resonance. Ancient as well as modern observational records agree with these theoretical simulations to a very good degree. DO - 10.1111/maps.12117 C1 - eprint: arXiv:1303.2928 SN - 1086-9379 ER - TY - Journal T1 - Dust production of comet 21P/Giacobini-Zinner using broadband photometry A1 - Blaauw, Rhiannon C. A1 - Suggs, Robert M. A1 - Cooke, William J. JO - Meteoritics and Planetary Science VL - 49 Y1 - 2014/1/1 SP - 45 EP - 51 UR - http://adsabs.harvard.edu/abs/2014M%26PS...49...45B N2 - Presented here are results from photometric analysis on broadband images taken of comet 21P/Giacobini-Zinner from May 24, 2011 to October 24, 2011. As the parent body of the Draconids, a meteor shower known for outbursting, 21P was studied for its dust production activity, Afrho, focusing on how it changes with heliocentric distance. An expected increase in dust production with a decrease in heliocentric distance was observed. The comet went from heliocentric distance of 3.05 -1.77 AU during the observed time that corresponded to an apparent magnitude of 19.61 to 15.72 and Afrho of 16.48 cm to 284.17 cm. These values can be extrapolated to estimate a peak Afrho value at perihelion of 3824 cm. The images were obtained using a 0.5-meter f/8.1 Ritchey-Chrétien telescope located in Mayhill, New Mexico. DO - 10.1111/maps.12115 SN - 1086-9379 ER - TY - Journal T1 - Dust coma of comet C/2009 P1 (Garradd) by imaging polarimetry A1 - Hadamcik, E. A1 - Sen, A. K. A1 - Levasseur-Regourd, A. C. A1 - Roy Choudhury, S. A1 - Lasue, J. A1 - Gupta, R. A1 - Botet, R. JO - Meteoritics and Planetary Science VL - 49 Y1 - 2014/1/1 SP - 36 EP - 44 UR - http://adsabs.harvard.edu/abs/2014M%26PS...49...36H N2 - Comet C/2009 P1 (Garradd) was observed by imaging polarimetry for nearly 5 months from October 2011 to March 2012, over an intermediate phase angle range (28°-35°). Two months before perihelion and one month after, dust particles seem to be ejected all around the optocenter and jets extend to distances greater than 40,000 km. An increase of activity is noticed in intensity and polarization after perihelion. Two months before perihelion and one month after, the dust emission seems to be all around the optocenter. Two and three months after perihelion the jets are mainly toward the solar direction with an extension of more than 20,000 km projected on the sky. The values of the aperture polarization are comparable to those of other comets. On the polarization maps in October 2011 and January 2012 the higher polarization zones extend in large regions perpendicularly to the solar direction where jets are also observed. In February and March 2012, the polarization in the jets is larger in the solar direction than in the surrounding coma. By its activity visible on intensity images and polarization maps at large distances from the nucleus, comet Garradd probably belongs to the high-Pmax class of comets. DO - 10.1111/maps.12114 SN - 1086-9379 ER - TY - Journal T1 - Negative ion chemistry in the coma of comet 1P/Halley A1 - Cordiner, M. A. A1 - Charnley, S. B. JO - Meteoritics and Planetary Science VL - 49 Y1 - 2014/1/1 SP - 21 EP - 27 UR - http://adsabs.harvard.edu/abs/2014M%26PS...49...21C N2 - Negative ions (anions) were identified in the coma of comet 1P/Halley during in situ Electron Electrostatic Analyzer measurements performed by the Giotto spacecraft in 1986. These anions were detected with masses in the range 7-110 amu, but with insufficient mass resolution to permit unambiguous identification. We present details of a new chemical-hydrodynamic model for the coma of comet Halley that includes---for the first time---atomic and molecular anions, in addition to a comprehensive hydrocarbon chemistry. Anion number densities are calculated as a function of radius in the coma, and compared with the Giotto results. Important anion production mechanisms are found to include radiative electron attachment, polar photodissociation, dissociative electron attachment, and proton transfer. The polyyne anions C4H- and C6H- are found to be likely candidates to explain the Giotto anion mass spectrum in the range 