Low-mass Stars with Extreme Mid-Infrared Excesses: Potential Signatures of Planetary Collisions
Dissertation Defense Talk
Christopher A. Theissen July 17, 2017 Driving Questions
• How often do low-mass stars in the field exhibit extreme MIR excesses?
• What are the physical trends we observe for low- mass stars exhibiting extreme MIR excesses?
• Do binary systems exhibit extreme MIR excesses more often than single stars? Star/planet formation in a nutshell
Spectral Energy Distribution
Peaks in the far-IR < 10,000 years
Peak flux moves to shorter wavelengths ~100,000 years
Star is now visible in the optical ~ 1 million years
Flux dominated by star, with a potential small >10 million years MIR excess André (1994) “Extreme” MIR Excesses
Weinberger+ (2011) “Extreme” MIR Excesses
1 billion year old binary system!
Weinberger+ (2011) What is the interpretation?
Credit: NASA/JPL Collisions between terrestrial planets What is the interpretation?
Credit: NASA/JPL
Credit: S. Raymond Seven systems currently known
HD 23514 HD 15407 ID8
360 AU 1200 AU
120 Myr 80 Myr 35 Myr
P1121 TYC-8241-2652-1 BD +20 307 TYC-8830-410-1
0.04 AU
80 Myr 10 Myr 1 Gyr ? Seven systems currently known
HD 23514 HD 15407 ID8
360 AU 1200 AU All solar-type (FGK) stars. 120 Myr 80 Myr 35 Myr Why are there no low-mass stars in the sample? P1121 TYC-8241-2652-1 BD +20 307 TYC-8830-410-1
0.04 AU
80 Myr 10 Myr 1 Gyr ? What exactly is a “low-mass” star? • Less than 60% the mass of the Sun
• Cool stars (Temperatures < 4600 K)
• Red dwarfs
• M dwarfs
Credit: NASA They have incredibly long (main sequence) lifetimes
Current Age of the Universe 10
1
0.1
Lifetime (billion yrs) 0.01
0.9M ⇠ 0.001 0 10 20 30 40 Mass (M ) They have incredibly long (main sequence) lifetimes
Low-mass stars live here Current Age of the Universe 10
1
0.1
Lifetime (billion yrs) 0.01
0.9M ⇠ 0.001 0 10 20 30 40 Mass (M ) Low-mass Stars are Everywhere
Todd J. Henry1 Ten Parsec Census 2010 Mark R. Boyd2 Serge Dieterich1 www.recons.org Charlie T. Finch3 Wei-Chun Jao1 Adric R. Riedel1 John P. Subasavage4 Jennifer G. Winters1
1GSU, 2GaTech, 3USNO, 4CTIO
~70% of all stars are low-mass stars
2010 20 4 6 20 44 246 4 9 13+8 WD A F G K M L T P 2000 18 4 6 20 44 198 0 1 2+8
Credit: RECONS Low-mass Stars are Everywhere (with Earth-sized Planets!)
Todd J. Henry1 Ten Parsec Census 2010 Mark R. Boyd2 Serge Dieterich1 www.recons.org Charlie T. Finch3 Wei-Chun Jao1 Adric R. Riedel1 John P. Subasavage4 Jennifer G. Winters1
1GSU, 2GaTech, 3USNO, 4CTIO
• ~70% of all stars are low-mass stars
2010 20 4 6 20 44 246 4 9 13+8 WD A F G K M L T P 2000 18 4 6 20 44 198 0 1 2+8
Credit: RECONS Planets orbit close-in
Credit: Muirhead+ (2012)/NASA Planets orbit close-in
Credit: Gillon+ (2016, 2017)/NASA The Kepler Dichotomy
Kepler has found lots of multi- and single-transiting planetary systems. • Both populations cannot be explained by the same planetary architecture (Ballard & Johnson 2016).
Multi-planet model excluding Multi-planet model Multi-planet model single-transiting systems with eccentricities
Ballard & Johnson (2016) The Kepler Dichotomy Mixture model for a dual population
Singles Multis
slower stellar faster stellar rotation rates rotation rates
farther from the closer to the Galactic plane Galactic plane
Ballard & Johnson (2016) The Kepler Dichotomy Mixture model for a dual population
Singles Multis Older? Younger? slower stellar faster stellar rotation rates rotation rates
farther from the closer to the Galactic plane Galactic plane
Ballard & Johnson (2016) Driving Questions
• How often do low-mass stars in the field exhibit extreme MIR excesses?
• What are the physical trends we observe for low- mass stars exhibiting extreme MIR excesses?
