Treasure Hunting in Photometric Seas:A Search for Eclipsing

Binary StarsA Thesis Presentation

byJonathan Devor

(Harvard)

February 27, 2008

Why Eclipsing Binaries?

• Eclipsing binaries provide the most direct and accurate method of measuring both the masses and radii of stars.

• We need to know both the masses and radii of stars to constrain their structure and to solve the ongoing discrepancy between theory and observations found in low-mass dwarfs.

What are Eclipsing Binary Stars?

Primary eclipse

SecondaryeclipseOut-of-eclipse

“plateau”

Animation from Wikipedia

Light curve

EB = eclipsing binary

LC = light curve

Circular and Eccentric Orbits

a

Circular orbit

Eccentric orbit

Outline

1. Where our data comes from- The OGLE II and TrES multi-epoch photometric surveys

2. How I analyzed the data- The automated DEBiL/MECI pipeline

3. Results- Discovery of low-mass eclipsing binaries Testing tidal circularization theory Finding “abnormal” eclipsing binaries

4. Future work

Searching Through the

OGLE II Bulge Fields

(N = 218,699 LCs)

Bohdan Paczynski Lyman Spitzer Jr. Professor of Astrophysics (Princeton)

Feb 8, 1940 - Apr 19, 2007

OGLE:The Optical Gravitational Lensing Experiment

The Warsaw Telescope Las Campanas Observatory, Chile

OGLE website

• Located at Las Campanas Observatory, Chile

• 1.3m physical aperture• I-band photometric observations• Magnitude limit I < 19• ~200 observations per LC, compiled

over three years (1997-1999) • Analyzed 49 bulge fields, totaling

218,699 LCs

Specs:

“It is a common situation nowadays that the ability to generate data far exceeds the ability to process it, and even more so, to comprehend it.”

(Wozniak et al. 2002)

Release all the data to the public

Many discoveries, most of which had nothing to do with the original survey motivations

(e.g. pulsating stars, transiting exoplanets, population statistics, irregular variables, eclipsing binaries, etc.)

How to Find Eclipsing Binaries

(Devor 2005)

(Devor 2005)

Fitting Eclipsing Binaries with DEBiL

DEBiL = Detached Eclipsing Binary Light curves

A fully-automated program for fitting detached EBs.Solves for the geometry of the binary.

• Fractional radii (rA,B), where rA.B = RA,B / a• Component magnitude (magA,B)• Orbital inclination (i)• Orbital eccentricity (e)• Epoch of perihelion (t0)• Argument of perihelion (ω)

Fitted parameters:

[Devor 2005, The Astrophysical Journal, 628, 411]

Binary Component HR-Diagram

Primarycomponents

Secondarycomponents

(Devor 2005)

Radius-Radius Diagram

(Devor 2005)rA.B = RA,B / a

Density-Color Diagram

(Devor 2005)

Calculating a binary’s“mean density”:

The Orbital Period Distribution

(Devor 2005)

Finding Absolute Parameters Using the MECI Analysis

MECI Maximum-Likelihood Analysis[J. Devor & D. Charbonneau 2006, The Astrophysical Journal, 653, 647]

MECI = Method for Eclipse Component Identification

A fully-automated program to fit the absolute parametersof an eclipsing binary using stellar isochrones tables.

Fitted Parameters:

•Binary component masses (MA,B)•Binary age

(Devor & Charbonneau 2006)

The MECI Flow-Chart

(Devor & Charbonneau 2006)

(Yi et al. 2001)

The Yonsei-Yale theoretical isochrones

Main-sequence

Lo

g L

um

ino

sity

Log Temperature

Testing MECI with Known Systems(Lacy et al. 2002) (Lacy et al. 2003)

(Devor & Charbonneau 2006)

Searching Through

10 Sleuth Fields

(N = 185,445 LCs)

TrES/Sleuth

TrES = Trans-atlantic Exoplanet Survey

• Sleuth is one of three robotic telescopes in the TrES network.• Located at Palomar Obs., CA• 10 cm physical aperture• 30“ photometric aperture radius• r - band photometric observations• Magnitude limit r < 15• Effective 9-minute cadence (5 x 90sec)• ~2000 observations per LC• Analyzed 10 fields, totaling 185,445 LCs

Specs:

Large field / bright targets easier to follow-up

http://solas.dnsalias.org/~ftod//tres/sleuth.html

A Catalog of 773 TrES Eclipsing Binaries

• 34 - EBs with eccentric orbits• 290 – Circular orbit• 103 – Circular/ambiguous• 23 – Inverted• 318 – Non-detached• 5 – “Abnormal”

[J. Devor, D. Charbonneau, F. T. O'Donovan, G. Mandushev, & G. Torres 2008,The Astronomical Journal, 135, 850]

(Devor et al. 2008)

(+15 circular abnormals)

