Presentation on theme: "Jonathan Tennyson Physics and Astronomy, University College London Ohio, June 2011 Molecular line lists for exoplanet & other atmospheres Artist’s impression."— Presentation transcript:
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
Transit of Venus June 8th June planets detected Extrasolar planets: Exoplanets Don’t miss it on 6 June 2012
Radial Period = days Mass = 0.69 ±0.05 M Jupiter Radius = 1.35 ±0.04 R Jupiter Density = 0.35 ±0.05 g/cm 3 HD b Transiting exoplanets
Beaulieu et al., 2007 Knutson et al., 2007 HD189733b: Primary transit with Spitzer
Tinetti et al., Nature, 448, 163 (2007) Water, different T-P Water line list: BT2 Barber et al., 2006
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)
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
Cool atmospheres : dominated by molecular absorption Brown Dwarf M-dwarf The molecular opacity problem ( m) Exoplanets?
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
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
Modeling molecular 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
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
Ab initio calculation of rotation-vibration spectra
Potentials: Ab initio or Spectroscopically determined
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
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 % of Vidler & Tennyson’s value at 3,000K BT2 linelist Barber et al, MNRAS 368, 1087 (2006).
Energy file : N J sym n E/cm -1 v 1 v 2 v 3 J K a K c
E E E E E E E E E E E E E E-03 Transitions file: N f N i A if 12.8 Gb Divided into 16 files by frequency for downloading
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).
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, (2009). Hot (ie T ~ 1500 K). Levels up to J=41, E <18000 cm -1 1 Improved spectroscopic potential, lines “BYTe” S.N. Yurchenko, R.J. Barber & J. Tennyson, MNRAS, 413, 1828 (2011)
BeforeAfter Refinement of the PES: Very elaborate Fine tuning potential
NH 3 : Comparison of our predictions with HITRAN ).
Ammonia absorption as a function of temperature
Ammonia linelists: hot initial applications 1.Ultra cool (T ~ 450 K) brown dwarf, UGPSJ 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
Spitzer observations of exoplanet GJ436b J-P Beaulieu et al,, ApJ 731 (2011) 16
G GJ436b spectrum by molecule methane Ammonia water
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 UCL by
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
About the first edition “The best book for anyone who is embarking on research in astronomical spectroscopy” Contemporary Physics (2006) Just published