Christopher M. Johns-Krull (Rice University)

IGRINS Science Workshop: August 26, 2010

Exploring the Planet Forming Environments of Young Suns

Star and Planet Formation

Central Engine & Fate of Disk

Incorporated into Planets

Accreted onto Star

Lost in an Outflow

Shu et al. (1994)

Edwards et al. (1994)

Disk locking

Stellar Magnetic Fields

kG1.0d

P

1.0R

R

yrM10

M

1M

M

0.50.35 3.43B

7/6

*

-3

*

1/2

1-

7-

5/6

*

7/47/6

*

kG1d

P

1R

R

yrM10

M

1M

M 1.10B

29/24

*

-3

*

23/40

1-

7-

2/3

*1/3-*

kG1d

P

1R

R

yrM10

M

1M

M

0.923 3.38B

7/6

*

-3

*

1/2

1-

7-

5/6

*

-7/4

x*

Theoretical Predictions

Konigl (1991):

Cameron & Campbell (1993):

Shu et al. (1994):

Measuring Fields from the Zeeman Effect

Zeeman Desaturation of Optical Lines

• Basri et al. (1992): 2 TTS

• Basri & Marcy (1994): Several dKe stars

• Guenther et al. (1999): 4 TTS

• Very sensitive to Teff

Model with B/Model Without B

Bf = 1.5 kGBf = 1.7 kG

Tap 35

EQ Vir

Bf = 0? kG

LkCa 16

Direct Zeeman BroadeningInitial optical 2 line analyses were faulty

M Dwarf Fields in the Optical

Johns-Krull & Valenti (1996, ApJ, 459, L95)

McD

on

ald

Ob

serv

ato

ry 2

dC

ou

de

Fe I

Ti I

TiOTiO

vsini = 4.5 km/s

Getting Rid of the TiOM

cDon

ald

Ob

serv

ato

ry 2

dC

ou

de

Johns-Krull & Valenti (1996, ApJ, 459, L95)

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

Saar & Linsky (1985)

Johns-Krull et al. (1999)

TW Hya: CTTSYang, Johns-Krull, & Valenti (2005)

Hubble 4: NTTSJohns-Krull, Valenti, & Saar (2004)

Predicted vs. Observed Mean Fields

Caveats:• Theory assumes dipole• We measure mean field• Uncertainty on x-axis difficult to quantify

Additionally: no correlation with rotation rate, Rossby number, etc.

Johns-Krull (2007)

YSOs in Other RegionsYang & Johns-Krull (2010)

Yang et al. (2008)

V1348 Ori B = 3.3 kG

V1123 Ori B = 2.8 kG

TWA 9A B = 3.2 kG

WL 17 B = 2.9 kG

Johns-Krull et al. (2009)

Building Planets: Mechanisms

Timescale?

Core Accretion

Gravitational Instabilities

The Brown Dwarf DesertGrether 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.

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

Observational Clues

X 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.

Marois et al. (2008)

HR 8799

HL Tau

Greaves et al. (2008)

Dodson-R

obinson et al. (2009)

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

Herbst et al. (2002)

Photometric VariabilityValenti et al. (1993)

• Coude spectrograph for stability• observe faint and bright RV standards for uncertainties • Th-Ar comps & cross correlation analysis

Approach: Harlan J. Smith 2.7m telescope

McDonald Young Planet Search

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

Collaborators:

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• observed photometrically and spectroscopically

Hatzes (1995)

V410 Tau

Line distortions also lead to apparent radial velocity variations

Spots and Reflex Motion

Can We Tell the Difference?

• bisector span should correlate with the radial velocity if a spot is present

• yes (maybe!)• spots induce spectral line asymmetries

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

• Some clearly spotted stars!

Huerta et al. (2008)

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)

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

Overall: 69 m/s

RV Precision

Ruling Out Interesting Candidates

V827 Tau DN Tau

Prato et al. (2008)

TW Hya: Planet or Spot?

• Setiawan et al. (2008): no line bisector radial velocity correlation?• Huelamo et al. (2008): find correlation between line bisector and radial velocity

Radial Velocity (m/s)-400 +400

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

Pevtsov et al. (2003)

Saar (1996)• Field strength set by pressure balance with quiet photosphere

• Excellent Correlation with X-ray emission

• f and Bf correlated with rotation

Transition DisksMarois et al. (2008)

Kalas et al. (2008)

HR 8799

NASA

Transition Disks

Najita et al. (2007)

Transition Disks

Najita et al. (2007)

Accretion onto the Star

A T Tauri starf ~ 0.01-1

sun8 yr M10~ M

Valenti et al. (1993)

Garcia-Lopez et al. (2006)

Gullbring et al. (1998)

T Tauri Stars: Magnetically Controlled Accretion

Shu et al. (1994)

• Rotation correlated with disk signatures• Balmer line profiles• Accretion shock models reproduce optical veiling

Edwards et al. (1994)

Disk lockingTheory gives field at some point in the disk

Shu et al. (1994)

X-ray Luminosity vs Magnetic Flux

F, G, and K DwarfsSaar (1996)

Solar Active RegionsFisher et al. (1998)

Solar X-rayBright PointsLongcope et al.(2001)

Quiet Sun at Solar MinimumPevtsov & Acton (2000)

T Tauri StarsJohns-Krull &Valenti (2000)

Pevtso

v e

t al. (2

003

)

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)