Synthesizing Spectra from 3D Radiation Hydrodynamic Models of Massive Stars Using Monte Carlo Radiation Transport
Observations indicate that turbulent motions are present on most massive star surfaces. Starting from the observed phenomena of spectral lines with widths that are much larger than their thermal broadening (e.g., micro- and macroturbulence), and considering the detection of stochastic low-frequency...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/acb701 |
| _version_ | 1797697163465064448 |
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| author | William C. Schultz Benny T.-H. Tsang Lars Bildsten Yan-Fei Jiang |
| author_facet | William C. Schultz Benny T.-H. Tsang Lars Bildsten Yan-Fei Jiang |
| author_sort | William C. Schultz |
| collection | DOAJ |
| description | Observations indicate that turbulent motions are present on most massive star surfaces. Starting from the observed phenomena of spectral lines with widths that are much larger than their thermal broadening (e.g., micro- and macroturbulence), and considering the detection of stochastic low-frequency variability (SLFV) in the Transiting Exoplanet Survey Satellite photometry, these stars clearly have large-scale turbulent motions on their surfaces. The cause of this turbulence is debated, with near-surface convection zones, core internal gravity waves, and wind variability being proposed. Our 3D gray radiation hydrodynamic (RHD) models previously characterized the convective dynamics of the surfaces, driven by near-surface convection zones, and provided reasonable matches to the observed SLFV of the most luminous massive stars. We now explore the complex emitting surfaces of these 3D RHD models, which strongly violate the 1D assumption of a plane-parallel atmosphere. By post-processing the gray RHD models with the Monte Carlo radiation transport code Sedona , we synthesize stellar spectra and extract information from the broadening of individual photospheric lines. The use of Sedona enables the calculation of the viewing angle and temporal dependence of spectral absorption line profiles. By combining uncorrelated temporal snapshots together, we compare the turbulent broadening from the 3D RHD models to the thermal broadening of the extended emitting region, showing that our synthesized spectral lines closely resemble the observed macroturbulent broadening from similarly luminous stars. More generally, the new techniques that we have developed will allow for systematic studies of the origins of turbulent velocity broadening from any future 3D simulations. |
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| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-12T03:36:20Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj.art-0b36c12d106341feaaa12af02b7e3e722023-09-03T13:08:50ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-0194515810.3847/1538-4357/acb701Synthesizing Spectra from 3D Radiation Hydrodynamic Models of Massive Stars Using Monte Carlo Radiation TransportWilliam C. Schultz0https://orcid.org/0000-0003-1796-9849Benny T.-H. Tsang1https://orcid.org/0000-0002-6543-2993Lars Bildsten2https://orcid.org/0000-0001-8038-6836Yan-Fei Jiang3https://orcid.org/0000-0002-2624-3399Department of Physics, University of California , Santa Barbara, CA 93106, USA ; wcschultz@physics.ucsb.eduDepartment of Astronomy and Theoretical Astrophysics Center, University of California , Berkeley, CA 94720, USADepartment of Physics, University of California , Santa Barbara, CA 93106, USA ; wcschultz@physics.ucsb.edu; Kavli Institute for Theoretical Physics, University of California , Santa Barbara, CA 93106, USACenter for Computational Astrophysics, Flatiron Institute , New York, NY 10010, USAObservations indicate that turbulent motions are present on most massive star surfaces. Starting from the observed phenomena of spectral lines with widths that are much larger than their thermal broadening (e.g., micro- and macroturbulence), and considering the detection of stochastic low-frequency variability (SLFV) in the Transiting Exoplanet Survey Satellite photometry, these stars clearly have large-scale turbulent motions on their surfaces. The cause of this turbulence is debated, with near-surface convection zones, core internal gravity waves, and wind variability being proposed. Our 3D gray radiation hydrodynamic (RHD) models previously characterized the convective dynamics of the surfaces, driven by near-surface convection zones, and provided reasonable matches to the observed SLFV of the most luminous massive stars. We now explore the complex emitting surfaces of these 3D RHD models, which strongly violate the 1D assumption of a plane-parallel atmosphere. By post-processing the gray RHD models with the Monte Carlo radiation transport code Sedona , we synthesize stellar spectra and extract information from the broadening of individual photospheric lines. The use of Sedona enables the calculation of the viewing angle and temporal dependence of spectral absorption line profiles. By combining uncorrelated temporal snapshots together, we compare the turbulent broadening from the 3D RHD models to the thermal broadening of the extended emitting region, showing that our synthesized spectral lines closely resemble the observed macroturbulent broadening from similarly luminous stars. More generally, the new techniques that we have developed will allow for systematic studies of the origins of turbulent velocity broadening from any future 3D simulations.https://doi.org/10.3847/1538-4357/acb701Astrophysical fluid dynamicsHydrodynamicsComputational methodsRadiative transfer simulationsStellar spectral linesStellar convection envelopes |
| spellingShingle | William C. Schultz Benny T.-H. Tsang Lars Bildsten Yan-Fei Jiang Synthesizing Spectra from 3D Radiation Hydrodynamic Models of Massive Stars Using Monte Carlo Radiation Transport The Astrophysical Journal Astrophysical fluid dynamics Hydrodynamics Computational methods Radiative transfer simulations Stellar spectral lines Stellar convection envelopes |
| title | Synthesizing Spectra from 3D Radiation Hydrodynamic Models of Massive Stars Using Monte Carlo Radiation Transport |
| title_full | Synthesizing Spectra from 3D Radiation Hydrodynamic Models of Massive Stars Using Monte Carlo Radiation Transport |
| title_fullStr | Synthesizing Spectra from 3D Radiation Hydrodynamic Models of Massive Stars Using Monte Carlo Radiation Transport |
| title_full_unstemmed | Synthesizing Spectra from 3D Radiation Hydrodynamic Models of Massive Stars Using Monte Carlo Radiation Transport |
| title_short | Synthesizing Spectra from 3D Radiation Hydrodynamic Models of Massive Stars Using Monte Carlo Radiation Transport |
| title_sort | synthesizing spectra from 3d radiation hydrodynamic models of massive stars using monte carlo radiation transport |
| topic | Astrophysical fluid dynamics Hydrodynamics Computational methods Radiative transfer simulations Stellar spectral lines Stellar convection envelopes |
| url | https://doi.org/10.3847/1538-4357/acb701 |
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