11:45 AM - 12:00 PM
[PCG19-11] Spectral Line Profile Measurement of Methane for Investigating the Atmospheres Rich in H2 and He in Substellar Objects
Keywords:High-resolution Spectra, Instrumental development, Molecule, Atmosphere, Gas-giants, Brown dwarf
High-resolution spectral analysis is becoming a key method for exploring the atmospheres of substellar objects. While there are available line lists like HITEMP and Exomol for analysis, accurately modeling atmospheric spectra, especially for gas giants and brown dwarfs abundant in hydrogen and helium, presents challenges due to the lack of experimental data on the pressure-induced broadening parameter of molecular absorption lines.
To address this, we developed an experimental setup designed to estimate the line profile parameters by measuring the high-resolution transmission spectra of target molecules, within an environment simulating solar composition gases at specified pressures (0.1 - 1 bar) and temperatures (300 - 1400K). Employing the Hamiltonian Monte Carlo (HMC) method, our system is capable of estimating the Lorentzian coefficient(γ0) and its temperature dependence (n) for these environments along with the associated error. As a prototype experiment, we successfully captured several methane absorption lines at temperatures up to 1000K, with a wavelength of λ=1.62μm and a wavelength resolution of R=640000, and obtained the results including a significant value difference between the existing databases. Our ongoing efforts aim to extend the wavelength range of λ=1.60 - 1.63μm, where significant discrepancies exist between current models by existing databases and observed spectra. We also planning to measure carbon monoxide around λ=2.3μm as the next step.
We will present an overview of our system's design, analysis methods, and how our findings compare with those from existing databases.
To address this, we developed an experimental setup designed to estimate the line profile parameters by measuring the high-resolution transmission spectra of target molecules, within an environment simulating solar composition gases at specified pressures (0.1 - 1 bar) and temperatures (300 - 1400K). Employing the Hamiltonian Monte Carlo (HMC) method, our system is capable of estimating the Lorentzian coefficient(γ0) and its temperature dependence (n) for these environments along with the associated error. As a prototype experiment, we successfully captured several methane absorption lines at temperatures up to 1000K, with a wavelength of λ=1.62μm and a wavelength resolution of R=640000, and obtained the results including a significant value difference between the existing databases. Our ongoing efforts aim to extend the wavelength range of λ=1.60 - 1.63μm, where significant discrepancies exist between current models by existing databases and observed spectra. We also planning to measure carbon monoxide around λ=2.3μm as the next step.
We will present an overview of our system's design, analysis methods, and how our findings compare with those from existing databases.