文章基本信息

标题：DZ Chamaeleontis: a bona fide photoevaporating disc ⋆
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作者：H. Canovas ; B. Montesinos ; M. R. Schreiber 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2018
卷号：610
DOI：10.1051/0004-6361/201731640
语种：English
出版社：EDP Sciences
摘要：Context.DZ Cha is a weak-lined T Tauri star (WTTS) surrounded by a bright protoplanetary disc with evidence of inner disc clearing. Its narrowHαline and infrared spectral energy distribution suggest that DZ Cha may be a photoevaporating disc.Aims.We aim to analyse the DZ Cha star + disc system to identify the mechanism driving the evolution of this object.Methods.We have analysed three epochs of high resolution optical spectroscopy, photometry from the UV up to the sub-mm regime, infrared spectroscopy, andJ-band imaging polarimetry observations of DZ Cha.Results.Combining our analysis with previous studies we find no signatures of accretion in theHαline profile in nine epochs covering a time baseline of~20 yr. The optical spectra are dominated by chromospheric emission lines, but they also show emission from the forbidden lines [SII] 4068 and [OI] 6300Åthat indicate a disc outflow. The polarized images reveal a dust depleted cavity of~7 au in radius and two spiral-like features, and we derive a disc dust mass limit ofMdust< 3MEarthfrom the sub-mm photometry. No stellar (M⋆> 80MJup) companions are detected down to0.̋07(~8 au, projected).Conclusions.The negligible accretion rate, small cavity, and forbidden line emission strongly suggests that DZ Cha is currently at the initial stages of disc clearing by photoevaporation. At this point the inner disc has drained and the inner wall of the truncated outer disc is directly exposed to the stellar radiation. We argue that other mechanisms like planet formation or binarity cannot explain the observed properties of DZ Cha. The scarcity of objects like this one is in line with the dispersal timescale (≲105yr) predicted by this theory. DZ Cha is therefore an ideal target to study the initial stages of photoevaporation.
关键词：enaccretion, accretion disksprotoplanetary disksstars: variables: T Tauri, Herbig Ae/Be