Now showing items 1-20 of 32

    • The chemistry of episodic accretion in embedded objects : 2D radiation thermo-chemical models of the post-burst phase 

      Rab, Ch.; Elbakyan, V.; Vorobyov, E.; Güdel, M.; Dionatos, O.; Audard, M.; Kamp, I.; Thi, W.-f.; Woitke, P.; Postel, A. (2017-08) - Journal article
      Context. Episodic accretion is an important process in the evolution of young stars and their environment. The observed strong luminosity bursts of young stellar objects likely have a long lasting (i.e. longer than the ...
    • The chemistry of protoplanetary fragments formed via gravitational instabilities 

      Ilee, J. D.; Forgan, D. H.; Evans, M. G.; Hall, C.; Booth, R.; Clarke, C. J.; Rice, W. K. M.; Boley, A. C.; Caselli, P.; Hartquist, T. W.; Rawlings, J. M. C. (2017-11) - Journal article
      In this paper, we model the chemical evolution of a 0.25 M⊙ protoplanetary disc surrounding a 1 M⊙ star that undergoes fragmentation due to self-gravity. We use smoothed particle hydrodynamics including a radiative transfer ...
    • Cloud formation in metal-rich atmospheres of hot super-Earths like 55 Cnc e and CoRoT7b 

      Mahapatra, G.; Helling, Ch.; Miguel, Y. (2017-11-21) - Journal article
      Clouds form in the atmospheres of planets where they can determine the observable spectra, the albedo and phase curves. Cloud properties are determined by the local thermodynamical and chemical conditions of an atmospheric ...
    • A comparison of simulated JWST observations derived from equilibrium and non-equilibrium chemistry models of giant exoplanets 

      Blumenthal, Sarah D.; Mandell, Avi M.; Hébrard, Eric; Batalha, Natasha E.; Cubillos, Patricio E.; Rugheimer, Sarah; Wakeford, Hannah R. (2018-01-30) - Journal article
      We aim to see if the difference between equilibrium and disequilibrium chemistry is observable in the atmospheres of transiting planets by the James Webb Space Telescope (JWST). We perform a case study comparing the dayside ...
    • Consistent dust and gas models for protoplanetary disks : II. Chemical networks and rates 

      Kamp, I.; Thi, W. F.; Woitke, P.; Rab, C.; Bouma, S.; Ménard, F. (2017-11-06) - Journal article
      Aims.  We aim to define a small and large chemical network which can be used for the quantitative simultaneous analysis of molecular emission from the near-IR to the submm. We also aim to revise reactions of excited molecular ...
    • Consistent dust and gas models for protoplanetary disks I. Disk shape, dust settling, opacities, and PAHs 

      Woitke, Peter; Min, M.; Pinte, C.; Thi, W. -F.; Kamp, I.; Rab, C.; Anthonioz, F.; Antonellini, S.; Baldovin-Saavedra, C.; Carmona, A.; Dominik, C.; Dionatos, O.; Greaves, Jane Sophia; Güdel, M.; Ilee, John David; Liebhart, A.; Ménard, F.; Rigon, Laura; Waters, L. B. F. M.; Aresu, G.; Meijerink, R.; Spaans, M. (2016-02-02) - Journal article
      We propose a set of standard assumptions for the modelling of Class II and III protoplanetary disks, which includes detailed continuumradiative transfer, thermo-chemical modelling of gas and ice, and line radiative transfer ...
    • Disk evolution, element abundances and cloud properties of young gas giant planets 

      Helling, C.; Woitke, P.; Rimmer, P.B.; Kamp, I.; Thi, W.-F.; Meijerink, R. (2014-04-14) - Journal article
      We discuss the chemical pre-conditions for planet formation, in terms of gas and ice abundances in a protoplanetary disk, as function of time and position, and the resulting chemical composition and cloud properties in the ...
    • Dust in brown dwarfs and extra-solar planets. IV. Assessing TiO2 and SiO nucleation for cloud formation modelling 

      Lee, G.; Helling, Christiane; Giles, H.; Bromley, S. T. (2015-03) - Journal article
      Clouds form in atmospheres of brown dwarfs and planets. The cloud particle formation processes are similar to the dust formation process studied in circumstellar shells of AGB stars and in Supernovae. Cloud formation ...
    • Dust in brown dwarfs and extrasolar planets : V. Cloud formation in carbon- and oxygen-rich environments 

      Helling, Ch; Tootill, D.; Woitke, P.; Lee, G. (2017-07) - Journal article
      Context. Recent observations indicate potentially carbon-rich (C/O > 1) exoplanet atmospheres. Spectral fitting methods for brown dwarfs and exoplanets have invoked the C/O ratio as additional parameter but carbon-rich ...
    • Equlibrium chemistry down to 100 K : impact of silicates and phyllosilicates on carbon/oxygen ration 

      Woitke, Peter; Helling, Christiane; Hunter, G.H.; Millard, J.D.; Turner, G.E.; Worters, M.; Blecic, J.; Stock, J.W. (2018-06) - Journal article
      We have introduced a fast and versatile computer code, GGchem, to determine the chemical composition of gases in thermo-chemical equilibrium down to 100 K, with or without equilibrium condensation. We have reviewed the ...
    • The fate of formamide in a fragmenting protoplanetary disk 

      Quénard, David; Ilee, John D.; Jiménez-Serra, Izaskun; Forgan, Duncan H.; Hall, Cassandra; Rice, Ken (2018-11-13) - Journal article
      Recent high-sensitivity observations carried out with the Atacama Large Millimeter Array have revealed the presence of complex organic molecules (COMs) such as methyl cyanide (CH3CN) and methanol (CH3OH) in relatively ...
    • G11.92-0.61-MM2 : a bonafide massive prestellar core? 

