P. Riviere-Marichalar, F. Ménard, W. F. Thi, I. Kamp, B. Montesinos, G. Meeus, P. Woitke, C. Howard, G. Sandell, L. Podio, W. R. F. Dent, I. Mendigutí, C. Pinte, G. J. White, D. Barrado
Line spectra of 68 Taurus T Tauri stars were obtained with the Herschel-PACS
(Photodetector Array Camera & Spectrometer) instrument as part of the GASPS
(Gas Evolution in Protoplanetary Systems) survey of protoplanetary discs. A
careful examination of the line scans centred on the [OI] 63.18 microns
fine-structure line unveiled a line at 63.32 micron in some of these spectra.
We identify this line with a transition of ortho-water. It is detected
confidently (i.e., >3 sigma) in eight sources, i.e., 24% of the sub-sample with
gas-rich discs. Several statistical tests were used to search for correlations
with other disc and stellar parameters such as line fluxes of [OI]] 6300
Armstrong and 63.18 microns; X-ray luminosity and continuum levels at 63
microns and 850 microns. Correlations are found between the water line fluxes
and the [OI] 63.18 microns line luminosity, the dust continuum, and possibly
with the stellar X-ray luminosity. This is the first time that this line of
warm water vapour has been detected in protoplanetary discs. We discuss its
origins, in particular whether it comes from the inner disc and/or disc surface
or from shocks in outflows and jets. Our analysis favours a disc origin, with
the observed water vapour line produced within 2-3AU from the central stars,
where the gas temperature is of the order of 500-600 K.
View original:
http://arxiv.org/abs/1112.4850
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