Meredith Rawls' PhD Defense
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Red Giants in Eclipsing Binaries as a Benchmark for Asteroseismology
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Meredith Rawls' PhD Defense
- 1. Red Giants in Eclipsing Binaries as a Benchmark for Asteroseismology Meredith L. Rawls Department of Astronomy New Mexico State University April 8, 2016 • PhD Thesis Defense @merrdiff Image: G Perez, IAC, SMM
- 2. Meredith L. Rawls • @merrdiff ✦ Eclipsing binaries with light curves and radial velocities let us directly measure M, R ✦ Asteroseismology is a powerful tool to characterize lots of stars quickly, using light curves alone ✦ We can study oscillating stars in eclipsing binaries from two independent perspectives ✦ A set of well-characterized binaries lets us explore why some don’t oscillate when we think they should How to measure stellar properties?
- 3. An asteroseismic revolution Meredith L. Rawls • @merrdiff Figure: Huber et al. 2014
- 4. An asteroseismic revolution Meredith L. Rawls • @merrdiff Figure: Huber et al. 2014
- 5. Meredith L. Rawls • @merrdiff ✦ Larger stars oscillate more slowly ✦ Evolved giants: hours–days ✦ Sun-like stars: minutes Stochastic “ringing” oscillations in stars’ convective zones 100 μHz 1 mHz 500 Hz Figure concept: P. Gaulme
- 6. Solar-like oscillations tell us about a star’s mean gravity and density Meredith L. Rawls • @merrdiff Δν νmax Power Frequency ν ✦ Acoustic pressure modes ✦ Buoyant gravity modes ✦ Scaling relations
- 7. Meredith L. Rawls • @merrdiff Chaplin & Miglio 2013 left side x-axis range MS MS Subgiant Subgiant RGB base RGB RGB RGB Red clump
- 8. Meredith L. Rawls • @merrdiff ✦ Kepler red giant catalog: ~14,000 ✦ Kepler eclipsing binary catalog: 2,500+ ✦ After cross-correlating: 19 ✦ Most systems are SB2, but 4 are SB1 ✦ Most are oscillators, but 4 are not Searching for red giants in eclipsing binary systems Gaulme et al. 2013, 2014
- 9. Meredith L. Rawls • @merrdiff ✦ Process light curves to “fill” eclipses and remove gaps ✦ Single set of oscillations ✦ Broad and damped modes ✦ Evolved onto the red clump Characterizing a star: asteroseismology 70 80 90 100 110 120 130 140 Frequency (µHz) 0 100 200 300 400 500 600 700 800 SmoothedPowerDensity(ppm2 µHz−1 ) 0 100 200 300 400 500 600 700 800 KIC 9246715 Reference star Rawls et al. 2016 KIC 9246715
- 10. Meredith L. Rawls • @merrdiff Characterizing a star: binary modeling ✦ Process Kepler light curve to preserve eclipses ✦ Extract radial velocities from spectra via the broadening function ✦ Get all velocities on one zeropoint ✦ Suite of broadening function programs in python: github.com/mrawls/BF-rvplotter Rawls et al. 2016 0.0 0.2 0.4 0.773 φ 2012-03-01 TRES 0.831 φ 2012-03-11 TRES 0.960 φ 2012-04-02 TRES 0.170 φ 2012-05-08 TRES 0.0 0.2 0.4 0.275 φ 2012-05-26 TRES 0.316 φ 2012-06-02 TRES 0.374 φ 2012-06-12 ARCES 0.460 φ 2012-06-27 ARCES 0.0 0.2 0.4 0.479 φ 2012-06-30 TRES 0.618 φ 2012-07-24 TRES 0.811 φ 2012-08-26 ARCES 0.812 φ 2012-08-26 ARCES 0.0 0.2 0.4 0.817 φ 2012-08-27 ARCES 0.864 φ 2012-09-04 ARCES 0.869 φ 2012-09-05 TRES 0.015 φ 2012-09-30 TRES 0.0 0.2 0.4 0.155 φ 2012-10-24 TRES 0.318 φ 2012-11-21 TRES 0.091 φ 2013-04-02 TRES −60 −40 −20 0 20 40 60 0.196 φ 2013-04-20 ARCES −60 −40 −20 0 20 40 60 0.0 0.2 0.4 0.511 φ 2013-06-13 ARCES −60 −40 −20 0 20 40 60 0.982 φ 2013-09-02 ARCES −60 −40 −20 0 20 40 60 0.023 φ 2013-09-09 ARCES Smoothed BF Two-Gaussian fit Uncorrected Radial Velocity (km s−1 ) BroadeningFunction KIC 9246715