“Abnormal” Eclipsing Binaries P = 24.073 days P = 1.046 days

P = 0.485 days P = 0.310 days

P = 0.538 days

(Devor et al. 2008)

Binary Mass-Mass Plot

(Devor et al. 2008)

Tidal Circularization

• First studied by (Darwin 1879)Eccentricity dissipates exponentially: exp(-t / tcirc)

• Dynamical tides ; radiative dissipation for massive stars (Zahn 1975 ; Zahn 1977)

• Equilibrium tides ; turbulent dissipation in low-mass stars (Zahn 1977 ; Hut 1981)

• Hydrodynamics (Tassoul 1988)

• Circularization during the Hayashi phase (Zahn & Bouchet 1989)

• Theories systematically underestimate the circularization timescales of clusters, except for the Hyades (Meibom & Mathieu 2005)

Tidal Circularization for Individual EBs

(Devor et al. 2008)

(Zahn 1975, 1977)

Searching for Low-Mass

Eclipsing Binaries

Testing the Magnetic Disruption Hypothesis

(Ribas 2006; Torres et al. 2006;López-Morales 2007; Chabrier et al. 2007)

T-Lyr1-17236:A long-period low-mass EB

[J. Devor, D. Charbonneau, G. Torres, C. H. Blake, R. White, M. Rabus,F. T. O'Donovan, G. Mandushev, G. Bakos, & A. SzentgyorgyiTo be submitted to The Astrophysical Journal]

P = 8.429441 ± 0.000033 days(Devor et al., in prep.)

Determining the Radii

(Devor et al., in prep.)

Mass-Radius Relation

(Devor et al., in prep.)

(Baraffe et al. 1998)

Future Work

T-CrB0-10759Equal eclipses

0.60 + 0.58 M (K7+K8)

T-Cyg1-12664Disparate eclipses

0.62 + 0.32 M (K6+M3)

T-Tau0-04859Disparate eclipses, yet similar massesYoung system (?)

0.66 + 0.62 M (K5+K6)

T-Tau0-07388Disparate eclipses with O’Connell effectYoung system (?)

0.65 + 0.47 M (K6+M1)

T-Dra0-07116

Equal eclipses

Uncertain masses(late K + late K) or (early M + early M)

A Pulsating Eclipsing Binary: T-Cas0-07656

Probably one component δ-Scuti type variable

Can be used to determine system parameters from two independent approaches

Ideal test case for constraining theory of pulsating star mechanism

A Binary with Large Eclipse Timing Variations

C

Conclusions

• Photometric data is produced at a rate that far exceeds the ability to process it. This situation will become far more severe with the operation of Pan-STARRS and LSST.

• Using the DEBiL/MECI automated pipeline I was able to determine population statistics and locate rare targets for follow-up.

• Located over a dozen low-mass EBs, which are necessary for resolving the mass-radius relation discrepancy, and spectroscopically confirmed five of them.

• One of these confirmed low-mass EBs, T-Lyr1-17236, has a period of 8.4 days, making it an ideal test-case for the magnetic disruption hypothesis. Though the derived uncertainties are large, this system is consistent with the hypothesis.

TrES/PSST(LC)

Lowell Obs., AZ

TrES/Slueth(LC)

Palomar Obs., CA

NIRSPEC(RV)

Mauna Kea, HI

TRES(RV)

FLWO, AZ

HATNet(LC)

Mauna Kea, HI& FLWO, AZ

IAC80(LC)

Observatorio del Teide Canary Islands

Markus Rabus

Gaspar Bakos

Georgi MandushevDave Charbonneau

Francis O'DonovanDave Charbonneau

John BaileyCullen BlakeDave CharbonneauRussel White

Gabor FureszDoug MinkAndy SzentgyorgyiBill Wyatt

MECI + DEBiLpipeline

Acknowledgments

I would like to thank…

• Dave Charbonneau (CfA)• Willie Torres (CfA)• Tsevi Mazeh (TAU)• Laurent Eyer (Observatoire de Genève)• Przemek Wozniak (LANL)• Kris Stanek (Ohio State)• Avishai Dekel (HUJI)

Thank You!

• Jean Collins• Peggy Herlihy

Questions

Extra slides

Summery- our pipeline:• Step 1: Step :Determine the period.• Step 2: If a distinct secondary eclipse is not observed, add an entry

with twice the period.• Step 3: Fit the orbital parameters with DEBiL.• Step 4: Fine-tune the period using eclipse timing.• Step 5: Refine the orbital parameters with DEBiL using the revised

period.• Step 6: Remove contaminated LCs.• Step 7: Visually assess the quality of the EB models.• Step 8: Match the LC sources with external databases.• Step 9: Estimate the absolute physical properties of the binary

components using MECI.• Step 10: Classify the resulting systems using both automatic and

manual criteria.

The Wilson Method