Double (X-ray) Vision: The Close Binary, Accreting T Tauri System V4046 Sgr Joel Kastner Center for Imaging Science, Rochester Institute of Technology Collaborators: Germano Sacco (RIT), David Huenemoerder (MIT), Thierry Montmerle (Grenoble), and the V4046 Sgr XMM Large Project team; David Rodriguez (UCLA), Thierry Forveille (Grenoble), Pierre Hily-Blant (Grenoble), David Wilner (SAO/CfA), Charlie Qi (SAO/CfA)

Chandra & XMM imaging has made clear: X-ray emission is a signature property of low-mass, pre-MS stars Chandra X-ray image of the Orion Nebula Cluster (10-day COUP observation; Feigelson et al. 2005)

Nearby (D < 100 pc) pre-MS stars of age ~10-30 Myr are particularly conspicuous and easy to study in X-rays* Kastner et al. (1997)Zuckerman & Song (2004) *Object of our NASA ADA program: use HEASARC X-ray archives to uncover additional examples of such stars (see Kastner, Zuckerman, & Bessell 2008, A&A 491, 829)

But…what is the nature of young-star X- ray emission? (Kastner et al. 2002) Top: from Huenemoerder et al. (2007) Bottom: from Kastner et al. (2004) HD O VII Ne IX Ne IX: r, i, f See poster (and paper-in-press) by G. Sacco on modeling T Tauri accretion shocks

TW Hya: after ~10 Myr, still accreting material from a dusty, molecular disk Top left: HST/NICMOS coronagraphic imaging of the TW Hya disk (Weinberger et al. 2002) Top right: JCMT radio molecular line spectra of TW Hya (Kastner et al. 1997) Left: Submillimeter Array velocity maps of CO emission from TW Hya (Qi et al. 2004)

TW Hya: unusual, but not unique…

V4046 Sgr and TW Hya: “separated at birth”*? Both T~4500 K, “isolated”, nearby, “old” T Tauri stars –TW Hya: namesake of the TW Hya Association Age ~8 Myr, (Hipparcos) distance 56 pc –V4046 Sgr: probable member of the beta Pic Moving Group Age ~12 Myr, distance 72 pc (Torres et al. 2006) Both display IR spectral energy distributions characteristic of dusty circumstellar disks w/ inner “holes” –Strong mid-to-far-IR emission from cool dust (T < 300 K) –Little or no near-IR emission from hot (T > 500 K) dust Both show evidence for ongoing accretion in visible, UV, and X-ray regimes –Star formation proceeds even as Jovian planets are forming (or have formed)? *with apologies to Spy Magazine…

V4046 Sgr and TW Hya: “separated at birth”? Left: visible/IR SEDs (courtesy J. Rhee, UCLA) Above: X-ray gratings spectra (Guenther et al. 2006) Wavelength [A]

V4046 Sgr and TW Hya: “separated at birth”?!

V4046 Sgr: a Keplerian, circumbinary disk SMA imaging of CO emission Left: movie of velocity-resolved SMA CO images (courtesy D. Rodriguez, UCLA) Above: animation of a Keplerian molecular disk (by RIT Digital Cinema student J. Traver)

V4046 Sgr: a Keplerian, circumbinary disk SMA imaging of CO emission Blue: P-V diagram constructed from SMA data Red: best-fit Keplerian disk model (Rodriguez, Kastner, Wilner & Qi 2010, ApJ, submitted)

Regarding V4046 Sgr: there is one little detail I haven’t reminded you about yet… V4046 Sgr is a CLOSE BINARY star system! Nearly equal-mass components of ~0.9 M sun separated by ~9 R sun (Stempels & Gahm 2004); system inclination estimated at i ~ 35 o (Quast et al. 2000)

The rotating, inner, circumbinary disk of V4046 Sgr Left: Phase-resolved Balmer emission line monitoring of V4046 Sgr Above: Schematic diagram illustrating model to interpret Balmer emission line profile variability (from Stempels & Gahm 2004)

V4046 Sgr: XMM Large Project T. Montmerle (PI) & a cast of dozens*… 300 ks total exposure w/ XMM/RGS –Obtained in three 100 ks pieces in Sept Coverage of two consecutive orbits Well-spaced in orbital phase Goals: –Phase-resolved X-ray spectroscopy of an accreting T Tauri system Take advantage of well-established star(s)-disk geometry of V4046 Sgr –Phase-dependent changes in X-ray accretion diagnostics? –Near-simultaneous optical spectroscopy, photometry, spectropolarimetry Accurate phase determination Track EW & RV variations in optical absorption & emission lines Magnetic field mapping (ESPADONS) Preliminary results: some highlights… –X-ray vs. optical light curve –Emission measure distribution –f/i ratios of He-like ions * T. Montmerle (PI, LAOG), J. Bouvier, E. Alecian (LAOG), D. Huenemoerder (MIT), J. Kastner, G. Sacco (RIT), C. Argiroffi(UNIPA), A. Maggio, F. Damiani (OAPA), M. Gudel (ETH, Zurich), M. Audard (Obs. Geneve) S. Gregory (Exeter), J. F. Donati (Toulouse), G. Wade (Kingston, Canada), G. Hussain (ESO), V. Holzwarth (Freiburg), S. Alencar (UFMG)

V4046 Sgr XMM Large Project preliminary results: X-ray vs. optical light curves

V4046 Sgr XMM Large Project preliminary results: soft vs. hard X-ray light curves

V4046 Sgr XMM Large Project preliminary results: emission measure distribution (V4046 Sgr vs. TW Hya)

V4046 Sgr XMM Large Project preliminary results: f/i ratios

V4046 Sgr XMM Large Project preliminary results: variation of f/i ratios

TW Hya, V4046 Sgr…so what’s next? Left: VLT/VISIR line profile of [Ne II] emission from V4046 Sgr (Sacco et al, in prep) Right: APEX detection of CO orbiting MP Mus (Kastner et al., in prep)

Recall: L x /L bol increases during the first ~ Myr of evolution, for low-mass stars Pre-MS stars w/ ages <~1 Myr Ages ~10 Myr Are we seeing the effects of pre-MS X-rays on disk gas? Kastner et al. (1997)

Left: from Lepp & Dalgarno (1996) “X-ray-induced chemistry of molecular clouds” V4046 Sgr and TW Hya: evidence for X-ray ionization of molecular disks…

Summary V4046 Sgr: “twin twin” to TW Hya –Two of the half-dozen known examples of accreting T Tauri star- disk systems within ~100 pc Both show strong evidence for X-ray irradiation (possibly X-ray-induced chemical evolution) of disk material XMM/RGS Large Project: preliminary results –EMD dominated by low-temperature plasma Strikingly similar to TW Hya –Plasma densities ~10 12 cm -3 ; anticorrelated w/ termperature Strikingly similar to TW Hya –Light curve shows broad modulation punctuated by flaring Variation of plasma density -- anticorrelated w/ X-ray modulation?

V4046 Sgr and TW Hya: “separated at birth”! (and aging gracefully together) From Kastner et al. (2008) Pre-MS stars w/ ages <~1 Myr Ages ~10 Myr Pre-MS stars w/ ages <~1 Myr Ages ~10 Myr

V4046 Sgr: evidence that giant planets can form in circumbinary disks orbiting (short- period) binary stars At least 20 Earth masses of gas remain in orbit between 20 AU and 250 AU from central 9 R sun separation binary