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Paper: Spectro-Astrometry of Herbig Ae/Be Stars
Volume: 355, Stars With the B[e] Phenomenon
Page: 99
Authors: Oudmaijer, R.D.; Baines, D.; Porter, J.M.; Pozzo, M.
Abstract: In this contribution we present the results of high quality spectroastrometry of a sample of 31 Herbig Ae/Be stars. Based on the spectra, we find that the B[e] phenomenon is ubiquitous amongst these pre-main sequence stars. A third of the sample objects is found to have forbidden [OI] and [FeII] line emission, while a further 20% displays the forbidden [OI] line, but not the [FeII] line emission. The spectro-astrometry we employ is a variant of long-slit spectroscopy where spatially unresolved features can be studied. It has the potential to resolve circumstellar disks at milli-arcsecond scales and has been particularly successful in discovering binary systems with flux ratios of more than a thousand. We discover many new binaries, bringing the binary fraction of Herbig Ae/Be stars to around 70% - no other single technique has been able to find such a high frequency. We find that there is no significant difference between the binary properties of the Herbig Ae/B[e] and the Herbig Ae/Be stars. Where known, the position angles of the circumstellar disks of the primaries in the binary systems are aligned with the binary PA, indicating that the binary was formed during fragmentation rather than capture or mergers.
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