期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 351, 期 2, 页码 L39-L43出版社
OXFORD UNIV PRESS
DOI: 10.1111/j.1365-2966.2004.07959.x
关键词
accretion : accretion discs; techniques : spectroscopic; planets and satellites : formation; stars : formation; stars : pre-main sequence; open clusters and associations : individual : eta Chamaeleontis
High-resolution spectroscopic study of late-type members of the approximate to9-Myr-old eta Chamaeleontis star cluster shows that four stars, RECX 5, 9, 11 and ECHA J0843.3-7905, have broad Halpha profiles indicative of ballistic accretion of material from circumstellar discs first identified by virtue of their infrared (IR) excess emission. Quantitative analysis of the profiles finds accretion in eta Cha stars at rates comparable to that derived by Muzerolle et al. for members of the similarly aged TW Hydrae Association (TWA); rates 1-3 orders of magnitude lower than in younger classical T Tauri (CTT) stars. Together these studies indicate that the fraction of long-lived inner discs can be significantly higher than that inferred from study of younger pre-main sequence (PMS) populations, which suggest a disc lifetime of <6 Myr. The detection of long-lived discs may have implications for the formation of planetary systems. If slow accretion processes are the dominant formation mechanism for Jovian planets then long-lived discs may be ideal sites to search for evidence for protoplanets.
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