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 binarySNII 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 - erraticSymbiotic: 3mag (erratic)XRB: HMXRB, LMXRB-ray BurstersRS CVn: F,G+KIV, spots

Pulsating: short P long P oddCepheids: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, 1-5magS-R: K, M

ß Ceph: B, 0.5dZZ Ceti: WD, min

Cataclysmic Variableswhite 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 10-45 min

Disk Polar

Intermediate Polar

DISK ACCRETION MAGNETIC

High M Low M. .

X-rays

108 K

9000-40000 K

ACCRETION

BL

For slowly rotating WD:

Ldisk = LBL = 1/2GMMwd/Rwd

.

Hard X-rays

Soft X-rays

Cyclotron

-WD accretes until thick degenerate envelope leads to TNR

-10-6 to 10-4 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 onthe average density. P 1/2 [P=(4π/3G)1/2]Low density long P, high amplitudeHigh 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, Mv = 0.5, P<1 day

Radial pulsators

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

• 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 axisk determines the number of times the pulsation wiggles from the center to the surface

Two flavors of ZZ Ceti stars (DAVs)

Teff = 11000K P ~ 1000s

Teff = 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 ~ 107K, 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 binarySNII 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 - erraticSymbiotic: 3mag (erratic)XRB: HMXRB, LMXRB-ray BurstersRS CVn: F,G+KIV, spots

Pulsating: short P long P oddCepheids: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, 1-5magS-R: K, M

ß Ceph: B, 0.5dZZ Ceti: WD, min

SupernovaeMorford,OrtezChadney/FowlerKongCampionSmith

X-ray BinariesStevensMarkertSlinkerSheetsGreenBelleciVosTimpe

CVsJenningsFilbrandtMagnuson

PulsatorsMayorgaHua

FlaresEvans

OthersDraperJewellHansen