scholarly journals X-rays from accretion shocks in classical T Tauri stars: 2D MHD modeling and the role of local absorption

2013 ◽  
Vol 9 (S302) ◽  
pp. 48-49
Author(s):  
C. Argiroffi ◽  
R. Bonito ◽  
S. Orlando ◽  
M. Miceli ◽  
F. Reale ◽  
...  

AbstractIn classical T Tauri stars (CTTS) strong shocks are formed where the accretion funnel impacts with the denser stellar chromosphere. Although current models of accretion provide a plausible global picture of this process, some fundamental aspects are still unclear: the observed X-ray luminosity in accretion shocks is order of magnitudes lower than predicted; the observed density and temperature structures of the hot post-shock region are puzzling and still unexplained by models.To address these issues we performed 2D MHD simulations describing an accretion stream impacting onto the chromosphere of a CTTS, exploring different configurations and strengths of the magnetic field. From the model results we then synthesized the X-ray emission emerging from the hot post-shock, taking into account the local absorption due to the pre-shock stream and surrounding atmosphere.We find that the different configurations and strengths of the magnetic field profoundly affect the hot post-shock properties. Moreover the emerging X-ray emission strongly depends also on the viewing angle under which accretion is observed. Some of the explored configuration are able to reproduce the observed features of X-ray spectra of CTTS.

2014 ◽  
Vol 64 ◽  
pp. 05004
Author(s):  
Bonito ◽  
Orlando ◽  
Argiroffi ◽  
Miceli ◽  
Reale ◽  
...  
Keyword(s):  
X Ray ◽  
T Tauri ◽  

2007 ◽  
Vol 3 (S243) ◽  
pp. 51-62 ◽  
Author(s):  
Moira Jardine ◽  
Scott G. Gregory ◽  
Jean-François Donati

AbstractOur present understanding of the coronal structure of T Tauri stars is fragmentary and observations in different wavelength regimes often appear to give contradictory results. X-ray data suggest the presence of magnetic loops on a variety of scales, from compact loops of size less than a stellar radius, up to very large loops of up to 10 stellar radii which may connect to the disk. While some stars show a clear rotational modulation in X-rays, implying distinct bright and dark regions, many do not. This picture is complicated by the accretion process itself, which also contributes to the X-ray emission. The location of the inner edge of the accretion disk and the nature of the magnetic field there are still hotly-contested issues. Accretion indicators often suggest the presence of discrete accretion funnels. This has implications for the structure of the corona, as does the presence of an outflowing wind. All of these factors are linked to the structure of the magnetic field, which we are now beginning to unravel through Zeeman-Doppler imaging. In this review I will describe the present state of our understanding of the magnetic structure of T Tauri coronae and the impact this has during such an early evolutionary stage.


2014 ◽  
Vol 795 (2) ◽  
pp. L34 ◽  
Author(s):  
R. Bonito ◽  
S. Orlando ◽  
C. Argiroffi ◽  
M. Miceli ◽  
G. Peres ◽  
...  
Keyword(s):  
X Ray ◽  
T Tauri ◽  

2018 ◽  
Vol 14 (S342) ◽  
pp. 137-140
Author(s):  
A. Ignesti ◽  
G. Brunetti ◽  
M. Gitti ◽  
S. Giacintucci

AbstractSeveral cool-core clusters are known to host a radio mini-halo, a diffuse, steep-spectrum radio source located in their cores, thus probing the presence of non-thermal components as magnetic field and relativistic particles on scales not directly influenced by the central AGN. The nature of the mechanism that produces a population of radio-emitting relativistic particles on the scale of hundreds of kiloparsecs is still unclear. At the same time, it is still debated if the central AGN may play a role in the formation of mini-halos by providing the seed of the relativistic particles. We aim to investigate these open issues by studying the connection between thermal and non-thermal components of the intra-cluster medium. We performed a point-to-point analysis of the radio and the X-ray surface brightness of a compilation of mini-halos. We find that mini-halos have super-linear scalings between radio and X-rays, with radio brightness declining more steeply than the X-ray brightness. This trend is opposite to that generally observed in giant radio halos, thus marking a possible difference in the physics of the two radio sources. Finally, using the scalings between radio and X-rays and assuming a hadronic origin of mini-halos we derive constraints on the magnetic field in the core of the hosting clusters.


1972 ◽  
Vol 14 ◽  
pp. 761-762
Author(s):  
G. Elwert ◽  
E. Haug

The polarization and angular distribution of solar hard X radiation above 10 keV was calculated under the assumption that the X rays originate as bremsstrahlung from energetic electrons moving in a preferred direction. The source electrons are supposed to have a power-law spectrum. These conditions are to be expected in the impulsive phase of an X-ray burst. The spiral orbits of the electrons around the magnetic field lines are taken into account.


2007 ◽  
Vol 466 (3) ◽  
pp. 1111-1121 ◽  
Author(s):  
H. M. Günther ◽  
J. H. M. M. Schmitt ◽  
J. Robrade ◽  
C. Liefke
Keyword(s):  
X Ray ◽  
T Tauri ◽  

2017 ◽  
Vol 24 (2) ◽  
pp. 449-455 ◽  
Author(s):  
Jun Miyawaki ◽  
Shigemasa Suga ◽  
Hidenori Fujiwara ◽  
Hideharu Niwa ◽  
Hisao Kiuchi ◽  
...  

A compact and portable magnet system for measuring magnetic dichroism in resonant inelastic soft X-ray scattering (SX-RIXS) has been developed at the beamline BL07LSU in SPring-8. A magnetic circuit composed of Nd–Fe–B permanent magnets, which realised ∼0.25 T at the center of an 11 mm gap, was rotatable around the axis perpendicular to the X-ray scattering plane. Using the system, a SX-RIXS spectrum was obtained under the application of the magnetic field at an angle parallel, nearly 45° or perpendicular to the incident X-rays. A dedicated sample stage was also designed to be as compact as possible, making it possible to perform SX-RIXS measurements at arbitrary incident angles by rotating the sample stage in the gap between the magnetic poles. This system enables facile studies of magnetic dichroism in SX-RIXS for various experimental geometries of the sample and the magnetic field. A brief demonstration of the application is presented.


2005 ◽  
Vol 432 (2) ◽  
pp. L35-L38 ◽  
Author(s):  
J. H. M. M. Schmitt ◽  
J. Robrade ◽  
J.-U. Ness ◽  
F. Favata ◽  
B. Stelzer

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