49-73 amu. The CN- anion probably makes a significant contribution to the mass spectrum at 26 amu. Larger carbon-chain anions such as C8H- can explain the peak near 100 amu provided there is a source of large carbon-chain-bearing molecules from the cometary nucleus. DO - 10.1111/maps.12082 SN - 1086-9379 ER - TY - Journal T1 - The Oort Cloud and long-period comets A1 - Rickman, Hans JO - Meteoritics and Planetary Science VL - 49 Y1 - 2014/1/1 SP - 8 EP - 20 UR - http://adsabs.harvard.edu/abs/2014M%26PS...49....8R N2 - This review starts with a brief historical overview of the subject, after which some recent papers attempting to improve the understanding of comet injection from the Oort Cloud and the origin of new comets are discussed. Special attention is paid to the importance of nongravitational effects in comet orbit determination, the synergy between stellar encounters and the galactic tides for the injection dynamics, and the role of planetary perturbations. The field is thus shown to be advancing rapidly, and brief comments on possible implications for studying the origin of the cloud are made. DO - 10.1111/maps.12080 SN - 1086-9379 ER - TY - Journal T1 - Gas and dust productions of Comet 103P/Hartley 2 from millimetre observations: Interpreting rotation-induced time variations A1 - Boissier, Jérémie A1 - Bockelée-Morvan, Dominique A1 - Biver, Nicolas A1 - Colom, Pierre A1 - Crovisier, Jacques A1 - Moreno, Raphael A1 - Zakharov, Vladimir A1 - Groussin, Olivier A1 - Jorda, Laurent A1 - Lis, Darek C. JO - Icarus VL - 228 Y1 - 2014/1/1 SP - 197 EP - 216 UR - http://adsabs.harvard.edu/abs/2014Icar..228..197B N2 - Comet 103P/Hartley 2 made a close approach to the Earth in October 2010. It was the target of an extensive observing campaign including ground- and orbit-based observatories and was visited by the Deep Impact spacecraft in the framework of its mission extension EPOXI. We present observations of HCN and CH3OH emission lines conducted with the IRAM Plateau de Bure interferometer on 22--23, 28 October and 4, 5 November 2010 at 1.1, 1.9 and 3.4 mm wavelengths. The thermal emission from the dust coma and nucleus is detected simultaneously. Interferometric images with unprecedented spatial resolution of Ëœ100 to Ëœ500 km are obtained. A sine--wave like variation of the thermal continuum is observed in the 23 October data, that we associate with the nucleus thermal light curve. The nucleus contributes up to 30--55% of the observed continuum emission. The dust thermal emission is used to measure the dust production rate. The inferred large dust-to-gas ratio (in the range 2--6) can be explained by the unusual activity of the comet for its size, which allows decimeter size particles and large boulders to be entrained by the gas due to the small nucleus gravity. The rotational temperature of CH3OH is measured with beam radii from Ëœ150 km to Ëœ1500 km. We attribute the increase from Ëœ35 K to Ëœ46 K with increasing beam size to radiative processes. The HCN production rate displays strong rotation-induced temporal variations, varying from Ëœ0.3 × 1025 s-1 to Ëœ2.0 × 1025 s-1 in the 4--5 November period. The HCN production curve, as well as the CO2 and H2O production curves measured by EPOXI, are interpreted with a geometric model which takes into account the complex rotational state of 103P/Hartley 2 and its shape. The HCN and H2O production curves are in phase, showing that these molecules have common sources. The Ëœ1.7 h delay, in average, of the HCN and H2O production curves with respect to the CO2 production curve suggests that HCN and H2O are mainly produced by subliming icy grains. The scale length of production of HCN is determined to be on the order of 500--1000 km, implying a mean velocity of 100--200 m s-1 for the icy grains producing HCN. From the time evolution of the insolation of the nucleus, we show that the CO2 production is modulated by the insolation of the small lobe of the nucleus. The three-cycle pattern of the production curves reported earlier is best explained by an overactivity of the small lobe in the longitude range 0--180°. The good