Hostname: page-component-cd9895bd7-mkpzs Total loading time: 0 Render date: 2024-12-25T05:05:00.718Z Has data issue: false hasContentIssue false
  • English
  • Français

Observations of accretion shocks

Published online by Cambridge University Press:  01 May 2007

David R. Ardila
David R. Ardila*
Affiliation:
Spitzer Science Center, Infrared Processing and Analysis Center, MS 220-6, California Institute of Technology, Pasadena, CA 91125, USA email: [email protected]
Rights & Permissions [Opens in a new window]

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

I review our current understanding of accretion shocks in classical T Tauri stars (CTTs), from a UV and X-ray perspective. The region of the accretion shock is a good candidate as a source of UV transition region lines from Li/Na-like ions, which are stronger in CTTs than in naked atmospheres. Disk gas captured by the stellar magnetic field produces a strong radiative shock upon falling on the stellar surface. Radiation from the shock creates a radiative precursor and heats the stellar surface resulting in a hot spot. Stellar and shock models indicate that unless the post-shock column is very large, it will be buried on the stellar photosphere. Models of the continuum emission produced by this configuration can roughly reproduce the observed excess spectra down to 1650 Å. Transition region lines in CTTs are broad, very variable, and present blueshifted, centered, and redshifted centroids. Detailed models of the line emission have so far failed to reproduce the fluxes, line shapes, and line ratios. High resolution X-ray line observations indicate the presence of larger amounts of cool plasma in CTTs with respect to WTTs. Observations of density sensitive line ratios of He-like ions suggest high plasma densities, as expected from lines originating in the accretion shock. For most stars, the interpretation of these ratios in terms of density remains equivocal due to the presence of the strong UV continuum.

Keywords

Stars: atmospherescoronaewindsoutflowsline: formationmagnetic fieldsultraviolet: starsX-rays: stars
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 3 , Symposium S243: Star-Disk Interaction in Young Stars , May 2007 , pp. 103 - 114
Copyright
Copyright © International Astronomical Union 2007

References

Alencar, S. H. P. & Batalha, C. 2002, ApJ, 571, 378CrossRefGoogle Scholar
Alexander, R. D., Clarke, C. J., Pringle, J. E. 2004, MNRAS, 354, 71Google Scholar
Alexander, R. D., Clarke, C. J., Pringle, J. E. 2005, MNRAS, 358, 283Google Scholar
Ardila, D. & Johns-Krull, C. M. 2007, in preparation.Google Scholar
Ardila, D. R., Basri, G., Walter, F. M., Valenti, J. A., Johns-Krull, C. M. 2002, ApJ, 566, 1100Google Scholar
Bergin, E., et al. 2004, ApJL, 614, L133CrossRefGoogle Scholar
Beristain, G., Edwards, S., Kwan, J. 2001, ApJ, 551, 1037Google Scholar
Calvet, N. & Gullbring, E. 1998, ApJ, 509, 802CrossRefGoogle Scholar
Calvet, N., Muzerolle, J., Briceño, C., Hernández, J., Hartmann, L., Saucedo, J. L., Gordon, K. D. 2004, AJ, 128, 1294Google Scholar
D'Antona, F. & Mazzitelli, I. 1997, MemSAI, 68, 807Google Scholar
Drake, J. J. 2005, in ESA Special Publication, Vol. 560, ESA Special Publication, ed. Favata, F. & et al. , 519Google Scholar
Feigelson, E. D., Broos, P., Gaffney, J. A. III, Garmire, G., Hillenbrand, L. A., Pravdo, S. H., Townsley, L., Tsuboi, Y. 2002, ApJ, 574, 258Google Scholar
Gómez de Castro, A. I. & Verdugo, E. 2007, ApJL, 654, L91CrossRefGoogle Scholar
Güdel, M., Skinner, S. L., Briggs, K. R., Audard, M., Arzner, K., Telleschi, A. 2005, ApJL, 626, L53Google Scholar
Güdel, M., Skinner, S. L., Mel'Nikov, S. Y., Audard, M., Telleschi, A., Briggs, K. R. 2007, A&A, 468, 529Google Scholar
Gullbring, E., Calvet, N., Muzerolle, J., Hartmann, L. 2000, ApJ, 544, 927Google Scholar
Gullbring, E., Hartmann, L., Briceno, C., Calvet, N. 1998, ApJ, 492, 323Google Scholar
Günther, H. M. & Schmitt, J. H. M. M. 2007, MemSAI, in pressGoogle Scholar
Günther, H. M., Schmitt, J. H. M. M., Robrade, J., Liefke, C. 2007, A&A, 466, 1111Google Scholar
Herczeg, G. J., Linsky, J. L., Valenti, J. A., Johns-Krull, C. M., Wood, B. E. 2002, ApJ, 572, 310Google Scholar
Herczeg, G. J., Linsky, J. L., Walter, F. M., Gahm, G. F., Johns-Krull, C. M. 2006, APJS, 165, 256CrossRefGoogle Scholar
Herczeg, G. J., et al. 2005, AJ, 129, 2777CrossRefGoogle Scholar
Herczeg, G. J., Wood, B. E., Linsky, J. L., Valenti, J. A., Johns-Krull, C. M. 2004, ApJ, 607, 369Google Scholar
Johns-Krull, C. M., Valenti, J. A., Linsky, J. L. 2000, ApJ, 539, 815CrossRefGoogle Scholar
Joy, A. H. 1945, Contributions from the Mount Wilson Observatory / Carnegie Institution of Washington, 709, 1Google Scholar
Lamzin, S. A. 2000, Astron. Rep., 44, 323Google Scholar
Lamzin, S. A. 2003, Astron. Rep., 47, 498Google Scholar
Mazzotta, P., Mazzitelli, G., Colafrancesco, S., Vittorio, N. 1998, A&AS, 133, 403Google Scholar
Muzerolle, J., Calvet, N., Hartmann, L. 1998, ApJ, 492, 743Google Scholar
Ness, J.-U., Güdel, M., Schmitt, J. H. M. M., Audard, M., Telleschi, A. 2004, A&A, 427, 667Google Scholar
Ness, J.-U. & Schmitt, J. H. M. M. 2005, A&A, 444, L41Google Scholar
Preibisch, T., et al. 2005, APJS, 160, 401Google Scholar
Robrade, J. & Schmitt, J. H. M. M. 2006, A&A, 449, 737Google Scholar
Stelzer, B. & Schmitt, J. H. M. M. 2004, A&A, 418, 687Google Scholar
Telleschi, A., Güdel, M., Briggs, K. R., Audard, M., Palla, F. 2007a, A&A, 468, 425Google Scholar
Telleschi, A., Güdel, M., Briggs, K. R., Audard, M., Scelsi, L. 2007b, A&A, 468, 443Google Scholar