A Model of the C iv λ λ1548, 1550 Doublet Line in T Tauri Stars
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 acc...
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2024-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/ad7b2d |
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| author | Thanawuth Thanathibodee Connor E. Robinson Nuria Calvet Catherine C. Espaillat Caeley V. Pittman Nicole Arulanantham Kevin France Hans Moritz Günther Seok-Jun Chang P. Christian Schneider |
| author_facet | Thanawuth Thanathibodee Connor E. Robinson Nuria Calvet Catherine C. Espaillat Caeley V. Pittman Nicole Arulanantham Kevin France Hans Moritz Günther Seok-Jun Chang P. Christian Schneider |
| author_sort | Thanawuth Thanathibodee |
| collection | DOAJ |
| description | 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 the 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% 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 | Article |
| id | doaj-art-88a4783572b64a5d957f6cbc862608ea |
| institution | OA Journals |
| issn | 1538-4357 |
| language | English |
| publishDate | 2024-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj-art-88a4783572b64a5d957f6cbc862608ea2025-08-20T02:19:07ZengIOP PublishingThe Astrophysical Journal1538-43572024-01-01975219310.3847/1538-4357/ad7b2dA Model of the C iv λ λ1548, 1550 Doublet Line in T Tauri StarsThanawuth Thanathibodee0https://orcid.org/0000-0003-4507-1710Connor E. Robinson1https://orcid.org/0000-0003-1639-510XNuria Calvet2https://orcid.org/0000-0002-3950-5386Catherine C. Espaillat3https://orcid.org/0000-0001-9227-5949Caeley V. Pittman4https://orcid.org/0000-0001-9301-6252Nicole Arulanantham5https://orcid.org/0000-0003-2631-5265Kevin France6https://orcid.org/0000-0002-1002-3674Hans Moritz Günther7https://orcid.org/0000-0003-4243-2840Seok-Jun Chang8https://orcid.org/0000-0002-0112-5900P. Christian Schneider9https://orcid.org/0000-0002-5094-2245Institute for Astrophysical Research, Department of Astronomy, Boston University , 725 Commonwealth Avenue, Boston, MA 02215, USA ; thanathi@bu.edu; Department of Physics, Faculty of Science, Chulalongkorn University , 254 Phayathai Road, Pathumwan, Bangkok 10330, Thailand ; thanawuth.t@chula.ac.thDivision of Physics and Astronomy, Alfred University , 1 Saxon Drive, Alfred, NY 14802, USADepartment of Astronomy, University of Michigan , 1085 South University Avenue, Ann Arbor, MI 48109, USAInstitute for Astrophysical Research, Department of Astronomy, Boston University , 725 Commonwealth Avenue, Boston, MA 02215, USA ; thanathi@bu.eduInstitute for Astrophysical Research, Department of Astronomy, Boston University , 725 Commonwealth Avenue, Boston, MA 02215, USA ; thanathi@bu.eduSpace Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USALaboratory for Atmospheric and Space Physics, University of Colorado Boulder , Boulder, CO 80303, USAKavli Institute for Astrophysics and Space Research , Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USAMax-Planck-Institut für Astrophysik , Karl-Schwarzschild-Straβe 1, 85748 Garching b. München, GermanyHamburger Sternwarte , Gojenbergsweg 112, D-21029, Hamburg, GermanyThe 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 the 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% 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.https://doi.org/10.3847/1538-4357/ad7b2dT Tauri starsStellar accretionUltraviolet astronomyProtoplanetary disksAstronomical modelsRadiative transfer |
| spellingShingle | Thanawuth Thanathibodee Connor E. Robinson Nuria Calvet Catherine C. Espaillat Caeley V. Pittman Nicole Arulanantham Kevin France Hans Moritz Günther Seok-Jun Chang P. Christian Schneider A Model of the C iv λ λ1548, 1550 Doublet Line in T Tauri Stars The Astrophysical Journal T Tauri stars Stellar accretion Ultraviolet astronomy Protoplanetary disks Astronomical models Radiative transfer |
| title | A Model of the C iv λ λ1548, 1550 Doublet Line in T Tauri Stars |
| title_full | A Model of the C iv λ λ1548, 1550 Doublet Line in T Tauri Stars |
| title_fullStr | A Model of the C iv λ λ1548, 1550 Doublet Line in T Tauri Stars |
| title_full_unstemmed | A Model of the C iv λ λ1548, 1550 Doublet Line in T Tauri Stars |
| title_short | A Model of the C iv λ λ1548, 1550 Doublet Line in T Tauri Stars |
| title_sort | model of the c iv λ λ1548 1550 doublet line in t tauri stars |
| topic | T Tauri stars Stellar accretion Ultraviolet astronomy Protoplanetary disks Astronomical models Radiative transfer |
| url | https://doi.org/10.3847/1538-4357/ad7b2d |
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