| 1. |
- Meech, K. J., et al.
(författare)
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EPOXI: Comet 103P/Hartley 2 Observations from a Worldwide Campaign
- 2011
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Ingår i: Astrophysical Journal Letters. - London : IOP. - 2041-8213 .- 2041-8205. ; 734:L1, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- 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 2 -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.
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| 2. |
- Kueppers, Michael, et al.
(författare)
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Triple F-a comet nucleus sample return mission
- 2009
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Ingår i: Experimental astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 23:3, s. 809-847
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Tidskriftsartikel (refereegranskat)abstract
- The Triple F (Fresh From the Fridge) mission, a Comet Nucleus Sample Return, has been proposed to ESA's Cosmic Vision program. A sample return from a comet enables us to reach the ultimate goal of cometary research. Since comets are the least processed bodies in the solar system, the proposal goes far beyond cometary science topics (like the explanation of cometary activity) and delivers invaluable information about the formation of the solar system and the interstellar molecular cloud from which it formed. The proposed mission would extract three sample cores of the upper 50 cm from three locations on a cometary nucleus and return them cooled to Earth for analysis in the laboratory. The simple mission concept with a touch-and-go sampling by a single spacecraft was proposed as an M-class mission in collaboration with the Russian space agency ROSCOSMOS.
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| 3. |
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Highlights from the first year of Odin observations
- 2003
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 402, s. L39-L46
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Tidskriftsartikel (refereegranskat)abstract
- Key Odin operational and instrumental features and highlights from our sub-millimetre and millimetre wave observations of H2O, H218O, NH3, 15NH3 and O2 are presented, with some insights into accompanying Odin Letters in this A&A issue. We focus on new results where Odin's high angular resolution, high frequency resolution, large spectrometer bandwidths, high sensitivity or/and frequency tuning capability are crucial: H2O mapping of the Orion KL, W3, DR21, S140 regions, and four comets; H2O observations of Galactic Centre sources, of shock enhanced H2O towards the SNR IC443, and of the candidate infall source IRAS 16293-2422; H218O detections in Orion KL and in comet Ikeya-Zhang; sub-mm detections of NH3 in Orion KL (outflow, ambient cloud and bar) and ρ Oph, and very recently, of 15NH3 in~Orion KL. Simultaneous sensitive searches for the 119 GHz line of O2 have resulted in very low abundance limits, which are difficult to accomodate in chemical models. We also demonstrate, by means of a quantitative comparison of Orion KL H2O results, that the Odin and SWAS observational data sets are very consistently calibrated. Odin is a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes), and the Centre National d'études Spatiales (CNES, France). The Swedish Space Corporation (SSC) has been the prime industrial contractor, and is also responsible for the satellite operation from its Odin Mission Control Centre at SSC in Solna and its Odin Control Centre at ESRANGE near Kiruna in northern Sweden. See also the SNSB Odin web page: http://www.snsb.se/eng_odin_intro.shtml
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| 4. |
- Pagani, L., et al.
(författare)
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Low upper limits on the O2 abundance from the Odin satellite
- 2003
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 402, s. L77-L81
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Tidskriftsartikel (refereegranskat)abstract
- For the first time, a search has been conducted in our Galaxy for the 119 GHz transition connecting to the ground state of O2, using the Odin satellite. Equipped with a sensitive 3 mm receiver (Tsys(SSB) = 600 K), Odin has reached unprecedented upper limits on the abundance of O2, especially in cold dark clouds where the excited state levels involved in the 487 GHz transition are not expected to be significantly populated. Here we report upper limits for a dozen sources. In cold dark clouds we improve upon the published SWAS upper limits by more than an order of magnitude, reaching N(O2)/N(H2) <= 10-7 in half of the sources. While standard chemical models are definitively ruled out by these new limits, our results are compatible with several recent studies that derive lower O2 abundances. Goldsmith et al. (\cite{SWAS2002}) recently reported a SWAS tentative detection of the 487 GHz transition of O2 in an outflow wing towards rho Oph A in a combination of 7 beams covering approximately 10arcmin x 14arcmin . In a brief (1.3 hour integration time) and partial covering of the SWAS region (~65% if we exclude their central position), we did not detect the corresponding 119 GHz line. Our 3 sigma upper limit on the O2 column density is 7.3x 1015 cm-2. We presently cannot exclude the possibility that the SWAS signal lies mostly outside of the 9\arcmin Odin beam and has escaped our sensitive detector. Based on observations with Odin, a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes) and Centre National d'Études Spatiales (CNES). The Swedish Space Corporation was the industrial prime contractor and is operating Odin.