correlation between the insolation of the small lobe and CO2 production is consistent with CO2 being produced from small depths below the surface. The time evolution of the velocity offset of the HCN lines, as well as the displacement of the HCN photocenter in the interferometric maps, are overall consistent with this interpretation. Other localized sources of gas on the nucleus surface are also suggested. DO - 10.1016/j.icarus.2013.10.010 C1 - eprint: arXiv:1310.2600 SN - 0019-1035 ER - TY - Journal T1 - Pre- and post-perihelion observations of C/2009 P1 (Garradd): Evidence for an oxygen-rich heritage? A1 - DiSanti, Michael A. A1 - Villanueva, Geronimo L. A1 - Paganini, Lucas A1 - Bonev, Boncho P. A1 - Keane, Jacqueline V. A1 - Meech, Karen J. A1 - Mumma, Michael J. JO - Icarus VL - 228 Y1 - 2014/1/1 SP - 167 EP - 180 UR - http://adsabs.harvard.edu/abs/2014Icar..228..167D N2 - We conducted pre- and post-perihelion observations of Comet C/2009 P1 (Garradd) on UT 2011 October 13 and 2012 January 8, at heliocentric distances of 1.83 and 1.57 AU, respectively, using the high-resolution infrared spectrometer (NIRSPEC) at the Keck II 10-m telescope on Mauna Kea, HI. Pre-perihelion, we obtained production rates for nine primary volatiles (native ices): H2O, CO, CH3OH, CH4, C2H6, HCN, C2H2, H2CO, and NH3. Post-perihelion, we obtained production rates for three of these (H2O, CH4, and HCN) and sensitive upper limits for three others (C2H2, H2CO, and NH3). CO was enriched and C2H2 was depleted, yet C2H6 and CH3OH were close to their current mean values as measured in a dominant group of Oort cloud comets. This may indicate processing of its pre-cometary ices in a relatively oxygen-rich environment. DO - 10.1016/j.icarus.2013.09.001 SN - 0019-1035 ER - TY - Journal T1 - Photometry of Comet C/2011 L4 (PANSTARRS) at 4.4--4.2 AU heliocentric distances A1 - Ivanova, Oleksandra A1 - Borysenko, Serhii A1 - Golovin, Alex JO - Icarus VL - 227 Y1 - 2014/1/1 SP - 202 EP - 205 UR - http://adsabs.harvard.edu/abs/2014Icar..227..202I N2 - We present an analysis of the photometric data of Comet C/2011 L4 (PANSTARRS) observed at heliocentric distance of 4.4--4.2 AU. The Comet C/2011 L4 (PANSTARRS) shows one significant activity, despite of its quite large heliocentric distance. The color indexes, dust mass-loss rates and radius of the comet are measured. DO - 10.1016/j.icarus.2013.08.026 SN - 0019-1035 ER - TY - Journal T1 - Probing Oort Cloud and Local Interstellar Medium Properties via Dust Produced in Cometary Collisions A1 - Howe, Alex R. A1 - Rafikov, Roman R. JO - The Astrophysical Journal VL - 781 Y1 - 2014/1/1 SP - 52 KW - celestial mechanics/ comets: general/ ISM: general/ Oort Cloud UR - http://adsabs.harvard.edu/abs/2014ApJ...781...52H N2 - The Oort cloud remains one of the most poorly explored regions of the solar system. We propose that its properties can be constrained by studying a population of dust grains produced in collisions of comets in the outer solar system. We explore the dynamics of mum-sized grains outside the heliosphere (beyond ~250 AU), which are predominantly affected by the magnetic field of the interstellar medium (ISM) flow past the Sun. We derive analytic models for the production and motion of small particles as a function of their birth location in the cloud and calculate the particle flux and velocity distribution in the inner solar system. These models are verified by direct numerical simulations. We show that grains originating in the Oort cloud have a unique distribution of arrival directions, which should easily distinguish them from both interplanetary and interstellar dust populations. We also demonstrate that the distribution of particle arrival velocities is uniquely determined by the mass distribution and dust production rate in the cloud. Cometary collisions within the cloud produce a flux of mum-sized grains in the inner solar system of up to several m--2 yr--1. The next generation dust detectors may be sensitive enough to detect and constrain this dust population, which will illuminate the Oort cloud's properties. We also show that the recently