An Astronomy GradNet Tech Talk:

Searching for Eclipsing Binary Stars

Jonathan Devor, Ph.D.

October 20, 2008

Stellar structure:understanding how stars work

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.

• This is especially needed to understand low-mass stars, which don’t conform well to currently stellar models.

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 the data comes from- The 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

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.)

TrES/Sleuth – a robotic telescope

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

(Devor 2005)

“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)

A Binary with Large Eclipse Timing Variations

The Orbital Period Distribution

(Devor 2005)

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

(Devor & Charbonneau 2006)

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

(Devor & Charbonneau 2006)

Binary Mass-Mass Plot

(Devor et al. 2008)

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

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. SzentgyorgyiThe Astrophysical Journal]

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