Circumstellar disks around Herbig Be stars

Alonso-Albi, T.; Fuente, A.; Bachiller, R.; Neri, R.; Planesas, P.; Testi, L.; Berné, O.; Joblin, C.

doi:10.1051/0004-6361/200810401

Cited by 99 publications

(138 citation statements)

References 41 publications

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“…These results on the disk masses are in accordance with other studies of MYSOs (e.g. Murakawa et al 2008) and also with some evolved early-type Herbig Be stars (Alonso-Albi et al 2009). Were the disk outer radius much smaller than the assumed 500 AU and similar to the small outer radii found for the Herbig Be stars, then the disk mass should be scaled down accordingly: a 50 AU outer radius results in a disk mass of 5 × 10 −4 M .…”

Section: The Contribution Of An Accretion Disksupporting

confidence: 92%

The origin of mid-infrared emission in massive young stellar objects: multi-baseline VLTI observations of W33A

Wit

Hoare

Oudmaijer

et al. 2010

A&A

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Aims. In this paper we aim to determine the structure on 100 AU scales of the massive young stellar object W33A, using interferometric observations in the mid-infrared. This emission could be caused by a variety of elements, for example, the inner protostellar envelope, outflow cavity walls, or a dusty or gaseous accretion disk. Methods. We used the Unit Telescopes of the VLT Interferometer in conjunction with the MIDI instrument to obtain spectrally dispersed visibilities in the N-band on 4 baselines with an angular resolution between 25 and 60 milli-arcsec (equivalent to 95 and 228 AU at 3.8 kpc). The visibility spectra and spectral energy distribution were compared to 2D-axi-symmetric dust radiative transfer models with a geometry that includes a rotationally flattened envelope and outflow cavities. We assumed an O 7.5 ZAMS star as the central source, consistent with the observed bolometric luminosity. The observations were compared to models with and without (dusty and gaseous) accretion disks. Results. The visibilities are between 5% and 15%, and the non-spherically symmetric emitting structure has a typical size of 100 AU. A satisfactory model is constructed to reproduce the visibility spectra for each (u, v) point. It fits the N-band flux spectrum, the midinfrared slope, the far-infrared peak, and the (sub)mm regime of the SED. It produces a 350 μm morphology consistent with the observations. Conclusions. The mid-infrared emission of W33A on 100 AU scales is dominated by the irradiated walls of the cavity sculpted by the outflow. The protostellar envelope has an equivalent mass infall rate of 7.5 × 10 −4 M yr −1 , and an outflow opening angle of 2θ = 20 • . The visibilities rule out the presence of any dust disk with total (gas and dust) mass more than 0.01 M . Within the model, this implies a diskṀ acc of less than 1.1 × 10 −7 (α/0.01) M yr −1 , where α is the viscosity of the Shakura-Sunyaev prescription. However, optically thick accretion disks, which are inside the dust sublimation radius, are allowed to accrete at rates equalling the envelope's mass infall rate (up to 10 −3 M yr −1 ) without substantially affecting the visibilities due to the extinction by the extremely massive envelope of W33A.

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Section: The Contribution Of An Accretion Disksupporting

confidence: 92%

The origin of mid-infrared emission in massive young stellar objects: multi-baseline VLTI observations of W33A

Wit

Hoare

Oudmaijer

et al. 2010

A&A

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“…We applied only the a max = 1000.0 μm dust model in the entire disk. This disk geometry is typical of T Tauri and Herbig Ae stars and is similar to the ones estimated from the observations at 1.3 mm continuum (F06) and a previous radiative transfer model (Alonso-Albi et al 2009). For the D3 model, the disk height is from previous CO emission line observations and modeling (F06).…”

Section: Disk Geometrysupporting

confidence: 83%

“…The extension of the polarization disk is closer to the CO gas phase disk (1500 AU ∼ 4 ) and the central feature in the 2.7 mm continuum (3000 AU ∼ 8 ) than is detected both in the 1.3 mm continuum and an estimated disk radius of 150 AU (∼0. 4) by a previous modeling (Alonso-Albi et al 2009). The disk height of the gas phase disk was estimated to be 1500 AU at the outer disk radius of 1500 AU (F06).…”

