Statistical Equilibrium Model Atmospheres for Early-Type Stars. III. Hydrogen and Helium Continua

Mihalas, Dimitri; Stone, Michael E.

doi:10.1086/149437

Cited by 32 publications

(27 citation statements)

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“…He ii, we use the effective collision strengths of Aggarwal et al (1991Aggarwal et al ( , 1992; collisional ionisation coefficients from Mihalas & Stone (1968); and the spontaneous emission coefficients are those of Allen (1973).…”

Section: Modelling Of An Eruptive Prominencementioning

confidence: 99%

Effect of motions in prominences on the helium resonance lines in the extreme ultraviolet

Labrosse¹,

Gouttebroze

Vial

2006

A&A

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Context. Extreme ultraviolet resonance lines of neutral and ionised helium observed in prominences are difficult to interpret as the prominence plasma is optically thick at these wavelengths. If mass motions are taking place, as is the case in active and eruptive prominences, the diagnostic is even more complex. Aims. We aim at studying the effect of radial motions on the spectrum emitted by moving prominences in the helium resonance lines and at facilitating the interpretation of observations, in order to improve our understanding of these dynamic structures. Methods. We develop our non-local thermodynamic equilibrium radiative transfer code formerly used for the study of quiescent prominences. The new numerical code is now able to solve the statistical equilibrium and radiative transfer equations in the non-static case by using velocity-dependent boundary conditions for the solution of the radiative transfer problem. This first study investigates the effects of different physical conditions (temperature, pressure, geometrical thickness) on the emergent helium radiation.Results. The motion of the prominence plasma induces a Doppler dimming effect on the resonance lines of He i and He ii. The velocity effects are particularly important for the He ii λ 304 Å line as it is mostly formed by resonant diffusion of incident radiation under prominence conditions. The He i resonance lines at 584 and 537 Å also show some sensitivity to the motion of the plasma, all the more when thermal emission is not too important in these lines. We also show that it is necessary to consider partial redistribution in frequency for the scattering of the incident radiation.Conclusions. This set of helium lines offers strong diagnostic possibilities that can be exploited with the SOHO spectrometers and with the EIS spectrometer on board the Hinode satellite. The addition of other helium lines and of lines from other elements (in particular hydrogen) in the diagnostics will further enhance the strength of the method.

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Section: Modelling Of An Eruptive Prominencementioning

confidence: 99%

Effect of motions in prominences on the helium resonance lines in the extreme ultraviolet

Labrosse¹,

Gouttebroze

Vial

2006

A&A

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“…For hydrogen and singly ionized helium these values are computed using polynomials given by Giovanardi et al (1987). For neutral helium the collision strengths are taken from Berrington & Kingston (1987) to levels with n ≤ 4 and from Auer and Mihalas & Stone (1968) to the other ones.…”

Section: Summary Of the Modelmentioning

confidence: 99%

HR Carinae: New spectroscopic data and physical parameters

Machado

Araújo

Pereira

et al. 2002

A&A

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“…For H and HeII these values are computed using polynomials given by Giovanardi et al (1987). For HeI the collision strengths are taken from Berrington & Kingston (1987) for levels with n ≤ 4 and from Auer & Mihalas (1968) and Mihalas & Stone (1968) to the other ones.…”

Section: Summary Of the Modelmentioning

confidence: 99%

The peculiar B-type supergiant HD 327083

Machado

Araújo

Lorenz-Martins

2001

A&A

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Abstract. Coudé spectroscopic data of a poorly-studied peculiar supergiant, HD 327083, are presented. Hα and Hβ line profiles have been fitted employing a non-LTE code adequate for spherically expanding atmospheres. Line fits lead to estimates of physical parameters. These parameters suggest that HD 327083 may be close to the Luminous Blue Variable phase but it is also possible that it could be a B[e] Supergiant.

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Statistical Equilibrium Model Atmospheres for Early-Type Stars. III. Hydrogen and Helium Continua

Cited by 32 publications

References 0 publications

Effect of motions in prominences on the helium resonance lines in the extreme ultraviolet

Effect of motions in prominences on the helium resonance lines in the extreme ultraviolet

HR Carinae: New spectroscopic data and physical parameters

The peculiar B-type supergiant HD 327083

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