Theoretical investigation of energy levels and transition for Ce IV

Rynkun, Pavel; Banerjee, Smaranika; Gaigalas, Gediminas; Tanaka, Masaomi; Radžiūtė, Laima; Kato, Daiji

doi:10.1051/0004-6361/202141513

Cited by 23 publications

(9 citation statements)

References 45 publications

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“…Different atomic codes adopt different approaches: for example, the Flexible Atomic Code (FAC; Gu 2008) determines the potential in a self-consistent manner. Nevertheless, comparison of atomic data calculated by HULLAC and the more ab initio GRASP2018 code (Froese Fischer et al 2019) shows a good match for various ions with ionization <V (e.g., Tanaka et al 2018;Gaigalas et al 2019;Rynkun et al 2022). Similar comparison for highly ionized lanthanides remains within the scope of future work.…”

Section: Methodsmentioning

confidence: 81%

“…Breit interaction and quantum electrodynamic correction are also taken into account. More details of the HULLAC calculations for heavy elements can be found in the previous studies (e.g., Tanaka et al 2018;Rynkun et al 2022;Banerjee et al 2022).…”

Section: Atomic Structure Calculationsmentioning

confidence: 99%

“…In the past decade, calculations of the atomic opacity have been the intense focus of research (e.g., Kasen et al 2013;Tanaka & Hotokezaka 2013;Fontes et al 2015;Wollaeger et al 2017;Tanaka et al 2018;Gaigalas et al 2019;Tanaka et al 2020;Fontes et al 2020;Rynkun et al 2022;Fontes et al 2023;Flörs et al 2023), although all of these studies focus on the relatively lower ionized elements, maximum up to third (or IV in spectroscopic notation; hereafter used to describe the ionization), which are important for the kilonova at late times (t > 1 day).…”

Section: Introductionmentioning

confidence: 99%

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Opacity of the Highly Ionized Lanthanides and the Effect on the Early Kilonova

Banerjee

Tanaka

Kato

et al. 2022

ApJ

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We investigate the effect of the presence of lanthanides (Z = 57–71) on the kilonova at t ∼ 1 hr after the neutron star merger for the first time. For this purpose, we calculate the atomic structures and the opacities for selected lanthanides: Nd (Z = 60), Sm (Z = 62), and Eu (Z = 63). We consider the ionization degree up to 10th (XI), applicable for the ejecta at t ∼ a few hours after the merger, when the temperature is T ∼ 105 K. We find that the opacities for the highly ionized lanthanides are exceptionally high, reaching κ exp ∼ 1000 cm 2 g − 1 for Eu, due to the highly dense energy levels. Using the new opacity, we perform radiative transfer simulations to show that the early light curves become fainter by a (maximum) factor of four, in comparison to lanthanide-free ejecta at t ∼ 0.1 days. However, the period at which the light curves are affected is relatively brief owing to the rapid time evolution of the opacity in the outermost layer of the ejecta. We predict that for a source at a distance of ∼100 Mpc, UV brightness for lanthanide-rich ejecta shows a drop to ∼21–22 mag at t ∼ 0.1 days and the UV peaks around t ∼ 0.2 days with a magnitude of ∼19 mag. Future detection of such a kilonova by an existing UV satellite like Swift or the upcoming UV satellite ULTRASAT will provide useful constraints on the abundance in the outer ejecta and the corresponding nucleosynthesis conditions in the neutron star mergers.

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Section: Methodsmentioning

confidence: 81%

Section: Atomic Structure Calculationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Opacity of the Highly Ionized Lanthanides and the Effect on the Early Kilonova

Banerjee

Tanaka

Kato

et al. 2022

ApJ

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“…Recent studies in theoretical atomic data for heavy r-process elements have made great advances in the completeness and accuracy of energy levels and transition probabilities (Einstein A-values) (see e.g. Kasen et al 2013;Gaigalas et al 2019Gaigalas et al , 2020Banerjee et al 2020;Fontes et al 2020;Radžiūtė et al 2020;Bromley et al 2020;Carvajal Gallego et al 2021;Rynkun et al 2022;Domoto et al 2022;McCann et al 2022;Flörs et al 2023). These advances, and in particular recent efforts to calibrate theoretical data to experimental values, are extremely useful for the spectral modelling of KNe across all epochs.…”

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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“…Galle go, P almeri & Quinet 2021 ; Rynkun et al 2022 ). As such, there are now LTE expansion opacities available for all r-process elements.…”

mentioning

confidence: 99%

NLTE effects on kilonova expansion opacities

Pognan

Jerkstrand

Grumer

2022

Monthly Notices of the Royal Astronomical Society

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A binary neutron star merger produces a rapidly evolving transient known as a kilonova (KN), which peaks a few days after merger. Modelling of KNe has often been approached assuming local thermodynamic equilibrium (LTE) conditions in the ejecta. We present the first analysis of non-local thermodynamic equilibrium (NLTE) level populations, using the spectral synthesis code sumo, and compare these to LTE values. We investigate the importance of the radiation field by conducting NLTE excitation calculations with and without radiative transfer. Level populations, in particular higher lying ones, start to show deviations from LTE several days after merger. Excitation is lower in NLTE for the majority of ions and states, and this tends to give lower expansion opacities. While the difference is small for the first few days, it grows to factors 2-10 after this. Our results are important both for demonstrating validity of LTE expansion opacities for an initial phase (less than a week), while highlighting the need for NLTE modelling during later phases. Considering also NLTE ionisation, our results indicate that NLTE can give both higher or lower opacities, depending on composition and wavelength, sometimes by orders of magnitudes.

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Theoretical investigation of energy levels and transition for Ce IV

Cited by 23 publications

References 45 publications

Opacity of the Highly Ionized Lanthanides and the Effect on the Early Kilonova

Opacity of the Highly Ionized Lanthanides and the Effect on the Early Kilonova

NLTE spectra of kilonovae

NLTE effects on kilonova expansion opacities

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