``But I am constant as the Northern Star Of whose true-fixed and resting quality There is no fellow in the firmament.'' William Shakespeare, Julius Caesar, 3, 1 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 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 J0806.3+1527 5) Supernovae a) Type II G11.2-0.3, SN2006gy b) Type Ia DEM L71, Kepler’s SNR C. Strangers in the Night: V838 Mon Light Curves – Variation over Time Maximum (Maxima) Minimum (Minima) Period Apparent Magnitude vs Julian Day 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 Semiregular Mira Instability Strip 2) Cepheid Variable Stars W Virginis (Type 2) [Periods of .8 – 35 days, .3 – 1.2 mag] 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. 3) RR Lyrae Variable Stars AH Leo [Periods of .2 – 1 day, .3 – 2.0 mag] Cepheid and RR Lyrae Variable Stars Period-Luminosity Relationship and The Distance Modulus: M = m - 5log10 (r) 10 [Mv = 0.75] Cepheid Instability Strip Semiregular RR Lyrae Mira Instability Strip B. Cataclysmic (Eruptive) Variables 1) R Coronae Borealis [Irregular Period, up to 3 mag] RY Sagittarii 2) Flare Stars – faint cool red dwarfs UV Ceti [irregular and unpredictable] 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] 4) X-Ray Binaries – Close Binary Systems White Dwarf, Neutron Star, or Black Hole accreting material from a Companion Star a) GRO J1655-40 b) RX J0806.3+1527 5) Supernovae a) Type II – Core Collapse of a Massive Star G11.2-0.3 SN 2006gy b) Type Ia – Thermonuclear Destruction of a White Dwarf in a Binary System DEM L71 Kepler’s SNR Supernovae Light Curves C. Strangers in the Night V838 Mon 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, RXJ0806.3+1527 ??? V838 Mon ? ? Cosmological Distances ÎCepheids The Distance Modulus: M = m - 5log10 (r) 10 ÎType Ia Supernovae – Standard Candle Mv = -19.5 Basic Equations and Relationships The Distance Modulus: M = m - 5log10 (r) 10 rd 3 Kepler’s 3 Law: (MA + MB) = a 2 p 2 2 v = d ; a = v ; 2π a = vP ; Fc = mac ; ac = v = rω 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 Phase Diagrams 1) Cepheid Light Curve 2) Superposition of Periods 3) Same Data Plotted Twice 4) Same data starting at Maxima O – C Diagrams (Observed minus Calculated) Theory Matches Observation Perfectly Periodic Perfectly Periodic Perfectly Periodic Correct Epoch Change in Period Wrong Period Correct Epoch **True Period Shorter Correct Period **True Period longer then Lenthens Perfectly Periodic Periodic NOT Perfectly Periodic Period Unchanged Correct Period Epoch has Changed Wrong Epoch Different Period Each Day ** The slope of each line is the difference between its period and the estimated period. Stellar Evolution – A Journey with Chandra Stellar Evolution – A Journey with Chandra Stellar Cycles Sets and Cosmic Connections Request URL: http://chandra.harvard.edu/edu/epo/request_special.html [email protected] Stellar Cycles Card Set: Additional Resources: The American Association of Variable Star Observers http://www.soinc.org/store/TG-DVD-06v10.htm UPDATED COACHES MANUAL COMING SOON!!! (AVAILABLE ONLINE AT THE NSO WEBSITE).