an observational study of accretion dynamics in …greg herczeg (kavli institute) christopher...
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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
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Binary Accretion DQ Tau: e=0.57; q=0.96 P=15.8d
TWA 3A: e=0.63; q=0.84 P=34.9d
Tofflemire 2018/01/12
Binary Accretion
Tofflemire 2018/01/12
Muñoz & Lai 2016
Time-Series Spectroscopy with SALT
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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)
Tofflemire 2018/01/12