PowerPoint Presentation - Chandra X-Ray Observatory _CXC_

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					          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-
Ne IX: r, i,
f
                   ray emission?                                    O VII




                                                                    Ne IX




                                       HD 98800




               (Kastner et al. 2002)      Top: from Huenemoerder et al. (2007)
                                          Bottom: from Kastner et al. (2004)
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”?




                                             Wavelength [A]




                       Left: visible/IR SEDs (courtesy J. Rhee, UCLA)

                       Above: X-ray gratings spectra (Guenther et al. 2006)
V4046 Sgr and TW Hya: “separated at birth”?!
V4046 Sgr: a Keplerian, circumbinary disk
                  SMA imaging of CO emission




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                                          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
                                       Msun separated by
                                       ~9 Rsun (Stempels &
                                       Gahm 2004);
                                       system inclination
                                       estimated at i ~ 35o
                                       (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. 2009
                     • 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: Lx/Lbol increases during the first ~30-100
      Myr of evolution, for low-mass stars




                                                       Ages ~10 Myr

                                        Pre-MS stars
                                        w/ ages <~1
                                        Myr



      Kastner et al. (1997)


            Are we seeing the effects of pre-MS
                   X-rays on disk gas?
V4046 Sgr and TW Hya: evidence for
X-ray ionization of molecular disks…




Left: from Lepp & Dalgarno (1996)
“X-ray-induced chemistry of
molecular clouds”
                         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 ~1012 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?

				
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posted:5/22/2013
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