ORCID Profile
0000-0002-4994-5238
Current Organisations
Institut National de Recherche pour l'Agriculture l'Alimentation et l'Environnement
,
University College London
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Publisher: Springer Science and Business Media LLC
Date: 02-08-2012
Publisher: Springer Science and Business Media LLC
Date: 07-2007
DOI: 10.1038/NATURE06002
Abstract: Water is predicted to be among the most abundant (if not the most abundant) molecular species after hydrogen in the atmospheres of close-in extrasolar giant planets ('hot Jupiters'). Several attempts have been made to detect water on such planets, but have either failed to find compelling evidence for it or led to claims that should be taken with caution. Here we report an analysis of recent observations of the hot Jupiter HD 189733b (ref. 6) taken during the transit, when the planet passed in front of its parent star. We find that absorption by water vapour is the most likely cause of the wavelength-dependent variations in the effective radius of the planet at the infrared wavelengths 3.6 mum, 5.8 mum (both ref. 7) and 8 mum (ref. 8). The larger effective radius observed at visible wavelengths may arise from either stellar variability or the presence of clouds/hazes. We explain the report of a non-detection of water on HD 189733b (ref. 4) as being a consequence of the nearly isothermal vertical profile of the planet's atmosphere.
Publisher: IOP Publishing
Date: 09-08-2019
Abstract: We publish three Roadmaps on photonic, electronic and atomic collision physics in order to celebrate the 60th anniversary of the ICPEAC conference. In Roadmap II we focus on electron and antimatter interactions. Modern theoretical and experimental approaches provide detailed insight into the many body quantum dynamics of leptonic collisions with targets of varying complexity ranging from neutral and charged atoms to large biomolecules and clusters. These developments have been driven by technological progress and by the needs of adjacent areas of science such as astrophysics, plasma physics and radiation biophysics. This Roadmap aims at looking back along the road, explaining the evolution of the field, and looking forward, collecting contributions from eighteen leading groups from the field.
Publisher: Oxford University Press (OUP)
Date: 13-07-2020
Abstract: The spectrum of dicarbon (C2) is important in astrophysics and for spectroscopic studies of plasmas and flames. The C2 spectrum is characterized by many band systems with new ones still being actively identified astronomical observations involve eight of these bands. Recently, Furtenbacher et al. presented a set of 5699 empirical energy levels for 12C2, distributed among 11 electronic states and 98 vibronic bands, derived from 42 experimental studies and obtained using the MARVEL (Measured Active Rotational-Vibrational Energy Levels) procedure. Here, we add data from 13 new sources and update data from 5 sources. Many of these data sources characterize high-lying electronic states, including the newly detected 3 3Πg state. Older studies have been included following improvements in the MARVEL procedure that allow their uncertainties to be estimated. These older works in particular determine levels in the C 1Πg state, the upper state of the insufficiently characterized Deslandres–d’Azambuja (C 1Πg–A 1Πu) band. The new compilation considers a total of 31 323 transitions and derives 7047 empirical (marvel) energy levels spanning 20 electronic and 142 vibronic states. These new empirical energy levels are used here to update the 8states C2 ExoMol line list. This updated line list is highly suitable for high-resolution cross-correlation studies in astronomical spectroscopy of, for ex le, exoplanets, as 99.4 per cent of the transitions with intensities over 10−18 cm molecule−1 at 1000 K have frequencies determined by empirical energy levels.
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6FD90077A
Publisher: American Astronomical Society
Date: 04-07-2023
Abstract: In idual vibrational band spectroscopy presents an opportunity to examine exoplanet atmospheres in detail, by distinguishing where the vibrational state populations of molecules differ from the current assumption of a Boltzmann distribution. Here, retrieving vibrational bands of OH in exoplanet atmospheres is explored using the hot Jupiter WASP-33b as an ex le. We simulate low-resolution spectroscopic data for observations with the JWST's NIRSpec instrument and use high-resolution observational data obtained from the Subaru InfraRed Doppler instrument (IRD). Vibrational band–specific OH cross-section sets are constructed and used in retrievals on the (simulated) low- and (real) high-resolution data. Low-resolution observations are simulated for two WASP-33b emission scenarios: under the assumption of local thermal equilibrium (LTE) and with a toy non-LTE model for vibrational excitation of selected bands. We show that mixing ratios for in idual bands can be retrieved with sufficient precision to allow the vibrational population distributions of the forward models to be reconstructed. A fit for the Boltzmann distribution in the LTE case shows that the vibrational temperature is recoverable in this manner. For high-resolution, cross-correlation applications, we apply the in idual vibrational band analysis to an IRD spectrum of WASP-33b, applying an “unpeeling” technique. In idual detection significances for the two strongest bands are shown to be in line with Boltzmann-distributed vibrational state populations, consistent with the effective temperature of the WASP-33b atmosphere reported previously. We show the viability of this approach for analyzing the in idual vibrational state populations behind observed and simulated spectra, including reconstructing state population distributions.
