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RR Lyrae Stars

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RR Lyrae Stars By: Mike Lundquist What Are They Old Stars, Over 10 Billion Years Old Helium Burning, Horizontal Branch Stars Variable Stars With Periods of 0.2 to 1.1 ... – PowerPoint PPT presentation

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Title: RR Lyrae Stars


1
RR Lyrae Stars
  • By Mike Lundquist

2
What Are They
  • Old Stars, Over 10 Billion Years Old
  • Helium Burning, Horizontal Branch Stars
  • Variable Stars With Periods of 0.2 to 1.1 days
  • 0.7 Solar Masses
  • 4-6 Solar Radii
  • Metal Poor Stars

3
RR Lyrae Stars In M3
4
  • Evolution
  • Ascend RGB
  • Helium Flash onto HB
  • Enter Instability Strip
  • Ascend AGB
  • Forms Planetary Nebula
  • Becomes a White Dwarf

5
Types of RR Lyrae Stars
RRab -- Fundamental Mode --Rapid Increase to the
Peak of the Light Curve, with a Relatively Slow
Decrease
RRc -- Overtone Mode -- Increase in the Light
Curve Nearly Equal to the Decrease
RRd Pulsate in both the RRab and RRc modes.
6
  • RRab Type Stars Have Longer Periods
  • RRab Type Stars Are Easier to Find than RRc
  • Most RR Lyrae stars found are RRab Type
  • RR Lyrae Stars are Very Common in Globular
    Clusters

7
Pulsation
Ionized Helium Layers Absorb Heat Pressure and
Luminosity Increase Star Expands and
Cools Pressure and Luminosity Decrease Star
Compresses Ionized Helium Absorbs Heat Cycle
Continues
8
The Blazhko Effect
9
The Blazhko Effect
  • Periodic Variations in Light Curve
  • Only Mostly in RRab Type.
  • Leading Theories
  • Result of Resonance
  • Result of Magnetic Field and Rotation

10
Other Important Uses
  • Standard Candles
  • Accurate to 10 Distance
  • Real Time Stellar Evolution

11
Standard Candles
  • Absolute magnitudes MV 0.6
  • Accurate Distance Measurements

12
Metallicity Relationship
13
Real Time Stellar Evolution?
  • RR Lyrae Star V79
  • Between 1962 and 1996, Pulsations in the First
    Overtone Increased Significantly, while the
    Period has Decreased.
  • Decrease in Period Suggests Blueward Stellar
    Evolution

14
Summary
  • Good For Calculating Distances
  • Good For Testing Pulsation Models
  • Insight into Stellar Evolution of Low Mass Stars

RR Lyrae Properties
Period 0.2-1.1 days Mv 0.6 0.2 Te 7400 K
6100 K Log g 2.5-3.0 Fe/H 0.0
-2.5 Mass 0.7 Solar Masses Radius 4-6 Solar
Radii
15
For More Information
  • Principles of Stellar Evolution and
    Nucleosynthesis By Donald D. Clayton
  • RR Lyrae Stars By Horace A. Smith
  • http//www.aavso.org/
  • http//www.journals.uchicago.edu/doi/pdf/10.1086/3
    16352
  • http//www.astronomy.ohio-state.edu/ryden/ast162_
    4/notes16.html
  • http//www.pa.msu.edu/people/smith/
  • http//spiff.rit.edu/classes/phys230/lectures/mw_s
    ize/mw_size.html
  • http//antwrp.gsfc.nasa.gov/apod/ap041012.html
  • http//www.aanda.org/index.php?optionarticleacce
    ssbibcodebibcode2006A2526A...459..577KPDF
  • http//www.journals.uchicago.edu/doi/pdf/10.1086/5
    06198
  • http//www.aanda.org/index.php?optionarticleacce
    ssbibcodebibcode2007A2526A...474..557MPDF
  • http//adsabs.harvard.edu/abs/2004rrls.book.....S
  • http//articles.adsabs.harvard.edu/cgi-bin/nph-iar
    ticle_query?1998ASPC..135..385Fampdata_typePDF_
    HIGHampwhole_paperYESamptypePRINTERampfile
    type.pdf
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