X-ray diagnostics of magnetospheric accretion in TTS Thierry Montmerle Laboratoire d'Astrophysique de Grenoble and Institut d’Astrophysique de Paris, France Thierry Montmerle Laboratoire d'Astrophysique de Grenoble and Institut d’Astrophysique de Paris, France CC2YSO (17-19/5/10 1

X-rays vs. Accretion shocks X-rays only probe of accretion shocks (free-fall velocities from circumstellar disk: ≈ km/s) Very hard to detect, because of many other sources of X-rays in the environment of young stars: –Magnetic activity ("coronal" X-rays): x1000 –Jet/outflow shocks (ejection and accretion ~ same velocities !): ~ 10 individual cases known In other words, accretion is the signal, flares are the noise ! CC2YSO (17-19/5/10 2

Basic magnetic structure of a "classical" (= accreting) T Tauri star Stassun 2001 CC2YSO (17-19/5/10 3

A complex X-ray emitting accretion-ejection configuration... X X X X Channeled Wind Hot Coronal Wind ? Hot-base, Cool Cooling Disk X HAeBe ? CC2YSO (17-19/5/10 4

Soft X-rays (E ≲ 0.8 keV) Post-shock zone T ~ 10 6 K Pre-shock zone T ~ 10 4 K n e ~ cm -3 chromosphere T ~ 10 4 K Shock surface v acc ~ km/s (Lamizin 1998, Calvet & Gullbring 1998) Example: M = 1 M  M acc = M  /yr R T = 5 R  Magnetospheric accretion and X-rays: some numbers T = 3 MK L X = 7 x erg/s ~ 10 5 x L X,  (© G. Sacco, 2009) CC2YSO (17-19/5/10 5

X-ray accretion diagnostics (in a nutshell) First detection: TW Hya (CTTS) –Chandra HETGS (Kastner et al. 2002) –Characteristics: soft spectra (T X ~ 2 MK), high plasma densities (log n e ~ 13: ~ x coronal) –Key diagnostic: He-like triplets (OVII, NeIX…) Line ratios: Direct, independent determinations of n e and T X Found in no more than ~ 10 individual stars so far –Requires HRS [high-resolution spectroscopy: E/  E = f(E) ~ ] (XMM RGS; Chandra HETGS): lots of photons ! –Some statistical evidence from low-resolution spectroscopy [E/  E ~ 20-50] (Chandra ACIS, XMM EPIC): "soft excess" (T X ≲ 1 keV, e.g., XEST survey; flux too weak for HRS => n e impossible to determine) –Deepest study (very long exposures): V4046 Sgr CC2YSO (17-19/5/10 6

The OVII and NeIX triplets: signature of accretion ? Brickhouse et al. 2010: Chandra f(forbidden)/i(intercombination) line ratio sensitive to plasma density f/i ~0.05 => n e ~ cm -3 (f+i)/r(resonance) line ratio sensitive to temperature T X (MK) CC2YSO (17-19/5/10 7 TW Hya

Key questions… Location of accretion shock wrt the stellar photosphere (HD + transfer problem) Interplay between coronal loops and accretion funnels (MHD problem) –Magnetic field topology Intrinsic variability (bursts…) => 2D MHD modeling (Palermo group: Orlando et al. 2008, Sacco et al. 2010; Brickhouse et al. 2010…) –Accretion stream falling along magnetic “tube”  photosphere –=> accretion rate, confinement efficiency, instabilities, etc. –(private show if interested…) CC2YSO (17-19/5/10 8

Case study: XMM “Large Program” on the “twin binary” V4046 Sgr (preliminary results) “VSag consortium”: TM, E. Alecian & J. Bouvier (LAOG), with C. Argiroffi, F. Damiani, & A. Maggio (Palermo), S. Alencar (Belo Horizonte), M. Audard (Geneva), J.-F. Donati (Toulouse), S. Gregory (Exeter), M. Güdel (Vienna), V. Holzwarth (Freiburg), D. Huenemoerder (MIT), J. Kastner, R. Montez & G. Sacco (Rochester), G. Wade (Kingston) CC2YSO (17-19/5/10 9

V4046 Sgr Identity card Two almost identical components, at d ~ 83 pc; with M ~ 0.9 M a, R ~ 1.2 R a ; L ~ 0.4 L a perhaps a 3rd companion (binary ?) at AU Orbital period ~ 2.42 d (close binary => synchronous rotation) i = 35°, sep. ~ 4.5 R a CTTS: circumbinary disk accretion flow seen in H  … Age ~ few Myr => main goal: look for orbital modulation of accretion parameters CC2YSO (17-19/5/10 10 Stempels & Gahm 2004

LAOG (26-27/6/08)) 11

LAOG (26-27/6/08)) 12

Coordinated space/ground observations XMM “Large Program” (3x100 ksec; 500 ksec total): –3 consecutive revolutions (2d = 173 ksec), each partially sampled –Looking for orbital/rotational modulation –3 instruments: EPIC, RGS, + OM (Optical Monitor) Coordinated ground-based observations: –Spectrophotometry (optical) –Photometry (optical, NIR) REM (La Silla) Pico dos Dias (Brazil) (Canary Islands) CC2YSO (17-19/5/10 13 ✪ ✪ ✪ ✪

CC2YSO (17-19/5/10 14 Pico dos Dias: —— —— — REM A. Maggio 2010 ESPaDOnS

LAOG (26-27/6/08)) 15 A. Maggio 2010 CC2YSO (17-19/5/10 15

LAOG (26-27/6/08)) 16 CC2YSO (17-19/5/10 16 EPIC (pn + 2xMOS)

LAOG (26-27/6/08)) 17 CC2YSO (17-19/5/10 17 EPIC (pn + 2xMOS)

LAOG (26-27/6/08)) 18 CC2YSO (17-19/5/10 18

LAOG (26-27/6/08)) 19 CC2YSO (17-19/5/10 19

CC2YSO (17-19/5/10 20

LAOG (26-27/6/08)) 21 CC2YSO (17-19/5/10 21

LAOG (26-27/6/08)) 22 CC2YSO (17-19/5/10 22 (to be continued…)

Epilogue: IXO (? ~ 2020 ?) ESA/NASA/JAXA CC2YSO (17-19/5/10 23 ~ 20m

High-resolution spectra of T Tauri stars with IXO XMS matrix: 2.5eV resol. (E/  E ~ 1000) IXO/XGS(+XMS) potential: good S/N spectra in < 100 ksec for TTS up to 500 pc (Taurus, Cha, Orion, etc)  n e in CTTS  accretion vs. corona time-resolved high-resolution spectroscopy (~ 10 ksec exp. for bright TTS)  exposure/30 compared to XMM  n e variations probing accretion structure  n e variations in stellar flares CC2YSO (17-19/5/10 24 (after B. Stelzer 2010)

Additional material: modeling accretion shocks LAOG (26-27/6/08)) 26

MP Mus: Spectral synthesis Observed spectrum (XMM- RGS) Spectrum synthesized from the simulations (taking into account instrumental response, distance and interstellar absorption and assuming accretion flow cross section) Temperature diagnostic density diagnostic (Sacco et al. 2008) CC2YSO (17-19/5/10 27

n e = cm -3 v = 450 km s -1 B = 1, 10, 50 G MP Mus 2D MHD simulations Orlando et al CC2YSO (17-19/5/10 28

B = 1 G CC2YSO (17-19/5/10 29

B = 10 G CC2YSO (17-19/5/10 30

B = 50 G CC2YSO (17-19/5/10 31