Muñoz & Lai 2016

Ben Tofflemire Advised by Robert Mathieu University of Wisconsin – Madison Starting Postdoc at UT-Austin this Fall SPF2 – March 12th, 2018 Collaborators: David Ardila (JPL) Greg Herczeg (Kavli Institute) Christopher Johns-Krull (Rice Univ.) Rachel Akeson (IPAC) David R. Ciardi (IPAC) Lisa Prato (Lowell Observatory)

AN OBSERVATIONAL STUDY OF ACCRETION DYNAMICS IN

PRE-MAIN SEQUENCE BINARIES

The Star-Disk Interaction

ASA/JPL-Caltech/R. Hurt (SSC)

Tofflemire 2018/01/12

Stellar Impact •  Gain ~10% of total mass

•  Disk-locking determines angular momentum evolution

Disk & Planet Impact •  Disk evolution timescale &

stability •  Consumption rate: accretion & outflow (winds, jets) •  Planet Formation & Migration

•  Disk Chemistry/Photoevaporation •  Hard radiation from accretion & magnetic activity (rotation)

"

The Star-Disk Interaction Stellar Impact •  Gain ~10% of total mass

•  Disk-locking determines angular momentum evolution

Disk & Planet Impact •  Disk evolution timescale &

stability •  Consumption rate: accretion & outflow (winds, jets) •  Planet Formation & Migration

•  Disk Chemistry/Photoevaporation •  Hard radiation from accretion & magnetic activity (rotation)

"

ASA/JPL-Caltech/R. Hurt (SSC)

Tofflemire 2018/01/12

The Binary-Disk Interaction

Tofflemire 2018/01/12

a > ~300 AU a < ~50 AU ~300 AU > a > ~50 AU

Eccentric Binary Accretion

Muñoz & Lai 2016

Simulation: •  AREPO

(Voronoi AMR) •  >2000 orbital

periods simulated •  Scale free •  e = 0.5; q=1.0 •  Includes gravity and

gas physics only

Results: •  Accretion streams at

every orbital period •  Periastron accretion

bursts Tofflemire 2018/01/12

Eccentric Binary Accretion

Tofflemire 2018/01/12

Muñoz & Lai 2016 Theory

LCO: Moderate-Cadence, Photometric Survey of Pre-MS Binaries

Sample: •  9 PMS binaries •  Periods: 2 – 90 days •  Eccentricities: 0.0 – 0.63 •  Spectral Types: G5 – M4

Observations: •  20 Visits per orbit

-  Visit = UBVRIY (Hα and Hβ) •  For ~10 orbital periods •  ~1000 hr over 3 semesters

DQ Tau TWA 3A Orbital Parameters: •  P = 15.8 days •  e = 0.57 •  a = 0.13 AU •  q = 0.94 (M1~M2~0.6M⨀)

(Czekala et al. 2016)

Orbital Parameters: •  P = 34.9 days •  e = 0.63 •  a ~ 0.16 AU •  q = 0.84 (M1~0.25M⨀)

(Kellogg et al. 2017)

DQ Tau: Observed Accretion Rate

Tofflemire 2018/01/12

Binary Accretion DQ Tau: e=0.57; q=0.96 P=15.8d

TWA 3A: e=0.63; q=0.84 P=34.9d

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Binary Accretion

Tofflemire 2018/01/12

Muñoz & Lai 2016

Time-Series Spectroscopy with SALT

Tofflemire 2018/01/12

15 SALT/HRS Spectra of TWA 3A •  R~30,000 (3800 - 8700Å) •  Trace coherent velocity structures in

stream material •  Determine which star is the

dominant accretor

Preferential Accretion

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Secondary as Dominant Accretor: •  Prediction of most hydrodynamic simulations •  Material at the circumbinary disk gap has specific

angular momentum closer to the secondary (Artymowicz & Lubow 1996, Gerosa et al 2015)

Primary as the Dominant Accretor: •  Prediction of MHD simulations •  Magnetic breaking lowers the specific angular

momentum of circumbinary material, closer to primary (Zhao & Li 2013)

Depends on Disk Asymmetry: •  Munoz & Lai 2016 predict the dominant accretor varies

based on the precession of a disk asymmetry

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After Periastron

(High Accretion)

Apastron (Little/No Accretion)

Before Periastron

(High Accretion) He I emission favors the

primary’s velocity, suggesting it is

the primary accretor

He I 5876 – Velocity Profile (in progress)

Tofflemire 2018/01/12

After Periastron

(High Accretion)

Apastron (Little/No Accretion)

Before Periastron

(High Accretion) He I emission favors the

primary’s velocity, suggesting it is

the primary accretor

He I 5876 – Velocity Profile (in progress)

~160 orbital cycles earlier

Summary Eccentric, short-period binaries exhibit periodic, pulsed accretion events near periastron passage •  Results in fairly good agreement with numerical

simulations (Tofflemire et al. 2017a; 2017b)

Accretion events favor the primary star in TWA 3A •  Trend holds in two widely separated epochs

(~160 orbits) •  Favoring magnetic/disk asymmetry models

(Tofflemire et al 2018, in prep)

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