Publisher: American Astronomical Society
Date: 17-03-2011
Publisher: IOP Publishing
Date: 04-04-2017
Publisher: Royal Society of Chemistry (RSC)
Date: 1988
DOI: 10.1039/F29888401555
Publisher: American Astronomical Society
Date: 16-03-2018
Publisher: Informa UK Limited
Date: 05-12-2018
Publisher: Royal Society of Chemistry (RSC)
Date: 2010
DOI: 10.1039/C005126H
Abstract: Almost 500 extrasolar planets have been found since the discovery of 51 Peg b by Mayor and Queloz in 1995. The traditional field of planetology has thus expanded its frontiers to include planetary environments not represented in our Solar System. We expect that in the next five years space missions (Corot, Kepler and GAIA) or ground-based detection techniques will both increase exponentially the number of new planets discovered and lower the present limit of a approximately 1.9 Earth-mass object [e.g. Mayor et al., Astron. Astrophys., 2009, 507, 487]. While the search for an Earth-twin orbiting a Sun-twin has been one of the major goals pursued by the exoplanet community in the past years, the possibility of sounding the atmospheric composition and structure of an increasing s le of exoplanets with current telescopes has opened new opportunities, unthinkable just a few years ago. As a result, it is possible now not only to determine the orbital characteristics of the new bodies, but moreover to study the exotic environments that lie tens of parsecs away from us. The analysis of the starlight not intercepted by the thin atmospheric limb of its planetary companion (transit spectroscopy), or of the light emitted/reflected by the exoplanet itself, will guide our understanding of the atmospheres and the surfaces of these extrasolar worlds in the next few years. Preliminary results obtained by interpreting current atmospheric observations of transiting gas giants and Neptunes are presented. While the full characterisation of an Earth-twin might requires a technological leap, our understanding of large terrestrial planets (so called super-Earths) orbiting bright, later-type stars is within reach by current space and ground telescopes.
Publisher: IOP Publishing
Date: 06-12-2017
Publisher: Oxford University Press (OUP)
Date: 15-08-2016
Publisher: EDP Sciences
Date: 10-2020
DOI: 10.1051/0004-6361/202037863
Abstract: Context. We used the new ExoMol TiO rovibronic line lists to identify and model TiO isotopologue features in spectra of M dwarfs. Aims. We investigate problems involving the computation of electronic bands for different isotopologues of TiO by modelling optical spectra of late-type stars. Based on this, we determine their Ti isotopic abundances and compare the TiO isotopologue spectra computed using line lists by different authors. Methods. We fitted theoretical synthetic spectra to the observed stellar molecular bands of TiO. We modelled spectra of two M dwarfs, GJ 15A (M1V) and GJ 15B (M3 V), to determine Ti isotopic ratios in their atmospheres. Results. We demonstrate the accuracy of the ExoMol TOTO line list for different isotopologues of TiO and the possibility of determining accurate Ti isotope abundances in a number of spectral ranges. The 7580–7594 Å spectral range seems particularly useful, with two atomic lines of Fe I and molecular band heads of 50 Ti O, 49 Ti O, 48 Ti O, and 47 Ti O clearly observable in our two M-dwarf spectra. We determine non-solar Ti isotopic ratios of 46 Ti, 47 Ti, 48 Ti, 49 Ti, and 50 Ti of 7.9, 5.2, 72.8, 7.9, and 6.2 for GJ 15A and 7.4, 4.2, 76.6, 5.8, and 6.0 for GJ 15B with an accuracy of ±0.2. [Ti] = 0.040 and 0.199 and within an accuracy of ±0.10 were also determined for GJ 15A and GJ 15B, respectively. Conclusions. We find that the ExoMol TOTO TiO line list (a) describes the fine details in line position and intensity of the M-dwarf spectra better than other available TiO line lists, (b) correctly reproduces the positions and intensities of the TiO isotopologue band heads observed in M-dwarf spectra, and (c) can be used to determine Ti isotope abundances in atmospheres of M stars.
