But I am constant as the Northern Star Of whose truefixed and resting quality There is no fellow in

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But I am constant as the Northern StarOf whose
true-fixed and resting qualityThere is no fellow
in the firmament.'' William
Shakespeare,
Julius Caesar, 3, 1
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Astronomy C - Variable Stars - 2008
A. Pulsating Variables 1) Long Period
Variables a) Mira type b)
Semiregular 2) Cepheids 3) RR Lyrae B.
Cataclysmic (Eruptive) Variables 1) R
Coronae Borealis 2) Flare Stars 3)
Dwarf Novae 4) X-Ray Binaries 5)
Supernovae a) Type II b) Type
Ia C. Strangers in the Night
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Astronomy C - Variable Stars - 2008
A. Pulsating Variables 1) Long Period
Variables a) Mira type R Cygni
b) Semiregular V725 SGR 2) Cepheids W
Virginis 3) RR Lyrae AH Leo B. Cataclysmic
(Eruptive) Variables 1) R Coronae Borealis
RY Sagittarii 2) Flare Stars UV Ceti
3) Dwarf Novae SU Ursae Majoris 4) X-Ray
Binaries J1655-40, RX J0806.31527 5)
Supernovae a) Type II G11.2-0.3,
SN2006gy b) Type Ia DEM L71,
Keplers SNR C. Strangers in the Night V838 Mon

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Light Curves Variation over Time
Maximum (Maxima)

Minimum (Minima)
Period
Apparent Magnitude vs Julian Day
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A. Pulsating Variable Stars 1) Long Period
Variables (LPVs)
a) Miras
80 1000 days, 2.5 5.0 mag
R Cygni
b) Semiregular Variables
30 1000 days, 1.0 2.0 mag
V725 Sgr
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Semiregular
Mira Instability Strip
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2) Cepheid Variable Stars W Virginis (Type
2) Periods of .8 35 days, .3 1.2 mag
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Type I and Type II Cepheid Variable Stars
Type I (Classical) Cepheids Young
high-metallicity stars about 4 times more
luminous than Type II Cepheids Type II
Cepheids Older low-metallicity stars about 4
times less luminous than classical Cepheids.
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3) RR Lyrae Variable Stars AH Leo Periods
of .2 1 day, .3 2.0 mag
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Cepheid and RR Lyrae Variable Stars
Period-Luminosity Relationship and The Distance
Modulus
M m -
5log10 (r)
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Mv 0.75
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Cepheid Instability Strip
Semiregular
RR Lyrae
Mira Instability Strip
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B. Cataclysmic (Eruptive) Variables

• R Coronae Borealis

Irregular Period, up to 3 mag
RY Sagittarii
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2) Flare Stars faint cool red dwarfs
irregular and unpredictable
UV Ceti
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3) Dwarf Novae
Dwarf Novae Close Binary Systems Sun-like main
sequence star, white dwarf , accretion disk
SU Ursae Majoris
Period 30-500 days, 2-5 mag
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4) X-Ray Binaries Close Binary Systems
White Dwarf, Neutron Star, or Black Hole
accreting material from a Companion Star
GRO J1655-40
a)
RX J0806.31527
b)
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5) Supernovae a) Type II Core Collapse of
a Massive Star
G11.2-0.3
SN 2006gy
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b) Type Ia Thermonuclear Destruction of a
White Dwarf in a Binary System
Keplers SNR
DEM L71
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Supernovae Light Curves
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C. Strangers in the Night
V838 Mon
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AH Leo
W Virginis
R Cygni
V725 SGR
Type II G11.2-0.3, SN 2006gy Type Ia DEM L71,
Kepler
SU Ursae Majoris
RY Sagittarii
Flare Stars UV Ceti
X-Ray Binaries GRO J1655, RXJ0806.31527
???
V838 Mon
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?
?
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Cosmological Distances
Variables
Cepheids RR Lyrae
Spectroscopic Parallax
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Cosmological Distances
?Spectroscopic Parallax
The Distance Modulus M m - 5log10 (r)

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?Cepheids
d The Distance Modulus M m - 5log10 (r)

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Cosmological Distances Candles
?Type Ia Supernovae Standard Candle
Mv -19.5 
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Basic Equations and Relationships
The Distance Modulus M m - 5log10 (r)

10 Keplers 3rd Law (MA MB) a3

p2 v d a v 2p a
vP Fc mac ac v2 r?2 t
t
r 1 pc 206,265 au 3.26
ly 3.08 x 1016m 1 60 arcmin 60 1
60 arcsec 60? Inverse Square Law L
1/r2 Circumference, Area, Surface Area, and
Volume of a Sphere
REARRANGE ALL EQUATIONS FOR EACH VARIABLE
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Phase Diagrams
1) Cepheid Light Curve
2) Superposition of Periods
4) Same data starting at Maxima
3) Same Data Plotted Twice
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O C Diagrams (Observed minus
Calculated)
Theory Matches Observation
Perfectly Periodic
Perfectly Periodic
Perfectly Periodic
Correct Epoch
Change in Period
Wrong Period
Correct Epoch Correct Period
True Period Shorter then Lenthens
True Period longer
Perfectly Periodic
Periodic
NOT Perfectly Periodic
Period Unchanged Epoch has Changed
Correct Period Wrong Epoch
Different Period Each Day
The slope of each line is the difference
between its period and the estimated period.
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Stellar Evolution A Journey with Chandra
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Stellar Evolution A Journey with Chandra
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Stellar Cycles Sets and Cosmic Connections
Request URL
http//chandra.harvard.edu/edu/epo/request_special
.html
Stellar Cycles Card Set
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Additional Resources
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The American Association of Variable Star
Observers
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http//www.soinc.org/store/TG-DVD-06v10.htm
UPDATED COACHES MANUAL COMING SOON!!!
(AVAILABLE ONLINE AT THE NSO WEBSITE)