Frequency Redistribution Function for the Polarized Two-Term Atom

Casini, R.; Degl'Innocenti, Maurizio; Sainz, R. Manso; Degl’Innocenti, E. Landi; Landolfi, M.

doi:10.1088/0004-637x/791/2/94

Cited by 44 publications

(86 citation statements)

References 41 publications

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“…In the collisionless regime, this redistribution function with the branching ratio (the coefficient before the δ function) is in agreement with that derived in the metalevel heuristic approach by Landi Degl 'Innocenti et al (1997), and also derived by Casini et al (2014).…”

Section: In Considering Only Fine Structuresupporting

confidence: 89%

“…In the collisionless regime, this redistribution function is in agreement with that derived by Casini et al (2014), including the branching ratio (the coefficient before the δ function).…”

Section: Considering Also Hyperfine Structuresupporting

confidence: 87%

“…As the results of Casini et al (2014) can only be applied in the collisionless regime, the two possible normalizations described above are identical and are both equal to unity in this regime. The redistribution function normalization condition is based on the following normalization property of the irreducible spherical tensors for polarimetry (Landi Degl'Innocenti 1984) dΩ 4π…”

Section: Redistribution Function In the Presence Of A Magnetic Fieldmentioning

confidence: 99%

“…del Pino Alemán et al (2016) studied the polarization of the full Mg II h-k doublet, also taking into account the effects of fine structure and quantum interference in the upper term. They apply the formalism of Casini et al (2014), who derived a theoretical redistribution function including polarization, fine and hyperfine structure. However, the final result of Casini et al (2014) can be applied only in the collisionless regime (pure R II ).…”

Section: Introductionmentioning

confidence: 99%

“…They apply the formalism of Casini et al (2014), who derived a theoretical redistribution function including polarization, fine and hyperfine structure. However, the final result of Casini et al (2014) can be applied only in the collisionless regime (pure R II ). del Pino Alemán et al (2016) made use of a generalization of the formalism of Casini et al (2014) to include collisional effects by modifying the branching ratios in a "physically consistent" manner (following their words at the top of the left column, p. 2), but without providing explicit forms of these branching ratios.…”

Section: Introductionmentioning

confidence: 99%

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Master equation theory applied to the redistribution of polarized radiation in the weak radiation field limit

Bommier

2017

A&A

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Context. In previous papers of this series, we presented a formalism able to account for both statistical equilibrium of a multilevel atom and coherent and incoherent scatterings (partial redistribution). Aims. This paper provides theoretical expressions of the redistribution function for the two-term atom. This redistribution function includes both coherent (RII) and incoherent (RIII) scattering contributions with their branching ratios. Methods. The expressions were derived by applying the formalism outlined above. The statistical equilibrium equation for the atomic density matrix is first formally solved in the case of the two-term atom with unpolarized and infinitely sharp lower levels. Then the redistribution function is derived by substituting this solution for the expression of the emissivity. Results. Expressions are provided for both magnetic and non-magnetic cases. Atomic fine structure is taken into account. Expressions are also separately provided under zero and non-zero hyperfine structure. Conclusions. Redistribution functions are widely used in radiative transfer codes. In our formulation, collisional transitions between Zeeman sublevels within an atomic level (depolarizing collisions effect) are taken into account when possible (i.e., in the non-magnetic case). However, the need for a formal solution of the statistical equilibrium as a preliminary step prevents us from taking into account collisional transfers between the levels of the upper term. Accounting for these collisional transfers could be done via a numerical solution of the statistical equilibrium equation system.

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Section: In Considering Only Fine Structuresupporting

confidence: 89%

“…In the collisionless regime, this redistribution function is in agreement with that derived by Casini et al (2014), including the branching ratio (the coefficient before the δ function).…”

Section: Considering Also Hyperfine Structuresupporting

confidence: 87%

Section: Redistribution Function In the Presence Of A Magnetic Fieldmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Master equation theory applied to the redistribution of polarized radiation in the weak radiation field limit

Bommier

2017

A&A

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Magnetic field measurements of CP stars from hydrogen line cores

Kudryavtsev

Romanyuk

2012

Astron Nachr

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We present the results of measurements of magnetic fields of chemically peculiar (CP) stars, performed from the shifts between the circularly polarized components of metal and hydrogen lines (the Babcock method). The observations are carried out with an analyzer of circular polarization at the 6-m telescope of the SAO RAS. We found that for the absolute majority of the objects studied (in 22 CP stars out of 23), the magnetic fields, determined from the Zeeman shifts in the hydrogen line cores, are significantly lower than those obtained from metal lines in the same spectra. This disparity varies between the stars. We show that instrumental effects can not produce the above features, and discuss the possible causes of the observed effect. The discovered condition reveals a more complicated structure of magnetic fields of CP stars than a simple dipole, in particular, a reduction of the field strength in the upper atmosphere with the vertical gradient, significantly higher than the dipole.

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