Astronomy C - Variable Stars
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Transcript of Astronomy C - Variable Stars
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Astronomy C - Variable Stars
A. Pulsating Variables: 1) Long Period Variables a) Mira type b) Semiregular 2) Cepheids 3) RR Lyrae 4) RV TaruiB. Cataclysmic (Eruptive) Variables: 1) T Tauri 2) Novae 3) Dwarf Novae 4) Recurrent Novae 5) Supernovae a) Type II b) Type Ia
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Astronomy C - Variable Stars
A. Pulsating Variables: 1) Long Period Variables a) Mira type Mira b) Semiregular Betelgeuse 2) Cepheids Delta Cephei 3) RR Lyrae [Globular Clusters] 4) RV Tarui R ScutiB. Cataclysmic (Eruptive) Variables: 1) T Tauri [Protostars] 2) Novae GK Persei, Nova Aquilae 3) Dwarf Novae Z Cam, SS Cygni 4) Recurrent Novae [between Dwarf and Nova] 5) Supernovae a) Type II Cas A, SN 1987A, DEM L316 b) Type Ia Tycho’s SNR, DEM L316
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Light Curves – Variation over TimeMaximum (Maxima)
Minimum (Minima) Period
Apparent Magnitude vs Julian Day
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A. Pulsating Variable Stars; 1) Long Period Variables (LPVs)a) Miras
Omicron Ceti (Mira)
b) Semiregular Variables
80 – 1000 days, 2.5 – 5.0 mag
Betelgeuse (Alpha Orionis)
30 – 1000 days, 1.0 – 2.0 mag
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Mira Instability Strip
Semiregular
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2) Cepheid Variable Stars Delta Cephei
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2) Cepheids [Periods of 1 – 70 days, 1.0 – 2.0 mag]
Delta Cephei
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A Cepheid Variable Star in M100
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3) RR Lyrae Variable Stars
Periods of a few hours to one day, .3– 2.0 mag
47 Tuc
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Cepheid and RR Lyrae Variable Stars
[Mv = 0.75]
Period-Luminosity Relationship and The Distance Modulus: M = m - 5log10 (r) 10
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4) RV Tauri – a Stellar Missing Link?
R Scuti
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Mira Instability Strip
Semiregular
CepheidInstability Strip
RR Lyrae
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B. Cataclysmic (Eruptive) Variables1)T Tauri; proto-star stage
for mid-sized stars
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Mira Instability Strip
Semiregular
CepheidInstability Strip
RR Lyrae
T-Tauri
RV Tauri
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Stellar Nurseries - sites of protostar & T-Tauri formation
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M 42 – The Orion Nebula
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2) Novae Close binary systems – main sequence star & a
white dwarf 1 to 300 days, 7.0 – 16.00 mags
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Novae:
Nova Aquilae
GK Persei
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3) Dwarf NovaeDwarf Novae:Close binary systems – main sequence star, white dwarf and an accretion disk Two of three subclasses; U Gem – SS Cygni Z Cam – Z Cam
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SS Cygni
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Dwarf Novae: SS Cygni
Z Cam
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4) Recurrent NovaeClose binary systems – main sequence star & a white dwarf 1 to 300 days, 7.0 – 16.00 mags *** Similar to novae but often resemble dwarf novae
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5) Supernovae a) Type II
Cas A
SN 1987A
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b) Type Ia
Tycho’s SNR Mira
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Type Ia Supernova
Type II Supernova
DEM L316
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MZ 3 – The Ant Nebula (planetary nebula)
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Algol Beta Persei
Eclipsing Binary
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Cosmological Distances
Spectroscopic Parallax
Variables
Cepheids RR Lyrae
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Cosmological Distances
CepheidsThe Distance Modulus: M = m - 5log10 (r) 10
Spectroscopic Parallax The Distance Modulus: M = m -
5log10 (r) 10
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Type Ia Supernovae – Standard Candle
Cosmological Distances & Candles
Mv = -19.5
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Basic Equations and Relationships
The Distance Modulus: M = m - 5log10 (r) 10Kepler’s 3rd Law: (MA + MB) = a3
p2
v = d ; a = v ; 2π a = vP ; Fc = mac ; ac = v2 = rω2
t t r 1 pc = 206,265 au = 3.26 ly = 3.08 x 1016m1° = 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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JD 2449050
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JD 2449835
W Cyg
61 40
43
5559
53
6855
696967
67
64
75
74
70
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1) Cepheid Light Curve
3) Same Data Plotted Twice
2) Superposition of Periods
4) Same data starting at Maxima
Phase Diagrams
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Theory Matches Observation
Perfectly Periodic
Correct EpochCorrect Period
** The slope of each line is the difference between its period and the estimated period.
Perfectly Periodic
Correct Epoch
Wrong Period
**True Period longer
Perfectly Periodic
Change in Period
**True Period Shorter then Lenthens
Perfectly Periodic
Correct Period Wrong Epoch
Periodic
Period UnchangedEpoch has Changed
NOT Perfectly Periodic
Different Period Each Day
O – C Diagrams(Observed minus Calculated)
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Stellar Evolution – A Journey with Chandra