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Basics of Cataclysmic Variables

Basics of Cataclysmic Variables. Paula Szkody U of Washington. iPTF Summer School August 28, 2014. 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]

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Basics of Cataclysmic Variables

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  1. Basics of Cataclysmic Variables Paula Szkody U of Washington iPTF Summer School August 28, 2014

  2. A Cataclysmic Variable : • is a close binary system • has a white dwarf primary • has a cool low mass secondary • actively transfers mass

  3. 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]

  4. MAGNETIC DISKACCRETION ACCRETION . For slowly rotating WD: Ldisk = LBL = 1/2GMMwd/Rwd . . High M Low M 108K X-rays 9000-4000 K BL Hard X-rays Soft X-rays Cyclotron

  5. CV Types Polar Disk System LARP IntermediatePolar Steve Howell

  6. Possible evolution paths common envelope phase Pre-CV Angular momentum losses

  7. Model of CV Population Population models Log number of CVs Howell, Nelson, Rappaport 2001, ApJ, 550 PG, Hamburg Where are detached magnetic WDs + M stars? Magnetic braking . SDSS g radiation

  8. SDSS showed: CVs mostly blue but color range too wide to find objects -- need color + variability + spectra to find true populations

  9. What we learned from SDSS: Need lots of follow-up spectra for ID and properties! CVs in SDSS 2000-2008 Szkody et al. AJ 2002-2011 Papers I-VIII

  10. Summary of Variability and timescales for Interacting Binaries

  11. Science from DN Outbursts • Long term heating of WD • Mass accreted • Irradiation of secondary • Disk heating and cooling

  12. Dwarf novae Repeated disk instability AAVSO outbursts of SS Cygni . Long Porb, High M, outburst ~1/month

  13. Z Cam system standstills

  14. July 23 . Short Porb, Low M outburst ~ 1/20 yrs

  15. GW Lib 2007outburst: amp ~ 9 mag AAVSO data plotted by Matt Templeton Apr12 07 27 days Return to quiescence at V=17 > 4 yrs

  16. ER UMA Type Supercycles V1159 Ori

  17. Superhumps at SOB ApJ, 1984, 282, 236

  18. Positive SH NOFS P= 1.9 hr MRO MRO Tramposch et al. 2005, PASP 117, 262 Negative SH

  19. outburst rise quiescence

  20. Novalike systems with periods of 3-4 hrs Low states Honeycutt & Kafka, 2004, AJ, 128, 1279

  21. Totally Unknown: Long term variability Honeycutt, Turner & Adams 2003 Roboscope

  22. 2 like this now known SDSS1238: Phot P: 40.25 min Spect P: 80.5 min Long P: 8-12 hrs

  23. 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)

  24. Hot spot P=2.4hr NOFS P=3.96hr Eclipsing systems- WD goes behind M star

  25. Eclipse of accretion column by M star Polar USNO

  26. SDSS1344+20 KPNO 2.1m 2011

  27. PTF candidate magnetics (Margon, Levitan,Prince, Hallinan 2013 ASPCS)

  28. B=30 MG Theta= 90 deg Wickramasinghe & Ferrario 2000, PASP higher opt depth

  29. MQ Dra 7/9 LARPs found in SDSS TiO B ~ 60 MG T < 1keV cyclotron harmonics . M~10-14M /yr P=4.4 hrs D=100pc 4 3 Szkody et al. ApJ, 583, 902, 2003 WD Temp = 5000-8000K

  30. Typical LARP B=60 MG, Mdot = 10-14 solar mass/yr ApJ, 683, 967, 2008

  31. Finding LARPs is not easy - Cyclotron harmonics result in strange colors

  32. Low Accretion Rate Polars as a function of magnetic field Schmidt et al. 2005, ApJ, 630, 1037

  33. Science from Pulsations, Spins Pulsations • 16 White Dwarfs in Instability Strip • Periods about 2-20 min • Amplitudes < 0.1 mag • Gives info about WD interior Spins • Magnetic White Dwarfs • Periods 10 - 60 min (IP), hrs (polars) • Amplitudes 0.01-0.5 mag • Gives info on magnetic field

  34. 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

  35. SDSS finds 9/16 accreting pulsators Light curves & DFTs of accreting pulsator SDSS0745+45 Mukadam et al. 2007 AJ

  36. pulse SH

  37. Spin from Intermediate Polar FO Aqr Patterson et al. 1998 PASP Pspin= 21 min

  38. Science from Flickering • Signature of active accretion (blobs?) • Timescales of sec (Polars) • Timescales of min (disk) • Origin from spot, column or inner disk

  39. Flickering Examples Recurrent nova (Dobratka et al. 2010) Novalike LS Peg

  40. 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

  41. Examples from CSS

  42. ~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

  43. Observe and enjoy the unpredictability of CVs! szkody@astro.washington.edu

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