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astro1snuackrigrinsmaterialigrins_workshop20.ppt

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					         Exploring the Planet Forming
         Environments of Young Suns




Christopher M. Johns-Krull (Rice University)
                   IGRINS Science Workshop: August 26, 2010
Star and Planet Formation
     Central Engine & Fate of Disk

Lost in an                  Edwards et al. (1994)
Outflow

                       Shu et al. (1994)

                                     Disk Planets
                       Incorporated into locking


                           Accreted onto Star
Stellar Magnetic Fields
         Theoretical Predictions

Konigl (1991):
                                                         5/6                 1/2              -3
                  M*                                                R*            P* 
                  7/6             7/4                                                                     7/6
                                                                    M
 B*  3.43         
                           
                                                               10 M yr -1   1.0R
                                                                -7                        
                                                                                             1.0d  kG
           0.35   0.5   1M                                                              

Cameron & Campbell (1993):
                                       2/3                 23/40               -3
                 -1/3  M *                               R*                P* 
                                                  M                                        29/24

      B*  1.10      1M         
                                             -7
                                              10 M yr -1   1R
                                                                              
                                                                               1d                  kG
                                                                           


Shu et al. (1994):
                                                   5/6                 1/2             -3
                                M*                               R*          P* 
                           -7/4                                                                     7/6
                                                              M
     B*  3.38  x               
                                   1M         
                                                         -7
                                                          10 M yr -1   1R
                                                                                     kG
                                                                                     1d
                0.923                                                          
Measuring Fields from the Zeeman Effect
            Zeeman Desaturation of Optical Lines
                                            EQ Vir



                              Tap 35
                                                Bf = 1.7 kG
                           Bf = 1.5 kG

       Model with B/Model Without B

• Basri et al. (1992): 2 TTS                 LkCa 16
• Basri & Marcy (1994): Several dKe stars
• Guenther et al. (1999): 4 TTS
• Very sensitive to Teff                             Bf = 0? kG
Direct Zeeman Broadening
            Initial optical 2 line analyses were faulty
M Dwarf Fields in the Optical
   Johns-Krull & Valenti (1996, ApJ, 459, L95)

                       Fe I




                                                 McDonald Observatory 2dCoude
                                     TiO
   TiO
                   s          s
            Ti I              vsini = 4.5 km/s
Getting Rid of the TiO
   Johns-Krull & Valenti (1996, ApJ, 459, L95)




                                                 McDonald Observatory 2dCoude
            Going to the Infrared
• Kitt Peak 4m + FTS & NASA IRTF (3m) +
CSHELL spectrometer
• R ~ 35,000-44,000 spectra
• Excess Broadening Seen in the Ti I line

               Johns-Krull et al. (1999)

                                            Saar & Linsky (1985)
TW Hya: CTTS
               Yang, Johns-Krull, & Valenti (2005)
Hubble 4: NTTS
                 Johns-Krull, Valenti, & Saar (2004)
Predicted vs. Observed Mean Fields
   Johns-Krull (2007)   Caveats:
                        • Theory assumes
                        dipole
                        • We measure mean
                        field
                        • Uncertainty on x-
                        axis difficult to
                        quantify

                        Additionally: no
                        correlation with
                        rotation rate, Rossby
                        number, etc.
  YSOs in Other Regions
Yang & Johns-Krull (2010)




                                                     Johns-Krull et al. (2009)
                             WL 17 B = 2.9 kG



V1348 Ori B = 3.3 kG




                                                Yang et al. (2008)
                            TWA 9A B = 3.2 kG



V1123 Ori B = 2.8 kG
Building Planets: Mechanisms




                       Gravitational Instabilities

                                   Timescale?




           Core Accretion
The Brown Dwarf Desert
        Grether and Lineweaver (2006)
Observational Clues



                              Core Accretion: Dust
                             collides and sticks
                             together, building up
                             larger bodies. May take
                             about 10 Myr to build
                             Jupiter.
                             X GI: Gravitational
                             instability leads to rapid
                             planet formation.



                Santos et al. (2004)
              Fisher & Valenti (2005)
          Observational Clues




                                                                            Dodson-Robinson et al. (2009)
           Marois et al. (2008)




HR 8799




             HL Tau
                                                        X Core Accretion: Dust
                                  Greaves et al. (2008) collides and sticks
                                                        together, building up
                                                        larger bodies. May take
                                                        about 10 Myr to build
                                                        Jupiter.
                                                       X GI: Gravitational
                                                       instability leads to rapid
                                                       planet formation.
Origin of the Desert




          • Some feature (disk mass, disk
          lifetime, etc.) of the planet formation
          process prevents brown dwarfs
          forming
          • Brown dwarfs do form, but then
          migrate in (Armitage & Bonnell 2002)
Search for Planets Around Young Stars
        Young Star Properties
• ages 1-few Myr
• rotation periods 1-15 days
• visible photospheres
• classical & weak T Tauri
       Stars
                 Valenti et al. (1993)
                                               Photometric Variability




