[en] Context. As the ESA Rosetta mission approached, orbited, and sent a lander to comet 67P/Churyumov-Gerasimenko in 2014, a large campaign of ground-based observations also followed the comet. <BR /> Aims: We constrain the total activity level of the comet by photometry and spectroscopy to place Rosetta results in context and to understand the large-scale structure of the comet's coma pre-perihelion. <BR /> Methods: We performed observations using a number of telescopes, but concentrate on results from the 8 m VLT and Gemini South telescopes in Chile. We use R-band imaging to measure the dust coma contribution to the comet's brightness and UV-visible spectroscopy to search for gas emissions, primarily using VLT/FORS. In addition we imaged the comet in near-infrared wavelengths (JHK) in late 2014 with Gemini-S/Flamingos-2. <BR /> Results: We find that the comet was already active in early 2014 at heliocentric distances beyond 4 au. The evolution of the total activity (measured by dust) followed previous predictions. No gas emissions were detected despite sensitive searches. <BR /> Conclusions: The comet maintains a similar level of activity from orbit to orbit, and is in that sense predictable, meaning that Rosetta results correspond to typical behaviour for this comet. The gas production (for CN at least) is highly asymmetric with respect to perihelion, as our upper limits are below the measured production rates for similar distances post-perihelion in previous orbits. Based on observations made with ESO telescopes at the La Silla Paranal Observatory under programme IDs 592.C-0924, 093.C-0593, 094.C-0054, and at Gemini South under GS-2014B-Q-15 and GS-2014B-Q-76.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Snodgrass, Colin; Planetary and Space Sciences, Department of Physical SciencesThe Open University, Milton Keynes, MK7 6AA, UK ; Max-Planck-Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077, Göttingen, Germany
Jehin, Emmanuel ; Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Origines Cosmologiques et Astrophysiques (OrCa)
Manfroid, Jean ; Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Département d'astrophys., géophysique et océanographie (AGO)
Opitom, Cyrielle ; Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Origines Cosmologiques et Astrophysiques (OrCa)
Fitzsimmons, Alan; Astrophysics Research Centre, School of Mathematics and Physics, Queen's University Belfast, Belfast, BT7 1NN, UK
Tozzi, Gian Paolo; INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50 125, Firenze, Italy
Faggi, Sara; INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50 125, Firenze, Italy
Yang, Bin; European Southern Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile
Knight, Matthew M.; University of Maryland, College Park, MD, 20742, USA ; Lowell Observatory, 1400 W. Mars Hill Rd, Flagstaff, AZ, 86001, USA
Conn, Blair C.; Gemini Observatory, Recinto AURA, Colina El Pino s/n, Casilla 603, La Serena, Chile
Lister, Tim; Las Cumbres Observatory Global Telescope Network, 6740B Cortona Drive, Goleta, CA, 93117, USA
Hainaut, Olivier; European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748, Garching bei München, Germany
Bramich, D. M.; Qatar Environment and Energy Research Institute (QEERI), HBKU, Qatar Foundation, Doha, Qatar
Lowry, Stephen C.; Centre for Astrophysics and Planetary Science, School of Physical Sciences, The University of Kent, Canterbury, CT2 7NH, UK
Rozek, Agata; Centre for Astrophysics and Planetary Science, School of Physical Sciences, The University of Kent, Canterbury, CT2 7NH, UK
Tubiana, Cecilia; Max-Planck-Institute for Solar System Research, Justus-von-Liebig-Weg 3, 37077, Göttingen, Germany
Guilbert-Lepoutre, Aurélie; Institut UTINAM, UMR 6213 CNRS-Université de Franche Comté, 25000, Besançon, France)
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