- 11. Meredith L. Rawls • @merrdiff Characterizing a star: binary modeling 9.30 9.35 9.40 9.45 9.50 Magnitude ELC Model −60 −40 −20 0 20 40 RadialVelocity(kms−1 ) 0.0 0.2 0.4 0.6 0.8 1.0 −0.004 0.000 0.004 −2 0 2 9.25 9.30 9.35 9.40 9.45 9.50 Magnitude 0.20 0.21 0.22 0.23 −0.004 0.000 0.004 0.49 0.50 0.51 0.52 Orbital Phase (conjunction at φ = 0.5) Secondary Primary ∆ ∆ ∆ ✦ Double red giant KIC 9246715 ✦ Stars are nearly twins; eclipse depths vary due to geometry ✦ Simultaneously fit radial velocities and light curve ✦ Minimize χ2 with 16 free parameters using DE-MCMC optimizers Rawls et al. 2016 Radial velocities Kepler light curve Eclipse zoom KIC 9246715
- 12. Meredith L. Rawls • @merrdiff Putting the pieces together KIC 9246715
- 13. Meredith L. Rawls • @merrdiff Putting the pieces together KIC 9246715 2.15 M⊙, 8.30 R⊙ 2.17 M⊙, 8.37 R⊙
- 14. Meredith L. Rawls • @merrdiff Putting the pieces together 200 400 600 800 1000 1200 1400 98.5 99 99.5 100 100.5 Time (BJD - 2454833) ∆I/I(%) ? KIC 9246715 Rawls et al. 2016 2.15 M⊙, 8.30 R⊙ 2.17 M⊙, 8.37 R⊙
- 15. Meredith L. Rawls • @merrdiff ✦ KIC 9246715 is in good company ✦ Oscillation modes are damped or missing in many red giant binaries ✦ All modes affected equally ✦ Compare properties of binaries with strong, damped, and no oscillations ✦ Determine what physical conditions prevent resonant convection zones Some other systems also show damped or absent oscillations — no oscillations νmax ~ 4 μHz νmax ~ 80 μHz Gaulme et al. 2013
- 16. Meredith L. Rawls • @merrdiff ✦ Fourier decomposition turns dozens of composite spectra into one spectrum per star ✦ Stellar atmosphere modeling ✦ Lines sensitive to magnetic fields ✦ Suite of python programs to assist with disentangling: github.com/mrawls/FDBinary-tools Disentangled spectra hold clues to magnetic activity One of 23 high-res spectra (light from both stars) Star 1, Teff = 4990 ± 90 K Star 2, Teff = 5030 ± 80 K KIC 9246715
- 17. Meredith L. Rawls • @merrdiff ✦ Magnetically sensitive Fe I lines don’t differ from non-sensitive ones ✦ Ca H & K lines too blue, noisy ✦ Ca II λλ8498,8542 show no emission ✦ Excess Hα absorption? ✦ Orbital solution + light ratio both needed for successful disentangling Disentangled spectra hold clues to magnetic activity5554 5557 5560 −0.4 −0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Fei, mag 5572 5575 5578 5581 Fei, non-mag 5686 5689 5692 5695 Fei, non-mag 6298 6301 6304 6307 Fei, mag 6559 6562 6565 Hα 6840 6844 −0.4 −0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Fei, mag 7088 7092 Fei, non-mag Observed Model Difference 8490 8500 8510 8520 8530 8540 8550 Caii λλ8498,8542 Wavelength (˚A) ScaledFlux 5554 5557 5560 −0.4 −0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Fei, mag 5572 5575 5578 5581 Fei, non-mag 5686 5689 5692 5695 Fei, non-mag 6298 6301 6304 6307 Fei, mag 6559 6562 6565 Hα 6840 6844 −0.4 −0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 Fei, mag 7088 7092 Fei, non-mag Observed Model Difference 8500 8510 8520 8530 8540 Caii λλ8498,8542 Wavelength (˚A) ScaledFlux Rawls et al. 2016 KIC 9246715