      Cyganowski, C.J.; Brogan, C.L.; Hunter, T.R.; Graninger, D.; Öberg, K.I.; Vasyunin, A.; Zhang, Q.; Friesen, R.; Schnee, S. (2014-11-20) - Journal article
      Core accretion models of massive star formation require the existence of stable massive starless cores, but robust observational examples of such objects have proven elusive. We report subarcsecond-resolution Submillimeter ...
    • Gas lines from the 5-Myr old optically thin disk around HD 141569A Herschel observations and modeling 

      Thi, W.-F.; Pinte, C.; Pantin, E.; Augereau, J.C.; Meeus, G.; Ménard, F.; Martin-Zaïdi, C.; Woitke, P.; Riviere-Marichalar, P.; Kamp, I.; Carmona, A.; Sandell, G.; Eiroa, C.; Dent, W.; Montesinos, B.; Aresu, G.; Meijerink, R.; Spaans, M.; White, G.; Ardila, D.; Lebreton, J.; Mendigutía, I.; Brittain, S. (2014-01) - Journal article
      Context. The gas- and dust dissipation processes in disks around young stars remain uncertain despite numerous studies. At the distance of ~99–116 pc, HD 141569A is one of the nearest HerbigAe stars that is surrounded by ...
    • Grand challenges in protoplanetary disc modelling 

      Haworth, Thomas J.; Ilee, John D.; Forgan, Duncan H.; Facchini, Stefano; Price, Daniel J.; Boneberg, Dominika M.; Booth, Richard A.; Clarke, Cathie J.; Gonzalez, Jean-François; Hutchison, Mark A.; Kamp, Inga; Laibe, Guillaume; Lyra, Wladimir; Meru, Farzana; Mohanty, Subhanjoy; Panić, Olja; Rice, Ken; Suzuki, Takeru; Teague, Richard; Walsh, Catherine; Woitke, Peter (2016) - Journal article
      The Protoplanetary Discussions conference—held in Edinburgh, UK, from 2016 March 7th–11th—included several open sessions led by participants. This paper reports on the discussions collectively concerned with the multi-physics ...
    • Gravitational instabilities in a protosolar-like disc - I. Dynamics and chemistry 

      Evans, M. G.; Ilee, John David; Boley, A. C.; Caselli, P.; Durisen, R. H.; Hartquist, T. W.; Rawlings, J. M. C. (2015-10-21) - Journal article
      To date, most simulations of the chemistry in protoplanetary discs have used 1 + 1D or 2D axisymmetric α-disc models to determine chemical compositions within young systems. This assumption is inappropriate for non-axisymmetric, ...
    • Influence of galactic arm scale dynamics on the molecular composition of the cold and dense ISM : I. Observed abundance gradients in dense clouds 

      Ruaud, M.; Wakelam, V.; Gratier, P.; Bonnell, I. A. (2018) - Journal article
      Aim. We study the effect of large scale dynamics on the molecular composition of the dense interstellar medium during the transition between diffuse to dense clouds. Methods. We followed the formation of dense clouds (on ...
    • The influence of galactic cosmic rays on ion-neutral hydrocarbon chemistry in the upper atmospheres of free-floating exoplanets 

      Rimmer, P.B.; Helling, C.; Bilger, C. (2014-04-01) - Journal article
      Cosmic rays may be linked to the formation of volatiles necessary for prebiotic chemistry. We explore the effect of cosmic rays in a hydrogen-dominated atmosphere, as a proof-of-concept that ion–neutral chemistry may be ...
    • Is lightning a possible source of the radio emission on HAT-P-11b? 

      Hodosán, Gabriella; Rimmer, Paul B.; Helling, Christiane (2016-09-11) - Journal article
      Lightning induced radio emission has been observed on Solar System planets. There have been many attempts to observe exoplanets in the radio wavelength, however, no unequivocal detection has been reported. Lecavelier des ...
    • The mineral clouds on HD 209458b and HD 189733b 

      Helling, Christiane; Lee, G.; Dobbs-Dixon, I.; Mayne, N.; Amundsen, D. S.; Khaimova, J.; Unger, A. A.; Manners, J.; Acreman, D.; Smith, C. (2016-07-21) - Journal article
      3D atmosphere model results are used to comparatively study the kinetic, non-equilibrium cloud formation in the atmospheres of two example planets guided by the giant gas planets HD 209 458b and HD 189 733b. Rather ...
    • Modelling mid-infrared molecular emission lines from T Tauri stars 

      Woitke, P.; Min, M.; Thi, W. -F.; Roberts, C.; Carmona, A.; Kamp, I.; Ménard, F.; Pinte, C. (2018-10-11) - Journal article
      We introduce a new modelling framework including the Fast Line Tracer (FLITS) to simulate infrared line emission spectra from protoplanetary discs. This paper focusses on the mid-IR spectral region between 9.7 and 40 μm ...