Prospective studies of star forming regions and cool stars with ? (IXO)

1. Prospective studies of star forming regions and cool stars with ? (IXO) Marc Audard (University of Geneva) IXO Conference, Roma, 14-16 March 2011

2. Introduction Why should we care about stellar science with IXO? Stars are nearby cosmic plasmas ideal to study MHD physics, the importance of magnetic fields, winds, jets, and X-ray photons on the surrounding environment (chemical enrichment, energy input; habitability of planets; irradiation of accretion disks)

3. XMM-Newton/Chandra The high-resolution grating spectra on-board XMM-Newton and Chandra have allowed excellent, new science to be done on stars: • Abundance studies (FIP and inverse FIP effect) • Average density & opacity measurements • Eclipse & Doppler mapping of corona (limited by spectral resolution & resolution) • Density measurements in a handful of young stars (excitement! Accretion may produce sufficient X-rays) • Detection of Fe Ka at 6.4 keV: information on source size, height, mechanism (but very limited!) • Density variations during flares (rare! Low S/N) • Etc…

4. Science with IXO The large effective area of IXO will allow us to study, e.g., • Dynamical MHD processes at the <kilosecond time scale • Routine imaging, high spectral resolution spectra of stars/star forming regions deeper (≤kiloparsec) in our Galaxy

5. A dynamical picture Audard et al. (2003) • Chromospheric evaporation can lead to mass motions into the corona with speeds of a few 100 km/s • Non-equilibrium conditions in the fast rise phase Rise time < 100s Flares of a few ks

7. Proxima Centauri F ~ ne2V  V ~ F/ne2 M ~ F/ne Güdel et al. (2002)

8. Same application for accretion disks Testa et al. (2008). See also Osten et al. (2007), Giardino et al. (2007), Drake et al. (2008), Stelzer et al. (2010)

9. Detailed flare studies Model: 1/10 of AB Dor flare (2-T; 20+80 MK; Maggio et al. 2000), i.e., about 6x quiescence Bai et al. (1979) model for Fe Ka XMS: 1800-1950 c/s Fe Ka

10. Caveat: moving flare plasma dominates the emission (but not so unreasonable for large flares) Caveat2: line of sight effects! 100 km/sshift Even better at 7keV XGS very good at long wavelengths, but probes lower-T plasma HXI may detect thermal tail and possibly non-thermal tail during flares, but cannot observe XMS and HXI simultaneously (but with WFI)

11. ne ≈ 1011-12 cm-3 ne ≈ 109-10 cm-3 Ne IX O VII r i f Fe lines r i f AB Dor in quiescence: 300-325 c/s (XMS) 35 c/s (XGS-gl) ne ≈ 108-9 cm-3 C VI XGS clear advantage for blends, line shifts and broadening and picking up faint emission lines (e.g., N VI) However, XGS count rate lower, and less sensitive below 12A (but XMS kicks in) Important for specific goals (line shifts, Doppler mapping, densities in crowded ranges, etc) Simultaneous(?) with XMS N VI Ar r i f

12. High densities in accreting stars • High i/f ratio in He-like triplets of TW Hya indicate ne≈1013 cm-3 (Kastner et al. 2002; Stelzer & Schmitt 2004). Also Fe XVII (Ness & Schmitt 2005) • Plasma T≈3 MK consistent with adiabatic shocks from gas in free fall (v≈150-300 km s-1) • High densities in accreting young stars (Schmitt et al. 2005; Robrade & Schmitt 2006; Günther et al. 2006; Argiroffi et al. 2007), but not all (Telleschi et al. 2007; Güdel et al. 2007) or variable densities (Argiroffi et al. 2011; etc) • Very limited sample, with poor signal-to-noise ratio in grating spectra Günther et al. (2007) Seealso talk by Argiroffi

13. From present challengesto future observations • Many grating spectra of magnetically active stars (esp. young pre-main sequence stars) suffer from low to average signal-to-noise ratios • It will be possible to obtain densities in many sources within 500 pc relatively quickly (<50 ks, e.g., Taurus, Ophiuchus, Chamaeleon, Orion, etc) • Access to low-T plasma from C VI and N VII as well (but NH!) XMM-Newton RGS 131ks IXO, XMS 10ks XGS: little continuum, but lines are boosted Schmitt et al. (2005)

14. Orion distance (500pc) Survey with IXO XMS (50 ks) thousands of stars

15. Si XIII Mg XI r i f r i f Ne IX O VII r i f r i f

16. Fx ≈ 10-15-10-14 erg s-1 cm-2 Audard et al. (2010) Hartmann (1997) During outbursts in young stars, due to the increase in accretion rate in the outburst, the accretion disk closes in and may have disrupted the magnetic loops, modifying the magnetospheric configuration (Kastner et al. 2004; 2006; Grosso et al. 2005; Audard et al. 2005; 2010)

17. Model: 8 MK, NH=4x1021 cm-2, Z=0.17, LX=3.5 1030 erg s-1 IXO XMS: 0.3 c/s Chandra & XMM-Newton: < 0.01 c/s In addition to higher S/N spectra, the IXO XMS data could, in similar exposures, help us obtain densities during the outburst

18. Conclusions • Dynamical processes will (finally) be studied with a good to high S/N • Stochastic processes, however, require some integration time (20-50 ks) to capture flares with sufficient energy and signal • IXO will also probe deeper into the X-ray sky: routine plasma T and density measurements in reasonable amount of exposure time < 1 kpc • XMS polyvalent (spatial resolution, high count rates, good spectral resolution  Integral Field Spectroscopy!) • XGS better aimed for brighter sources and for specific goals (line mapping, crowded line regions, etc). But it is(?) always present!  • XGS helpful for blends and to pick up faint emission lines • WFI useful for star forming region surveys (and for HXI) • High count rates in nearby stars: XMS diffuser should be OK, except in crowded regions  contamination by other sources likely. Possibility to consider snapshot observations in a standard fashion? • Optical contamination: should be OK for most cool-star targets (based on ASTRO-H filter documentation).