活動詳細資訊 Event Information
活動詳細資訊 Event Information
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活動訊息最後更新時間 : 2017-08-18 16:53:20
開始日期 Starting Date:2017-08-24  14:00
結束日期 Ending Date:2017-08-24  15:30
會議狀態 State:確定 Definitive
主/協辦單位 Organizer:天文及天文物理研究所 Institute of Astronomy and Astrophysics
活動地點 Venue:R1203 of the Astronomy-Mathematics Building, National Taiwan University
活動備忘 Event Memo:

Abstract

The abundances of heavy elements in planetary nebulae reveal the evolutionary past of the central star, and the future of the interstellar medium, but suffer from a major systematic uncertainty: abundances derived from emission lines formed by recombination exceed those from collisionally excited lines by a factor ranging from ~2 to nearly three orders of magnitude in the most extreme case. The discrepancy has been known since the 1940s but only now are its causes being tracked down. There is now substantial evidence for the presence of cold hydrogen-deficient material within the normal hydrogen-rich gas of planetary nebulae, which gives rise to strongly enhanced recombination line emission.
It has recently become clear that the most extreme abundance discrepancies occur in nebulae which have a close binary central star. I will discuss my recent work which has doubled the sample of nebulae with a close binary central star and known chemistry, placing new constraints on the origin of hydrogen deficient material and the cause of the abundance discrepancy.