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Jonathan Tennyson Physics and Astronomy, University College London Ohio, June 2011 Molecular line lists for exoplanet & other atmospheres Artist’s impression of HD189733b C. Carreau, ESA
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Transit of Venus June 8th 2004. June 2011 600+ planets detected Extrasolar planets: Exoplanets Don’t miss it on 6 June 2012
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Radial Period = 3.524738 days Mass = 0.69 ±0.05 M Jupiter Radius = 1.35 ±0.04 R Jupiter Density = 0.35 ±0.05 g/cm 3 HD 209458b Transiting exoplanets
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Beaulieu et al., 2007 Knutson et al., 2007 HD189733b: Primary transit with Spitzer
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Tinetti et al., Nature, 448, 163 (2007) Water, different T-P Water line list: BT2 Barber et al., 2006
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Confirmation of Water,methane and hazes! Beaulieu et al., 2007 Knutson et al., 2007 Swain et al., 2008 Pont et al., 2007 G. Tinetti (private communication, 2008)
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Giovanna Tinetti, UCL So far discovered: Water H 2 O Methane CH 4 Carbon dioxide CO 2 Carbon monoxide CO (Others ???) On HD189733b with more to come
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Exoplanets
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Cool atmospheres : dominated by molecular absorption Brown Dwarf M-dwarf The molecular opacity problem ( m) Exoplanets?
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Cool stars: T = 2000 – 4000 K Thermodynamics equilibrium, 3-body chemistry C and O combine rapidly to form CO. M-Dwarfs: Oxygen rich, n(O) > n(C) H 2, H 2 O, TiO, ZrO, etc also grains at lower T C-stars: Carbon rich, n(C) > n(O) H 2, CH 4, HCN, C 3, HCCH, CS, etc S-Dwarfs: n(O) = n(C) Rare. H 2, FeH, MgH, no polyatomics Also (primordeal) ‘metal-free’ stars H, H 2, He, H , H 3 + only at low T
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Also sub-stellar objects: CO less important Brown Dwarfs: T ~ 1500 K H 2, H 2 O, CH 4 T-Dwarfs: T ~ 1000K ‘methane stars’ Y-Dwarfs: T < 1000K ammonia signature? How common are these objects? Deuterium burning test using HDO? Exoplanets: hot Jupiters super-Earths Burn D only No nuclear synthesis
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Modeling molecular spectra @ 1000 -3000 K Spectra very dense – cannot get T from black-body fit. Synthetic spectra require huge databases > 10 6 vibration-rotation transitions per triatomic molecule Sophisticated opacity sampling techniques. Partition functions also important
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Opacity of cool stars, brown dwarfs & exoplanets Closed shell diatomics: H 2, CO, HeH +, etc Transition metal diatomics: TiO, FeH, etc Triatomic molecules: H 2 O, HCN, H 3 +, H 2 S, C 3 etc (CO 2, O 3 ) Tetratomic molecule: NH 3, HCCH Pentatomic: CH 4 Larger molecules: Hydrocarbons: C 2 H 4, C 2 H 6, others? biomarkers eg HNO 3
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Ab initio calculation of rotation-vibration spectra
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Potentials: Ab initio or Spectroscopically determined
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Viti & Tennyson computed VT2 linelist Partridge & Schwenke (PS), NASA Ames Barber & Tennyson (BT2) Also Ludwig, SCAN, MT, HITEMP....... Computed Water opacity Variational nuclear motion calculations High accuracy potential energy surface Ab initio dipole surface
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50,000 processor hours. Wavefunctions > 0.8 terabites 221,100 energy levels (all to J=50, E = 30,000 cm ) 14,889 experimentally known 506 Million transitions (PS list has 308M) >100,000 experimentally known with intensities Partition function 99.9915% of Vidler & Tennyson’s value at 3,000K BT2 linelist Barber et al, MNRAS 368, 1087 (2006). http://www.tampa.phys.ucl.ac.uk/ftp/astrodata/water/BT2/
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Energy file : N J sym n E/cm -1 v 1 v 2 v 3 J K a K c
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1448481461833.46E-04 1153091085207.42E-04 1960181984131.95E-04 703177031.13E-02 1491761501231.69E-04 81528787342.30E-01 80829782378.83E-04 2096722108762.51E-01 2070262032412.72E-04 1889721849711.25E-01 1524711533991.12E-02 39749374791.46E-07 10579158826.90E-05 34458356171.15E-03 Transitions file: N f N i A if 12.8 Gb Divided into 16 files by frequency for downloading
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Obs: A. Coppalle & P. Vervisch, JQSRT, 35, 121 (1986) New edition of HITEMP: LS Rothman, IE Gordon, RJ Barber, H Dothe, RR Gamache, A Goldman, VI Perevalov, SA Tashkun + J Tennyson, JQSRT, 111, 2139 (2010).