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| 5. |
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| 6. |
- Hartogh, P., et al.
(författare)
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HIFI observations of water in the atmosphere of comet C/2008 Q3 (Garradd)
- 2010
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 518:Article Number: L150
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Tidskriftsartikel (refereegranskat)abstract
- High-resolution far-infrared and sub-millimetre spectroscopy of water lines is an important tool to understand the physical and chemical properties of cometary atmospheres. We present observations of several rotational ortho- and para-water transitions in comet C/2008 Q3 (Garradd) performed with HIFI on Herschel. These observations have provided the first detection of the 2(12)-1(01) (1669 GHz) ortho and 1(11)-0(00) (1113 GHz) para transitions of water in a cometary spectrum. In addition, the ground-state transition 1(10)-1(01) at 557 GHz is detected and mapped. By detecting several water lines quasi-simultaneously and mapping their emission we can constrain the excitation parameters in the coma. Synthetic line profiles are computed using excitation models which include excitation by collisions, solar infrared radiation, and radiation trapping. We obtain the gas kinetic temperature, constrain the electron density profile, and estimate the coma expansion velocity by analyzing the map and line shapes. We derive water production rates of 1.7-2.8 x 10(28) s(-1) over the range r(h) = 1.83-1.85 AU.
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| 7. |
- Roth, Nathan X., et al.
(författare)
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Molecular Outgassing in Centaur 29P/Schwassmann-Wachmann 1 during Its Exceptional 2021 Outburst: Coordinated Multiwavelength Observations Using nFLASH at APEX and iSHELL at the NASA-IRTF
- 2023
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Ingår i: Planetary Science Journal. - 2632-3338. ; 4:9
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Tidskriftsartikel (refereegranskat)abstract
- The extraordinary 2021 September-October outburst of Centaur 29P/Schwassmann-Wachmann 1 afforded an opportunity to test the composition of primitive Kuiper disk material at high sensitivity. We conducted nearly simultaneous multiwavelength spectroscopic observations of 29P/Schwassmann-Wachmann 1 using iSHELL at the NASA Infrared Telescope Facility (IRTF) and nFLASH at the Atacama Pathfinder EXperiment (APEX) on 2021 October 6, with follow-up APEX/nFLASH observations on 2021 October 7 and 2022 April 3. This coordinated campaign between near-infrared and radio wavelengths enabled us to sample molecular emission from a wealth of coma molecules and to perform measurements that cannot be accomplished at either wavelength alone. We securely detected CO emission on all dates with both facilities, including velocity-resolved spectra of the CO (J = 2-1) transition with APEX/nFLASH and multiple CO (v = 1-0) rovibrational transitions with IRTF/iSHELL. We report rotational temperatures, coma kinematics, and production rates for CO and stringent (3σ) upper limits on abundance ratios relative to CO for CH4, C2H6, CH3OH, H2CO, CS, and OCS. Our upper limits for CS/CO and OCS/CO represent their first values in the literature for this Centaur. Upper limits for CH4, C2H6, CH3OH, and H2CO are the most stringent reported to date, and are most similar to values found in ultra CO-rich Oort cloud comet C/2016 R2 (PanSTARRS), which may have implications for how ices are preserved in cometary nuclei. We demonstrate the superb synergy of coordinated radio and near-infrared measurements, and advocate for future small-body studies that jointly leverage the capabilities of each wavelength.
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| 8. |
- Biver, N., et al.