Publisher: American Astronomical Society
Date: 24-01-2012
Publisher: Oxford University Press (OUP)
Date: 14-04-2018
DOI: 10.1093/MNRAS/STY939
Publisher: Oxford University Press (OUP)
Date: 04-2015
DOI: 10.1093/MNRAS/STV586
Publisher: Oxford University Press (OUP)
Date: 17-11-2010
Publisher: IOP Publishing
Date: 14-07-2017
Publisher: Springer Singapore
Date: 2019
Publisher: Elsevier BV
Date: 11-2020
Publisher: Oxford University Press (OUP)
Date: 22-07-2019
Abstract: Accurate line lists are crucial for correctly modelling a variety of astrophysical phenomena, including stellar photospheres and the atmospheres of extrasolar planets. This paper presents a new line database Toto for the main isotopologues of titanium oxide (TiO): $^{46}\\text{Ti}^{16}\\text{O}$, $^{47}\\text{Ti}^{16}\\text{O}$, $^{48}\\text{Ti}^{16}\\text{O}$, $^{49}\\text{Ti}^{16}\\text{O}$, and $^{50}\\text{Ti}^{16}\\text{O}$. The $^{48}\\text{Ti}^{16}\\text{O}$ line list contains transitions with wave-numbers up to 30 000 cm−1, i.e. longwards of 0.33 μm. The Toto line list includes all dipole-allowed transitions between 13 low-lying electronic states (X 3Δ, a1Δ, d 1Σ+, E 3Π, A 3Φ, B3Π, C 3Δ, b 1Π, c1Φ, f1Δ, e 1Σ+). Ab initio potential energy curves (PECs) are computed at the icMRCI level and combined with spin–orbit and other coupling curves. These PECs and couplings are iteratively refined to match known empirical energy levels. Accurate line intensities are generated using ab initio dipole moment curves. The Toto line lists are appropriate for temperatures below 5000 K and contain 30 million transitions for $^{48}\\text{Ti}^{16}\\text{O}$ it is made available in electronic form via the CDS data centre and via www.exomol.com. Tests of the line lists show greatly improved agreement with observed spectra for objects such as M-dwarfs GJ876 and GL581.
Publisher: Elsevier BV
Date: 09-2016
Publisher: MDPI AG
Date: 22-12-2020
DOI: 10.3390/NU13010005
Abstract: Metabolic syndrome (MetS) characteristics include chronic inflammation and elevated oxidative stress. This study assessed associations between circulating concentrations of micronutrients hytochemicals and inflammatory/oxidative stress markers with MetS and MetS components. Adults (N = 606) from the European Health Examination Survey in Luxembourg (2013–2015) were randomly selected. We performed a multivariable logistic regression model using the least absolute shrinkage and selection operator to identify MetS-associated variables. Participants with MetS had higher concentrations of C-reactive protein (CRP), 8-iso-prostaglandin F2α, leptin, insulin, and vitamins E/A, but lower concentrations of adiponectin, beta-carotene, and oxidized low-density lipoprotein. A one-unit increase in log-CRP was associated with 51% greater odds of MetS (OR = 1.51 (95% CI: 1.16, 1.98)). Adults with a one-unit increase in log-leptin were 3.1 times more likely to have MetS (3.10 (2.10, 4.72)). Women with a one-unit increase in vitamin A were associated with 3% increased odds of MetS (1.03 (1.01, 1.05)), while those with a one-unit increase in log-adiponectin were associated with 82% decreased odds (0.18 (0.07, 0.46)). Chronic inflammation best characterized adults with MetS, as CRP, adiponectin, and leptin were selected as the main MetS determinants. Micronutrients did not seem to affect MetS, except for vitamin A in women.
Publisher: IOP Publishing
Date: 18-06-2020
Abstract: We present benchmark integrated and differential cross-sections for electron collisions with H 2 using two different theoretical approaches, namely, the R-matrix and molecular convergent close-coupling. This is similar to comparative studies conducted on electron–atom collisions for H, He and Mg. Electron impact excitation to the b 3 Σ u + , a 3 Σ g + , B 1 Σ u + , c 3 Π u , E F 1 Σ g + , C 1 Π u , e 3 Σ u + , h 3 Σ g + , B ′ 1 Σ u + and d 3 Π u excited electronic states are considered. Calculations are presented in both the fixed nuclei and adiabatic nuclei approximations, where the latter is shown only for the b 3 Σ u + state. Good agreement is found for all transitions presented. Where available, we compare with existing experimental and recommended data.
