Title: Stellar mergers and near-mergers, seen and unseen    

　　Speaker: Stephen Justham (NAOC)       

　　Time & place: Thursday, 3:00pm, May 21st, lecture Hall, 3rd floor       

　　Abstract: Abstract: Mergers of stars may explain the production of numerous exotic astronomical objects and events. In addition, near-mergers of stars are strongly believed to be crucial in forming several of the highest-profile classes of stellar system in astrophysics. This near-merger process is called “common-envelope evolution” (CEE) and involves two stars temporarily merging before the envelope of one or both of them is ejected. The physics involved in these processes is extremely complex, with multiple areas of significant disagreement and uncertainty. Not only has our theoretical understanding of mergers and CEE developed very slowly, the observational evidence has mostly remained very indirect. I will give examples of the importance of these events, and of recent progress in improving our understanding. I will also explain how, somewhat unexpectedly, direct observations might be revolutionary for the field.    

　　Biog: Stephen Justham works in the National Astronomical Observatories of the Chinese Academy of Science. Following an undergraduate physics education in Cambridge, he completed a PhD at the Open University, then enjoyed time as a postdoc in Oxford before coming to China, first at KIAA and now NAOC. Stephen has mainly worked on topics relating to compact binary formation and supernovae.