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Rotationally modulated X-ray emission from the accretion shock in CTTS

Rotationally modulated X-ray emission from the accretion shock in CTTS. V2129 Oph Project C. Argiroffi, E. Flaccomio, J. Bouvier, J.-F. Donati, K. V. Getman, S. G. Gregory, G. A. J. Hussain, M. M. Jardine, M. B. Skelly and F. M. Walter. V4046 Sgr Project

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Rotationally modulated X-ray emission from the accretion shock in CTTS

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  1. Rotationally modulated X-ray emission from the accretion shock in CTTS V2129 Oph Project C. Argiroffi, E. Flaccomio, J. Bouvier, J.-F. Donati, K. V. Getman, S. G. Gregory, G. A. J. Hussain, M. M. Jardine, M. B. Skelly and F. M. Walter V4046 Sgr Project C. Argiroffi, A. Maggio, T. Montmerle, D. P. Huenemoerder, E. Alecian, M. Audard, J. Bouvier, F. Damiani, J.-F. Donati, S. G. Gregory, M. Güdel, G. A. J. Hussain, J. H. Kastner and G. G. Sacco The X-ray Universe - Berlin, 27 June 2011 Costanza Argiroffi

  2. ACCRETION IN YOUNG LOW MASS STARS MAGNETOSPHERIC ACCRETION MODEL (Konigl 1991) X-RAYS • X-rays from accretion in CTTS: • predicted by Ulrich (1976) • observational evidences by Kastner et al. (2002) The X-ray Universe - Berlin, 27 June 2011 Costanza Argiroffi

  3. WHY STUDY X-RAYS FROM ACCRETION • to constrain the total amount of X-rays emitted from CTTS (to constrain the evolution of circumstellar disks) • to set the energy balance of the accretion-shock region (to infer the mass accretin rate) • to probe the properties (i.e. density, velocity) of the accretion stream (to understand how accretion occurs) • to probe the chemical composition of the inner disk (to check the chemical evolution of circumstellar disks) INAF - OAPA, 27 April 2011 Costanza Argiroffi

  4. X-RAYS FROM ACCRETION: OPEN ISSUES • Observed X-rays significantly lower than predicted • Observability of the X-rays from accretion • Density vs temperature pattern: observations vs models INAF - OAPA, 27 April 2011 Costanza Argiroffi

  5. AIMS: SEARCH FOR ROTATIONAL MODULATION IN X-RAYS Expected periodic variations in: • plasma densities • plasma average temperatures • EM of plasma at temperatures of 1-5 MK • Observing programs: • Long X-ray monitoring of a CTTS • with simultaneous optical observations • Projects: • V2129 Ophiuchi • V4046 Sagittari The X-ray Universe - Berlin, 27 June 2011 Costanza Argiroffi

  6. TARGETS: V2129 OPHIUCHI & V4046 SGR 200 ks with Chandra/HETGS 360 ks with XMM The X-ray Universe - Berlin, 27 June 2011 Costanza Argiroffi

  7. X-RAY MONITORING OF V2129 OPH seg. 1 seg. 2 (Donati et al. 2011, Argiroffi et al. 2011) We have analyzed X-ray spectra integrated over: ~ 100 ks = 1 segment = 0.18 Prot The X-ray Universe - Berlin, 27 June 2011 Costanza Argiroffi

  8. VARIATIONS IN THE COOL EMD COMPONENT Cool lines (long wavelengths) are stronger in seg.1 than in seg. 2 EMD1 > EMD2 at 3-4 MK The X-ray Universe - Berlin, 27 June 2011 Costanza Argiroffi

  9. VARIATIONS IN PLASMA DENSITY Densities are higher in seg.1 than in seg. 2 The X-ray Universe - Berlin, 27 June 2011 Costanza Argiroffi

  10. INTERPRETATION OF THE OBSERVED VARIABILITY • Results summary: • EM at ~4 MK is higher in seg.1 than seg.2 • Ne at 4 MK is higher in seg. 1 than in seg. 2 (Argiroffi et al. 2011) The X-ray Universe - Berlin, 27 June 2011 Costanza Argiroffi

  11. V4046 SAGITTARI (Stempels & Gahm 2004) The X-ray Universe - Berlin, 27 June 2011 Costanza Argiroffi

  12. X-RAY MONITORING OF V4046 SGR • Each segment is 120 ks • The X-ray observation covered 2.2 system rotations • We have analyzed X-ray spectra integrated over: ~25 ks = 0.12 Prot The X-ray Universe - Berlin, 27 June 2011 Costanza Argiroffi

  13. TIME RESOLVED X-RAY SPECTROSCOPY Lines detected at 1 sigma in all the time intervals The X-ray Universe - Berlin, 27 June 2011 Costanza Argiroffi

  14. VARIABILITY: COOL LINES (Argiroffi et al. 2011, ApJ submitted) Best fit period = 1.22 +/- 0.01 days (rot. period = 2.42 days) The X-ray Universe - Berlin, 27 June 2011 Costanza Argiroffi

  15. VARIABILITY: HOT vs COOL LINES Cool lines: Hot lines: The X-ray Universe - Berlin, 27 June 2011 Costanza Argiroffi

  16. V4046 SGR X-RAY MONITORING: RESULTS • High density • Cool plasma is compatible with being material heated in the accretion shock • Cool plasma is not symmetrically distributed with respect to the stellar poles • Rot. modulation • Obs. period = half the system period • X-ray vs optical results • Naturally explained if high-density cool plasma is located on both the stellar components • X-rays are likely produced only by a fraction of the accretion shock region The X-ray Universe - Berlin, 27 June 2011 Costanza Argiroffi

  17. CONCLUSIONS • CTTS display variability in their soft X-rays • This variability can be explained in terms of X-rays emitted in the accretion shock and seen with different viewing angles during stellar rotation. • Soft X-rays, like all the other accretion indicators, display rotational modulation The X-ray Universe - Berlin, 27 June 2011 Costanza Argiroffi

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