【9.21; Seminar】2026年粒子天体物理全国重点实验室系列学术报告 #26: Advancing X-ray reflection spectroscopy: exploring accretion geometries from GRMHD

时间/Time：2026年9月21日（周一）上午10:00 / Monday, September 21, 2026, 10:00 a.m. 

地点/Location：多学科大楼312 / Room 312, Multidisciplinary Building 

报告人/Speaker：Dr. Swarnim Shashank (University of Tuebingen)

题目/Title：Advancing X-ray reflection spectroscopy: exploring accretion geometries from GRMHD

主持人/Host：陶炼 研究员 / Prof. Lian TAO

摘要/Abstract：

X-ray reflection models are widely used to analyze accreting systems and have achieved considerable success in measuring black hole spins. However, they tend to infer very high spins in X-ray binary systems, raising the question of whether these measurements are affected by systematic biases. A key limitation is that current reflection models rely on simplified analytical assumptions about the accretion geometry.  General relativistic magnetohydrodynamic (GRMHD) simulations provide a more realistic description of accretion flows from first principles. I use GRMHD simulations to model X-ray reflection from accreting black hole systems and generate synthetic spectra to test the ability of current reflection models to recover the input parameters after folding the spectra through an instrumental response. I also present a new model, REFLUX, specifically designed to analyze reflection features in super-Eddington systems, where reflection may originate from slim disks or optically thick winds.  Such advances will be particularly important for the next generation of X-ray observatories like eXTP.

个人简介/Biography：

Swarnim Shashank is currently a teaching fellow at the Institute for Astronomy and Astrophysics, University of Tuebingen, Germany; working in the group of Prof. Andrea Santangelo. He completed his PhD in 2023 from Fudan University, Shanghai with Prof. Cosimo Bambi. Following which he received the super postdoctoral fellowship award from the Shanghai government to continue his postdoc at Fudan University. His main work is in the field of relativistic astrophysics. He has worked on modeling of X-ray emissions of accreting black holes and tests of general relativity with X-ray and gravitational wave observations. He also works on GRMHD simulations of accreting black holes and numerical relativity simulations of neutron stars.