Correspondence

Porter, Basil; Seidelman, WilliamE.

doi:10.1111/j.1365-2923.1992.tb00214.x

Cited by 23 publications

(25 citation statements)

References 1 publication

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“…Viscous outflowing discs have received less attention –Popham & Narayan (1991), Pringle (1991) and Narita, Kiguchi & Hayashi (1994) discuss the case in which angular momentum is added to the disc at the inner edge by the central source. Lee et al (1991), Okazaki (1997) and Porter (1999) discuss viscous outflowing discs in the context of Be stars.…”

Section: Theorymentioning

confidence: 99%

“…Okazaki (2001) presents time independent solutions of the disc density and velocity structure of such discs. These viscous outflowing discs (sometimes named ‘decretion’ or ‘excretion’ discs in the literature) have been found to be able to fulfill several observational criteria: as they are close to Keplerian, they can become unstable to one‐armed oscillations and hence produce the observed line‐profile variations (Okazaki 2001), they can also reproduce the observed IR continuum excesses (Porter 1999), and can explain the slow, equatorial, outflow velocities (Clark, Tarasov & Panko 2003).…”

Section: Introductionmentioning

confidence: 99%

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The circumstellar envelopes of Be stars: viscous disc dynamics

Jones

Sigut

Porter

2008

Monthly Notices RAS

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We have constructed models of axisymmetric, circumstellar envelopes for Be star discs by successfully combining two numerical codes: a non‐local thermodynamic equilibrium (non‐LTE) radiative transfer code which calculates the level populations and disc temperature distribution self‐consistently, and a hydrodynamical code. The output of one code is used as input to the other code, and hence evolving density and thermal structures may be examined. The temperatures, disc density and velocity distribution are used to investigate the outflowing viscous disc model for Be stars. We find that these simulations place constraints on the power‐law density decrease in the disc with increasing distance from the star. We find that the power‐law index for the line‐forming region of the disc lies between 3 and 3.5 with a small dispersion.

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Section: Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The circumstellar envelopes of Be stars: viscous disc dynamics

Jones

Sigut

Porter

2008

Monthly Notices RAS

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“…The radial velocity of the disc is smaller than a few km s −1 , at least within ∼10 stellar radii (Hanuschik 1994, 2000; Waters & Marlborough 1994). Although there is no widely accepted model for discs around Be stars, the viscous decretion disc model proposed by Lee, Saio & Osaki (1991) explains many of the observed features and thus seems promising (Porter 1999; see also Okazaki 2001). In this model, the matter supplied from the equatorial surface of the star drifts outwards because of the viscous effect and forms the disc.…”

Section: Introductionmentioning

confidence: 99%

Viscous effects on the interaction between the coplanar decretion disc and the neutron star in Be/X-ray binaries

Okazaki

Bate

Ogilvie

et al. 2002

Monthly Notices of the Royal Astronomical Society

193

277

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We study the viscous effects on the interaction between the coplanar Be‐star disc and the neutron star in Be/X‐ray binaries, using a three‐dimensional, smoothed particle hydrodynamics code. For simplicity, we assume the Be disc to be isothermal at the temperature of half the stellar effective temperature. In order to mimic the gas ejection process from the Be star, we inject particles with the Keplerian rotation velocity at a radius just outside the star. Both the Be star and the neutron star are treated as point masses. We find that the Be‐star disc is effectively truncated if the Shakura–Sunyaev viscosity parameter αSS≪ 1, which confirms the previous semi‐analytical result. In the truncated disc, the material decreted from the Be star accumulates, so that the disc becomes denser more rapidly than if around an isolated Be star. The resonant truncation of the Be disc results in a significant reduction of the amount of gas captured by the neutron star and a strong dependence of the mass‐capture rate on the orbital phase. We also find that an eccentric mode is excited in the Be disc through direct driving as a result of a one‐armed bar potential of the binary. The strength of the mode becomes greater in the case of a smaller viscosity. In a high‐resolution simulation with αSS= 0.1, the eccentric mode is found to precess in a prograde sense. The mass‐capture rate by the neutron star modulates as the mode precesses.

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“…Note that stellar winds from early‐type‐B main sequence stars and classical Be stars usually reach velocities in excess of 1500 km s −1 (see e.g. Porter 1999), much higher than the 600 and 450 km s −1 observed for HD 52721 and HD 53367 in the wings of the Si iv lines (Fig. 7) and the 340 and 370 km s −1 in the wing of the λ 1548 C iv line.…”

Section: Summary and Discussionmentioning

confidence: 85%

The stellar composition of the star formation region CMa R1 -- II. Spectroscopic and photometric observations of nine young stars

Djie

Ancker

Blondel

et al. 2001

Monthly Notices of the Royal Astronomical Society

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We present new high‐ and low‐resolution spectroscopic and photometric data of nine members of the young association CMa R1. All the stars have circumstellar dust at some distance, as could be expected from their association with reflection nebulosity. Four stars (HD 52721, HD 53367, LkHα 220 and LkHα 218) show Hα emission and we argue that they are Herbig Be stars with discs. Our photometric and spectroscopic observations of these stars reveal new characteristics of their variability. We present first interpretations of the variability of HD 52721, HD 53367 and the two LkHα stars in terms of a partially eclipsing binary, a magnetic activity cycle and circumstellar dust variations, respectively. The remaining five stars show no clear indications of Hα emission in their spectra, although their spectral types and ages are comparable with those of HD 52721 and HD 53367. This indicates that the presence of a disc around a star in CMa R1 may depend on the environment of the star. In particular we find that all Hα emission stars are located at or outside the arc‐shaped border of the H ii region, which suggests that the stars inside the arc have lost their discs through evaporation by UV photons from nearby O stars, or from the nearby (<25 pc) supernova, about 1 Myr ago.

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Correspondence

Cited by 23 publications

References 1 publication

The circumstellar envelopes of Be stars: viscous disc dynamics

The circumstellar envelopes of Be stars: viscous disc dynamics

Viscous effects on the interaction between the coplanar decretion disc and the neutron star in Be/X-ray binaries

The stellar composition of the star formation region CMa R1 -- II. Spectroscopic and photometric observations of nine young stars

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