Multiconfiguration Dirac–Hartree–Fock radiative parameters for emission lines in Ce <scp>ii</scp>–<scp>iv</scp>ions and cerium opacity calculations for kilonovae

Gallego, Helena Carvajal; Palmeri, P.; Quinet, Pascal

doi:10.1093/mnras/staa3729

Cited by 18 publications

(1 citation statement)

References 23 publications

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“…In order to compute these opacities, we used exactly the same procedure as the one employed in all our aforementioned papers (such as Carvajal Gallego et al (2021Gallego et al ( , 2022aGallego et al ( , 2022bGallego et al ( , 2023aGallego et al ( , 2023b). As a reminder, in a dynamic environment that expands rapidly, such as the one observed in the ejecta from neutron star mergers, the bound-bound transitions can be evaluated using the expansion formalism (Karp et al 1977, Eastman and Pinto 1993, Kasen et al 2006 according to which the contributions of a large number of lines to the monochromatic opacity are approximated by a discretization involving the summation of lines falling within a spectral width, while the radiative transfer is considered by the Sobolev (1960) approximation.…”

Section: Expansion Opacitiesmentioning

confidence: 99%

Statistical RTA simulations of atomic data for astrophysical opacity modeling in the context of kilonova emission

Carvajal Gallego,

Pain,

Godefroid

et al. 2024

J. Phys. B: At. Mol. Opt. Phys.

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When considering some complex lanthanide ions characterized by half-filled 4fsubshell, the atomic structure Hamiltonian matrix sizes are so big that their diagonalizationis challenging and therefore the atomic data of these ions are hardly provided for computingthe expansion opacity of a kilonova. In order to avoid this problem, we propose a statisticalsimulation method for computing kilonova expansion opacities based on the ResolvedTransition Array (RTA) method of Bauche et al (1991, Phys. Rev. A 44, 5707). Theatomic structure HFR method has been employed to compute the radial integrals necessaryto our statistical RTA simulations where the atomic data are randomly drawn using theircorresponding statistical distributions and to determine the exact expansion opacities wherethe atomic data are obtained by the diagonalization of the Hamiltonian matrix. The statisticalRTA simulations carried out in two specific ions, i.e. Sm VIII and Eu VI, for which it isstill possible to diagonalize the Hamiltonian matrix, reproduce well the expansion opacitiescomputed using HFR atomic data. Based on these good agreements, the statistical RTA methodhas been used to compute the expansion opacity of Dy VIII which is hardly determined throughdiagonalization. The proposed statistical RTA simulation method allows to compute reliableastrophysical expansion opacities which are of paramount importance for kilonova light curvemodeling and spectral analysis.

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Section: Expansion Opacitiesmentioning

confidence: 99%

Statistical RTA simulations of atomic data for astrophysical opacity modeling in the context of kilonova emission

Carvajal Gallego,

Pain,

Godefroid

et al. 2024

J. Phys. B: At. Mol. Opt. Phys.

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Theoretical investigation of energy levels and transition for Ce IV

Rynkun

Banerjee

Gaigalas

et al. 2022

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Aims. We present extensive energy level and transition data for the Ce IV spectrum. By providing accurate atomic data, we evaluate the impact of atomic data on the opacity in the neutron star merger ejecta. Methods. We performed energy spectra and transition data calculations using the GRASP2018 package, which is based on the multiconfiguration Dirac-Hartree-Fock and relativistic configuration interaction methods, and the HULLAC code, which is based on a parametric potential method. Results. We present energy spectra calculated for the 225 levels for the Ce 3+ ion. Energy levels are compared with recommended values from the NIST Atomic Spectra Database and other available works. The root-mean-square (rms) deviations obtained for the GRASP2018 energy levels of the 5p 6 nl configurations from the NIST data are 1270 cm −1 . The rms deviations for the HULLAC results from the NIST data are 5780 cm −1 . Furthermore, electric dipole (E1) transition data, line strengths, weighted oscillator strengths, and transition rates are computed between the above levels. The computed transition rates are compared with other theoretical computations. We also evaluate the accuracy of the wave functions and transition parameters by analyzing the dependencies of the line strength S on the gauge parameter G. The gauge dependency method also allows us to determine the transitions for which the ratio between the Babushkin and Coulomb gauges shows real agreement between forms and the transitions for which the agreement between both gauges is random. Using the GRASP2018 and HULLAC data, the opacities in the neutron star merger ejecta are also calculated. We find that the opacity of Ce IV is higher than that presented by previous works, which is because of the higher completeness of our atomic data. Although the differences in the energy levels and transition probabilities cause different features in the opacity spectrum, the Planck mean opacities of both data sets agree within 20 %.

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Atomic data and expansion opacity calculations in two representative 4d transition elements, niobium and silver, of interest for kilonovae studies

Ben Nasr,

Carvajal Gallego,

Deprince

et al. 2023

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Aims. Neutron star (NS) mergers are thought to be a source of heavy trans-iron element production. The latter can be detected in the spectra of the ejected materials, from which bright electromagnetic radiation is emitted. This latter is due to the radioactive decay of the produced heavy r-process nuclei and is known as kilonova. Because of their complex atomic structures – characterized by configurations involving unfilled nd or nf subshells – the heavy elements of the kilonova ejecta often give rise to numerous absorption lines generating significant opacities. The determination of the latter, which are of paramount importance for the analysis of kilonova light curves, requires knowledge of the radiative parameters of the spectral lines belonging to the ions expected to be present in the kilonova ejecta. The aim of the present work is to provide new atomic opacity data for two representative 4d elements, niobium (Nb) and silver (Ag), in their first four charge states, namely for Nb I–IV and Ag I–IV. Methods. Large-scale calculations based on the pseudo-relativistic Hartree-Fock (HFR) method were performed to obtain the atomic structure and radiative parameters while the expansion formalism was used to estimate the opacities. Results. Wavelengths and oscillator strengths were computed for several million spectral lines in Nb I–IV and Ag I–IV ions. The reliability of these parameters was estimated by comparison with the few previously published experimental and theoretical results. The newly obtained atomic data were then used to calculate expansion opacities for typical kilonova conditions expected one day after NS merger, a density of ρ = 10−13 g cm−3, and temperatures ranging from T = 5000 K to T =15 000 K.

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Multiconfiguration Dirac–Hartree–Fock radiative parameters for emission lines in Ce ii–ivions and cerium opacity calculations for kilonovae

Cited by 18 publications

References 23 publications

Statistical RTA simulations of atomic data for astrophysical opacity modeling in the context of kilonova emission

Statistical RTA simulations of atomic data for astrophysical opacity modeling in the context of kilonova emission

Theoretical investigation of energy levels and transition for Ce IV

Atomic data and expansion opacity calculations in two representative 4d transition elements, niobium and silver, of interest for kilonovae studies

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