A Model of the C IV $λλ$ 1548, 1550 Doublet Line in T Tauri Stars
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arXiv
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| Auteurs principaux: | , , , , , , , , , |
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| Format: | Preprint |
| Publié: |
2024
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| _version_ | 1866910605493927936 |
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| author | Thanathibodee, Thanawuth Robinson, Connor Calvet, Nuria Espaillat, Catherine Pittman, Caeley Arulanantham, Nicole France, Kevin Günther, Hans Moritz Chang, Seok-Jun Schneider, P. Christian |
| author_facet | Thanathibodee, Thanawuth Robinson, Connor Calvet, Nuria Espaillat, Catherine Pittman, Caeley Arulanantham, Nicole France, Kevin Günther, Hans Moritz Chang, Seok-Jun Schneider, P. Christian |
| contents | The C IV doublet in the UV has long been associated with accretion in T Tauri stars. However, it is still unclear where and how the lines are formed. Here, we present a new C IV line model based on the currently available accretion shock and accretion flow models. We assume axisymmetric, dipolar accretion flows with different energy fluxes and calculate the properties of the accretion shock. We use Cloudy to obtain the carbon level populations and calculate the emerging line profiles assuming a plane-parallel geometry near the shock. Our model generally reproduces the intensities and shapes of the C IV emission lines observed from T Tauri stars. We find that the narrow component is optically thin and originates in the postshock, while the broad component is optically thick and emerges from the preshock. We apply our model to seven T Tauri stars from the Hubble Ultraviolet Legacy Library of Young Stars as Essential Standards Director's Discretionary program (ULLYSES), for which consistently determined accretion shock properties are available. We can reproduce the observations of four stars, finding that the accretion flows are carbon-depleted. We also find that the chromospheric emission accounts for less than 10 percent of the observed C IV line flux in accreting T Tauri stars. This work paves the way toward a better understanding of hot line formation and provides a potential probe of abundances in the inner disk. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2409_10361 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | A Model of the C IV $λλ$ 1548, 1550 Doublet Line in T Tauri Stars Thanathibodee, Thanawuth Robinson, Connor Calvet, Nuria Espaillat, Catherine Pittman, Caeley Arulanantham, Nicole France, Kevin Günther, Hans Moritz Chang, Seok-Jun Schneider, P. Christian Solar and Stellar Astrophysics Earth and Planetary Astrophysics The C IV doublet in the UV has long been associated with accretion in T Tauri stars. However, it is still unclear where and how the lines are formed. Here, we present a new C IV line model based on the currently available accretion shock and accretion flow models. We assume axisymmetric, dipolar accretion flows with different energy fluxes and calculate the properties of the accretion shock. We use Cloudy to obtain the carbon level populations and calculate the emerging line profiles assuming a plane-parallel geometry near the shock. Our model generally reproduces the intensities and shapes of the C IV emission lines observed from T Tauri stars. We find that the narrow component is optically thin and originates in the postshock, while the broad component is optically thick and emerges from the preshock. We apply our model to seven T Tauri stars from the Hubble Ultraviolet Legacy Library of Young Stars as Essential Standards Director's Discretionary program (ULLYSES), for which consistently determined accretion shock properties are available. We can reproduce the observations of four stars, finding that the accretion flows are carbon-depleted. We also find that the chromospheric emission accounts for less than 10 percent of the observed C IV line flux in accreting T Tauri stars. This work paves the way toward a better understanding of hot line formation and provides a potential probe of abundances in the inner disk. |
| title | A Model of the C IV $λλ$ 1548, 1550 Doublet Line in T Tauri Stars |
| topic | Solar and Stellar Astrophysics Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2409.10361 |