期刊
ASTROPHYSICAL JOURNAL
卷 702, 期 1, 页码 724-732出版社
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/702/1/724
关键词
accretion, accretion disks; infrared: stars; planetary systems: protoplanetary disks; stars: individual (TW Hya, CS Cha, T Cha, VW Cha, Sz 73, Sz 102, HD 34700)
资金
- NASA [90035375]
The lifetime of isolated protoplanetary disks is thought to be set by the combination of viscous accretion and photoevaporation driven by stellar high-energy photons. Observational evidence for magnetospheric accretion in young Sun-like stars is robust. Here we report the first observational evidence for disk photoevaporation driven by the central star. We acquired high-resolution (R similar to 30,000) spectra of the [Ne II] 12.81 mu m line from seven circumstellar disks using VISIR on Melipal/VLT. We show that the three transition disks in the sample all have [Ne II] line profiles consistent with those predicted by a photoevaporative flow driven by stellar extreme-ultraviolet (EUV) photons. The similar to 6 km s(-1) blueshift of the line from the almost face-on disk of TW Hya is clearly inconsistent with emission from a static disk atmosphere and convincingly points to the presence of a photoevaporative wind. We do not detect any [Ne II] line close to the stellar velocity from the sample of classical optically thick (nontransition) disks. We conclude that most of the spectrally unresolved [Ne II] emission in these less-evolved systems arises from jets/outflows rather than from the disk. The pattern of the [Ne II] detections and nondetections suggests that EUV-driven photoevaporation starts only at a later stage in the disk evolution.
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