TW Hya: Spectral variability, X-rays, and accretion diagnostics

The nearest accreting T Tauri star, TW Hya was intensively and continuously observed over ∼17days with spectroscopic and photometric measurements from four continents simultaneous with a long segmented exposure using the Chandra satellite. Contemporaneous optical photometry from WASP-S indicates a 4...

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Detalles Bibliográficos
Publicado: 2012
Materias:
accretion, accretion disks
stars: individual (TW Hydrae)
stars: pre-main sequence
stars: variables: T Tauri, Herbig Ae/Be
stars: winds, outflows
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v750_n1_p_Dupree
http://hdl.handle.net/20.500.12110/paper_0004637X_v750_n1_p_Dupree
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id paper:paper_0004637X_v750_n1_p_Dupree
record_format dspace
spelling paper:paper_0004637X_v750_n1_p_Dupree2023-06-08T14:29:05Z TW Hya: Spectral variability, X-rays, and accretion diagnostics accretion, accretion disks stars: individual (TW Hydrae) stars: pre-main sequence stars: variables: T Tauri, Herbig Ae/Be stars: winds, outflows The nearest accreting T Tauri star, TW Hya was intensively and continuously observed over ∼17days with spectroscopic and photometric measurements from four continents simultaneous with a long segmented exposure using the Chandra satellite. Contemporaneous optical photometry from WASP-S indicates a 4.74day period was present during this time. The absence of a similar periodicity in the Hα flux and the total X-ray flux which are dominated by accretion processes and the stellar corona, respectively, points to a different source of photometric variations. The Hα emission line appears intrinsically broad and symmetric, and both the profile and its variability suggest an origin in the post-shock cooling region. An accretion event, signaled by soft X-rays, is traced spectroscopically for the first time through the optical emission line profiles. After the accretion event, downflowing turbulent material observed in the Hα and Hβ lines is followed by He I (λ5876) broadening near the photosphere. Optical veiling resulting from the heated photosphere increases with a delay of ∼2hr after the X-ray accretion event. The response of the stellar coronal emission to an increase in the veiling follows ∼2.4hr later, giving direct evidence that the stellar corona is heated in part by accretion. Subsequently, the stellar wind becomes re-established. We suggest a model that incorporates the dynamics of this sequential series of events: an accretion shock, a cooling downflow in a supersonically turbulent region, followed by photospheric and later, coronal heating. This model naturally explains the presence of broad optical and ultraviolet lines, and affects the mass accretion rates determined from emission line profiles. © 2012. The American Astronomical Society. All rights reserved. 2012 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v750_n1_p_Dupree http://hdl.handle.net/20.500.12110/paper_0004637X_v750_n1_p_Dupree
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic accretion, accretion disks
stars: individual (TW Hydrae)
stars: pre-main sequence
stars: variables: T Tauri, Herbig Ae/Be
stars: winds, outflows
spellingShingle accretion, accretion disks
stars: individual (TW Hydrae)
stars: pre-main sequence
stars: variables: T Tauri, Herbig Ae/Be
stars: winds, outflows
TW Hya: Spectral variability, X-rays, and accretion diagnostics
topic_facet accretion, accretion disks
stars: individual (TW Hydrae)
stars: pre-main sequence
stars: variables: T Tauri, Herbig Ae/Be
stars: winds, outflows
description The nearest accreting T Tauri star, TW Hya was intensively and continuously observed over ∼17days with spectroscopic and photometric measurements from four continents simultaneous with a long segmented exposure using the Chandra satellite. Contemporaneous optical photometry from WASP-S indicates a 4.74day period was present during this time. The absence of a similar periodicity in the Hα flux and the total X-ray flux which are dominated by accretion processes and the stellar corona, respectively, points to a different source of photometric variations. The Hα emission line appears intrinsically broad and symmetric, and both the profile and its variability suggest an origin in the post-shock cooling region. An accretion event, signaled by soft X-rays, is traced spectroscopically for the first time through the optical emission line profiles. After the accretion event, downflowing turbulent material observed in the Hα and Hβ lines is followed by He I (λ5876) broadening near the photosphere. Optical veiling resulting from the heated photosphere increases with a delay of ∼2hr after the X-ray accretion event. The response of the stellar coronal emission to an increase in the veiling follows ∼2.4hr later, giving direct evidence that the stellar corona is heated in part by accretion. Subsequently, the stellar wind becomes re-established. We suggest a model that incorporates the dynamics of this sequential series of events: an accretion shock, a cooling downflow in a supersonically turbulent region, followed by photospheric and later, coronal heating. This model naturally explains the presence of broad optical and ultraviolet lines, and affects the mass accretion rates determined from emission line profiles. © 2012. The American Astronomical Society. All rights reserved.
title TW Hya: Spectral variability, X-rays, and accretion diagnostics
title_short TW Hya: Spectral variability, X-rays, and accretion diagnostics
title_full TW Hya: Spectral variability, X-rays, and accretion diagnostics
title_fullStr TW Hya: Spectral variability, X-rays, and accretion diagnostics
title_full_unstemmed TW Hya: Spectral variability, X-rays, and accretion diagnostics
title_sort tw hya: spectral variability, x-rays, and accretion diagnostics
publishDate 2012
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_0004637X_v750_n1_p_Dupree
http://hdl.handle.net/20.500.12110/paper_0004637X_v750_n1_p_Dupree
_version_ 1768542671254585344

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