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ACCRETION ONTO YOUNG STARS WITH IXO PowerPoint Presentation
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ACCRETION ONTO YOUNG STARS WITH IXO

ACCRETION ONTO YOUNG STARS WITH IXO

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ACCRETION ONTO YOUNG STARS WITH IXO

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  1. ACCRETION ONTO YOUNG STARS WITH IXO Costanza Argiroffi1, 2 1 Dip. diFisica, Universita’ degliStudidi Palermo 2 INAF – OsservatorioAstronomicodi Palermo Costanza Argiroffi IXO science meeting, Rome, March 2011

  2. X-RAYS FROM ACCRETION WHY IT IS IMPORTANT Young low mass stars (CTTS) are bright X-ray sources. X-rays come from two components: Coronal plasma Plasma heated in the accretion shocks • X-rays from young stars: • heat and ionize circumstellar material. Influence the physics, the chemistry, and the lifetime of circumstellar disks. • X-rays from accretion: • probe the shock region; • probe the velocity, the density, the chemical composition of accreting material. Costanza Argiroffi IXO science meeting, Rome, March 2011

  3. X-RAYS FROM YOUNG STARS Costanza Argiroffi IXO science meeting, Rome, March 2011

  4. MAGNETOSPHERIC ACCRETION MODEL • Young stars are surrounded by circumstellar disks • Stellar magnetic field disrupts the inner disk and guides infalling material • Infall velocities: 200-500 km/s • Post-shock temperatures: 1-5 MK • Post-shock densities: N > 1011 cm-3 • High Lx for typical accretion rates Costanza Argiroffi IXO science meeting, Rome, March 2011

  5. X-RAYS FROM ACCRETION: CHANDRA AND XMM Density diagnostic • high density • shock-heated plasma • low density • coronal plasma Density measurements: high resolution X-ray spectra • 8 CTTS investigated by Chandra and XMM • 7 CTTS display high density plasma at 2-4 MK Cool high-density plasma in CTTS is material heated in the accretion shock Costanza Argiroffi IXO science meeting, Rome, March 2011

  6. X-RAYS FROM ACCRETION WITH IXO/XGS IXO/XGS spectral resolution (R=3000): • Doppler shift measurements Post-shock plasma: vpost~ vpre/4 ~ 100 km/s Costanza Argiroffi IXO science meeting, Rome, March 2011

  7. X-RAYS FROM ACCRETION WITH IXO/XGS IXO/XGS effective area: • Study X-rays from accretion for stars up to 500 pc • Accretion-driven X-rays on short time scales Costanza Argiroffi IXO science meeting, Rome, March 2011

  8. OPEN ISSUES • Anomalous abundances of the accreting material • Disagreement between observed and predicted LX from accretion shocks • Source optical depth vs surrounding material absorption Costanza Argiroffi IXO science meeting, Rome, March 2011