On the sensitivity of uranium opacity with respect to the atomic properties in the context of kilonova emission modeling

Deprince, J.; Gallego, Helena Carvajal; Godefroid, Michel; Goriely, Stéphane; Palmeri, P.; Quinet, Pascal

doi:10.1140/epjd/s10053-023-00671-z

Cited by 5 publications

(4 citation statements)

References 44 publications

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“…The final radiative parameters obtained for the large amount of transitions considered in the opacity calculations were changed by at most a few percent. Moreover, we also showed in Deprince et al (2023) that even if some radial parameters, such as the configuration average energies, are adjusted to correct the calculated energy levels in order to better match experimental values available in the literature, thus slightly modifying the composition mixings of the eigenvectors, the resulting computed opacities are virtually not affected by such a semi-empirical procedure.…”

Section: Atomic Data Computationsmentioning

confidence: 88%

“…The method used for computing the atomic structures and radiative parameters was the pseudo-relativistic HFR approach developed by Cowan (1981). As discussed in some of our previous works (Flörs et al 2023;Deprince et al 2023), this method is particularly well adapted to the determination of opacities because it allows one to obtain atomic data of the same quality for the whole set of states belonging to all the electronic configurations included in a physical model since each of them is optimized by the variational principle, unlike some other commonly used methods, such as those implemented in AUTOSTRUC-TURE (Badnell 2011), HULLAC (Bar-Shalom et al 2001, FAC (Gu 2008), or the General Relativistic Atomic Structure Program (GRASP; Froese Fischer et al 2016Fischer et al , 2019 codes. Indeed, although the latter theoretical approaches may lead to better results for specific atomic states, the optimization of the calculation is carried out most of the time on a restricted number of configurations so that all the states belonging to the other configurations, namely, those not minimized by the variational principle, cannot be considered as spectroscopic and therefore risk not being of quality equivalent to the optimized states.…”

Section: Atomic Data Computationsmentioning

confidence: 99%

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Overview of the contributions from all lanthanide elements to kilonova opacity in the temperature range from 25 000 to 40 000 K

Gallego,

Deprince,

Maison

et al. 2024

A&A

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It is now well established that the neutron star (NS) merger is at the origin of the production of trans-iron heavy elements in the universe. These elements are therefore present in large quantities in the ejected matter, whose electromagnetic radiation, called kilonova, is characterized by a significant opacity due to the high density of spectral lines belonging to many heavy ions. Among these, the lanthanide ions play an essential role since, with their open 4f subshell, they have a considerable number of transitions that can absorb emitted light. The knowledge of the atomic structure and the radiative parameters of these ions as well as the determination of the corresponding opacities is therefore of paramount importance for the spectral analysis of kilonovae. The main goal of the present work is to determine the relative contributions of the different lanthanide elements to the opacity of the emission spectrum of a kilonova in its early phase, that is, a few hours after the NS merger, where the conditions are such that the temperature is between 25000 and 40000 K. At these temperatures, the lanthanide ions whose charge states are between V and VII are predominant. We used the pseudo-relativistic Hartree-Fock (HFR) method extensively to calculate the relevant atomic data (energy levels, wavelengths, and oscillator strengths) in La-Lu V-VII ions. The corresponding monochromatic opacities were estimated from the expansion formalism. We calculated the spectroscopic parameters for a total of more than 800 million radiative transitions in all the ions considered. These data were used to estimate the expansion opacities and Planck mean opacities for all the lanthanide elements at early-phase kilonova conditions between 25000 and 40000 K, making it possible to deduce the respective contributions of each element as a function of temperature. Atomic calculations were also carried out with the fully relativistic Multiconfiguration Dirac-Hartree-Fock (MCDHF) method in the specific case of the Yb V ion, as the available experimental data had not yet been compared with the theoretical calculations in our previous studies on lanthanide ions.

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Section: Atomic Data Computationsmentioning

confidence: 88%

Section: Atomic Data Computationsmentioning

confidence: 99%

Overview of the contributions from all lanthanide elements to kilonova opacity in the temperature range from 25 000 to 40 000 K

Gallego,

Deprince,

Maison

et al. 2024

A&A

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“…In some of the aforementioned studies, the results from the HULLAC method can be obtained for charge states up to XI, unless the model representing the ion is restricted to a few configurations (such as in the Banerjee et al (2022Banerjee et al ( , 2023 works). If the convergence of a model is tested by increasing the number of configurations (such as in the Deprince et al (2023) paper for U III), computational methods rapidly show their limits and the statistical approach could be a reliable alternative.…”

Section: Introductionmentioning

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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“…Identifying the presence or absence of groups of elements based on properties such as expansion opacity is an also an avenue currently being explored (see e.g. Tanaka & Hotokezaka 2013;Tanvir et al 2017;Tanaka et al 2020;Banerjee et al 2020Banerjee et al , 2022Domoto et al 2022;Fontes et al 2023;Deprince et al 2023;Carvajal Gallego et al 2023).…”

Section: Introductionmentioning

confidence: 99%

NLTE spectra of kilonovae

Pognan,

Grumer,

Jerkstrand

et al. 2023

Monthly Notices of the Royal Astronomical Society

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The electromagnetic transient following a binary neutron star merger is known as a kilonova (KN). Owing to rapid expansion velocities and small ejecta masses, KNe rapidly transition into the non-local thermodynamic equilibrium (NLTE) regime. In this study, we present synthetic NLTE spectra of KNe from 5 to 20 d after merger using the sumo spectral synthesis code. We study three homogeneous composition, 1D multizone models with characteristic electron fractions of Ye ∼ 0.35, 0.25, and 0.15. We find that emission features in the spectra tend to emerge in windows of reduced line blocking, as the ejecta are still only partially transparent even at 20 d. For the Ye ∼ 0.35 (lanthanide-free) ejecta, we find that the neutral and singly ionized species of Rb, Sr, Y, and Zr dominate the spectra, all with good potential for identification. We directly test and confirm an impact of Sr on the 10 000 Å spectral region in lanthanide-free ejecta, but also see that its signatures may be complex. We suggest the Rb i$\rm {5p^{1}}$–$\rm {5s^{1}}$ 7900 Å transition as a candidate for the λ0 ∼ 7500–7900 Å P-Cygni feature in AT2017gfo. For the Ye ∼ 0.25 and 0.15 compositions, lanthanides are dominant in the spectral formation, in particular Nd, Sm, and Dy. We identify key processes in KN spectral formation, notably that scattering and fluorescence play important roles even up to 20 d after merger, implying that the KN ejecta are not yet optically thin at this time.

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On the sensitivity of uranium opacity with respect to the atomic properties in the context of kilonova emission modeling

Cited by 5 publications

References 44 publications

Overview of the contributions from all lanthanide elements to kilonova opacity in the temperature range from 25 000 to 40 000 K

Overview of the contributions from all lanthanide elements to kilonova opacity in the temperature range from 25 000 to 40 000 K

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

NLTE spectra of kilonovae

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