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Radiative accretion shocks along nonuniform stellar magnetic fields in classical T Tauri stars

Authors :
Titos Matsakos
Chantal Stehlé
Marco Miceli
Salvatore Orlando
Costanza Argiroffi
J.-P. Chièze
Thierry Lanz
L. Ibgui
Fabio Reale
Rosaria Bonito
L. de Sá
Giovanni Peres
Istituto di Astrofisica Spaziale e Fisica cosmica - Palermo (IASF-Pa)
Istituto Nazionale di Astrofisica (INAF)
Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique (LERMA)
École normale supérieure - Paris (ENS-PSL)
Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris
Université Paris sciences et lettres (PSL)-Université de Cergy Pontoise (UCP)
Université Paris-Seine-Université Paris-Seine-Centre National de la Recherche Scientifique (CNRS)
Service des Photons, Atomes et Molécules (SPAM)
Commissariat à l'énergie atomique et aux énergies alternatives (CEA)
Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112))
Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)
Joseph Louis LAGRANGE (LAGRANGE)
Université Nice Sophia Antipolis (1965 - 2019) (UNS)
COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur
COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)
Orlando, S
Bonito, R
Argiroffi, C
Reale, F
Peres, G
Miceli, M
Matsakos, T
Stehlé, C
Ibgui, L
de Sa, L
Chièze, J
Lanz, T
École normale supérieure - Paris (ENS Paris)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris
PSL Research University (PSL)-PSL Research University (PSL)-Université de Cergy Pontoise (UCP)
Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112))
Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)
Université Nice Sophia Antipolis (... - 2019) (UNS)
Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur
Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS)
École normale supérieure - Paris (ENS Paris)
Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS)
COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur
Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)
Source :
Astronomy and Astrophysics-A&A, Astronomy and Astrophysics-A&A, 2013, 559, pp.A127. ⟨10.1051/0004-6361/201322076⟩, Astronomy and Astrophysics-A&A, EDP Sciences, 2013, 559, pp.A127. ⟨10.1051/0004-6361/201322076⟩
Publication Year :
2013
Publisher :
HAL CCSD, 2013.

Abstract

(abridged) AIMS. We investigate the dynamics and stability of post-shock plasma streaming along nonuniform stellar magnetic fields at the impact region of accretion columns. We study how the magnetic field configuration and strength determine the structure, geometry, and location of the shock-heated plasma. METHODS. We model the impact of an accretion stream onto the chromosphere of a CTTS by 2D axisymmetric magnetohydrodynamic simulations. Our model takes into account the gravity, the radiative cooling, and the magnetic-field-oriented thermal conduction. RESULTS. The structure, stability, and location of the shocked plasma strongly depend on the configuration and strength of the magnetic field. For weak magnetic fields, a large component of B may develop perpendicular to the stream at the base of the accretion column, limiting the sinking of the shocked plasma into the chromosphere. An envelope of dense and cold chromospheric material may also develop around the shocked column. For strong magnetic fields, the field configuration determines the position of the shock and its stand-off height. If the field is strongly tapered close to the chromosphere, an oblique shock may form well above the stellar surface. In general, a nonuniform magnetic field makes the distribution of emission measure vs. temperature of the shocked plasma lower than in the case of uniform magnetic field. CONCLUSIONS. The initial strength and configuration of the magnetic field in the impact region of the stream are expected to influence the chromospheric absorption and, therefore, the observability of the shock-heated plasma in the X-ray band. The field strength and configuration influence also the energy balance of the shocked plasma, its emission measure at T > 1 MK being lower than expected for a uniform field. The above effects contribute in underestimating the mass accretion rates derived in the X-ray band.<br />11 pages, 11 Figures; accepted for publication on A&A. Version with full resolution images can be found at http://www.astropa.unipa.it/~orlando/PREPRINTS/sorlando_accretion_shocks.pdf

Details

Language :
English
ISSN :
00046361
Database :
OpenAIRE
Journal :
Astronomy and Astrophysics-A&A, Astronomy and Astrophysics-A&A, 2013, 559, pp.A127. ⟨10.1051/0004-6361/201322076⟩, Astronomy and Astrophysics-A&A, EDP Sciences, 2013, 559, pp.A127. ⟨10.1051/0004-6361/201322076⟩
Accession number :
edsair.doi.dedup.....38329ca4bab8b17c29520771e49fa50c