Spatially Resolved Circumstellar Structure of Herbig Ae/Be Stars in the Near-Infrared

By R. Millan-Gabet, F. Schloerb, Wesley A. Traub. 2000

184 citations recorded by the source corpus.

We have conducted the first systematic study of Herbig Ae/Be stars using the technique of long baseline stellar interferometry in the near-infrared, with the objective of characterizing the distribution and properties of the circumstellar dust responsible for the excess near-infrared fluxes from these systems. The observations for this work have been conducted at the Infrared Optical Telescope Array (IOTA). The principal result of this paper is that the interferometer resolves the source of infrared excess in 11 of the 15 systems surveyed. A new binary, MWC 361-A, has been detected interferometrically for the first time. The visibility data for all the sources has been interpreted within the context of four simple models which represent a range of plausible representations for the brightness distribution of the source of excess emission: a Gaussian, a narrow uniform ring, a flat blackbody disk with a single temperature power law, and an infrared companion. We find that the characteristic sizes of the near-infrared emitting regions are larger than previously thought (0.5-5.9 AU, as given by the FWHM of the Gaussian intensity). A further major result of this paper is that the sizes measured, when combined with the observed spectral energy distributions, essentially rule out accretion disk models represented by blackbody disks with the canonical T(r) ∝ r-3/4 law. We also find that, within the range observed in this study, none of the sources (except the new binary) shows varying visibilities as the orientation of the interferometer baseline changes. This is the expected behavior for sources which appear circularly symmetric on the sky, and for the sources with the largest baseline position angle coverage (AB Aur, MWC 1080-A) asymmetric brightness distributions (such as inclined disks or binaries) become highly unlikely. Taken as an ensemble, with no clear evidence in favor of axisymmetric structure, the observations favor the interpretation that the circumstellar dust is distributed in spherical envelopes (the Gaussian model) or thin shells (the ring model). This interpretation is also supported by the result that the measured sizes, combined with the excess near-infrared fluxes, imply emission of finite optical depth, as required by the fact that the central stars are optically visible. The measured sizes and brightnesses do not correlate strongly with the luminosity of the central star. Moreover, in two cases, the same excess is observed from circumstellar structures that differ in size by more than a factor of 2 and surround essentially identical stars. Therefore, different physical mechanisms for the near-infrared emission may be at work in different cases, or alternatively, a single underlying mechanism with the property that the same infrared excess is produced on very different physical scales.

Subfields: Astronomy and Astrophysics, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/d91e2933f30fa9a29a6499d0a7a44d592ceb4d94

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. J. Monnier
2. A. Natta
3. Andrea Isella
4. C. Dullemond
5. R. Millan-Gabet
6. M. Benisty
7. R. Neri
8. J. Bouwman

In Spectroscopy

1. J. Monnier
2. A. Natta
3. Andrea Isella
4. R. Millan-Gabet
5. R. Neri
6. M. Benisty
7. C. Dullemond
8. S. Andrews

Citations in the corpus

• On the Interferometric Sizes of Young Stellar Objects (2002, background): “The majority of measurements come from the IOTA interferometer (Millan-Gabet et al. 1999b; Millan-Gabet 1999; Millan-Gabet et al. 2001).”
• A reconsideration of disk properties in Herbig Ae stars (2001, background): “We suggest that the recent interferometric observations of AB Aur obtained by Millan-Gabet et al. (2001) in H and K detect exactly the emission of this wall, which at these wavelengths looks like a ring on the plane of the sky.”
• Processing of silicate dust grains in Herbig Ae/Be systems (2001, background): “Indeed, HD 150193 shows the smallest grains producing the silicate feature and has a large inner hole of about 0.6 AU (Millan-Gabet et al. 2001).”
• The shape of the inner rim in proto-planetary disks (2005, methodology): “…in the majority of cases the observed visibility curves are not well reproduced by flared disk models; rather, they are consistent with the emission of a ring of uniform brightness, of radius similar to the dust evaporation distance from the star (Millan-Gabet et al. 2001, Tuthill et al. 2001).”
• Few Skewed Disks Found in First Closure-Phase Survey of Herbig Ae/Be Stars (2006, methodology): “In this section, we carry-out the (now) standard procedure of YSO size estimation, first outlined by Millan-Gabet et al. (2001).”