- 18. Meredith L. Rawls • @merrdiff ✦ Robotically-controlled 1m telescope at APO ✦ Kepler cannot measure color ✦ Goal: compare eclipse fluxes with out-of-eclipse flux ✦ Especially useful for red giants with faint companions Multi-band photometry potentially constrains light ratio and temperatures
- 19. Meredith L. Rawls • @merrdiff ✦ Two non-oscillators ✦ Mix of orbital periods (19 – 235 days) ✦ Three with variability > 1% ✦ Two with phase effects ✦ Mix of eccentricities (< 0.001 – 0.38) ✦ Observed the most in 1m campaign Choosing a representative subset of red giant binaries
- 20. Meredith L. Rawls • @merrdiff Modeling red giants with faint companions 279.764 279.766 279.768 10000 30000 50000 T0 conj −0.15652 −0.15648 −0.15644 5000 15000 25000 e cos ω 0.1650 0.1660 0.1670 10000 30000 50000 e sin ω 89.0 89.4 10000 30000 50000 i 1.12 1.16 1.20 5000 15000 25000 M1 5800 6200 6600 20000 60000 100000 Teff, 1 0.73 0.75 0.77 5000 15000 25000 T2/T1 0.0086 0.0088 0.0090 5000 15000 25000 R1/a 0.0688 0.0692 0.0696 5000 15000 25000 R2/a 25.5 26.5 5000 15000 25000 K1 0.05 0.15 0.25 5000 15000 25000 LD1 q1 0.56 0.60 0.64 10000 30000 50000 LD1 q2 0.4 0.6 0.8 10000 30000 50000 LD2 q1 0.35 0.45 0.55 10000 30000 50000 LD2 q2 0.01 0.03 0.05 20000 60000 100000 Kepler contam 207.1076 207.1080 207.1084 5000 15000 25000 Period KIC 3955867 Broadening function fits KIC 10001167 Disentangled giant spectrum KIC 7037405 ELC fit parameter distributions
- 21. Meredith L. Rawls • @merrdiff KIC 8702921 P = 19.4 days e = 0.10 variability ~ 1.4% No Ca II emission Deep Hα line The only SB1 in the sample 0.27 M⊙ 0.29 R⊙ 1.67 M⊙ 5.32 R⊙ 1/7
- 22. Meredith L. Rawls • @merrdiff KIC 9291629 1.11 M⊙ 1.83 R⊙ 1.13 M⊙ 7.93 R⊙ P = 20.7 days e = 0.0006 variability ~ 16% Ca II net emission Normal Hα line Fast rotator BVRI used in fit 2/7
- 23. Meredith L. Rawls • @merrdiff KIC 3955867 0.92 M⊙ 0.97 R⊙ 1.10 M⊙ 8.24 R⊙ P = 33.7 days e = 0.01 variability ~ 23% Ca II net emission Hα not too deep Fast rotator 3/7
- 24. Meredith L. Rawls • @merrdiff KIC 10001167 0.81 M⊙ 0.97 R⊙ 0.86 M⊙ 12.73 R⊙ P = 120.4 days e = 0.16 variability ~ 0.4% No Ca II emission Deep Hα line Phase effects 4/7
- 25. Meredith L. Rawls • @merrdiff KIC 5786154 1.02 M⊙ 1.56 R⊙ 1.06 M⊙ 11.01 R⊙ P = 197.9 days e = 0.38 variability ~ 0.2% No Ca II emission Deep Hα line Most eccentric 5/7
- 26. Meredith L. Rawls • @merrdiff KIC 7037405 1.15 M⊙ 1.74 R⊙ 1.27 M⊙ 13.72 R⊙ P = 207.1 days e = 0.23 variability ~ 0.2% No Ca II emission Deep Hα line 25 APOGEE RVs McKeever+ in prep 6/7
- 27. Meredith L. Rawls • @merrdiff KIC 9970396 1.00 M⊙ 1.08 R⊙ 1.17 M⊙ 7.70 R⊙ P = 235.3 days e = 0.18 variability ~ 0.2% No Ca II emission Deep Hα line Kepler LC gaps BVRI used in fit 7/7
- 28. Meredith L. Rawls • @merrdiff ✦ Seismic M, R are both too large ✦ Densities and gravities nearly agree ✦ Stars least like the Sun differ the most ✦ Spectroscopic gravities are too high The scaling relations are not perfect Coming soon: Gaulme et al. 2016 Mass Radius Density (Δν) Gravity (νmax)
