邀请人 (Invited by): 胡一鸣

时间 (Time): 星期三，2023/07/12-14:00-15：30 

地点 (Location): 珠海校区天琴中心1416会议室

摘要 (Abstract): 

Pulsar Timing Arrays (PTAs) search for nHz gravitational waves by timing the radio signals from a network of stable millisecond pulsars and looking for a spatially correlated common signal in the data set. We expect to find a gravitational wave background (GWB) first, followed by possible individual sources. PTAs have reported the finding of a spectrally similar but spatially uncorrelated signal in various data sets, namely North American Nanohertz Observatory for Gravitational waves (NANOGrav), Australian Parkes PTA, European PTA, together with the Indian PTA they form the International PTA. We hope to deepen collaboration with Chinese and South African PTA colleagues. 

I will present the recent results that the EPTA+InPTA, NANOGrav, PPTA, and CPTA collaborations have published in a coordinated process, each using their own independent data sets and analysis tools. All PTAs report consistent results of a common signal with a nominal amplitude of around 2-3e-15. Measurements of the characteristic spatial correlations required for a GWB vary between the different PTAs. However, a general positive trend can be noticed with some evidence in favour of the gravitational wave origin of the common signal. This putative signal can be tested against both cosmological and astrophysical sources for a GWB and be used to put constraints for various theories. Efforts are ongoing to combine these new data sets to form the basis for the next IPTA DR3 combination in the coming year. The IPTA DR3 should provide the best sensitivity for searching and characterising the common signal yet.

主讲人简介 (Speaker's CV): 

Siyuan Chen received his PhD in Physics and Astronomy from the University of Birmingham in the UK under the supervision of Prof. Alberto Sesana in 2018. He has been awarded the AE Hills studentship to cover the tuition fees. From 2018 to 2021, he has worked as a postdoctoral researcher at the Centre national de la recherche scientifique (CNRS) in Orleans, France, in the Laboratory for space and evironmental physics and chemistry (LPC2E). During his studies and reasearch, Siyuan Chen has been strongly involved  strongly with the European Pulsar Timing Array (EPTA), where he serves as the co-coordinator of the data analysis and astrophysics working group. Recently, he has taken a position on the Executive Committee of the EPTA. Other collaborations include the Large European Array for Pulsars (LEAP), North American Nanohertz Observatory for Gravitational waves (NANOGrav) and International Pulsar Timing Array (IPTA). At the end of 2021, he has joined the Kavli Institute for Astronomy and Astrophysics at Peking University as a postdoctoral fellow.