Astro-seminar by Haitao Li: X-ray occultation for the planetary atmosphere diagnostics

In the era of multi-wavelength astronomy, X-ray occultation emerges as a promising technique for probing planetary atmospheres, particularly the upper and tenuous layers of both solar system planets and exoplanets. This method leverages the absorption of X-rays by atmospheric constituents during occultation events, providing unique insights into atmospheric density, composition, etc. that complement UV, optical and infrared observations. The primary objective of this study is to develop a comprehensive framework for X-ray occultation-based planetary atmosphere diagnostics. This includes constructing forward models to simulate X-ray transmission through planetary atmospheres, as well as implementing Bayesian data processing and inversion techniques to retrieve atmospheric parameters from observed occultation light curves and spectra. The methodology encompasses laboratory experiments to validate X-ray absorption properties, analysis of in-orbit data from Earth-orbiting satellites for empirical verification, and detailed observational simulations to assess feasibility across various planetary scenarios. This talk will systematically introduce previously published results, ongoing work, and future research directions. Key results include recent findings from the Hard X-ray Modulation Telescope (HXMT) in-orbit data, demonstrating successful atmospheric profiling, laboratory validations and simulation studies targeting terrestrial planets and gas giants within the solar system. This work systematically advances X-ray occultation methods, integrating detection instrumentation with Bayesian analysis, and validates their efficacy through laboratory tests, satellite data, and simulations. Future prospects involve applying these techniques to data from the Macau Science Satellite-1B (MSS-1B), enhanced X-ray Timing and Polarimetry (eXTP) mission enhancing capabilities for planetary observations. The significance of this approach lies in its unique atmospheric diagnostic capabilities for solar system and exoplanetary science, enabling precise measurements of elusive upper atmospheric regions and supporting future missions in planetary exploration.