detected mysterious population of large (mum-sized) unbound particles, which seems to arrive with the ISM flow, is unlikely to be generated by collisions of comets in the Oort cloud. DO - 10.1088/0004-637X/781/1/52 C1 - eprint: arXiv:1310.2933 SN - 0004-637X ER - TY - Journal T1 - Hubble Space Telescope Pre-perihelion ACS/WFC Imaging Polarimetry of Comet Ison (c/2012 s1) at 3.81 AU A1 - Hines, Dean C. A1 - Videen, Gorden A1 - Zubko, Evgenij A1 - Muinonen, Karri A1 - Shkuratov, Yuriy A1 - Kaydash, Vadim G. A1 - Knight, Matthew M. A1 - Sitko, Michael L. A1 - Lisse, Carey M. A1 - Mutchler, Max A1 - Hammer, Derek A1 - Yanamandra-Fisher, Padmavati A. JO - The Astrophysical Journal Letters VL - 780 Y1 - 2014/1/1 SP - L32 KW - comets: general/ comets: individual: C/2012 S1 (ISON)/ instrumentation: polarimeters/ techniques: polarimetric UR - http://adsabs.harvard.edu/abs/2014ApJ...780L..32H N2 - We present polarization images of Comet ISON (C/2012 S1) taken with the Hubble Space Telescope (HST) on UTC 2013 May 8 (r h = 3.81 AU, Delta = 4.34 AU), when the phase angle was alpha ≈ 12.°16. This phase angle is approximately centered in the negative polarization branch for cometary dust. The region beyond 1000 km (~0.32 arcsec ≈ 6 pixels) from the nucleus shows a negative polarization amplitude of p% ~ --1.6%. Within 1000 km of the nucleus, the polarization position angle rotates to be approximately perpendicular to the scattering plane, with an amplitude p% ~ +2.5%. Such positive polarization has been observed previously as a characteristic feature of cometary jets, and we show that Comet ISON does indeed harbor a jet-like feature. These HST observations of Comet ISON represent the first visible light, imaging polarimetry with subarcsecond spatial resolution of a Nearly Isotropic Comet beyond 3.8 AU from the Sun at a small phase angle. The observations provide an early glimpse of the properties of the cometary dust preserved in this Oort-Cloud comet. DO - 10.1088/2041-8205/780/2/L32 C1 - eprint: arXiv:1311.4896 SN - 0004-637X ER - TY - Journal T1 - Toward a Unique Nitrogen Isotopic Ratio in Cometary Ices A1 - Rousselot, Philippe A1 - Pirali, Olivier A1 - Jehin, Emmanuël A1 - Vervloet, Michel A1 - Hutsemékers, Damien A1 - Manfroid, Jean A1 - Cordier, Daniel A1 - Martin-Drumel, Marie-Aline A1 - Gruet, Sébastien A1 - Arpigny, Claude A1 - Decock, Alice A1 - Mousis, Olivier JO - The Astrophysical Journal Letters VL - 780 Y1 - 2014/1/1 SP - L17 KW - comets: general/ line: identification/ molecular data/ techniques: spectroscopic UR - http://adsabs.harvard.edu/abs/2014ApJ...780L..17R N2 - Determination of the nitrogen isotopic ratios in different bodies of the solar system provides important information regarding the solar system's origin. We unambiguously identified emission lines in comets due to the 15NH2 radical produced by the photodissociation of 15NH3. Analysis of our data has permitted us to measure the 14N/15N isotopic ratio in comets for a molecule carrying the amine (-NH) functional group. This ratio, within the error, appears similar to that measured in comets in the HCN molecule and the CN radical, and lower than the protosolar value, suggesting that N2 and NH3 result from the separation of nitrogen into two distinct reservoirs in the solar nebula. This ratio also appears similar to that measured in Titan's atmospheric N2, supporting the hypothesis that, if the latter is representative of its primordial value in NH3, these bodies were assembled from building blocks sharing a common formation location. DO - 10.1088/2041-8205/780/2/L17 SN - 0004-637X ER - TY - Journal T1 - Analysis of Asteroid (216) Kleopatra Using Dynamical and Structural Constraints A1 - Hirabayashi, Masatoshi A1 - Scheeres, Daniel J. JO - The Astrophysical Journal VL - 780 Y1 - 2014/1/1 SP - 160 KW - celestial mechanics/ comets: general/ methods: analytical/ methods: numerical/ minor planets/ asteroids: general/ minor planets/ asteroids: individual: 216 Kleopatra UR - http://adsabs.harvard.edu/abs/2014ApJ...780..160H N2 - This paper evaluates a dynamically and structurally stable size for Asteroid (216) Kleopatra. In particular, we investigate two different failure modes: material shedding from the surface and structural failure of the internal body. We construct zero-velocity curves in the vicinity of this asteroid to determine surface shedding, while we utilize a limit analysis to calculate the lower and upper bounds of structural failure under the zero-cohesion assumption. Surface shedding does not occur at the current spin period (5.385 hr) and cannot directly initiate the formation of the satellites. On the other hand, this body may be close to structural failure; in particular, the neck may be situated near a plastic state. In addition, the neck's sensitivity to structural failure changes as the body size varies. We conclude that plastic deformation has probably occurred around the neck part in the past. If the true size of this body is established through additional measurements, this method will provide strong constraints on the current friction angle for the body. DO - 10.1088/0004-637X/780/2/160 C1 - eprint: arXiv:1312.4976 SN - 0004-637X ER - TY - Journal T1 - Uncorrelated Volatile Behavior during the 2011 Apparition of Comet C/2009 P1 Garradd A1 - Feaga, Lori M. A1 - A'Hearn, Michael F. A1 - Farnham, Tony L. A1 - Bodewits, Dennis A1 - Sunshine, Jessica M. A1 - Gersch, Alan M. A1 - Protopapa, Silvia A1 - Yang, Bin A1 - Drahus, Michal A1 - Schleicher, David G. JO - The Astronomical Journal VL - 147 Y1 - 2014/1/1 SP - 24 KW - comets: general/ comets: individual: C/2009 P1 Garradd/ infrared: planetary systems/ techniques: spectroscopic UR - http://adsabs.harvard.edu/abs/2014AJ....147...24F N2 - The High Resolution Instrument Infrared Spectrometer (HRI-IR) on board the Deep Impact Flyby spacecraft detected H2O, CO2, and CO in the coma of the dynamically young Oort Cloud comet C/2009 P1 (Garradd) post-perihelion at a heliocentric distance of 2 AU. Production rates were derived for the parent volatiles, Q H2O = 4.6 ± 0.8 × 1028, Q CO2 = 3.9 ± 0.7 × 1027, and Q CO = 2.9 ± 0.8 × 1028 molecules s--1, and are consistent with the trends seen by other observers and within the error bars of measurements acquired during a similar time period. When compiled with other observations of Garradd's dominant volatiles, unexpected behavior was seen in the release of CO. Garradd's H2O outgassing, increasing and peaking pre-perihelion and then steadily decreasing, is more typical than that of CO, which monotonically increased throughout the entire apparition. Due to the temporal asymmetry in volatile release, Garradd exhibited the highest CO to H2O abundance ratio ever observed for any comet inside the water snow line at ~60% during the HRI-IR observations. Also, the HRI-IR made the only direct measurement of CO2, giving a typical cometary abundance ratio of CO2 to H2O of 8% but, with only one measurement, no sense of how it varied with orbital position. DO - 10.1088/0004-6256/147/1/24 C1 - eprint: arXiv:1311.4802 SN - 0004-6256 ER - TY - Journal T1 - The Unexpectedly Bright Comet C/2012 F6 (Lemmon) Unveiled at Near-infrared Wavelengths A1 - Paganini, Lucas A1 - DiSanti, Michael A. A1 - Mumma, Michael J. A1 - Villanueva, Geronimo L. A1 - Bonev, Boncho P. A1 - Keane, Jacqueline V. A1 - Gibb, Erika L. A1 - Boehnhardt, Hermann A1 - Meech, Karen J. JO - The Astronomical Journal VL - 147 Y1 - 2014/1/1 SP - 15 KW - astrochemistry/ comets: general/ comets: individual: C/2012 F6 (Lemmon)/ molecular processes/ Oort Cloud/ planets and satellites: formation UR - http://adsabs.harvard.edu/abs/2014AJ....147...15P N2 - We acquired near-infrared spectra of the Oort cloud comet C/2012 F6 (Lemmon) at three different heliocentric distances (R h) during the comet's 2013 perihelion passage, providing a comprehensive measure of the outgassing behavior of parent volatiles and cosmogonic indicators. Our observations were performed pre-perihelion at R h = 1.2 AU with CRIRES (on 2013 February 2 and 4), and post-perihelion at R h = 0.75 AU with CSHELL (on March 31 and April 1) and R h = 1.74 AU with NIRSPEC (on June 20). We detected 10 volatile species (H2O, OH* prompt emission, C2H6, CH3OH, H2CO, HCN, CO, CH4, NH3, and