Stellar Population Spectra Incorporating Detailed Binary Evolution using POSYDON

Abstract

The accuracy of stellar population properties inferred through spectral energy distribution fitting hinges on the reliability of the underlying spectral models. Binary interactions are fundamental for massive star evolution, and ignoring their spectral contribution can lead to incorrect results. We use the POSYDON binary population synthesis code to generate spectral models of stellar populations that include binaries at solar metallicity. Our framework incorporates a collection of spectral libraries that is designed to address key outcomes of binary stellar evolution like Wolf-Rayet stars, stripped helium stars, and a treatment for stellar mergers. Our models confirm previous results showing that the inclusion of binary interactions has a significant effect on the UV and ionizing regime of the integrated spectrum. In particular we find that Wolf-Rayet stars and other massive stars dominate the production of ionizing radiation at earlier times, but after ≃16 Myr stripped stars produced through mass transfer begin to dominate. Furthermore, we show that the production of ionizing He II photons is especially sensitive to the underlying population of stripped stars. While our results currently focus on high-mass stars (≥4 M_⊙) at Solar metallicity, they provide the framework for binary spectral synthesis across a range of metallicities and masses and lay the foundation for calculations of the emergent emission-line spectra in the UV, optical, and IR regimes. We make the spectral models from this work publicly available for use in a format that can be integrated into fitting codes.

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BibTeX RIS

BibTeX

@misc{kasdagli2026stellar,
  title = {{Stellar Population Spectra Incorporating Detailed Binary Evolution using POSYDON}},
  author = {Eirini Kasdagli and Jeff J. Andrews and Bret Lehmer and Rich Townsend and Manos Zapartas and Andreas Zezas and Ylva Götberg and Max Briel and Tassos Fragos and Seth Gossage and Philipp M. Srivastava and Elizabeth Teng},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2606.13351},
  eprint = {2606.13351},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2606.13351},
  note = {CC BY 4.0},
}

RIS

TY  - UNPB
TI  - Stellar Population Spectra Incorporating Detailed Binary Evolution using POSYDON
AU  - Eirini Kasdagli
AU  - Jeff J. Andrews
AU  - Bret Lehmer
AU  - Rich Townsend
AU  - Manos Zapartas
AU  - Andreas Zezas
AU  - Ylva Götberg
AU  - Max Briel
AU  - Tassos Fragos
AU  - Seth Gossage
AU  - Philipp M. Srivastava
AU  - Elizabeth Teng
PY  - 2026
DA  - 2026/10/23
PB  - arXiv
DO  - 10.48550/arxiv.2606.13351
UR  - https://arxiv.org/abs/2606.13351
AB  - The accuracy of stellar population properties inferred through spectral energy distribution fitting hinges on the reliability of the underlying spectral models. Binary interactions are fundamental for massive star evolution, and ignoring their spectral contribution can lead to incorrect results. We use the POSYDON binary population synthesis code to generate spectral models of stellar populations that include binaries at solar metallicity. Our framework incorporates a collection of spectral libraries that is designed to address key outcomes of binary stellar evolution like Wolf-Rayet stars, stripped helium stars, and a treatment for stellar mergers. Our models confirm previous results showing that the inclusion of binary interactions has a significant effect on the UV and ionizing regime of the integrated spectrum. In particular we find that Wolf-Rayet stars and other massive stars dominate the production of ionizing radiation at earlier times, but after ≃16 Myr stripped stars produced through mass transfer begin to dominate. Furthermore, we show that the production of ionizing He II photons is especially sensitive to the underlying population of stripped stars. While our results currently focus on high-mass stars (≥4 M_⊙) at Solar metallicity, they provide the framework for binary spectral synthesis across a range of metallicities and masses and lay the foundation for calculations of the emergent emission-line spectra in the UV, optical, and IR regimes. We make the spectral models from this work publicly available for use in a format that can be integrated into fitting codes.
ER  -

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