Atomic data for opacity calculations. VII. Energy levels, f values and photoionisation cross sections for He-like ions

Fernley, J.; Taylor, K T; Seaton, M. J.

doi:10.1088/0022-3700/20/23/032

Cited by 125 publications

(87 citation statements)

References 19 publications

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“…To check the validity of this assumption we compared the photoionization cross sections obtained from Eq. (3) to the recent calculations of the Opacity Project by Fernley et al (1987). In Fig.…”

Section: Radiative Recombination (Rr) Coefficients Ratesmentioning

confidence: 96%

X-ray photoionized plasma diagnostics with helium-like ions. Application to warm absorber-emitter in active galactic nuclei

Porquet

Dubau

2000

Astron. Astrophys. Suppl. Ser.

319

435

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Abstract. We present He-like line ratios (resonance, intercombination and forbidden lines) for totally and partially photoionized media. For solar plasmas, these line ratios are already widely used for density and temperature diagnostics of coronal (collisional) plasmas. In the case of totally and partially photoionized plasmas, He-like line ratios allow for the determination of the ionization processes involved in the plasma (photoionization with or without an additional collisional ionization process), as well as the density and the electronic temperature.With the new generation of X-ray satellites, Chandra/AXAF, XMM and Astro-E, it will be feasible to obtain both high spectral resolution and high sensitivity observations. Thus in the coming years, the ratios of these three components will be measurable for a large number of non-solar objects.In particular, these ratios could be applied to the Warm Absorber-Emitter, commonly present in Active Galactic Nuclei (AGN). A better understanding of the Warm Absorber connection to other regions (Broad Line Region, Narrow Line Region) in AGN (Seyferts type-1 and type-2, low-and high-redshift quasars...) will be an important key to obtaining strong constraints on unified schemes.We have calculated He-like line ratios, for Z = 6, 7, 8, 10, 12 and 14, taking into account the upper level radiative cascades which we have computed for radiative and dielectronic recombinations and collisional excitation. The atomic data are tabulated over a wide range of temperatures in order to be used for interpreting a large variety of astrophysical plasmas.

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Section: Radiative Recombination (Rr) Coefficients Ratesmentioning

confidence: 96%

X-ray photoionized plasma diagnostics with helium-like ions. Application to warm absorber-emitter in active galactic nuclei

Porquet

Dubau

2000

Astron. Astrophys. Suppl. Ser.

319

435

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“…The excitation and ionization state of the considered elements is derived from the statistical equilibrium (NLTE) equations. Ionic models are either adopted from the TLUSTY grid of model stellar atmospheres (Lanz & Hubeny 2003, 2007 or are prepared by us using the data from the Opacity and Iron Projects (Seaton 1987;Fernley et al 1987;Luo & Pradhan 1989;Sawey & Berrington 1992;Seaton et al 1992;Butler et al 1993;Nahar & Pradhan 1993;Hummer et al 1993;Bautista 1996;Nahar & Pradhan 1996;Zhang 1996;Bautista & Pradhan 1997;Zhang & Pradhan 1997;Chen & Pradhan 1999). As in Paper I, the solution of the radiative transfer equation for NLTE equations is artificially split into two parts, namely the radiative transfer in either the continuum or in lines.…”

Section: Basic Model Assumptionsmentioning

confidence: 99%

Comoving frame models of hot star winds

Krtička¹,

Kubát

2010

A&A

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We provide hot star wind models with radiative force calculated using the solution of comoving frame (CMF) radiative transfer equation. The wind models are calculated for the first stars, O stars, and the central stars of planetary nebulae. We show that without line overlaps and with solely thermal line broadening the pure Sobolev approximation provides a reliable estimate of the radiative force even close to the wind sonic point. Consequently, models with the Sobolev line force provide good approximations to solutions obtained with non-Sobolev transfer. Taking line overlaps into account, the radiative force becomes slightly lower, leading to a decrease in the wind mass-loss rate by roughly 40%. Below the sonic point, the CMF line force is significantly lower than the Sobolev one. In the case of pure thermal broadening, this does not influence the mass-loss rate, as the wind mass-loss rate is set in the supersonic part of the wind. However, when additional line broadening is present (e.g., the turbulent one) the region of low CMF line force may extend outwards to the regions where the mass-loss rate is set. This results in a decrease in the wind mass-loss rate. This effect can at least partly explain the low wind mass-loss rates derived from some observational analyses of luminous O stars.

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“…Project (Seaton 1987;Fernley et al 1987;Luo & Pradhan 1989;Sawey & Berrington 1992;Seaton et al 1992;Butler et al 1993;Nahar & Pradhan 1993;Hummer et al 1993;Bautista 1996;Nahar & Pradhan 1996;Zhang 1996;Bautista & Pradhan 1997;Zhang & Pradhan 1997;Chen & Pradhan 1999). A significant part of the ionic models was taken from the TLUSTY code (Lanz & Hubeny 2003.…”

Section: Model Assumptionsmentioning

confidence: 99%

X-ray emission from hydrodynamical simulations in non-LTE wind models

Krtička

Feldmeier

Oskinova

et al. 2009

A&A

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Hot stars are sources of X-ray emission originating in their winds. Although hydrodynamical simulations that are able to predict this X-ray emission are available, the inclusion of X-rays in stationary wind models is usually based on simplifying approximations. To improve this, we use results from time-dependent hydrodynamical simulations of the line-driven wind instability (seeded by the base perturbation) to derive the analytical approximation of X-ray emission in the stellar wind. We use this approximation in our non-LTE wind models and find that an improved inclusion of X-rays leads to a better agreement between model ionization fractions and those derived from observations. Furthermore, the slope of the L X − L relation is in better agreement with observations, however the X-ray luminosity is underestimated by a factor of three. We propose a possible solution for this discrepancy.

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Atomic data for opacity calculations. VII. Energy levels, f values and photoionisation cross sections for He-like ions

Cited by 125 publications

References 19 publications

X-ray photoionized plasma diagnostics with helium-like ions. Application to warm absorber-emitter in active galactic nuclei

X-ray photoionized plasma diagnostics with helium-like ions. Application to warm absorber-emitter in active galactic nuclei

Comoving frame models of hot star winds

X-ray emission from hydrodynamical simulations in non-LTE wind models

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