NH2), and obtained upper limits for two others (C2H2 and HDO). One-dimensional spatial profiles displayed different distributions for some volatiles, confirming either the existence of polar and apolar ices, or of chemically distinct active vents in the nucleus. The ortho-para ratio for water was 3.31 ± 0.33 (weighted mean of CRIRES and NIRSPEC results), implying a spin temperature >37 K at the 95% confidence limit. Our (3sigma) upper limit for HDO corresponds to D/H < 2.45 × 10--3 (i.e., <16 Vienna Standard Mean Ocean Water, VSMOW). At R h = 1.2 AU (CRIRES), the production rate for water was Q(H2O) = 1.9 ± 0.1 × 1029 s--1 and its rotational temperature was T rot ~ 69 K. At R h = 0.75 AU (CSHELL), we measured Q(H2O) = 4.6 ± 0.6 × 1029 s--1 and T rot = 80 K on March 31, and 6.6 ± 0.9 × 1029 s--1 and T rot = 100 K on April 1. At R h = 1.74 AU (NIRSPEC), we obtained Q(H2O) = 1.1 ± 0.1 × 1029 s--1 and T rot ~ 50 K. The measured volatile abundance ratios classify comet C/2012 F6 as rather depleted in C2H6 and CH3OH, while HCN, CH4, and CO displayed abundances close to their median values found among comets. H2CO was the only volatile showing a relative enhancement. The relative paucity of C2H6 and CH3OH (with respect to H2O) suggests formation within warm regions of the nebula. However, the normal abundance of HCN and hypervolatiles CH4 and CO, and the enhancement of H2CO, may indicate a possible heterogeneous nucleus of comet C/2012 F6 (Lemmon), possibly as a result of radial mixing within the protoplanetary disk. Based on observations obtained at the European Southern Observatory at Cerro Paranal, Chile, under program 290.C-5016, at the NASA's Infrared Telescope Facility, program 2013A_071, and Keck Observatory, program H233NS, at Mauna Kea, Hawaii. DO - 10.1088/0004-6256/147/1/15 SN - 0004-6256 ER - TY - Journal T1 - Observational results for eight long-period comets observed far from the Sun A1 - Mazzotta Epifani, E. A1 - Perna, D. A1 - Di Fabrizio, L. A1 - Dall'Ora, M. A1 - Palumbo, P. A1 - Snodgrass, C. A1 - Licandro, J. A1 - Della Corte, V. A1 - Tozzi, G. P. JO - Astronomy and Astrophysics VL - 561 Y1 - 2014/1/1 SP - 6 KW - comets: general UR - http://adsabs.harvard.edu/abs/2014A%26A...561A...6M N2 - Context. With this work we start a systematic analysis of the distant activity of several long-period comets in order to investigate the evolution of activity throughout the solar system and explore differences between comets that pass their perihelion at far or very close distances from the Sun.
Aims: We present observational data for eight long-period comets, observed for the first time beyond r = 5 AU. Three targets have been characterised on their inward orbital branch. The others have passed their perihelion at quite large heliocentric distances (rq from 4.5 to 7.5 AU).
Methods: We analyse multicolour broadband images (V,R, and I filters) taken at the Telescopio Nazionale Galileo to characterise the dust coma of the comets and investigate their morphology, photometry, colours, and dust production.
Results: The morphological analysis shows many differences among the sample, from the large twisted structure present in the coma of comet C/2005 L3 to the regular coma envelope of C/2010 R1. The colour of the dust coma of all the comets is redder than the Sun. The Afrho value (measured in a reference aperture of radius rho = 104 km) ranges from 114 ± 2 (C/2005 S4) to 5091 ± 47 (C/2005 L3) cm, depicting a scenario of bodies from moderately to very active. This is confirmed by the first-order quantitative estimate of the dust mass-loss rate for the comets that was obtained from the photometric data: assuming a grain velocity of v = 20 m/s, the dust production rate is comparable with, or even significantly larger than, that measured for many short-period ("old") comets at much smaller heliocentric distances. Based on observations collected at the Italian Telescopio Nazionale Galileo (TNG), operated on the island of La Palma by the Centro Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. DO - 10.1051/0004-6361/201321290 SN - 0004-6361 ER - TY - Journal T1 - Operation of CONSERT aboard Rosetta during the descent of Philae A1 - Hegler, Sebastian A1 - Statz, Christoph A1 - Hahnel, Ronny A1 - Plettemeier, Dirk A1 - Herique, Alain A1 - Kofman, Wlodek JO - Planetary and Space Science VL - 89 Y1 - 2013/12/1 SP - 151 EP - 158 UR - http://adsabs.harvard.edu/abs/2013P%26SS...89..151H N2 - This paper presents a study investigating the performance of using the CONSERT instrument aboard the Rosetta spacecraft as a radar sounder during the Separation--Descent--Landing (SDL) phase of the Rosetta mission. Gathering scientifically valuable data during this phase will support CONSERT's primary target, the reconstruction of the 3D permittivity distribution within the comet 67P/Churyumov--Gerasimenko, by providing a permittivity map of the surface around the landing site. Simulation results will show the performance of the instrument, using a realistic setup including the antenna characteristics of both orbiter and landing unit as well as a realistic orbitography for the descent phase. It will be shown that operating the CONSERT instrument will indeed provide very valuable data, thereby providing tremendous aid to the experiment's main objective. Furthermore, by including knowledge of the antenna characteristics, it is possible to calculate attitude and descent profile of the Philae lander during descent, using the data of the line-of-sight propagation path and the echoes reflected from the comet's surface. DO - 10.1016/j.pss.2013.09.015 SN - 0032-0633 ER - TY - Journal T1 - Polarimetric studies of comet C/2009 P1 (Garradd) A1 - Das, H. S. A1 - Medhi, B. J. A1 - Wolf, S. A1 - Bertrang, G. A1 - Deb Roy, P. A1 - Chakraborty, A. JO - Monthly Notices of the Royal Astronomical Society VL - 436 Y1 - 2013/12/1 SP - 3500 EP - 3506 KW - polarization/ scattering/ comets: general/ dust/ extinction UR - http://adsabs.harvard.edu/abs/2013MNRAS.436.3500D N2 - We present the optical imaging polarimetric observations of comet C/2009 P1 (Garradd) at three different phase angles e.g. 28.2°, 28.1° and 21.6°. The observations were carried out using the Inter University Centre for Astronomy and Astrophysics (IUCAA) Faint Object Spectrograph and Camera mounted on Cassegrain focus of the 2 m telescope of IGO, IUCAA, Pune, in Rcomet, R photometric bands, on 2012 March 21 and 22 and Aryabhatta Research Institute of observational sciencES (ARIES) Imaging Polarimeter mounted on Cassegrain focus of the 1.04 m Sampurnanand Telescope of ARIES, Nainital, in R photometric band, on 2012 May 23. We show the presence of a jet activity in the rotational-gradient-treated image of comet Garradd at phase angle 28.1°. These jets are mainly oriented towards the Sun and extended up to Ëœ5100 km from the cometary photocentre. The antisolar extension of the jet seems to be fainter, which is extended up to Ëœ1800 km. It is found that the comet Garradd shows negative polarization at phase angle 21.6°. The degree of polarization derived for Garradd is in good agreement with other comets at nearly similar phase angles e.g. comets 67P/Churyumov-Gerasimenko, 22P/Kopff, 1P/Halley, C/1990 K1 (Levy), 4P/Faye and C/1995 O1 (Hale-Bopp) at phase angle Ëœ28°, and 47P/Ashbrook-Jackson at phase angle Ëœ21.6°, respectively. It is also found that the degree of polarization of dusty coma of comet Garradd at phase angle Ëœ28° is high but not as high as in the case of comet Hale-Bopp. DO - 10.1093/mnras/stt1827 C1 - eprint: arXiv:1309.6960 SN - 0035-8711 ER - TY - Journal T1 - Observations of Comet P/2003 T12 = 2012 A3 (SOHO) at large phase angle in STEREO-B A1 - Hui, M.