Natalia A. Konovalova^1,*, Jose M. Madiedo², Josep M. Trigo-Rodríguez³

¹Institute of Astrophysics of the Academy of Sciences of the Republic of Tajikistan, Dushanbe, Tajikistan
²Facultad de Ciencias Experimentales, Universidad de Huelva, Huelva, Spain
³Facultat de Ciencies, Institute of Space Sciences (CSIC-IEEC), Campus UAB, Belaaterra, Spain

The results of the atmospheric trajectory, radiant, heliocentric orbit, and preliminary strewn field calculations for an extremely bright slow-moving fireball are presented. In the evening hours of July 23, 2008, a bright object entered Earth’s atmosphere over Tajikistan. The fireball had a −20.3 maximum absolute magnitude and a spectacularly long persistent dust trail remained visible over a widespread region of Tajikistan for about 28 minutes after sunset. The fireball was also recorded by a visible-light satellite system at 14 h 45 min 25 s UT, and the dust trail was imaged by video and photocameras. A unique aspect of this event is that it was detected by two infrasound and five seismic stations too. The bolide was first recorded at a height of 38.2 km, reached its maximum brightness at a height of 35.0 km, and finished at a height of 19.6 km. The first breakup occurred under an aerodynamic pressure of approximately 1.6 MPa, similar to the values derived for breakups of the scarcely reported meteorite-dropping bolides. The fireball’s trajectory and dynamic results suggest that meteorite survival is likely. The meteoroid followed an Apollo-like asteroid orbit comparable to those derived for previously recovered meteorites with accurately known orbits.

Reference
Konovalova NA, Madiedo JM and Trigo-Rodríguez JM (in press) The Tajikistan superbolide of July 23, 2008. I. Trajectory, orbit, and preliminary fall data. Meteoritics & Planetary Science
[doi:10.1111/maps.12217]
Published by arrangement with John Wiley & Sons

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Philippe Rousselot¹, Olivier Pirali², Emmanuël Jehin³, Michel Vervloet², Damien Hutsemékers³, Jean Manfroid³, Daniel Cordier¹, Marie-Aline Martin-Drumel², Sébastien Gruet², Claude Arpigny³, Alice Decock³, and Olivier Mousis¹

¹Institut UTINAM-UMR CNRS 6213, Observatoire des Sciences de l’Univers THETA, University of Franche-Comté, BP 1615, F-25010 Besançon Cedex, France
²Synchrotron SOLEIL, ligne AILES, UMR 8214 CNRS, L’orme des Merisiers, Saint-Aubin, F-91192 Gif-Sur-Yvette, France
³Département d’Astrophysique, de Géophysique et d’Océanographie, Université de Liège, Allée du Six Aohat ut, B-4000 Liège, Belgium

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.

Reference
Rousselot P, Pirali O, Jehin E, Vervloet M, Hutsemékers D, Manfroid J, Cordier D, Martin-Drumel M-A, Gruet S, Arpigny C, Decock A and Mousis O (2014) Toward a Unique Nitrogen Isotopic Ratio in Cometary Ices. The Astrophysical Journal – Letters 780:L17.
[doi:10.1088/2041-8205/780/2/L17]

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L. O’Rourke¹, D. Bockelée-Morvan², N. Biver², B. Altieri¹, D. Teyssier¹, L. Jorda³, V. Debout², C. Snodgrass⁴, M. Küppers¹, M. A’Hearn⁵, T. G. Müller⁶ and T. Farnham⁵

¹European Space Astronomy Centre, ESAC, ESA, 28691 Villanueva de la Cañada, Spain
²LESIA, Observatoire de Paris, CNRS, UPMC, Université Paris-Diderot, 5 place Jules Janssen, 92195 Meudon, France
³Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille), UMR 7326, 13388 Marseille, France
⁴Max Planck Institute for Solar System Research, Max-Planck-Str. 2, 37191 Katlenburg-Lindau, Germany
⁵Dept. of Astronomy, Univ. of Maryland, College Park, MD 20742-2421, USA
⁶Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, 85748 Garching, Germany

Context. The sungrazer comet C/2012 S1 (ISON) (perihelion at r_h = 0.0125 AU from the Sun) was bright and active when discovered in September 2012 at 6.3 AU from the Sun.
Aims. Our goal was to characterize the distant gaseous and dust activity of this comet, inbound, from observations of H₂O, CO and the dust coma in the far-infrared and submillimeter domains.
Methods. We report observations undertaken with the Herschel space observatory on 8 and 13 March 2013 (r_h = 4.54–4.47AU) and with the 30 m telescope of Institut de Radioastronomie Millimétrique (IRAM) in March and April 2013 (r_h = 4.45–4.18 AU). The HIFI instrument aboard Herschel was used to observe the H₂O 1₁₀ − 1₀₁ line at 557 GHz, whereas images of the dust coma at 70 μm and 160 μm were acquired with the PACS instrument. Spectra acquired at the IRAM 30 m telescope cover the CO J(2–1) line at 230.5 GHz. The spectral observations were analysed with excitation and radiative transfer models. A model of dust thermal emission taking into account a range of dust sizes is used to analyse the PACS maps.
Results. While H₂O was not detected in our 8 March 2013 observation, we derive a sensitive 3σ upper limit of Q_H2O < 3.5 × 10²⁶ molecules s^-1 for this date. A marginal 3.2σdetection of CO is found, corresponding to a CO production rate of Q_CO = 3.5 × 10²⁷ molecules s^-1. The Herschel PACS measurements show a clear detection of the coma and tail in both the 70 μm and 160 μm maps. Under the assumption of a 2-km radius nucleus, we infer dust production rates in the range 10–13 kg s^-1 or 40–70 kg s^-1, depending on whether a low or high gaseous activity from the nucleus surface is assumed. We constrain the size distribution of the emitted dust by comparing PACS 70 and 160 μm data, and considering optical data. Size indices between –4 and –3.6 are suggested. The morphology of the tail observed on 70 μm images can be explained by the presence of grains with ages older than 60 days.

Reference
O’Rourke L, Bockelée-Morvan D, Biver N, Altieri B, Teyssier D, Jorda L, Debout V, Snodgrass C, Küppers M, A’Hearn M, Müller TG and Farnham T (2013) Herschel and IRAM-30 m observations of comet C/2012 S1 (ISON) at 4.5 AU from the Sun. Astronomy & Astrophysics 560:A101.
[doi:10.1051/0004-6361/201322756]
Reproduced with permission © ESO

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