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Variable Stars clues: timescale, amplitude, light curve shape, spectrum

Variable Stars clues: timescale, amplitude, light curve shape, spectrum. Eclipsing: Algol ß Lyr W UMa. B8-M (hrs-days) B8-G3 F0-K0 (hrs) ‏. Eruptive: single binary. SNII 15-20 mag (yrs) flare 1-6 mag (<hr) K-M. WD: SNI -20mag (yrs)

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Variable Stars clues: timescale, amplitude, light curve shape, spectrum

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  1. Variable Stars clues: timescale, amplitude, light curve shape, spectrum Eclipsing: Algol ß LyrW UMa B8-M (hrs-days) B8-G3 F0-K0 (hrs)‏ Eruptive: single binary SNII 15-20 mag (yrs) flare 1-6 mag (<hr) K-M 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 Pulsating: short P long P odd Cepheids:F-K, 1-50d, 1.5mag RR Lyr: A-F, 0.5 day, 1 mag  Scuti: A-F, hrs, 0.02 mag Mira:M, yrs, 1-5mag S-R: K, M ß Ceph: B, 0.5d ZZ Ceti: WD, min

  2. 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]

  3. Massive X-ray Binaries (MXRBs)‏ Name P (days) Sp q Mx Vela X-1 9 B0Ia 12 1.9 Cen X-3 2.1 O7III 17 1 Cyg X-1 5.6 O9.7I 3 6 Low Mass X-ray Binaries (LMXRBs)‏ Name P(hrs) Sec Mx 1626-67 0.7 WD Cyg X-3 4.8 IR Her X-1 40.8 B-F 1

  4. long E >1051ergs short

  5. 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

  6. 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

  7. Asteroseismology • Pulsations Only systematic way tostudy the stellar interior • Pulsations are observed in starsall over the HR diagram ZZ Ceti stars

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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

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