Section: Introductionmentioning

confidence: 89%

Radiative transfer modeling of the dust disk of the Herbig Be star R Monocerotis

Murakawa

2010

A&A

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Our previous near-infrared (NIR), high-resolution polarimetric images of the Herbig Be star R Mon show that the polarization disk has a large, nearly constant angular size of ∼4 in the JHK bands, low polarizations of 1.1-1.5% in the H and K bands, and somewhat centro-symmetrical vector alignment. To derive the disk geometry parameters and grain sizes that explain this result, we modeled R Mon's dust disk by combining it with previously obtained spectral energy distribution and gas phase observations. Our model assumes an inner disk and outer envelope structure, dust of different populations for the disk and envelope, and a power-law size distribution of n (a) ∝ a −3.5 with 0.005 μm ≤ a ≤ a max μm. We obtained an outer disk radius of 3000 AU, a ratio of the height to the radius of the disk of H 0 = 0.4, a V-band optical depth of 4.2 in the disk midplane, and an a max of 1000.0 μm for the disk. Such a large extension of the disk is similar to the ones of the central feature detected in previous observations in the CO emission lines (1500 AU) and the 2.7 mm continuum (3000 AU). The shape and angular size of the polarization disk in our model fit the observations and approximately trace the projected appearance of the real disk. Since the estimated dust disk height has an intermediate value and is lower than the gas phase (CO) disk height (H 0 = 1.0), it is likely that the dust settling is ongoing. Our selected model with a large dust size with an a max of 1000.0 μm in the inner part of the disk and a disk mass of 0.02 M fit the near-infrared polarization towards the disk and the mid-infrared to millimeter fluxes well. Our estimated disk mass roughly agrees with a previous gas phase modeling of ∼0.01 M . Such a large grain model reproduces low NIR polarizations (1.6%), which is consistent with our observation. Not detecting the vector alignment is explained with this large grain model and an intermediate optical depth of the disk. We expect that R Mon's disk contrasts to the typical T Tauri and Herbig Ae disks in terms of an expected large outer disk radius and an intermediate optical depth. Evidence of the dust settling and large grains suggests that the dust in R Mon's disk grows faster than the disk accretion advances, which is theoretically predicted in typical T Tauri disks.

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“…Dullemond et al 2001) and magnetospheric accretion models describe the line profiles of Herbig Ae/Be stars , in close analogy to cTTS. However, the disk lifetime appears to be shorter for Herbig Ae/Be stars (Uzpen et al 2009;Carpenter et al 2005) and within the Herbig Ae/Be class there is a trend of more massive stars dispersing their disks more rapidly (Alonso-Albi et al 2009). Herbig Ae stars are closer analogs to TTS than Herbig Be stars.…”

Section: Introductionmentioning

confidence: 99%

Searching for a link between the magnetic nature and other observed properties of Herbig Ae/Be stars and stars with debris disks

Hubrig

Stelzer

Schöller

et al. 2009

A&A

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Context. Recently, evidence for the presence of weak magnetic fields in Herbig Ae/Be stars has been found in several studies. Aims. We seek to expand the sample of intermediate-mass pre-main sequence stars with circular polarization data to measure their magnetic fields, and to determine whether magnetic field properties in these stars are correlated with mass-accretion rate, disk inclination, companions, silicates, PAHs, or show a correlation with age and X-ray emission as expected for the decay of a remnant dynamo. Methods. Spectropolarimetric observations of 21 Herbig Ae/Be stars and six debris disk stars have been obtained at the European Southern Observatory with FORS 1 mounted on the 8 m Kueyen telescope of the VLT. With the GRISM 600B in the wavelength range 3250-6215 Å we were able to cover all hydrogen Balmer lines from Hβ to the Balmer jump. In all observations a slit width of 0. 4 was used to obtain a spectral resolving power of R ≈ 2000. Results. Among the 21 Herbig Ae/Be stars studied, new detections of a magnetic field were achieved in six stars. For three Herbig Ae/Be stars, we confirm previous magnetic field detections. The largest longitudinal magnetic field, B z = −454 ± 42 G, was detected in the Herbig Ae/Be star HD 101412 using hydrogen lines. No field detection at a significance level of 3σ was achieved in stars with debris disks. Our study does not indicate any correlation of the strength of the longitudinal magnetic field with disk orientation, disk geometry, or the presence of a companion. We also do not see any simple dependence on the mass-accretion rate. However, it is likely that the range of observed field values qualitatively supports the expectations from magnetospheric accretion models giving support for dipole-like field geometries. Both the magnetic field strength and the X-ray emission show hints of a decline with age in the range of ∼2-14 Myr probed by our sample, supporting a dynamo mechanism that decays with age. However, our study of rotation does not show any obvious trend of the strength of the longitudinal magnetic field with rotation period. Furthermore, the stars seem to obey the universal power-law relation between magnetic flux and X-ray luminosity established for the Sun and main-sequence active dwarf stars.

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Circumstellar disks around Herbig Be stars

Cited by 99 publications

References 41 publications

The origin of mid-infrared emission in massive young stellar objects: multi-baseline VLTI observations of W33A

The origin of mid-infrared emission in massive young stellar objects: multi-baseline VLTI observations of W33A

Radiative transfer modeling of the dust disk of the Herbig Be star R Monocerotis

Searching for a link between the magnetic nature and other observed properties of Herbig Ae/Be stars and stars with debris disks

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