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 mag (yrs) flare 1-6 mag (<hr) K-M WD: SNI -20mag (yrs) N -10mag (1000s yrs) DN 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

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, ~20/yr in MW 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 min

Disk Polar Intermediate Polar

DISK ACCRETION MAGNETIC High MLow M.. X-rays 10 8 K K ACCRETION BL For slowly rotating WD: L disk = L BL = 1/2GMM wd /R wd. Hard X-rays Soft X-rays Cyclotron

-WD accretes until thick degenerate envelope leads to TNR to solar masses ejected (dust can form) -Envelope returns to quasi-static equil (nuclear burning) -Envelopoe gradually ejected by winds, phot recedes, T increases and peak radiaiton in soft X-ray -Constant bol phase lasts until envelope exhausted (1-100 yrs)

Outburst cycle of the Dwarf Nova SS Cyg Cannizzo & Mattei, 1998, ApJ 505, 344 Outbursts are DISK instabilities Typical DN

Typical CV spectra in DR1 CVs in EDR in Szkody et al. 2002, AJ, 123, 430

Symbiotic stars Late type RG + WD + high excitation emission lines Possible progenitors of Type Ia SN?

RS CVn star (convection + high rotation gives spots) K0III

Pulsating stars: 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 [P=(4π/3G  ) 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 Cepheids: F-G SG, P-L relation, P ~ 2-60 days, HeII ionization zone pulsation mechanism RR Lyrae: A giants, M v = 0.5, P<1 day Radial pulsators

P-L relation 1) measure m v with CCD 2) find P from light curve 3) use P-L to get M v 4) m-M d

White dwarfs show non-radial g-modes on account of their high gravity Periods of 100s to 1000s These modes are characterized by quantum numbers (k,l,m) similar to atomic orbitals Spherical gravitational potential  Spherical electrostatic potential l determines the number of borders between hot and cool zones on the surface m is the number of borders that pass through the pole of the rotation axis k determines the number of times the pulsation wiggles from the center to the surface

Two flavors of ZZ Ceti stars (DAVs) T eff = 11000K P ~ 1000s T eff = 12000K P ~ 200s cool Larger amp, more modes, unstable amps hot Less modes, more stability

Mira - pulsating RG Period ~ 11 months

Flare Stars Flare <15s to 1 hr, repeats hrs - days Amplitude up to 4 mag Opt is thermal brem at T ~ 10 7 K, radio is non-thermal Between flares, spectrum is K-M with CaII, H emission

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 mag (yrs) flare 1-6 mag (<hr) K-M WD: SNI -20mag (yrs) N -10mag (1000s yrs) DN 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

Supernovae Morford, Ortez Chadney/Fowler Kong Campion Smith X-ray Binaries Stevens Markert Slinker Sheets Green Belleci Vos Timpe CVs Jennings Filbrandt Magnuson Pulsators Mayorga Hua Flares Evans Others Draper Jewell Hansen