Jonathan Tennyson Physics and Astronomy UCL

Molecular linelists for extrasolar planets Jonathan Tennyson Physics and Astronomy UCL Paris, Nov 2008 Artist’s impression of HD189733b C. Carreau, ESA

Infra red spectrum of an M-dwarf star

Planets

Triatomic spectra @ 1000 -3000 K • Spectra very dense – cannot get T from black-body fit • Synthetic spectra require huge databases • > 106 vibration-rotation transitions per triatomic molecule • Intensities often have to be calculated • Partition functions also important

The DVR3D program suite: triatomic vibration-rotation spectra J Tennyson, MA Kostin, P Barletta, GJ Harris OL Polyansky, J Ramanlal & NF Zobov Computer Phys. Comm. 163, 85 (2004). www.tampa.phys.ucl.ac.uk/ftp/vr/cpc03 Potential energy Surface,V(r1,r2,q) Dipole function m(r1,r2,q)

Linelists completed or under construction @ UCL H3+ (H2D+) H2O (HDO) HCN/HNC (H13CN/ H13CN) HeH+ NH3, HCCH, C3

Computed Water opacity • Variational nuclear motion calculations • High accuracy potential energy surface • Ab initio dipole surface Viti & Tennyson computed VT2 linelist Partridge & Schwenke (PS), NASA Ames New study by Barber & Tennyson (BT2) Also Ludwig, SCAN, MT, HITEMP .......

S.A. Tashkun, HiRus conference (2006) Obs: A. Coppalle & P. Vervisch, JQSRT, 35, 121 (1986)

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

Pont et al., 2007 Swain et al., 2008 Knutson et al., 2007 Beaulieu et al., 2007 Confirmation of Water,methane and hazes! G. Tinetti (private communication, 2008)

Why is ammonia of interest? • Present in: ISM, molecular clouds, late-type dwarfs, gas giants, exoplanets, comets etc. • NH3, CH4, H2O etc. in the spectra of exoplanets give additional information about P and T. NH3 also gives information about their nitrogen chemistry. • Accurate modelling of the atmospheres of late-type brown dwarfs, requires an NH3 line list. • Y-dwarfs (search is on) are characterised by NH3

Our Objectives • To create an ammonia line list that is complete and accurate enough for inclusion in model atmospheres of Y-dwarfs and exoplanets, and in the subsequent computation of synthetic absorption spectra for these objects with different chemistries, T and log g. • To achieve an accuracy for the stronger transitions that will enable individual NH3 lines to be assigned in the lab and a range of astrophysical objects including cometary coma and the ISM.

Absorption spectra of NH3 at T=300K Experiment: I. Kleiner, L.R. Brown, G. Tarrago et al., J. Mol. Spectrosc. 193, 46 (1999). New Calculations: RJ Barber, S Yurchenko and J Tennyson

Hot spectra of NH3: Vibrational intensity T = 1500 K T = 1000 K T = 300 K

Opacity of cool stars, brown dwarfs & exoplanets • Closed shell diatomics: H2, CO, etc • Transition metal diatomics: TiO, FeH, etc • Triatomic molecules: H2O, HCN, C3 etc (CO2, O3) • Tetratomic molecule: NH3, HCCH • Pentatomic: CH4 • Dust (other biomarkers eg HNO3?) Requires systematic collaborative project - PoSSO

www.worldscibooks.com/physics/p371.html “The best book for anyone who is embarking on research in astronomical spectroscopy” Contemporary Physics (2006)

Partition functions are important Model of cool, metal-free magnetic white dwarf WD1247+550 by Pierre Bergeron (Montreal) Is the partition function of H3+ correct?

Partition functions are important Model of WD1247+550 using ab initio H3+ partition function of Neale & Tennyson (1996)

Jonathan Tennyson Physics and Astronomy UCL