<i>Herschel</i>and IRAM-30 m observations of comet C/2012 S1 (ISON) at 4.5 AU from the Sun

O’Rourke, L.; Bockelée‐Morvan, Dominique; Biver, Nicolás; Altiéri, B.; Teyssier, D.; Jordá, L.; Debout, V.; Snodgrass, C.; Küppers, M.; A’Hearn, Michael F.; Müller, Thomas; Farnham, T. L.

doi:10.1051/0004-6361/201322756

Cited by 7 publications

(7 citation statements)

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“…Combining observations of rotational emission lines and dust thermal emission provide valuable constraints on the properties of the gaseous and dust activity in comets. The Herschel Space Observatory was a unique facility for obtaining sensitive observations of water emission in comets at large heliocentric distances (e.g., Bockelée-Morvan et al 2010a;O'Rourke et al 2013a), and imaging the thermal dust coma in two channels simultaneously at far infrared wavelengths (see e.g., Paper I; Meech et al 2011).…”

Section: Discussionmentioning

confidence: 99%

“…Water emission has been detected in the distant comet 29P/Schwassmann-Wachmann 1 (Bockelée-Morvan et al 2010a). Moreover, recent attempts have been made to directly detect sublimating water using Herschel in comets C/2006 W3 (Christensen) (Bockelée-Morvan et al 2010b) and C/2012 S1 (ISON) (O'Rourke et al 2013a) at large heliocentric distances, and also in active objects orbiting within the main asteroid belt, that is, main-belt comets (MBCs; see e.g., de Val-Borro et al 2012b;O'Rourke et al 2013b).…”

Section: Introductionmentioning

confidence: 99%

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Herschelobservations of gas and dust in comet C/2006 W3 (Christensen) at 5 AU from the Sun

Bockelée‐Morvan

Jehin

Hartogh

et al. 2014

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Context. Cometary activity at large heliocentric distances is thought to be driven by outgassing of molecular species more volatile than water that are present in the nucleus. The long-period comet C/2006 W3 (Christensen) was an exceptional target for a detailed study of its distant gaseous and dust activity. Aims. We aimed to measure the H 2 O and dust production rates in C/2006 W3 (Christensen) with the Herschel Space Observatory at a heliocentric distance of ∼5 AU and compared these data with previous post-perihelion Herschel and ground-based observations at ∼3.3 AU from the Sun. Methods. We have searched for emission in the H 2 O and NH 3 ground-state rotational transitions, J Ka Kc (1 10 -1 01 ) at 557 GHz and J K (1 0 -0 0 ) at 572 GHz, simultaneously, toward comet C/2006 W3 (Christensen) with the Heterodyne Instrument for the Far Infrared (HIFI) onboard Herschel on UT 1.5 September 2010. Photometric observations of the dust coma in the 70 µm and 160 µm channels were acquired with the Photodetector Array Camera and Spectrometer (PACS) instrument on UT 26.5 August 2010. Results. A tentative 4σ H 2 O line emission feature was found in the spectra obtained with the HIFI wide-band and high-resolution spectrometers, from which we derive a water production rate of (2.0 ± 0.5) × 10 27 molec s −1 . A 3σ upper limit for the ammonia production rate of <1.5 × 10 27 molec s −1 is obtained taking into account the contribution from all hyperfine components. The dust thermal emission was detected in the 70 µm and 160 µm filters, with a more extended emission in the blue channel. We fit the radial dependence of the surface brightness with radially symmetric profiles for the blue and red bands. The dust production rates, obtained for a dust size distribution index that explains the fluxes at the photocenters of the 70 µm and 160 µm PACS images, lie in the range 70 kg s −1 to 110 kg s −1 . Scaling the CO production rate measured post-perihelion at 3.20 AU and 3.32 AU, these values correspond to a dust-to-gas production rate ratio in the range 0.3-0.4. Conclusions. The blueshift of the water line detected by HIFI suggests preferential emission from the subsolar point. However, it is also possible that water sublimation occurs in small ice-bearing grains that are emitted from an active region on the nucleus surface at a speed of ∼0.2 km s −1 . The dust production rates derived in August 2010 are roughly one order of magnitude lower than in September 2009, suggesting that the dust-to-gas production rate ratio remained approximately constant during the period when the activity became increasingly dominated by CO outgassing.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Herschelobservations of gas and dust in comet C/2006 W3 (Christensen) at 5 AU from the Sun

Bockelée‐Morvan

Jehin

Hartogh

et al. 2014

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“…It was soon determined to be a sungrazing comet with a perihelion distance of 0.01244 AU (2.7 R ) to be reached on 2013 November 28. Due to an unprecedented lead time before perihelion, ISON became the subject of a broad and global observing campaign (http://www.isoncampaign.org/) with numerous ground-and space-based observatories making observations (e.g., Meech et al 2013;O'Rourke et al 2013;Bonev et al 2014;Cordiner et al 2014;Hines et al 2014;Shinnaka et al 2014;Knight and Schleicher 2015;Schmidt et al 2015). A fortuitous route through the inner solar system took the comet relatively close to Mars and Mercury, enabling observations from planetary spacecraft operating at those planets, before passing through the fields of view of the STEREO and SOHO solar observatories.…”