• Do binary systems exhibit extreme MIR excesses more often than single stars? Using M Dwarfs
The spectroscopic sample The photometric sample M0 M4 M6 M8 L0 105 WISE+SDSS+2MASS SDSS+2MASS 104 WISE+SDSS SDSS+USNO-B 103
102 # of Stars
101
Mass Increasing 100
100 Theissen+ (2016) West+ (2011)
1 10
2 10
3 10 Normazlied Distributions
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 r z Building the photometric sample Motion Verified Red Stars (MoVeRS)
3.5 5 5
3.0 SDSS + SDSS + SDSS 4 4 2.5 2MASS WISE
3 3 2.0 i z z − − − r 1.5 r r 2 2
1.0 1 1 0.5
0.0 0 0 0.00.51.01.52.0 0.51.01.52.02.53.0 1.01.52.02.53.03.54.04.55.0 i − z z − J z − W 1 Theissen+ (2016)
1 arcminute Building the photometric sample Motion Verified Red Stars (MoVeRS)
3.5 5 5
3.0 SDSS + SDSS + SDSS 4 4 2.5 2MASS WISE
3 3 2.0 i z z − − − r 1.5 r r 2 2
1.0 1 1 0.5
0.0 0 0 0.00.51.01.52.0 0.51.01.52.02.53.0 1.01.52.02.53.03.54.04.55.0 i − z z − J z − W 1 Theissen+ (2016)
1 arcminute …and the Late-Type Extension to MoVeRS (LaTE-MoVeRS)
600 9 3750 3500 500 10 3250 11 400 3000 J 12 2750 (K) 300 M 2500 e ↵ 13 T # of Stars 200 2250 14 2000 100 Field sequence 15 Young sequence 1750
0 0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0 50 100 150 200 250 300 350 400 450 J K Theissen+ (2017) d (pc) Theissen+ (2017)
~47,000 late-type objects with temperatures < 3800 K …and the Late-Type Extension to MoVeRS (LaTE-MoVeRS)
600 9 3750 3500 500 10 3250 11 400 3000 J 12 2750 (K) 300 M 2500 e ↵ 13 T # of Stars Complimentary to Gaia 200 2250 14 2000 100 Field sequence 15 Young sequence 1750
0 0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 0 50 100 150 200 250 300 350 400 450 J K Theissen+ (2017) d (pc) Theissen+ (2017)
~47,000 late-type objects with temperatures < 3800 K Selecting M Dwarfs with Excess MIR Flux
The spectroscopic sample The photometric sample 500 400 8 5 300 Full Sample 103 200 Excess significance 4
#stars 100 0 3 6 −10 01020304050 3 W σ′ 2 3 1
W 2 4 10
Stars with W − 1 1 excess W MIR flux 0 2
Clean Sample 101 Stars 2 # of Stars 0 3 234567891011 W MW 1 1
Theissen & West (2014) 1 100 W
0
Multiple criteria to select 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 r z Theissen & West (2017) stars with excess MIR flux. Spectral Energy Distributions for Extreme MIR Excesses The spectroscopic sample The photometric sample −10 9 152 SpT = dM1 SDSS +100 objID = 1237678920195637464 T +79 )] ∗ =3600 K −100 )] T = 3105 K 2MASS 2 21 +10 2 ⇤ − WISE TIR =175 K Tdust = 209 47K −10 10 ± cm −11 cm 1 1 − 11 (erg s (erg s λ −12 F F λ 12 Log [ Log [
13 −13 110 1 10 λ (µm) (µm) Theissen & West (2014) Theissen & West (2017) Aging M Dwarfs: Hydrogen Emission aka “Activity”
West+ (2008) Hydrogen Emission
Obtained DCT (and dM7 SDSS) optical spectra
dM6 of randomly selected
o ↵ set stars.
+ dM5
dM4 Scaled Flux dM3
dM2
dM0
6000 6500 7000 7500 8000 8500 Wavelength (A)˚
Adapted from Theissen & West (2017) Hydrogen Emission
Obtained DCT (and dM7 SDSS) optical spectra
dM6 of randomly selected
o ↵ set stars.
+ dM5
dM4 Stars later than M4 are inactive, indicating a Scaled Flux dM3 field population likely
dM2 Inactive Stars older than a few billion years dM0
6000 6500 7000 7500 8000 8500 Wavelength (A)˚
Adapted from Theissen & West (2017) Know Thy Star, Know Thy Disk
5000 6th Order Polynomial 105 Dartmouth ([Fe/H] = 0) 5 Gyr 4500 Dartmouth ([Fe/H] = 0) 10 Gyr 104 4000 Dartmouth ([Fe/H] = -2.4) 10 Gyr Mann et al. 2015 103 (K) 3500
e ↵ 2 T 3000 10 # of Stars 2500 101 2000 100 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Theissen & West (2017) r z 1.0 105 0.8 104