The X-Ray Life of Stars: Low-Mass and Pre-Main Sequence The X-Ray Life of Stars: Low-Mass and Pre-Main Sequence Manuel Güdel University of Vienna Manuel Güdel University of Vienna

On the main sequence: from the Sun back to ZAMS Younger still: Protoplanetary disks and accretion More massive: Herbig stars More embedded: Jets and outflows Eruptive variables Summary Outline

α Cen AB: solar-like behavior (Ayres+ 2009) cycles rotational modulation, slow changes in coronal T The Sun behaves like a normal X-ray G2V star and therefore as an example and anchor for stellar X-ray astronomy. The Sun Among Stars YEAR

Line Shifts: Contact Binary no eclipse near-polar on primary height R * (Huenemoerder+ 2006) (composite, 15 lines in MEG) Rapidly Rotating Giant (NeX 12.14A centroids, HEG) (Drake+ 2008) at rest redshift km/s line shift, broadening, Doppler im.,  near-polar region, ≤ 1R * (Drake+ 2008) FK ComVV Cep

(Flaring) Coronal Structure from Fluorescence Monte-Carlo modeling of fluorescent efficiency for different source heights (depending on flux > 7.11 keV): h < 0.3R * (Testa+ 2008; see also Osten et al. 2007: alternatively electron impact but inefficient)

Beyond the Limit of Stars: Brown Dwarfs (Berger+ 2010) (Preibisch+ 2005) * Young BDs (M6-M9): like stars (M6-M9): coronal activity depends on T eff, not mass! * Old BDs: X-ray faint – but not radio faint! Magnetic activity persists, but coronal heating declines. stars BDs L X /L bol log L X log L(H α ) log L R

Toward Forming Stars: Accretion and the „High-Energy“ Environment Shocks in accretion streams: T = 3  m H v 2 / 16k v  v ff = (2GM/R) 1/2  T = a few MK dM/dt = 4  R 2 fv ff n e m p  n e  cm -3 v ff f Dense, cool plasma in accretion shocks? (Kastner+ 2002, Stelzer & Schmitt 2004, Schmitt+ 2005, Günther+ 2006, Argiroffi+ 2007, Robrade & Schmitt 2006/07, Huenemoerder+ 2007, etc) n e = cm -3 (Günther+ 2006) r i f (Günther+ 2008)

OVIII 3-4 MKOVII 2 MK hot MK 1-2 MK non-accreting accreting X-Ray Soft Excess (Güdel 2006; Telleschi+ 2007; G&T 2007 ) MS stars CTTS WTTS cool Related to accretion AND coronal activity L(OVII) L(OVIII)

But Shocks are Complex... M X << M opt : need right conditions: too fast: chromospheric absorption too slow: T too low, no X-rays; mixture of structured flows (Sacco+2010) (Curran+ 2011) 0.3 dex 2.5 dex M X nearly constant! Not correl. with M opt. (Curran+ 2011): optical-depth effects increasing with accretion rate?...

Post-shock cools with distance. O VII should show higher densities higher absorption than Ne IX or Mg XII (Günther+ 2007) MgXI NeIX OVII Post-shock Observations: (TW Hya, Brickhouse+ 2010) OVII lower density OVII lower absorption: OVII N H = 4.1x10 20 cm -2 NeIX N H = 1.8x10 21 cm -2 shock (Brickhouse+ 2010) Problems with Cooling....

