A Population Study of Gaseous Exoplanets Tsiaras, A.; Waldmann, I. P.; Zingales, T. ...
The Astronomical journal,
04/2018, Letnik:
155, Številka:
4
Journal Article
Recenzirano
Odprti dostop
We present here the analysis of 30 gaseous extrasolar planets, with temperatures between 600 and 2400 K and radii between 0.35 and 1.9 RJup. The quality of the HST/WFC3 spatially scanned data ...combined with our specialized analysis tools allow us to study the largest and most self-consistent sample of exoplanetary transmission spectra to date and examine the collective behavior of warm and hot gaseous planets rather than isolated case studies. We define a new metric, the Atmospheric Detectability Index (ADI) to evaluate the statistical significance of an atmospheric detection and find statistically significant atmospheres in around 16 planets out of the 30 analyzed. For most of the Jupiters in our sample, we find the detectability of their atmospheres to be dependent on the planetary radius but not on the planetary mass. This indicates that planetary gravity plays a secondary role in the state of gaseous planetary atmospheres. We detect the presence of water vapour in all of the statistically detectable atmospheres, and we cannot rule out its presence in the atmospheres of the others. In addition, TiO and/or VO signatures are detected with 4 confidence in WASP-76 b, and they are most likely present in WASP-121 b. We find no correlation between expected signal-to-noise and atmospheric detectability for most targets. This has important implications for future large-scale surveys.
Thermal inversions have long been predicted to exist in the atmospheres of ultra-hot Jupiters. However, the detection of two species thought to be responsible – titanium oxide and vanadium oxide – ...remains elusive. We present a search for TiO and VO in the atmosphere of the ultra-hot Jupiter WASP-121b (
T
eq
≳ 2400 K), an exoplanet with evidence of VO in its atmosphere at low resolution which also exhibits water emission features in its dayside spectrum characteristic of a temperature inversion. We observed its transmission spectrum with the UV-Visual Echelle Spectrograph at the Very Large Telescope and used the cross-correlation method – a powerful tool for the unambiguous identification of the presence of atomic and molecular species – in an effort to detect whether TiO or VO were responsible for the observed temperature inversion. No evidence for the presence of TiO or VO was found at the terminator of WASP-121b. By injecting signals into our data at varying abundance levels, we set rough detection limits of VO ≲−7.9 and TiO ≲−9.3. However, these detection limits are largely degenerate with scattering properties and the position of the cloud deck. Our results may suggest that neither TiO or VO are the main drivers of the thermal inversion in WASP-121b; however, until a more accurate line list is developed for VO, we cannot conclusively rule out its presence. Future works will consist of a search for other strong optically-absorbing species that may be responsible for the excess absorption in the red-optical.
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.
•Line lists for 80 molecules and 190 isotopologues totaling 700 billion transition.•Partition functions, state lifetimes, cooling functions, Lande g-factors, cross sections, opacities, pressure ...broadening parameters, k-coeffcients and dipoles also provided.•Implementation of higher resolution line llsts based on the MARVEL protocol.
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The ExoMol database (www.exomol.com) provides molecular data for spectroscopic studies of hot atmospheres. While the data are intended for studies of exoplanets and other astronomical bodies, the dataset is widely applicable. The basic form of the database is extensive line lists; these are supplemented with partition functions, state lifetimes, cooling functions, Landé g-factors, temperature-dependent cross sections, opacities, pressure broadening parameters, k-coefficients and dipoles. This paper presents the latest release of the database which has been expanded to consider 80 molecules and 190 isotopologues totaling over 700 billion transitions. While the spectroscopic data are concentrated at infrared and visible wavelengths, ultraviolet transitions are being increasingly considered in response to requests from observers. The core of the database comes from the ExoMol project which primarily uses theoretical methods, albeit usually fine-tuned to reproduce laboratory spectra, to generate very extensive line lists for studies of hot bodies. The data have recently been supplemented by line lists derived from direct laboratory observations, albeit usually with the use of ab initiotransition intensities. A major push in the new release is towards accurate characterisation of transition frequencies for use in high resolution studies of exoplanets and other bodies.
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•ExoMol provides comprehensive spectroscopic data for key molecules.•The ExoMol data structure is defined.•A summary of present and future contents of the database is given.
The ...ExoMol database (www.exomol.com) provides extensive line lists of molecular transitions which are valid over extended temperature ranges. The status of the current release of the database is reviewed and a new data structure is specified. This structure augments the provision of energy levels (and hence transition frequencies) and Einstein A coefficients with other key properties, including lifetimes of individual states, temperature-dependent cooling functions, Landé g-factors, partition functions, cross sections, k-coefficients and transition dipoles with phase relations. Particular attention is paid to the treatment of pressure broadening parameters. The new data structure includes a definition file which provides the necessary information for utilities accessing ExoMol through its application programming interface (API). Prospects for the inclusion of new species into the database are discussed.
A global potential energy surface for H3 Mizus, Irina I.; Polyansky, Oleg L.; McKemmish, Laura K. ...
Molecular physics,
07/2019, Letnik:
117, Številka:
13
Journal Article
Recenzirano
A globally correct potential energy surface (PES) for the
molecular ion is presented. The Born-Oppenheimer (BO) ab initio grid points of Pavanello et al. J. Chem. Phys. 136, 184303 (2012) are ...refitted as BOPES75K, which reproduces the energies below dissociation with a root mean square deviation of 0.05 cm
−1
; points between dissociation and 75,000 cm
−1
are reproduced with the average accuracy of a few wavenumbers. The new PES75K+ potential combines BOPES75K with adiabatic, relativistic and quantum electrodynamics (QED) surfaces to provide the most accurate representation of the
global potential to date, overcoming the limitations on previous high accuracy
PESs near and above dissociation. PES75K+ can be used to provide predictions of bound rovibrational energy levels with an accuracy of approaching 0.1 cm
−1
. Calculation of rovibrational energy levels within PES75K+ suggests that the non-adiabatic correction remains a limiting factor. The PES is also constructed to give the correct asymptotic limit making it suitable for use in studies of the
prototypical chemical reaction. An improved dissociation energy for
is derived as
cm
−1
.
A global potential energy surface for H 3 Mizus, Irina I.; Polyansky, Oleg L.; McKemmish, Laura K. ...
Molecular physics,
07/2019, Letnik:
117, Številka:
13
Journal Article
The R-matrix method is a fully-quantum time-independent scattering method, used to simulate nuclear, electron-atom, electron-ion, electron-molecule scattering and more. Here, a novel R-matrix method, ...RmatReact, is presented as applied to ultracold (sub-Kelvin) atom-atom scattering. This is in response to experimental methods which in recent decades have facilitated the routine use of ultracold atoms and small molecules in experiments. This project lays the groundwork for future codes to eventually simulate polyatom-polyatom reactive collisions. Results are presented in this paper for numerical comparisons to other established methods, and for resonances in the elastic scattering of ultracold argon atoms.
Involving students in state-of-the-art research from an early age eliminates the idea that science is only for the scientists and empowers young people to explore STEM (Science, Technology, ...Engineering and Maths) subjects. It is also a great opportunity to dispel harmful stereotypes about who is suitable for STEM careers, while leaving students feeling engaged in modern science and the scientific method. As part of the Twinkle Space Mission's educational programme, EduTwinkle, students between the ages of 15 and 18 have been performing original research associated with the exploration of space since January 2016. The student groups have each been led by junior researchers-PhD and post-doctoral scientists-who themselves benefit substantially from the opportunity to supervise and manage a research project. This research aims to meet a standard for publication in peer-reviewed journals. At present the research of two ORBYTS teams have been published, one in the Astrophysical Journal Supplement Series and another in JQSRT; we expect more papers to follow. Here we outline the necessary steps for a productive scientific collaboration with school children, generalising from the successes and downfalls of the pilot ORBYTS projects.
Zirconium oxide (ZrO) is an important astrophysical molecule that defines the S-star classification class for cool giant stars. Accurate, empirical rovibronic energy levels, with associated labels ...and uncertainties, are reported for nine low-lying electronic states of the diatomic molecule. These 8088 empirical energy levels are determined using the Measured Active Rotational-Vibrational Energy Levels algorithm with 23,317 input assigned transition frequencies, 22,549 of which were validated during this study. A temperature-dependent partition function is presented alongside updated spectroscopic constants for the nine low-lying electronic states.
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