Section: C/2012 S1 Isonmentioning

confidence: 99%

The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets

et al. 2017

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This review addresses our current understanding of comets that venture close to the Sun, and are hence exposed to much more extreme conditions than comets that are typically studied from Earth. The extreme solar heating and plasma environments that these objects encounter change many aspects of their behaviour, thus yielding valuable information on both the comets themselves that complements other data we have on primitive solar system bodies, as well as on the near-solar environment which they traverse. We propose clear definitions for these comets: We use the term near-Sun comets to encompass all ob- jects that pass sunward of the perihelion distance of planet Mercury (0.307 AU). Sunskirters are defined as objects that pass within 33 solar radii of the Sun's centre, equal to half of Mercury's perihelion distance, and the commonly-used phrase sungrazers to be objects that reach perihelion within 3.45 solar radii, i.e. the fluid Roche limit. Finally, comets with orbits that intersect the solar photosphere are termed sundivers. We summarize past studies of these objects, as well as the instruments and facilities used to study them, including space-based platforms that have led to a recent revolution in the quantity and quality of relevant observations. Relevant comet populations are described, including the Kreutz, Marsden, Kracht, and Meyer groups, near-Sun asteroids, and a brief discussion of their origins. The importance of light curves and the clues they provide on cometary composition are emphasized, together with what information has been gleaned about nucleus parameters, including the sizes and masses of objects and their families, and their tensile strengths. The physical processes occurring at these objects are considered in some detail, including the disruption of nuclei, sublimation, and ionisation, and we consider the mass, momentum, and energy loss of comets in the corona and those that venture to lower altitudes. The different components of comae and tails are described, including dust, neutral and ionised gases, their chemical reactions, and their contributions to the near-Sun environment. Comet-solar wind interactions are discussed, including the use of comets as probes of solar wind and coronal conditions in their vicinities. We address the relevance of work on comets near the Sun to similar objects orbiting other stars, and conclude with a discussion of future directions for the field and the planned ground-and space-based facilities that will allow us to address those science topics.

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“…Its orbital elements are consistent with a dynamically new comet, with fresh ices not previously irradiated by sunlight. A worldwide observational campaign has extensively followed this comet from heliocentric distances beyond 4 au (O'Rourke et al 2013;Li et al 2013) to disappearance around perihelion (Knight & Battams 2014). C/2013 R1 (Lovejoy)hereafter Lovejoy-was discovered in September 2013 at r h = 1.94 au by Terry Lovejoy using a 0.2-m telescope (Guido et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Molecular observations of comets C/2012 S1 (ISON) and C/2013 R1 (Lovejoy): HNC/HCN ratios and upper limits to PH₃

Agúndez¹,

Biver²,

Santos-Sanz³

et al. 2014

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We present molecular observations carried out with the IRAM 30 m telescope at wavelengths around 1.15 mm towards the Oort cloud comets C/2012 S1 (ISON) and C/2013 R1 (Lovejoy) when they were at ∼0.6 and ∼1 au, respectively, from the Sun. We detect HCN, HNC, and CH 3 OH in both comets, together with the ion HCO + in comet ISON and a few weak unidentified lines in comet Lovejoy, one of which might be assigned to methylamine (CH 3 NH 2 ). The monitoring of the HCN J = 3-2 line showed a tenfold enhancement in comet ISON on November 14.4 UT due to an outburst of activity whose exact origin is unknown, although it might be related to some break-up of the nucleus. The set of CH 3 OH lines observed was used to derive the kinetic temperature in the coma, 90 K in comet ISON and 60 K in comet Lovejoy. The HNC/HCN ratios derived, 0.18 in ISON and 0.05 in Lovejoy, are similar to those found in most previous comets and are consistent with an enhancement of HNC as the comet approaches the Sun. Phosphine (PH 3 ) was also searched for unsuccessfully in both comets through its fundamental 1 0 -0 0 transition, and 3σ upper limits corresponding to PH 3 /H 2 O ratios 4-10 times above the solar P/O elemental ratio were derived.

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Herscheland IRAM-30 m observations of comet C/2012 S1 (ISON) at 4.5 AU from the Sun

Cited by 7 publications

References 29 publications

Herschelobservations of gas and dust in comet C/2006 W3 (Christensen) at 5 AU from the Sun

Herschelobservations of gas and dust in comet C/2006 W3 (Christensen) at 5 AU from the Sun

The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets

Molecular observations of comets C/2012 S1 (ISON) and C/2013 R1 (Lovejoy): HNC/HCN ratios and upper limits to PH₃

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Herscheland IRAM-30 m observations of comet C/2012 S1 (ISON) at 4.5 AU from the Sun

Cited by 7 publications

References 29 publications

Herschelobservations of gas and dust in comet C/2006 W3 (Christensen) at 5 AU from the Sun

Herschelobservations of gas and dust in comet C/2006 W3 (Christensen) at 5 AU from the Sun

The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets

Molecular observations of comets C/2012 S1 (ISON) and C/2013 R1 (Lovejoy): HNC/HCN ratios and upper limits to PH3

Contact Info

Product

Resources

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Molecular observations of comets C/2012 S1 (ISON) and C/2013 R1 (Lovejoy): HNC/HCN ratios and upper limits to PH₃