【6.3; Seminar】2026年粒子天体物理全国重点实验室系列学术报告 #20: Quasi-periodic oscillations and state transitions in XRBs: a spectral-timing perspective

时间/Time: 2026年6月3日周三上午10:00 / Wensday, June 3, 2026, 10:00 a.m. 

地点/Location: 多学科312会议室 / 312 Meeting Room, Multidisciplinary Building

报告人/Speaker: Dr. Federico García (Instituto Argentino de Radioastronomía (IAR, CONICET / UNLP / CICPBA))

题目/Title: Quasi-periodic oscillations and state transitions in XRBs: a spectral-timing perspective

主持人/Host: 张亮 副研究员 / Dr. Liang ZHANG

摘要/Abstract:

During transient outbursts, X-ray binaries (XRBs) undergo pronounced state transitions, evolving between corona-dominated hard states and thermal-dominated soft states. To analyze the rapid X-ray variability characterizing the intermediate and hard states, we employ spectral-timing Fourier techniques. By measuring variability amplitudes, phase lags, and coherence across different energy bands, these methods allow us to constrain the geometry of the inner accretion flow and the radiation propagation mechanisms near the compact object.

In this talk, I will present the application of a time-dependent Comptonization model to the quasi-periodic oscillations (QPOs) of these sources, showing how fast-timing analyses constrain the geometrical properties of the accretion flow. Furthermore, I will delve into the soft-to-hard transition during the outburst decay phase and discuss the physical implications of the recently detected narrow coherence drops, outlining how such timing signatures characterize the coupled evolution between the accretion disc and the corona.

个人简介/Biography:

Dr. Federico García is an Independent Staff Researcher from CONICET based at the Argentine Institute of Radioastronomy (IAR), where he has held a permanent position since 2021. He obtained his PhD from the National University of La Plata (UNLP) in 2016 and subsequently completed postdoctoral positions at IAR, the University of Paris Cité / CEA-Saclay in France, and the Kapteyn Astronomical Institute in the Netherlands. His primary research lies in high-energy astrophysics, specializing in accretion processes in X-ray binary systems containing black holes and neutron stars. Additionally, he conducts pulsar-timing studies based on radio observations from the IAR antennas.