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| Main Authors: | , , , , , , |
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| Format: | Preprint |
| Published: |
2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2512.05029 |
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| _version_ | 1866915654263635968 |
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| author | Mosallanezhad, Amin Knigge, Christian Scepi, Nicolas Long, Knox S. Matthews, James H. Sim, Stuart A. Wallis, Austen |
| author_facet | Mosallanezhad, Amin Knigge, Christian Scepi, Nicolas Long, Knox S. Matthews, James H. Sim, Stuart A. Wallis, Austen |
| contents | Radiation pressure on spectral lines is a promising mechanism for powering disc winds from accreting white dwarfs (AWDs) and active galactic nuclei (AGN). However, in radiation-hydrodynamic simulations, overionization reduces line opacity and quenches the line force, which suppresses outflows. Here, we show that small-scale clumping can resolve this problem. Adopting the microclumping approximation, our new simulations demonstrate that even modest volume filling factors ($f_V \sim 0.1-0.01$) can dramatically increase the wind mass-loss rate by lowering its ionization state -- raising $\dot{M}_{\rm wind}$ and yielding $\dot{M}_{\rm wind}/\dot{M}_{\rm acc}\!\gtrsim\!10^{-4}$ for such modest filling factors. Clumpy wind models produce the UV resonance lines that are absent from smooth wind models. They can also reprocess a significant fraction of the disc luminosity and thus dramatically modify the broad-band optical/UV SED. Given that theory and observations indicate that disc winds are intrinsically inhomogeneous, clumping offers a physically motivated solution. Together, these results provide the first robust, self-consistent demonstration that clumping can reconcile line-driven wind theory with observations across AWDs and AGNs. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2512_05029 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The critical role of clumping in line-driven disc winds Mosallanezhad, Amin Knigge, Christian Scepi, Nicolas Long, Knox S. Matthews, James H. Sim, Stuart A. Wallis, Austen Astrophysics of Galaxies High Energy Astrophysical Phenomena Radiation pressure on spectral lines is a promising mechanism for powering disc winds from accreting white dwarfs (AWDs) and active galactic nuclei (AGN). However, in radiation-hydrodynamic simulations, overionization reduces line opacity and quenches the line force, which suppresses outflows. Here, we show that small-scale clumping can resolve this problem. Adopting the microclumping approximation, our new simulations demonstrate that even modest volume filling factors ($f_V \sim 0.1-0.01$) can dramatically increase the wind mass-loss rate by lowering its ionization state -- raising $\dot{M}_{\rm wind}$ and yielding $\dot{M}_{\rm wind}/\dot{M}_{\rm acc}\!\gtrsim\!10^{-4}$ for such modest filling factors. Clumpy wind models produce the UV resonance lines that are absent from smooth wind models. They can also reprocess a significant fraction of the disc luminosity and thus dramatically modify the broad-band optical/UV SED. Given that theory and observations indicate that disc winds are intrinsically inhomogeneous, clumping offers a physically motivated solution. Together, these results provide the first robust, self-consistent demonstration that clumping can reconcile line-driven wind theory with observations across AWDs and AGNs. |
| title | The critical role of clumping in line-driven disc winds |
| topic | Astrophysics of Galaxies High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2512.05029 |