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Ammonia linelists Cold (ie T < 300 K). Levels up to J=12, E <12000 cm -1 TROVE nuclear motion program, spectroscopic potential S.N. Yurchenko, R.J. Barber, A. Yachmenev, W. Theil, P. Jensen & J. Tennyson, J. Phys. Chem. A, 113, 11845 (2009). Hot (ie T ~ 1500 K). Levels up to J=41, E <18000 cm -1 1 Improved spectroscopic potential, 1 137 650 964 lines “BYTe” S.N. Yurchenko, R.J. Barber & J. Tennyson, MNRAS, 413, 1828 (2011)
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BeforeAfter Refinement of the PES: Very elaborate Fine tuning potential
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NH 3 : Comparison of our predictions with HITRAN ).
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Ammonia absorption as a function of temperature
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Ammonia linelists: hot initial applications 1.Ultra cool (T ~ 450 K) brown dwarf, UGPSJ0722-0540 T9 dwarf, no ammonia observed ( The discovery of a very cool, very nearby brown dwarf in the Galactic plane, P Lucas et al,, MNRAS 408 (2010) L56) 2.Exoplanet GJ436b : a transiting “super Neptune”, also T ~ 500 K (J-P Beaulieu et al,, ApJ 731 (2011) 16) 3.Analysis of hot Lab spectra from University of York: 570 K < T < 1500 K. (NF Zobov et al, J Mol Spec, in press; RD09 Bernath) 4. (Re-)assigning HITRAN
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Spitzer observations of exoplanet GJ436b J-P Beaulieu et al,, ApJ 731 (2011) 16
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G GJ436b spectrum by molecule methane Ammonia water
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H 3 + Liesl Neale (H 2 D + Taha Sochi ) H 2 O Bob Barber (HDO Boris Voronin ) HCN/HNC ( H 13 CN/ H 13 CN ) Greg Harris HeH + Elodie Engel NH 3 Bob Barber & Sergei Yurchenko HCCH Andrea Urru H 2 S Ala’a Azzam PH 3 Clara Silva Linelists completed or under construction @ UCL by
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Primordial (Metal-poor) Terrestrial Planets (Oxidising) Giant-Planets & Cool Stars (Reducing atmospheres) Already available H 2, LiH HeH +, H 3 + H 2 D + OH, CO 2, O 3, NO H 2 O, HDO, NH 3 H 2, CN, CH, CO, CO 2, TiO HCN/HNC, H 2 O, NH 3, ExoMolO 2, CH 4, SO 2 HOOH, H 2 CO, HNO 3 CH 4, PH 3, C 2, C 3, HCCH, H 2 S, C 2 H 6, C 3 H 8, VO, O 2, AlO, MgO, CrH, MgH, FeH, CaH, AlH, SiH, TiH Molecular line lists for exoplanet & other atmospheres Available from elsewhere Already calculated at UCL Will be calculated under the ExoMol project
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www.worldscibooks.com/physics/7574.html About the first edition “The best book for anyone who is embarking on research in astronomical spectroscopy” Contemporary Physics (2006) Just published
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