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Variable Stars clues: timescale, amplitude, light curve shape, spectrum Eclipsing: Algol B8-M ß Lyr W UMa (hrs-days) B8-G3 Eruptive: single binary SNII 15-20 mag (yrs) flare 1-6 mag (<hr) K-M Pulsating: short P Cepheids:F-K, 1-50d, 1.5mag RR Lyr: A-F, 0.5 day, 1 mag Scuti: A-F, hrs, 0.02 mag F0-K0 (hrs) WD: SNI -20mag (yrs) N -10mag (1000s yrs) DN - 2-7 mag (weeks) NL - erratic Symbiotic: 3mag (erratic) XRB: HMXRB, LMXRB -ray Bursters RS CVn: F,G+KIV, spots long P Mira:M, yrs, 1-5mag S-R: K, M odd ß Ceph: B, 0.5d ZZ Ceti: WD, min Binary Evolution: Roche equipotential surfaces rc /A = 0.38 + 0.2 log q [0.3 < q < 2] rc /A = 0.46 (M1/M2 + M1)1/3 [0<q<0.3] Massive X-ray Binaries (MXRBs) Name P (days) Vela X-1 9 Cen X-3 2.1 Cyg X-1 5.6 Sp q B0Ia 12 O7III 17 O9.7I 3 Mx 1.9 1 6 Low Mass X-ray Binaries (LMXRBs) Name 1626-67 P(hrs) 0.7 Sec Mx WD Cyg X-3 4.8 IR Her X-1 40.8 B-F 1 long E >1051ergs short 20M + 8M P=5 days t = 1 million yrs transfers 15M in 30,000yrs 5M + 23M P=11 days P= 13 days t=10 million yrs X-ray binary for 10,000 yrs P = 4 hrs Cataclysmic Variables white dwarf primary with a low mass (G-M) secondary, orbital periods of 67 min-2 days Nova: TNR, high mass WD, outbursts 8-15 mag every few thousand yrs Dwarf nova: disk instability, outbursts 2-7 mag every week-30 yrs Novalike: high, low states on timescales of months, high accretion AM CVn: 2 white dwarfs, orbital periods of 10-45 min Asteroseismology • Pulsations Only systematic way to study the stellar interior • Pulsations are observed in stars all over the HR diagram ZZ Ceti stars Pulsations in a star Pulsation period and amplitude depend on the average density. P -1/2 Low density long P, high amplitude High density short P, low amplitude Density profile decides how deep the pulsations penetrate in the star. (Deeper the penetration more we learn about the interior) Centrally condensed stars like our Sun have shallow pulsations Uniform density stars like white dwarfs have deep pulsations Cepheids and RR Lyrae RR Lyrae: A giants, Mv = 0.5, P<1 day Cepheids: F-G SG, P-L relation, HeII ionization zone pulsation mechanism P-L relation 1) measure mv with CCD 2) find P from light curve 3) use P-L to get Mv 4) m-M d Two flavors of ZZ Ceti stars (DAVs) cool Teff = 11000K P ~ 1000s Larger amp, more modes, unstable amps hot Teff = 12000K P ~ 200s Less modes, more stability Flare Stars Flare <15s to 1 hr, repeats hrs - days Amplitude up to 4 mag Opt is thermal brem at T ~ 107K, radio is non-thermal Between flares, spectrum is K-M with CaII, H emission