Query : 2008A&A...491L..17S

2008A&A...491L..17S - Astronomy and Astrophysics, volume 491, L17-20 (2008/11-4)

X-ray emission from dense plasma in classical T Tauri stars: hydrodynamic modeling of the accretion shock.


Abstract (from CDS):

High spectral resolution X-ray observations of classical T Tauri stars (CTTSs) demonstrate the presence of plasma at temperature T∼2-3x106K and density ne∼1011-1013cm–3, which are unobserved in non-accreting stars. Stationary models suggest that this emission is due to shock-heated accreting material, but do not allow us to analyze the stability of the material and its position in the stellar atmosphere. We investigate the dynamics and stability of shock-heated accreting material in classical T Tauri stars and the role of the stellar chromosphere in determining the position and thickness of the shocked region. We perform one-dimensional hydrodynamic simulations of the impact of an accretion flow on the chromosphere of a CTTS, including the effects of gravity, radiative losses from optically thin plasma, thermal conduction and a well tested detailed model of the stellar chromosphere. We present the results of a simulation based on the parameters of the CTTS MP Mus. We find that the accretion shock generates an hot slab of material above the chromosphere with a maximum thickness of 1.8x109cm, density ne∼1011-1012cm–3, temperature T∼3x106K, and uniform pressure equal to the ram pressure of the accretion flow (∼450dyn/cm2). The base of the shocked region penetrates the chromosphere and remains at a position at which the ram pressure is equal to the thermal pressure. The system evolves with quasi-periodic instabilities of the material in the slab leading to cyclic disappearance and re-formation of the slab. For an accretion rate of ∼10–10M/yr, the shocked region emits a time-averaged X-ray luminosity of LX≃7x1029erg/s, which is comparable with the X-ray luminosity observed in CTTSs of identical mass. Furthermore, the X-ray spectrum synthesized from the simulation reproduces in detail all the main features of the OVIII and OVII lines of the star MP Mus.

Abstract Copyright:

Journal keyword(s): X-rays: stars - stars: formation - accretion, accretion disks - hydrodynamics - shock waves - methods: numerical

Simbad objects: 5

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Number of rows : 5
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 V* BP Tau Or* 04 19 15.8339827632 +29 06 26.926959492   13.13 12.12 11.89   K5/7Ve 659 0
2 V* TW Hya TT* 11 01 51.9053285064 -34 42 17.033218380   11.94 10.50 10.626 9.18 K6Ve 1850 1
3 CPD-68 1894 TT* 13 22 07.5421944624 -69 38 12.219391716   11.38 10.393   9.117 K1Ve 153 0
4 V* RU Lup TT* 15 56 42.3108692112 -37 49 15.473946900 9.27 10.07 9.60     K7/M0e 454 0
5 HD 319139 SB* 18 14 10.4818675368 -32 47 34.516836060   11.47 10.68   9.11 K5+K7 356 0

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