Title: X-ray relativistic Fe line and black hole spin in narrow-line Seyfert I galaxies / New frontiers in wide-field time-domain high-energy astrophysics

Speaker: Weimin Yuan (NAOC)  

Time & Place: Thursday, 3:00pm, November 20th, Lecture Hall, 3rd floor  

Abstract: Relativistic Fe emission line observed in the X-ray spectra of typical Seyfert galaxies is a powerful diagnostic of the spin and surroundings of the central black holes. A long-standing question is whether such a feature is also present in Narrow-Line Seyfert 1 (NLS1) galaxies, which are thought to be at an early phase of black hole growth. By stacking the XMM-Newton X- ray spectra of a large sample, we show that a relativistic Fe line may in fact be common in NLS1s. We find, for the first time, that the black holes are likely spinning at averagely low or moderate rates for NLS1 galaxies as a population. The implications of the results are discussed in the context of the black hole growth scenario.

Transients and variable sources pervade the X-ray universe, some as spectacular outbursts. The study of high-energy transients has greatly advanced our understanding of the dynamic Universe. In recent years new phenomena continue to be discovered and appeal for observations on a large scale for characterisation, while others are highly expected and await discovery. I will discuss the key science questions presented by these new developments in wide-field time- domain high-energy astrophysics, as well as the technology needed to open up new frontiers. Last, I will introduce briefly the Einstein Probe, which is a candidate mission in the CAS Pilot Space Science Program, as well as its promise to expand new frontiers in this exciting field.

Biog: Dr. Weimin Yuan is a research scientist at Space Science Division, National Astronomical Observatories of China. He received his PhD from Technology University of Munich/Max-Planck Institute for extraterrestrial Physics, Germany. Afterwards he became a postdoc at JAXA, Japan to work for the MAXI mission (an X-ray all-sky monitor currently operating on the International Space Station). He then moved to IoA, University of Cambridge, UK as a postdoc. He became a research staff at Yunnan Observatory, before moving to NAOC in Beijing. His research interests are mainly on observational studies of black holes, accretion and jets in active galactic nuclei, as well as on development of space-borne instruments in recent years. He is the PI of the Einstein Probe - a candidate space mission of the CAS.