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

Study of rotationally modulated X-ray emission from the accretion shock in Young Low Mass Stars using Chandra and XMM observations. Analysis of plasma densities, average temperatures, and energy balance to infer mass accretion rate and properties of the accretion stream.

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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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