Cataclysmic variables as hard X-ray emitters seen by INTEGRAL
Basics of Cataclysmic Variables
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Transcript of Basics of Cataclysmic Variables
Basics of Cataclysmic Variables
iPTF Summer School August 28, 2014
Paula Szkody U of Washington
A Cataclysmic Variable :
• is a close binary system
• has a white dwarf primary
• has a cool low mass secondary
• actively transfers mass
Types of cataclysmic variables:
• [Nova]
• Dwarf nova (U Gem, Z Cam, SU UMa, WZ Sge, ER UMa)
• Novalike (UX UMa, SW Sex, V Sge, Polar, IP)
• AM CVn
• [Type Ia SN, Symbiotic star]
DISK ACCRETION MAGNETIC
High M Low M
. .
X-rays
108 K
9000-4000 K
ACCRETION
BL
For slowly rotating WD:
Ldisk = LBL = 1/2GMMwd/Rwd
.
Hard X-rays
Soft X-rays
Cyclotron
Disk System Polar
Intermediate Polar
LARP
CV Types
Steve HowellSteve Howell
common envelope
Possible evolution paths
phase
Angular momentum losses
Pre-CV
Model of CV PopulationHowell, Nelson, Rappaport 2001, ApJ, 550
Log number of CVs
Population models
PG, Hamburg
SDSS.
Magnetic braking
g radiation
Where are detached magnetic WDs + M stars?
CVs mostly blue but color range too wide to find objects -- need color + variability + spectra to find true populations
SDSS showedSDSS showed::
CVs in SDSS
2000-2008
Szkody et al. AJ
2002-2011
Papers I-VIII
Need lots of follow-up spectra for ID and properties!
What we learned from SDSS:
Summary of Variability and timescales for Interacting Binaries
Science from DN Outbursts
• Long term heating of WD
• Mass accreted
• Irradiation of secondary
• Disk heating and cooling
AAVSO
outbursts of SS Cygni
Dwarf novaeRepeated disk instabilityRepeated disk instability
.
Z Cam system
standstills
July 23
Short Porb, Low M Short Porb, Low M outburst ~ 1/20 yrsoutburst ~ 1/20 yrs
..
AAVSO data plotted by Matt Templeton
Apr12 07
GW Lib 2007outburst: amp ~ 9 mag
27 days
Return to quiescence at V=17 > 4 yrs
V1159 Ori
ER UMA Type Supercycles
Superhumps at SOB
ApJ, 1984, 282, 236
MRO MRO
NOFS
Tramposch et al. 2005, PASP 117, 262
P= 1.9 hr
Positive SH
Negative SH
quiescence
outburst
rise
Novalike systems with periods of 3-4 hrs
Honeycutt & Kafka, 2004, AJ, 128, 1279
Low states
Honeycutt, Turner
& Adams 2003
Roboscope
Totally Unknown: Long term variability
2 like this now known
SDSS1238:Phot P:40.25 min
Spect P:80.5 min
Long P: 8-12 hrs
Science from Orbital variations• Eclipsing systems enable photometric model
• Can detect eclipse of disk, hot spot, WD
• Can parameterize accretion area in magnetic systems
• Porb (1.2-10 hrs) allows population, evolution study
Requires high time resolution (eclipses <15 min)
~30% of disk systems show orbital variations (spot);
100% of polars (amplitudes of 0.1-4 mags)
NOFS P=3.96hr
Eclipsing systems- WD goes behind M star
P=2.4hr
Hot spot
USNO
Eclipse of accretion column by M star Polar
SDSS1344+20 KPNO 2.1m 2011
PTF candidate magnetics (Margon, Levitan,Prince, Hallinan 2013 ASPCS)
Wickramasinghe & Ferrario 2000, PASP
B=30 MG
Theta= 90 deg
higher opt depth
TiO
cyclotron harmonics
Szkody et al. ApJ, 583, 902, 2003
WD Temp = 5000-8000K
7/9 LARPs found in SDSS
B ~ 60 MG
T < 1keV
M~10-14M /yr
P=4.4 hrs
D=100pc
.
34
MQ Dra
Typical LARP B=60 MG, Mdot = 10-14 solar mass/yrApJ, 683, 967, 2008
Cyclotron harmonics result in strange colors
Finding LARPs is not easy -
Low Accretion Rate Polars as a function of magnetic field
Schmidt et al. 2005, ApJ, 630, 1037
Science from Pulsations, Spins
• 16 White Dwarfs in Instability Strip• Periods about 2-20 min• Amplitudes < 0.1 mag• Gives info about WD interior
Pulsations
Spins• Magnetic White Dwarfs • Periods 10 - 60 min (IP), hrs (polars)• Amplitudes 0.01-0.5 mag• Gives info on magnetic field
• 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
Light curves & DFTs of accreting pulsator SDSS0745+45
SDSS finds 9/16 accreting pulsators
Mukadam et al. 2007 AJ
SH
pulse
FO Aqr Patterson et al. 1998 PASP Pspin= 21 min
Spin from Intermediate Polar
Science from Flickering
• Signature of active accretion (blobs?)
• Timescales of sec (Polars)
• Timescales of min (disk)
• Origin from spot, column or inner disk
Novalike LS PegNovalike LS Peg
Recurrent nova Recurrent nova (Dobratka et al. 2010)(Dobratka et al. 2010)
Flickering Examples
What we learn from CV variability : • flickering - info on accreting blobs
• pulsations - info on interior of WD, instability strip for accretors
• spin timescale of WD - info on mag field
• orbital variations - info on WD, spot, evolution
• outbursts - info on long term heating
Examples from CSS
~1000 potential CVs in CRTS(Drake et al.; Breedt et al. 2014 MNRAS)
• Only ~200 confirmed by spectra
• Most are short P (low M transfer)
• Most are dwarf novae
• Most in thick disk
unpredictability of CVs!Observe and enjoy the