(författare)
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Coma composition of comet 67P/Churyumov-Gerasimenko from radio-wave spectroscopy
- 2023
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 672
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Tidskriftsartikel (refereegranskat)abstract
- We present the results of a molecular survey of comet 67P/Churyumov-Gerasimenko undertaken with the Institut de RadioAstronomie Millimétrique (IRAM) 30-m radio telescope in November–December 2021, when it had its most favourable apparition in decades. Observations at IRAM 30-m during the 12–16 November period covered 8 GHz bandwidth at 3 mm, 16 GHz at 2 mm, and 60 GHz in the 1 mm window domain. These were completed by snapshots at 1 mm on 12–13 December and a short observation of the H2O line at 557 GHz with the Odin sub-millimetre observatory on 17.0 November 2021, and with 18-cm observations of OH with the Nançay radio telescope. Less sensitive observations obtained at a previous perihelion passage on 18–22 September 2015 with IRAM and 9–12 November 2015 with Odin are also presented. The gas outflow velocity, outgassing pattern, and temperature have been accurately constrained by the observations. They are perfectly consistent with those measured in situ with the Rosetta/MIRO sub-millimetre instrument in 2015. In particular, the asymmetry of the line is well represented by a jet concentrating three-quarters of the outgassing in about π steradians. We derived abundances relative to water for seven molecules and significant upper limits for approximately five others. The retrieved abundances were compared to those measured in situ at the previous perihelion with Rosetta. While those of HCN, CH3OH, and HNCO are comparable, 67P is found to be depleted in H2S and relatively normal in CS (H2S/CS ≈ 3) in strong contradiction with the Rosetta/ROSINA mass spectrometer measurement of the H2S/CS2 (≈100) abundance ratio. While the formaldehyde total abundance found with IRAM 30-m when assuming it to be mostly produced by a distributed source (Haser parent scale length ≈8000 km) is similar to the one derived by Rosetta/ROSINA, we find that the formaldehyde coming from the nucleus is one order of magnitude less abundant than measured in situ by Rosetta/ROSINA.
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| 9. |
- Biver, N., et al.
(författare)
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Isotopic ratios of H, C, N, O, and S in comets C/2012 F6 (Lemmon) and C/2014 Q2 (Lovejoy)
- 2016
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 589, s. Art. no. A78-
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Tidskriftsartikel (refereegranskat)abstract
- The apparition of bright comets C/2012 F6 (Lemmon) and C/2014 Q2 (Lovejoy) in March-April 2013 and January 2015, combined with the improved observational capabilities of submillimeter facilities, offered an opportunity to carry out sensitive compositional and isotopic studies of the volatiles in their coma. We observed comet Lovejoy with the IRAM 30 m telescope between 13 and 26 January 2015, and with the Odin submillimeter space observatory on 29 January-3 February 2015. We detected 22 molecules and several isotopologues. The (H2O)-O-16 and (H2O)-O-18 production rates measured with Odin follow a periodic pattern with a period of 0.94 days and an amplitude of similar to 25%. The inferred isotope ratios in comet Lovejoy are O-16/O-18 = 499 +/- 24 and D/H = 1.4 +/- 0.4 x 10(-4) in water, S-32/S-34 = 24.7 +/- 3.5 in CS, all compatible with terrestrial values. The ratio C-12/C-13 = 109 +/- 14 in HCN is marginally higher than terrestrial and N-14/N-15 = 145 +/- 12 in HCN is half the Earth ratio. Several upper limits for D/H or C-12/C-13 in other molecules are reported. From our observation of HDO in comet C/2014 Q2 (Lovejoy), we report the first D/H ratio in an Oort Cloud comet that is not larger than the terrestrial value. On the other hand, the observation of the same HDO line in the other Oort-cloud comet, C/2012 F6 (Lemmon), suggests a D/H value four times higher. Given the previous measurements of D/H in cometary water, this illustrates that a diversity in the D/H ratio and in the chemical composition, is present even within the same dynamical group of comets, suggesting that current dynamical groups contain comets formed at very different places or times in the early solar system.
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| 10. |
- Biver, N, et al.
(författare)
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Long-term evolution of the outgassing of comet Hale-Bopp from radio observations
- 1997
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Ingår i: EARTH MOON AND PLANETS. - : KLUWER ACADEMIC PUBL. - 0167-9295. ; 78:1-3, s. 5-11
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Tidskriftsartikel (refereegranskat)abstract
- C/1995 O1 (Hale-Bopp) has been observed on a regular basis since August 1995 at millimetre and submillimetre wavelengths using IRAM, JCMT, CSO and SEST radio telescopes. The production rates of eight molecular species (CO, HCN, CH3OH, H2CO, H2S, CS, CH3CN
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