                                         Herbst et al. (2002)
      McDonald Young Planet Search
        Approach:                     Harlan J. Smith 2.7m telescope
 • Coude spectrograph for stability
 • observe faint and bright RV
 standards for uncertainties
 • Th-Ar comps & cross correlation
 analysis


     Collaborators:
Lisa Prato (Lowell Observatory)
Naved Mahmud (Rice University)
Chris Crockett (Lowell Observatory)
Pat Hartigan (Rice University)
Dan Jaffe (University of Texas)
Marcos Huerta (AAS)
Testing the Approach




               • RV standards show RMS
               ~120 m/s
               • proof of concept:
               exoplanet HD 68988b
               (Butler+ 06)
               • P=6.28d
               • K=191m/s
        Very Large Spots
• young, low-mass stars fully
convective
• rotating rapidly
• convection and rotation drive
strong dynamo & superspots
• observed photometrically and
spectroscopically




              V410 Tau
        Very Large Spots
• young, low-mass stars fully
convective
• rotating rapidly
• convection and rotation drive
strong dynamo & superspots        Hatzes (1995)
• observed photometrically and
spectroscopically




              V410 Tau
      Spots and Reflex Motion

 Line distortions also lead to
apparent radial velocity
variations
       Can We Tell the Difference?




• yes (maybe!)
• spots induce spectral line
asymmetries
• bisector span should
correlate with the radial
velocity if a spot is present
    Young RV Planets to Date
• Setiawan et al. (2007)
identified long period
(852d) planet around 100
Myr old star HD 70573
• In 2008 team claimed
detection of a 10MJ, 10
Myr old planet @ TW Hya
      Some Results


• No brown dwarf
companions yet


                     Huerta et al. (2008)




                          • Some clearly
                          spotted stars!
Brown Dwarf: LP 944-20

Martín et al. (2006)
      Infrared Spectroscopy

• CSHELL
spectrograph,
cassegrain mounted
on telescope
• flexure? No I2 cell
• need Earth’s telluric
lines for  calibration
(e.g., Blake et al.
2007, 2008)
       Infrared Spectroscopy
Model composite target spectrum with combination of
stellar template (sunspot spectrum) and observed
telluric spectrum (Prato et al. 2008)


                                    RV Precision
                                 • Nov 2008: 61 m/s
                                 • Feb 2009: 31 m/s
                                 • Nov 2009: 44 m/s
                                 • Feb 2010: 97 m/s

                                   Overall: 69 m/s
  Ruling Out Interesting Candidates
                 Prato et al. (2008)




V827 Tau                      DN Tau
        TW Hya: Planet or Spot?




                                -400   Radial Velocity (m/s)   +400


• Setiawan et al. (2008): no
line bisector radial velocity
correlation?
• Huelamo et al. (2008): find
correlation between line
bisector and radial velocity
    IR RV Variations Due to Spots




V827 Tau             Hubble 4
High Precision IR RV
      Bean et al. (2010)
Thank You
Disks Are Commonly Observed
From Disks to Planets
Measuring Stellar Magnetic Fields
Field Geometry: Polarization
The Photospheric Field of BP Tau
Emission Line Polarization
                   He I Polarization




                                       Like looking
                                       only at the
                                       sunspots
Can “Map” the Stellar Field
                      7 nights in November 2009
       K and M Star Results
• Field strength set by pressure balance with   Saar (1996)
quiet photosphere
• Excellent Correlation with X-ray emission
• f and Bf correlated with rotation

           Pevtsov et al. (2003)
Transition Disks
                      Marois et al. (2008)

                            HR 8799




Kalas et al. (2008)




                                             NASA
Transition Disks
         Najita et al. (2007)
Transition Disks
         Najita et al. (2007)
                    Accretion onto the Star
                                                
                                                M ~ 108 Msun yr -1 f ~ 0.01
A T Tauri star




Gullbring et al. (1998)
                                                  Valenti et al. (1993)

                          Garcia-Lopez et al.
                          (2006)
       T Tauri Stars: Magnetically Controlled Accretion

• Rotation correlated with disk signatures
                                                Edwards et al. (1994)
• Balmer line profiles
• Accretion shock models reproduce optical
veiling                                    Shu et al. (1994)

                                                             Disk locking
                                   Theory gives
                                   field at some
                                   point in the disk




                                                              Shu et al. (1994)
X-ray Luminosity vs Magnetic Flux

              F, G, and K Dwarfs
                  Saar (1996)
   Solar X-ray




                                                      Pevtsov et al. (2003)
   Bright Points
   Longcope et al.                   T Tauri Stars
   (2001)                            Johns-Krull &
                                     Valenti (2000)

                        Solar Active Regions
                        Fisher et al. (1998)

        Quiet Sun at Solar Minimum
         Pevtsov & Acton (2000)
Collaborators
     Jeff Valenti (STScI)
     Hao Yang (JILA)
     Wei Chen (Rice)
     Lisa Prato (Lowell Observatory)
     Naved Mahmud (Rice University)
     Chris Crockett (Lowell Observatory)
     Pat Hartigan (Rice University)
     Dan Jaffe (University of Texas)
     Marcos Huerta (AIP/AVS)

				
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