Astron. Astrophys. 336, 565-586 (1998)
Continuum mapping at 1.3 mm turned out to be extremeful helpful to
uncover the circumstellar structure of the HAEBE and FU Orionis stars.
Together with near-infrared imaging we were able to relate the dust
emission to individual objects. In the case of
V 376 Cas/LkH 198, MWC 137,
CoD -42o11721, and V 1685 Cyg/V 1686 Cyg, the millimetre
emission is not related to the HAEBE stars. Four objects could not be
detected up to a 3 flux density limit of about
25 mJy. These are the HAEBE stars HK Ori, HD 250550,
LkH 25 and the FU Orionis star V 1515 Cyg.
The following conclusions can be drawn on the structure of the
The dusty environment of HAEBE and FU Orionis stars show two
markedly different structures which can be described as core and
core/envelope regions. Objects associated with only compact structures
include AB Aur and HD 163296 which are known to be surrounded by
The total masses obtained from the maps are usually much higher
than obtained from pointed On-On observations, especially in the case
of the objects associated with extended envelopes. The circumstellar
masses show a relatively broad variation between
0.03 and 1100 . The lowest
mass was derived for AB Aur with a value in quite good agreement with
recent interferometry measurements. The average densities in the cores
range from 105 to 108 cm-3. The
densities of the extended envelopes are of the order of 104
to 105 cm-3.
Radiative transfer calculations based on a spherically symmetric
model were performed for 4 objects (AB Aur, V 1331 Cyg, VY Mon,
LkH 234) in order to test if such models are able
to represent the SED of both the core and the core/envelope sources.
In all these cases including the compact-core objects AB Aur and
V 1331 Cyg, a satisfactory fit could be reached. This clearly
demonstrates that a good fit with a spherical model cannot be used as
an argument against the existence of a small-scale disk which is known
to exist in the case of AB Aur.
One of the selection criteria of Herbig (1960) for an HAEBE star
was its association with reflection nebulosities. As demonstrated by
this survey and already noted by Herbig (1994), this criterion can now
be replaced by the association with molecular-line or dust emission.
Future studies should address the kinematic relation between the HAEBE
stars and the associated circumstellar environment. Additional
interferometry searches are necessary to find out if more HAEBE stars
are related to disks with Keplerian velocity structures.
© European Southern Observatory (ESO) 1998
Online publication: July 20, 1998