- 29. Meredith L. Rawls • @merrdiff ✦ The most active giants lack oscillations, have short periods, and are rotationally synchronous ✦ They also show differential rotation ✦ Ca II net emission agrees with strongest photometric variability ✦ Hα may trace chromospheric activity Magnetic activity roundup Robinson et al. 1990
- 30. Meredith L. Rawls • @merrdiff 10 100 300 10 100 200 5866138 9246715 7377422 4473933 10015516 8430105 8435232 5179609 4569590 53087787133286 3955867 6307537 5193386 9291629 11235323 8702921 7943602 Porb [days] Pvar[days] 5 : 1 4 : 1 3 : 1 2 : 1 1 : 1 1 2 : 1 Evidence for orbital & rotational resonances More stellar variability Less stellar variability Stronger oscillations Weaker oscillations Gaulme et al. 2014 and Ravenel et al. in prep ✦ Binaries with no oscillations more likely to be synchronized ✦ Binaries with synchronization more likely to be active (variable)
- 31. Meredith L. Rawls • @merrdiff ✦ MESA: 1D stellar profiles over time ✦ Initialize model with M & metallicity; let star evolve to present R ✦ KIC 9246715 contains the only red clump stars in this sample ✦ Adjusted mixing-length parameter (increase efficiency of convection) to get sufficiently small RC stars Stellar evolution models constrain tidal history and age KIC 9246715
- 32. Meredith L. Rawls • @merrdiff ✦ Depends on stellar evolution and influence of companion star ✦ Δe is a function of M, M2/M, Porb, I(t) ✦ I(t) is a function of Teff(t), Menv(t), R(t) Tidal forces over time Verbunt & Phinney 1995 KIC 9246715
- 33. Meredith L. Rawls • @merrdiff ✦ Depends on stellar evolution and influence of companion star ✦ Δe is a function of M, M2/M, Porb, I(t) ✦ I(t) is a function of Teff(t), Menv(t), R(t) Tidal forces over time Verbunt & Phinney 1995 M2/M = 0.989KIC 9291629
- 34. Meredith L. Rawls • @merrdiff ✦ Rotation synchronization should happen before orbit circularization ✦ Two most active giants with short periods are nearly circularized ✦ Eccentric systems have not had enough time for tides to circularize ✦ Two outliers/in-between cases Predicted changes in eccentricity
- 35. Prediction: a range of oscillation populations Meredith L. Rawls • @merrdiff Tidally-induced “heartbeat” pulsations No solar-like oscillations Damped solar-like oscillations Oscillates like a single star 8702921 9291629 3955867 10001167 57861549246715 7037405 9970396
- 36. Meredith L. Rawls • @merrdiff ✦ Distances computed via theoretical bolometric corrections, updated KIC extinctions, & JHK magnitudes from 2MASS ✦ No clear galactic [Fe/H] gradient Galactic context Southworth et al. 2005
- 37. Meredith L. Rawls • @merrdiff Pipeline comparisons temperature surface gravity metallicity distance
- 38. Meredith L. Rawls • @merrdiff ✦ Solar-like oscillations are damped by magnetism & tides, which often occur together ✦ Most pronounced for short-period, spotty, synchronized and circularized systems ✦ The asteroseismic scaling relations are least accurate for stars least like the Sun ✦ Scaling relations overestimate giant M, R ✦ These stars are references for survey pipelines ✦ Asteroseismic surveys will tend to miss active stars and close binaries Red giant binaries are powerful benchmarks for asteroseismology