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Jonathan Tennyson Physics and Astronomy, University College London AELG-fest July 2010 Spectroscopic linelists for hot molecules of astrophysical importance.

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Presentation on theme: "Jonathan Tennyson Physics and Astronomy, University College London AELG-fest July 2010 Spectroscopic linelists for hot molecules of astrophysical importance."— Presentation transcript:

1 Jonathan Tennyson Physics and Astronomy, University College London AELG-fest July 2010 Spectroscopic linelists for hot molecules of astrophysical importance Artist’s impression of HD189733b C. Carreau, ESA

2 Spectrum of a hot star: black body-like

3 Infra red spectrum of an M-dwarf star

4 Cool atmospheres : dominated by molecular absorption Brown Dwarf M-dwarf The molecular opacity problem (  m) Exoplanets?

5 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 Model by GJ Harris, ALEG, S Miller + JT: ApJ, 600 (2004) 1025; 617 (2004) L143; MNRAS, 374 (2007) 337; 377 (2007) 1520.

6 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? Exoplanets: hot Jupiters super-Earths How common are these objects? Deuterium burning test using HDO? Burn D only No nuclear synthesis

7 Opacity of cool stars, brown dwarfs & exoplanets Closed shell diatomics: H 2, CO, etc Transition metal diatomics: TiO, FeH, etc Triatomic molecules: H 2 O, HCN, C 3 etc (CO 2, O 3 )‏ Tetratomic molecule: NH 3, HCCH Pentatomic: CH 4 Hydrocarbons: C 2 H 4, C 2 H 6, others? Dust (other biomarkers eg HNO 3 ?)‏

8 Opacity of cool stars, brown dwarfs & exoplanets Closed shell diatomics: H 2, CO, etc Transition metal diatomics: TiO, FeH, etc Triatomic molecules: H 2 O, HCN, C 3 etc (CO 2, O 3 )‏ Tetratomic molecule: NH 3, HCCH Pentatomic: CH 4 Hydrocarbons: C 2 H 4, C 2 H 6, others? Dust (other biomarkers eg HNO 3 ?)‏

9 Exoplanets

10 Modeling 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

11 Ab initio calculation of rotation-vibration spectra

12 Potentials: Ab initio or Spectroscopically determined

13 The DVR3D program suite : triatomic vibration-rotation spectra Potential energy Surface,V(r 1,r 2,  ) Dipole function  (r 1,r 2,  ) J Tennyson, MA Kostin, P Barletta, GJ Harris OL Polyansky, J Ramanlal & NF Zobov Computer Phys. Comm. 163, 85 (2004).

14 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 are best AELG, S Miller + JT, J Mol. Spec. 169 (1995) 458.

15 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).

16 Energy file : N J sym n E/cm -1 v 1 v 2 v 3 J K a K c

17 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

18 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 (in press)

19 Direct observation of star GQ Lupi and its planet GQ Lupi b Extra solar planets: 442 detected so far ~ 65 “transiting”

20 Transit of Venus June 8th 2004.

21 Radial velocity / Occultation 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

22 Beaulieu et al., 2007 Knutson et al., 2007 Primary transit + IR + Spitzer

23 Tinetti et al., Nature, 448, 163 (2007) ‏ Water, different T-P Water line list: BT2 Barber et al., 2006

24 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)‏

25 Why is ammonia of interest? Present in: ISM, molecular clouds, late-type dwarfs, gas giants, exoplanets, comets etc. NH 3, CH 4, H 2 O etc. in the spectra of exoplanets give additional information about P and T. NH 3 also gives information about nitrogen chemistry. Accurate modelling of the atmospheres of late- type brown dwarfs. Y-dwarfs (search is on) are characterised by NH 3

26 Ammonia linelist 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).

27 BeforeAfter Refinement of the PES: Very elaborate Fine tuning potential

28 NH 3 : Comparison of our predictions with HITRAN ).

29 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=30, E <12000 cm Improved spectroscopic potential, lines S.N. Yurchenko, R.J. Barber & J. Tennyson, MNRAS (to be submitted)

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31 Ammonia linelists: hot initial applications 1.Ultra cool (T ~ 520 +/- 40 K) brown dwarf, UGPSJ T9 dwarf, no ammonia observed ( Discovery of a very cool, very nearby brown dwarf in the Galactic plane P Lucas et al, arXiv:1004:0317 and MNRAS Let. In press) 2.Exoplanet GJ436b : a transiting “super Neptune”, also T ~ 500 K 3. Analysis of hot Lab spectra from University of York: 570 K < T < 1500 K.

32 Spitzer observations of exoplanet GJ436b J-P Beaulieu et al, Astrophys. J. (submitted)

33 G GJ436b spectrum by molecule methane Ammonia water J-P Beaulieu et al, Astrophys. J. (submitted)

34 Opacity of cool stars, brown dwarfs & exoplanets Closed shell diatomics: H 2, CO, etc Transition metal diatomics: TiO, FeH, etc Triatomic molecules: H 2 O, HCN, C 3 etc (CO 2, O 3 )‏ Tetratomic molecule: NH 3, HCCH Pentatomic: CH 4 Hydrocarbons: C 2 H 4, C 2 H 6, others? Dust (other biomarkers eg HNO 3 ?)‏

35 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 and Sergei Yurchenko (Dresden)‏ HCCH Andrea Urru C 3 Santina La Delfa and Taha Sochi Linelists completed or under UCL by

36 “The best book for anyone who is embarking on research in astronomical spectroscopy” Contemporary Physics (2006)


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