Shock-heated gas channeled back to the corona? „Accretion-fed corona“ (Brickhouse+ 2010) (2D simulations by Orlando+ 2010; B y =1 G, plasma-β >> 1) Or fibril-structured accretion streams, dense core developing shock deeper in chromosphere: NeIX from deep, dense layers, OVII only from outer, low-dens layer (Sacco+ 2010) shock accretion flow denser chromos- phere more N H OVII, NeIX NeIX

 Fe K  6.4 keV Fluorescence of cool disk material Disk Ionization by Stellar X-Rays: Fluorescence Fe XXV 6.7 keV (30 – 100 MK) (COUP, Tsujimoto+ 2005) (flaring protostar in COUP)

6.4 keV SXR flare 6.4 keV line during impulsive phase like HXR or radio: EW = 1.4 keV!! theoretical disks: <150 eV (George & Fabian 1991, Drake+ 2008) K shell electron ejection by nonthermal electrons? (Osten et al. 2007, Czesla & Schmitt 2007) rather inefficient (Czesla & Schmitt 2007) Orion YSO (COUP): (Drake+ 2008) source height EW calc 6.4 keV Irradiating hard source hidden: suppressed continuum:

CTTS AB Aur (HAe) Soft spectrum low density high T eff (10 kK) h (≈ 1600 Å) photoexcitation  X-ray source at R > 1.7R * (Telleschi et al. 2007) Herbig Ae/Be Stars

Magnetically Confined Winds in AB Aur? Accretion in HD A? NeIX: cm -3 (Testa+ 2008) Jets in HD ? (Günther+ 2009) And low-mass companions in many others? (Stelzer+ 2009)

L1551 IRS 5: (observations 2001, 2005, 2009) Star absorbed, but inner jet X-ray strong Cooling jet, dominated by expansion standing structure at 0.5-1” (Schneider+ 2011) Jets, Accretion Flows cooling

time DG Tau hard/hot Hard emission: coronal excessively absorbed by dust-depleted accretion flows. Jets, Accretion Flows soft/cool: constant low N H high N H >> N H (A V ) hard/hot: variable DG Tau: observations 2004, 2005/06, 2010 (Chandra LP; Güdel+ 2011) TAX spectrum during 1 week

ACIS-S image similar spectrum: soft “stellar” component and jet

Offset in 2010 identical to 2005/06 (Schneider+): standing structure; collimation region? 1pixel = ” Deconvolution of SER-treated ACIS data (Güdel+ 2011) 0.17” (40 AU along jet) 2-8 keV keV n = 10 5 cm -3 (Günther+ 2009)

Eruptive Variables FU Ori stars (FUors): disk dominates optical spectrum; large amplitude; yrs-decades EX Lup stars (EXors): star dominates optical spectrum; less energetic, shorter FUOrs not in immediate outburst: (Skinner+ 2009, 2011) very hard spectra excess absorption: due to accretion streams, winds, puffed-up inner disk? possibly X-ray overluminous for known/estimated masses (Skinner+ 2011) companion FU Ori

V1118 Ori: moderate X-ray increase; disk inner radius 0.4 to 0.2 AU due to increased accretion post-outburst: X-rays low disruption of magnetosphere by narrower disk? (Audard+ 2010) V1647 Ori: strong X-ray increase; correlated with accretion rate? induced magnetic reconnnection between star and disk? (Kastner+ 2006) Z CMa: no X-ray change (Stelzer+ 2009) EX Lup: correlated, accretion-funnel absorbed hard spectrum + accretion- related soft spectrum (Grosso+ 2010) X-rays

Summary Unexpected diversity of emission mechanisms and heating processes revealed in cool/pre-main sequence stars: Coronal radiation, T = MK accretion shocks ear photosphere in T Tauri stars internal or bow shocks in jets of T Tauris and Herbigs standing shocks (?) in jet collimation regions magnetically confined winds in Herbig stars protoplanetary disk ionisation and fluorescence disk-magnetosphere interactions in eruptive variables Rich field that has helped diagnose basic physical processes especially around young, pre-main sequence stars.

similar: Hamaguchi et al. (1.5 keV) Irradiating hard source hidden (behind star, disk, etc): suppressed continuum, strong fluorescent line NGC 2071 IRS1 (Skinner et al. 2007, 2010) Extreme Fluorescence? NGC 2071 IRS 1: - EW(6.4 keV) = 2.4 keV (Skinner+ 2007,10 )- constant over years - not accompanied by flares - no Fe XXV contribution! XMM : Chandra: