Astronomy and Astrophysics – Astrophysics
Scientific paper
Aug 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000a%26a...360..213b&link_type=abstract
Astronomy and Astrophysics, Vol. 360, p.213-226
Astronomy and Astrophysics
Astrophysics
74
Radiative Transfer, Stars: Circumstellar Matter, Stars: Formation, Stars: Individual: Ab Aur, Stars: Individual: Hd 163296, Stars: Pre-Main Sequence
Scientific paper
We have analysed the 2-200 μm ISO spectra of two bright Herbig Ae stars, AB Aur and HD 163296, in order to derive the composition and mass over temperature distribution of the circumstellar dust. We find that the two stars have a similar composition of the dust, however also with some important differences. We address the onset of the strong near-infrared emission between 1-4 μm. We show that this emission can be explained with thermal emission from metallic iron or dust species containing iron. The circumstellar dust surrounding both stars shows two distinct regimes in the mass over temperature distributions with temperatures of ~ 103 and ~ 102 K. Modelling of the ISO spectra further reveal a significant deviation of the derived grain sizes compared to the interstellar grain size distribution. A population of large (~ 1 mm) grains is required to explain the observed (sub-) millimetre fluxes of HD 163296. The presence of crystalline silicates and the larger grain sizes in HD 163296 compared to AB Aur suggests that the former star is a more evolved system. Amorphous silicates make out the bulk of the dust mass in both stars. It is likely that a significant fraction of the dust is carbon-rich. We find strong evidence for a 20-30 μm band which we tentatively attribute to FeO.
Bouwman Jeroen
de Koter Alex
van den Ancker Mario E.
Waters Laurens B. F. M.
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