-T. JO - Monthly Notices of the Royal Astronomical Society VL - 436 Y1 - 2013/12/1 SP - 1564 EP - 1575 KW - methods: data analysis/ techniques: photometric/ techniques: polarimetric/ comets: individual: P/2003 T12 = 2012 A3 (SOHO) UR - http://adsabs.harvard.edu/abs/2013MNRAS.436.1564H N2 - Comet P/2003 T12 = 2012 A3 (SOHO) was observed by the satellite STEREO-B during the period 2012 January 13-27. During its apparition, it ventured into the highest phase angle ever observed for a comet, and the forward-scattering enhancement in brightness was marked, as large as Ëœ8.5 mag. Therefore, it provided a precious opportunity to examine the compound Henyey-Greenstein (HG) comet-dust light-scattering model and it also offered valuable polarization data under an unprecedented observing geometry. Our analysis reveals that the compound HG model fits the observations very well until the phase angle exceeds Ëœ173°, where the brightness surge of the comet was obviously steeper than the prediction by the model. We have found that the reason for the greater steepness cannot be explained by contaminations from the proximal tail. Instead, the model of Mie spheres with radii greater than 1 mum, having a power-law distribution of power index Ëœ3, matches the observation very well, providing a best-fitting complex refractive index mu = 1.38 + i 0.006. The dust size was found to be consistent with the analysis of the comet's syndyne lines. The debiased polarization of the coma was Ëœ0 per cent in the phase angle range from 172.9° to 177.6°. . No convincing evidence of temporal variation of the polarization was detected. DO - 10.1093/mnras/stt1683 SN - 0035-8711 ER - TY - Journal T1 - Iron valence state of fine-grained material from the Jupiter family comet 81P/Wild 2 -- A coordinated TEM/STEM EDS/STXM study A1 - Stodolna, Julien A1 - Gainsforth, Zack A1 - Leroux, Hugues A1 - Butterworth, Anna L. A1 - Tyliszczak, Tolek A1 - Jacob, Damien A1 - Westphal, Andrew J. JO - Geochimica et Cosmochimica Acta VL - 122 Y1 - 2013/12/1 SP - 1 EP - 16 UR - http://adsabs.harvard.edu/abs/2013GeCoA.122....1S N2 - The oxidation state of transition metal elements is an indicator of the environmental conditions during formation and history of extraterrestrial materials. We studied the iron valence state of fine-grained material from a bulbous track extracted from the Stardust cometary collector. It likely originated from primitive material of the comet Wild 2. We used synchrotron-based Scanning Transmission X-ray Microscopy (STXM) to collect Fe L3-XANES spectra at a spatial resolution of about 20 nm. Maps of Fe valence state were combined with the elemental maps recorded by energy dispersive X-ray spectroscopy (EDS) with a transmission electron microscope (TEM), on the same areas and with a comparable electron probe size (5--20 nm). As for most Stardust fine-grained material, the samples are severely damaged by the hypervelocity impact in the aerogel collector blocks. They show of a wide range of oxidation state at a micrometer scale, from Fe metal to Fe3+. This heterogeneity of oxidation state can be due to the extreme conditions of the collection. Two major parameters can favor changes in redox state. The first is the high temperature regime, known to be highly heterogeneous and to have locally reached extreme values (up to 2000 K). The second is the local chemical environment. It may contain elements that could favor a reduction or oxidation reaction within the flash-heated Wild 2 fragments. Comparison of maps by STXM and EDS shows evidence for several correlation trends between element concentrations and the iron valence state. These observations, together with the study of a melted rim of a larger particle, suggest that the redox state was not completely redistributed within the impact melts. These local signatures are compatible with precursors that could have been close to primitive matrix material of chondrites or to chondritic interplanetary dust particles. On average, the fine-grained material from Wild 2 displays a molar fraction (Fe2+oxide + Fe3+oxide)/(total Fe) equal to 0.80 ± 0.10. It appears more oxidized than the average value measured for the comet, when done on larger particles (Westphal et al., 2009). This fine-grained material from Wild 2 does not seem to have sampled reducing environments in the solar nebulae in contrast with the larger particles of Wild 2. This observation confirms the high degree of diversity of materials in Wild 2 and is in good agreement with the dual distribution of high temperature minerals and matrices in carbonaceous chondrites. DO - 10.1016/j.gca.2013.08.006 SN - 0016-7037 ER -