Speaker
Description
On August 17, 2017, the LIGO-VIRGO collaboration observed a neutron star merger thanks to the first detection of gravitational waves. They also detected an explosion of hot and radioactive matter called a kilonova [1]. In the latter, there are nuclear reactions that form heavy nuclei (heavier than iron) such as lanthanides (Z = 57 – 71) which play a particular role. In fact, given their rich spectra, they strongly contribute to the opacity affecting radiation emission [2]. In order to interpret the spectrum of a kilonova, it is therefore crucial to precisely know the radiative parameters characterizing these elements. Over the past few years, several studies have been carried out (see e.g. [3-4]), for the first degrees of ionisation (up to 3+) but almost all these investigations were limited to the analysis of kilonovae in a temperature range below $20~000$ K. To extend the study to early phases of kilonovae (i.e. $T > 20~000$ K), it is essential to know the radiative parameters of lanthanide ions in higher charge stages (see e.g. [5-7]). Thanks to the calculation of lanthanides’ atomic data for different degrees of ionization, we can calculate the expansion opacities using the expansion formalism [8-10].
In all of the works mentioned (except in [7]) the partition function, $U(T)$, was approximated to the statistical weight of the ground level, $g_0$, for the computation of the Sobolev optical depth. This approximation has a significant impact on the computed opacities. The main goal of this present work is to show how it can affect the expansion opacity for a couple of lanthanide examples, namely for samarium (Sm) in the case of early-phase kilonova conditions ($t = 0.1$ day after the merger), which is associated with moderately-charged species (Sm V - XI) and for neodymium (Nd) in the case of plausible conditions in the kilonova ejecta that should take place about 1 day after the neutron star merger (NSM), corresponding to the presence of lowly-ionized elements in the ejecta (Nd II - IV) [11].
- B. Abbott et al., Phys. Rev. Lett. 119, 161101 (2017)
- D. Kasen et al., Nature 551, 80 (2017)
- Gaigalas G., Kato D., Rynkun P., Radziute L., Tanaka M., ApJS , 240, 29, (2019)
- Tanaka M., Kato D., Gaigalas G., Kawaguchi K., MNRAS , 496, 1369, (2020)
- Carvajal Gallego H., Berengut J. C., Palmeri P., Quinet P., MNRAS, 509,6138, (2022)
- Carvajal Gallego H., Berengut J. C., Palmeri P., Quinet P., MNRAS, 513,2302, (2022)
- Carvajal Gallego H., Deprince, J., Berengut J. C., Palmeri P., Quinet P., MNRAS, 518, 332-352, (2023)
- Karp H., Lasher G., Chan K. L., Salpeter E. E., ApJ , 214, 161, 1977
- Eastman R. G., Pinto P. A., ApJ, 412, 731, 1993
- Kasen D., Thomas R. C., Nugent P., ApJ, 651, 366, 2006
- Carvajal Gallego H., Deprince, J., Godefroid, M., Goriely, S., Palmeri P., Quinet P., Eur. Phys. J. D, submitted (2023)
| Presenting Author | Helena Carvajal Gallego |
|---|---|
| Presenting Author Email Address | helena.carvajalgallego@umons.ac.be |
| Presenting Author Affiliation | UMons |
| Country | Belgium |
| Presenting Author Gender | Female |
