Spectroscopic r-process Abundance Retrieval for Kilonovae. II. Lanthanides in the Inferred Abundance Patterns of Multicomponent Ejecta from the GW170817 Kilonova
In kilonovae, freshly synthesized r -process elements imprint features on optical spectra, as observed in AT2017gfo, the counterpart to the GW170817 binary neutron star merger. However, measuring the r -process compositions of the merger ejecta is computationally challenging. Vieira et al. introduce...
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IOP Publishing
2024-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/ad1193 |
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| author | Nicholas Vieira John J. Ruan Daryl Haggard Nicole M. Ford Maria R. Drout Rodrigo Fernández |
| author_facet | Nicholas Vieira John J. Ruan Daryl Haggard Nicole M. Ford Maria R. Drout Rodrigo Fernández |
| author_sort | Nicholas Vieira |
| collection | DOAJ |
| description | In kilonovae, freshly synthesized r -process elements imprint features on optical spectra, as observed in AT2017gfo, the counterpart to the GW170817 binary neutron star merger. However, measuring the r -process compositions of the merger ejecta is computationally challenging. Vieira et al. introduced Spectroscopic r -process Abundance Retrieval for Kilonovae ( SPARK ), a software tool to infer elemental abundance patterns of the ejecta and associate spectral features with particular species. Previously, we applied SPARK to the 1.4-day spectrum of AT2017gfo and inferred its abundance pattern for the first time, characterized by electron fraction Y _e = 0.31, a substantial abundance of strontium, and a dearth of lanthanides and heavier elements. This ejecta is consistent with wind from a remnant hypermassive neutron star and/or accretion disk. We now extend our inference to spectra at 2.4 and 3.4 days and test the need for multicomponent ejecta, where we stratify the ejecta in composition. The ejecta at 1.4 and 2.4 days is described by the same single blue component. At 3.4 days, a new redder component with lower Y _e = 0.16 and a significant abundance of lanthanides emerges. This new redder component is consistent with dynamical ejecta and/or neutron-rich ejecta from a magnetized accretion disk. As expected from photometric modeling, this component emerges as the ejecta expands, the photosphere recedes, and the earlier bluer component dims. At 3.4 days, we find an ensemble of lanthanides, with the presence of cerium most concrete. This presence of lanthanides has important implications for the contribution of kilonovae to the r -process abundances observed in the Universe. |
| first_indexed | 2024-03-08T05:46:07Z |
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| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-08T05:46:07Z |
| publishDate | 2024-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj.art-d822e4a9577c4ae091a08a461918233a2024-02-05T11:32:06ZengIOP PublishingThe Astrophysical Journal1538-43572024-01-0196213310.3847/1538-4357/ad1193Spectroscopic r-process Abundance Retrieval for Kilonovae. II. Lanthanides in the Inferred Abundance Patterns of Multicomponent Ejecta from the GW170817 KilonovaNicholas Vieira0https://orcid.org/0000-0001-7815-7604John J. Ruan1https://orcid.org/0000-0001-8665-5523Daryl Haggard2https://orcid.org/0000-0001-6803-2138Nicole M. Ford3https://orcid.org/0000-0001-8921-3624Maria R. Drout4https://orcid.org/0000-0001-7081-0082Rodrigo Fernández5https://orcid.org/0000-0003-4619-339XTrottier Space Institute at McGill and Department of Physics, McGill University , 3600 rue University, Montreal, QC H3A 2T8, Canada nicholas.vieira@mail.mcgill.caDepartment of Physics and Astronomy, Bishop's University , 2600 rue College, Sherbrooke, QC J1M 1Z7, CanadaTrottier Space Institute at McGill and Department of Physics, McGill University , 3600 rue University, Montreal, QC H3A 2T8, Canada nicholas.vieira@mail.mcgill.caTrottier Space Institute at McGill and Department of Physics, McGill University , 3600 rue University, Montreal, QC H3A 2T8, Canada nicholas.vieira@mail.mcgill.caDavid A. Dunlap Department of Astronomy and Astrophysics, University of Toronto , 50 St. George Street, Toronto, ON M5S 3H4, CanadaDepartment of Physics, University of Alberta , Edmonton, AB T6G 2E1, CanadaIn kilonovae, freshly synthesized r -process elements imprint features on optical spectra, as observed in AT2017gfo, the counterpart to the GW170817 binary neutron star merger. However, measuring the r -process compositions of the merger ejecta is computationally challenging. Vieira et al. introduced Spectroscopic r -process Abundance Retrieval for Kilonovae ( SPARK ), a software tool to infer elemental abundance patterns of the ejecta and associate spectral features with particular species. Previously, we applied SPARK to the 1.4-day spectrum of AT2017gfo and inferred its abundance pattern for the first time, characterized by electron fraction Y _e = 0.31, a substantial abundance of strontium, and a dearth of lanthanides and heavier elements. This ejecta is consistent with wind from a remnant hypermassive neutron star and/or accretion disk. We now extend our inference to spectra at 2.4 and 3.4 days and test the need for multicomponent ejecta, where we stratify the ejecta in composition. The ejecta at 1.4 and 2.4 days is described by the same single blue component. At 3.4 days, a new redder component with lower Y _e = 0.16 and a significant abundance of lanthanides emerges. This new redder component is consistent with dynamical ejecta and/or neutron-rich ejecta from a magnetized accretion disk. As expected from photometric modeling, this component emerges as the ejecta expands, the photosphere recedes, and the earlier bluer component dims. At 3.4 days, we find an ensemble of lanthanides, with the presence of cerium most concrete. This presence of lanthanides has important implications for the contribution of kilonovae to the r -process abundances observed in the Universe.https://doi.org/10.3847/1538-4357/ad1193Nuclear abundancesR-processRadiative transfer simulationsSpectral line identification |
| spellingShingle | Nicholas Vieira John J. Ruan Daryl Haggard Nicole M. Ford Maria R. Drout Rodrigo Fernández Spectroscopic r-process Abundance Retrieval for Kilonovae. II. Lanthanides in the Inferred Abundance Patterns of Multicomponent Ejecta from the GW170817 Kilonova The Astrophysical Journal Nuclear abundances R-process Radiative transfer simulations Spectral line identification |
| title | Spectroscopic r-process Abundance Retrieval for Kilonovae. II. Lanthanides in the Inferred Abundance Patterns of Multicomponent Ejecta from the GW170817 Kilonova |
| title_full | Spectroscopic r-process Abundance Retrieval for Kilonovae. II. Lanthanides in the Inferred Abundance Patterns of Multicomponent Ejecta from the GW170817 Kilonova |
| title_fullStr | Spectroscopic r-process Abundance Retrieval for Kilonovae. II. Lanthanides in the Inferred Abundance Patterns of Multicomponent Ejecta from the GW170817 Kilonova |
| title_full_unstemmed | Spectroscopic r-process Abundance Retrieval for Kilonovae. II. Lanthanides in the Inferred Abundance Patterns of Multicomponent Ejecta from the GW170817 Kilonova |
| title_short | Spectroscopic r-process Abundance Retrieval for Kilonovae. II. Lanthanides in the Inferred Abundance Patterns of Multicomponent Ejecta from the GW170817 Kilonova |
| title_sort | spectroscopic r process abundance retrieval for kilonovae ii lanthanides in the inferred abundance patterns of multicomponent ejecta from the gw170817 kilonova |
| topic | Nuclear abundances R-process Radiative transfer simulations Spectral line identification |
| url | https://doi.org/10.3847/1538-4357/ad1193 |
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