Publisher: SPIE
Date: 27-08-2022
DOI: 10.1117/12.2641373
Publisher: SPIE
Date: 29-07-2016
DOI: 10.1117/12.2232370
Publisher: The Royal Society
Date: 05-08-2019
Abstract: Accurately modelling cold and ultracold reactive collisions occurring over deep potential wells, such as D + + H 2 → H + + HD , requires the development of new theoretical and computational methodologies. One potentially useful framework is the R -matrix method adopted widely for electron–molecule collisions which has more recently been applied to non-reactive heavy-particle collisions such as Ar–Ar. The existing treatment of non-reactive elastic and inelastic scattering needs to be substantially extended to enable modelling of reactive collisions: this is the subject of this paper. Herein, we develop the general mathematical formulation for non-reactive elastic and inelastic scattering, photoassociation, photodissociation, charge exchange and reactive scattering using the R -matrix method. Of particular note is that the inner region, of central importance to calculable R -matrix methodologies, must be finite in all scattering coordinates rather than a single scattering coordinate as for non-reactive scattering. This article is part of a discussion meeting issue ‘Advances in hydrogen molecular ions: H 3 + , H 5 + and beyond’.
Publisher: Elsevier BV
Date: 03-1997
Publisher: Elsevier BV
Date: 11-1997
Publisher: Informa UK Limited
Date: 10-05-2019
Publisher: Elsevier BV
Date: 06-1997
Publisher: IOP Publishing
Date: 05-05-2016
Publisher: Cambridge University Press (CUP)
Date: 10-2010
DOI: 10.1017/S1743921311020448
Abstract: The science of extra-solar planets is one of the most rapidly changing areas of astrophysics and since 1995 the number of planets known has increased by almost two orders of magnitude. A combination of ground-based surveys and dedicated space missions has resulted in 560-plus planets being detected, and over 1200 that await confirmation. NASA's Kepler mission has opened up the possibility of discovering Earth-like planets in the habitable zone around some of the 100,000 stars it is surveying during its 3 to 4-year lifetime. The new ESA's Gaia mission is expected to discover thousands of new planets around stars within 200 parsecs of the Sun. The key challenge now is moving on from discovery, important though that remains, to characterisation: what are these planets actually like, and why are they as they are? In the past ten years, we have learned how to obtain the first spectra of exoplanets using transit transmission and emission spectroscopy. With the high stability of Spitzer, Hubble, and large ground-based telescopes the spectra of bright close-in massive planets can be obtained and species like water vapour, methane, carbon monoxide and dioxide have been detected. With transit science came the first tangible remote sensing of these planetary bodies and so one can start to extrapolate from what has been learnt from Solar System probes to what one might plan to learn about their faraway siblings. As we learn more about the atmospheres, surfaces and near-surfaces of these remote bodies, we will begin to build up a clearer picture of their construction, history and suitability for life. The Exoplanet Characterisation Observatory, EChO, will be the first dedicated mission to investigate the physics and chemistry of Exoplanetary Atmospheres. By characterising spectroscopically more bodies in different environments we will take detailed planetology out of the Solar System and into the Galaxy as a whole. EChO has now been selected by the European Space Agency to be assessed as one of four M3 mission candidates.
Publisher: American Astronomical Society
Date: 08-02-2017
Publisher: American Astronomical Society
Date: 26-10-2018
Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C6FD00110F
Abstract: Techniques for producing cold and ultracold molecules are enabling the study of chemical reactions and scattering at the quantum scattering limit, with only a few partial waves contributing to the incident channel, leading to the observation and even full control of state-to-state collisions in this regime. A new R-matrix formalism is presented for tackling problems involving low- and ultra-low energy collisions. This general formalism is particularly appropriate for slow collisions occurring on potential energy surfaces with deep wells. The many resonance states make such systems hard to treat theoretically but offer the best prospects for novel physics: resonances are already being widely used to control diatomic systems and should provide the route to steering ultracold reactions. Our R-matrix-based formalism builds on the progress made in variational calculations of molecular spectra by using these methods to provide wavefunctions for the whole system at short internuclear distances, (a regime known as the inner region). These wavefunctions are used to construct collision energy-dependent R-matrices which can then be propagated to give cross sections at each collision energy. The method is formulated for ultracold collision systems with differing numbers of atoms.
Publisher: Informa UK Limited
Date: 15-09-2016
Location: France
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Jonathan Tennyson.