Astronomy and Astrophysics – Astrophysics – Solar and Stellar Astrophysics
Scientific paper
2010-11-16
Astronomy and Astrophysics
Astrophysics
Solar and Stellar Astrophysics
96 pages, 34 figures; Accepted by ApJ
Scientific paper
We have acquired sub-millimeter observations of 33 fields containing 37 Herbig Ae/Be (HAEBE) stars or potential HAEBE stars, including SCUBA maps of all but two of these stars. Nine target stars show extended dust emission. The other 18 are unresolved, suggesting that the dust envelopes or disks around these stars are less than a few arcseconds in angular size. In several cases we find that the strongest sub-millimeter emission originates from younger, heavily embedded sources rather than from the HAEBE star, which means that previous models must be viewed with caution. These new data, in combination with far-infrared flux measurements available in the literature, yield SEDs from far-infrared to millimeter wavelengths for all the observed objects. Isothermal fits to these SEDs demonstrate excellent fits, in most cases, to the flux densities longward of 100 {\mu}m. We find that a smaller proportion of B-type stars than A and F-type stars are surrounded by circumstellar disks, suggesting that disks around B stars dissipate on shorter time scales than those around later spectral types. Our models also reveal that the mass of the circumstellar material and the value of beta are correlated, with low masses corresponding to low values of beta. Since low values of beta imply large grain sizes, our results suggest that a large fraction of the mass in low-beta sources is locked up in very large grains. Several of the isolated HAEBE stars have disks with very flat sub-millimeter SEDs. These disks may be on the verge of forming planetary systems.
Hamidouche Murad
Sandell Göran
Weintraub David A.
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