ECLIPSING BINARY STAR ANALYSIS THROUGH PHOTOMETRIC METHODS

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ECLIPSING BINARY STARANALYSIS THROUGH
PHOTOMETRIC METHODS
JUNE SHIH Advisor Dr. Anthony Shoup Prof.
Gaurang Yodh

• University Of California, Irvine
• May 11, 2002

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UCI OBSERVATORY

• Located in dark fields on outskirts of campus
• Only beige colored observatory dome known.
• UCI Astronomy Club, Visitor Nights, Advanced Lab

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TELESCOPE

• Onsite Remote Commands
• Primary Mirror 24 Secondary 8.5
• CCD CAMERAS
• Imaging ST-9E
• Spectrograph ST-8E
• Finder Scope ST-6

Telescope At Night
In Home Position
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WHAT IS A BINARY STAR?

• Two stars orbiting around common center of mass
• Gravitationally bound to each other
• Formed at the same time
• Makes up 50 of stellar systems

Images http//astrosun.tn.cornell.edu/courses/ast
ro201/binstar.htm
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TYPES OF BINARY STARS
Binary stars are classified according to the
method by which they were observed

• Visual Binary
• Both stars visible in telescope
• Spectroscopic Binary
• Image of single star
• Two stars determined by periodic Doppler Shift of
  spectrum lines
• Eclipsing Binary
• Image of single star
• Two stars determined by observable eclipses
  through a periodic Light Curve

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LIGHT CURVE
Light flux through time
Period
Secondary Eclipse
Primary Eclipse
Image www.physics.sfasu.edu/astro/binstar.html
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TYPES OF ECLIPSING BINARIES
S
S
P
P
Algol Type
ß Lyrae Type

• Flat topped Continuously variable
• Small effects due to proximity Quite
  different surface
• of the stars brightness
• Large difference in minima Large difference
  in minima
• depths depths

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W UMA TYPE
S
P
P
S

• Continuously variable Small Periods
• Small difference in minima depths
• Similar surface brightness

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LIGHT CURVE RELATIONSHIP SIMULATION
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RADIAL VELOCITY RELATIONSHIP
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CALCULATIONS

• Light Curve period of system (p)
• Radial Velocity velocities of stars (v)
• Circumference of Orbit distance (d)
• Basic Velocity Equation
• Keplers Third Law
• Period, Velocity, Mass, Radius,

d v t
p2 ( m1 m2 ) a3
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AW Ursa Major

• Binary Type W UMa
• Location RA 113004 Dec 295752
• Period 0.4387299 days
• Epoch Heliocentric JD 2438044.7815
• Other Names GSC 1984-0113, HD 99946

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AW UMa
Actual Image Scale 6 x 6 armin
(3) GSC 1984-0495
AW UMa
(2) GSC 1984-0145
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PHOTOMETRY

• Accurate measurement for the brightness of a
  star.
• Most precise and accurate means for obtaining
  flux measurements
• Use of Imaging CCDs to obtain data

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ACCURACY CALIBRATIONS
APERATURE Subtracts out background light of
pixels in Star n Median pixel value of B m S
B (n m) STARLIGHT!
Background Light
STAR
Starlight Background
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FLATS

• Accounts for
• Variations from pixel to pixel and dust
• Uniform light source
• Divided into CCD image

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DARKS

• Accounts for
• Thermal Noise
• Shutter on CCD closed
• Subtracted from CCD image

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DIFFERENTIAL PHOTOMETRY

• Takes out effects due to
• Atmosphere
• Phase
• 1 Variable Star
• 2 Comparison Star
• 3 Check Star

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1
2
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Variable Star (1)
Comparison (2) Check (3) Star

• Comparison and check stars are non-variable stars
• Difference in brightness between the two remain
  constant

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WHY STUDY THEM?

• Most common stellar system (50)
• Easily observed with photometry and spectroscopy
• Determination of fundamental properties mass,
  radii, velocities, surface brightness,
  luminosities, period
• Provides information about non-binary stars in
  the same population
• Helps develop stellar evolution stellar
  structure theories

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June Shih University of California, Irvine Dr.
Anthony Shoup Gaurang Yodh