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

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

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

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

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See detailLarge Excess of Heavy Nitrogen in Both Hydrogen Cyanide and Cyanogen from Comet 17P/Holmes
Bockelée-Morvan, D.; Biver, N.; Jehin, Emmanuel ULg et al

in Astrophysical Journal (2008), 679(Letters), 49-52

From millimeter and optical observations of the Jupiter-family comet 17P/Holmes performed soon after its huge outburst of 2007 October 24, we derive [SUP]14[/SUP]N/[SUP]15[/SUP]N = 139 +/- 26 in HCN and ... [more ▼]

From millimeter and optical observations of the Jupiter-family comet 17P/Holmes performed soon after its huge outburst of 2007 October 24, we derive [SUP]14[/SUP]N/[SUP]15[/SUP]N = 139 +/- 26 in HCN and [SUP]14[/SUP]N/[SUP]15[/SUP]N = 165 +/- 40 in CN, establishing that HCN has the same nonterrestrial isotopic composition as CN. The same conclusion is obtained for the long-period comet C/1995 O1 (Hale-Bopp) after a reanalysis of previously published measurements. These results are compatible with HCN being the prime parent of CN in cometary atmospheres. The [SUP]15[/SUP]N excess relative to the Earth's atmospheric value indicates that N-bearing volatiles in the solar nebula underwent important N isotopic fractionation at some stage of solar system formation. HCN molecules never isotopically equilibrated with the main nitrogen reservoir in the solar nebula before being incorporated in Oort Cloud and Kuiper Belt comets. The [SUP]12[/SUP]C/[SUP]13[/SUP]C ratios in HCN and CN are measured to be consistent with the terrestrial value. [less ▲]

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See detailDeep Impact: High-Resolution Optical Spectroscopy with the ESO VLT and the Keck I Telescope
Jehin, Emmanuel ULg; Manfroid, Jean ULg; Hutsemekers, Damien ULg et al

in Astrophysical Journal (2006), 641(Letters), 145-148

We report on observations of comet 9P/Tempel 1 carried out before, during, and after the NASA Deep Impact event (UT July 4), with the optical spectrometers UVES and HIRES mounted on the telescopes Kueyen ... [more ▼]

We report on observations of comet 9P/Tempel 1 carried out before, during, and after the NASA Deep Impact event (UT July 4), with the optical spectrometers UVES and HIRES mounted on the telescopes Kueyen of the ESO VLT (Chile) and Keck I on Mauna Kea (Hawaii), respectively. A total observing time of about 60 hr, distributed over 15 nights around the impact date, allowed us (1) to find a periodic variation of 1.709 +/- 0.009 days in the CN and NH flux, explained by the presence of two major active regions; (2) to derive a lifetime >~5 × 10[SUP]4[/SUP] s (at 1.5 AU) for the parent of the CN radical from a simple modeling of the CN light curve after the impact; (3) to follow the gas and dust spatial profiles' evolution during the 4 hr following the impact and derive the projected velocities (400 and 150 m s[SUP]-1[/SUP], respectively); and (4) to show that the material released by the impact has the same carbon and nitrogen isotopic composition as the surface material ([SUP]12[/SUP]C/[SUP] 13[/SUP]C = 95 +/- 15 and [SUP]14[/SUP]N/[SUP]15[/SUP]N = 145 +/- 20). [less ▲]

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See detailThe Anomalous 14N/15N Ratio in Comets 122P/1995 S1 (de Vico) and 153P/2002 C1 (Ikeya-Zhang)
Jehin, Emmanuel ULg; Manfroid, Jean ULg; Cochran, A. L. et al

in Astrophysical Journal (2004), 613(Letters), 161-164

High-resolution (R~60,000) spectra of the CN B[SUP]2[/SUP]Sigma[SUP]+[/SUP]-X[SUP]2[/SUP]Sigma[SUP]+[/SUP] (0, 0) band (near 3880 Å) in the Halley-type comet 122P/1995 S1 de Vico (with a period of 74 yr ... [more ▼]

High-resolution (R~60,000) spectra of the CN B[SUP]2[/SUP]Sigma[SUP]+[/SUP]-X[SUP]2[/SUP]Sigma[SUP]+[/SUP] (0, 0) band (near 3880 Å) in the Halley-type comet 122P/1995 S1 de Vico (with a period of 74 yr) and the ``intermediate-period'' comet 153P/2002 C1 Ikeya-Zhang (P~370 yr) were obtained with the 2dcoudé spectrograph at the 2.7 m Harlan J. Smith telescope of the McDonald Observatory. The comets were within 1 AU from the Sun (0.66 and 0.92 AU, respectively) at the time of the observations. While the measured [SUP]12[/SUP]C/[SUP]13[/SUP]C isotope ratios of both comets (90+/-10 and 90+/-25, respectively) are in very good agreement with the solar system value, the [SUP]14[/SUP]N/[SUP]15[/SUP]N ratios (140+/-20 and 170+/-50, respectively) are approximately half the value in Earth's atmosphere. The similarity is striking between these ratios and those obtained recently for two other long-period Oort Cloud comets, C/1995 O1 (Hale-Bopp) and C/2000 WM1 (LINEAR). While these optical determinations of [SUP]14[/SUP]N/[SUP]15[/SUP]N are consistent with each other, they disagree with those obtained in comet Hale-Bopp from submillimeter measurements of HCN, generally believed to be the main parent of CN. This puzzling difference points toward the existence of (an)other unknown parent(s) of CN, with an even higher [SUP]15[/SUP]N excess. Organic compounds like those found in interplanetary dust particles are good candidates. [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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See detailA fluorescence model of the C[SUB]3[/SUB] radical in comets
Rousselot, P.; Arpigny, Claude ULg; Rauer, H. et al

in Astronomy and Astrophysics (2001), 368

Theoretical resonance fluorescence calculations are presented of the triatomic C[SUB]3[/SUB] radical and are compared with observations of the C[SUB]3[/SUB] emission in comets Hale-Bopp and de Vico. A ... [more ▼]

Theoretical resonance fluorescence calculations are presented of the triatomic C[SUB]3[/SUB] radical and are compared with observations of the C[SUB]3[/SUB] emission in comets Hale-Bopp and de Vico. A theoretical model of the C[SUB]3[/SUB] vibration-rotational structure in the A[SUP]1[/SUP]Pi[SUB]u[/SUB] - X[SUP]1[/SUP]Sigma[SUB]g[/SUB] [SUP]+[/SUP] electronic system is introduced. The model takes into account the detailed structure of the bending mode nu[SUB]2[/SUB] which is responsible for the emission of the 4050 à group. A total of 1959 levels are considered, with 515 levels in the ground state. The main effort is to model high-resolution spectra of the 4050 à emission in comets C/1995 O1 Hale-Bopp and 122P/1995 S1 de Vico. The agreement between observed and theoretical spectra is good for a value of the dipole moment derivative of dmu/dr ~ 2.5 Debye à [SUP]-1[/SUP]. The modeled C[SUB]3[/SUB] emission exhibits a pronounced Swings effect. Based on observations made with William Herschel Telescope operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, and on observations made at the McDonald Observatory, which is operated by the University of Texas at Austin, USA. [less ▲]

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