Creating a Legacy of High QualityCreating a Legacy of High QualityCOS Far Ultraviolet Spectra of COS Far Ultraviolet Spectra of

Cataclysmic Variable Stars Cataclysmic Variable Stars

Edward M. SionEdward M. SionDepartment of Astronomy and Astrophysics Department of Astronomy and Astrophysics

Villanova UniversityVillanova University

Collaborators

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• Orbital angular momentum loss drives mass transfer rate onto the WD via gravitational wave emission and magnetic stellar wind braking.

• WD temperature is linked to long term compressional heating and hence the time-averaged rate of accretion onto the WD (Sion 1995, Townsley and Bildsten 2003).

• CVs as potential Type Ia SN progenitors via the single degenerate model; Accretion onto the WD leads to Chandrasekhar Limit Mass.

• Do the masses of WDs in CVs increase or decrease with time?

• Thermal timescale mass transfer systems (e.g. supersoft X-ray Binaries) are the stable H-burning progenitors of the CVs with CNO-processed chemical Abundances but their WDs did not reach the Chandrasekhar Limit; hence they are “Failed” Type Ia SN.

Overview

Far Ultraviolet SpectraFar Ultraviolet Spectra

IUE ArchivalIUE Archival

HST FOS, GHRS, STIS, COSHST FOS, GHRS, STIS, COS

FUSEFUSE

EUVEEUVE

Synthetic Spectra Synthetic Spectra

High Gravity LTE and NLTE Model High Gravity LTE and NLTE Model Atmospheres (TLUSTY200, SYNSPEC98)Atmospheres (TLUSTY200, SYNSPEC98)

Optically Thick, Steady State, Accretion Optically Thick, Steady State, Accretion Disk Models (TLUSDISK200)Disk Models (TLUSDISK200)

Accretion Belt ModelsAccretion Belt Models

Accretion RingsAccretion Rings

Accretion Curtain ModelsAccretion Curtain Models

Figure 6

Sion, E. M. et al. (2008), ApJ, 681, 543

SS AurSS Aur Godon, P. et al. (2008), ApJ, in press

Figure 1

Sion, E.M. et al. (2008), ApJ, 681, 543

Object Mass(Msun ) Type Method

U Gem 1.12 Dwarf Nova S

IP Peg 1.09 Dwarf Nova S

SDSS1035+05 0.94 Dwarf Nova E

SDSS1702+32 0.94 Dwarf Nova E

V1500 Cyg >0.9 Dwarf Nova S

OU Vir 0.89 Dwarf Nova E

AM Her 0.88 Polar S

WZ Sge 0.85 Dwarf Nova S

SDSS0926+36 0.84 AM CVn E

GY Cnc 0.82 Dwarf Nova S

QS Vir 0.78 Dwarf Nova S

ST LMi 0.76 Polar S

EX Dra 0.75 Dwarf Nova E

MR Ser 0.71 Polar S

QQ Vul 0.70 Polar S

OY Car 0.69 Dwarf Nova E

HT Cas 0.61 Novalike E

DQ Her 0.60 Nova S

Z Cha 0.54 Dwarf Nova E

Sion, E. and Szkody, P. 2012, White Dwarfs in CVs, in press

Object Type Porb Teff

GW Lib DN 76.8 14,700

BW Scl DN 78.2 14,800

LL And DN 79.2 14,300

HS2331 DN 81 10,500

SDSS1610 DN 81 14,500

WZ Sge DN 81.6 14,900

AL Com DN 81.6 16,300

SW UMa DN 81.8 13,900

SDSS1339 DN 82.5 12,500

HV Vir DN 83.5 13,300

WX Cet DN 83.9 14,500

T Leo DN 84.7 16,000

EG Cnc DN 86.4 13,300

BC UMa DN 90.2 15,200

VY Aqr DN 90.8 14,000

EK Tra DN 91.6 18,800

SDSS0131 DN 98 14,500

VW Hyi DN 106.9 22,000

CU Vel DN 113.0 18,500

Object Type Porb Teff

EF Peg DN 123 16,600

MV Lyr NL 191.0 47,000

DW UMa NL 198.0 46,000

TT Ari NL 198.0 39,000

UU Aql DN 235.5 27,000

WW Ceti DN 253 26,000

U Gem DN 254.7 31,000

SS Aur DN 263.2 31,000

RX And DN 302.2 34,000

Z Cam DN 417.4 57,000

RU Peg DN 539.4 70,000

CH UMa DN 0.343d 40,000

BV Cen DN 878.6 40,000

SDSS2205 DN 15,000

V794 Aql NL >47,000

V895 Cen Polar 285.9 13,800

V1043 Cen Polar 251.4 15,000

EF Eri Polar 81.0 9,500

HU Aqr Polar 125.0 14,000

RXJ0232-3718

CONCLUSION

• GAIA will be launched next year, and will deliver HST/FGS-like parallaxes for practically all known CVs, turning fluxes and magnitudes into luminosities and accretion rate.

• SDSS and Other Ground-based surveys provide a deep, homogeneous population of CVs.

• HST/COS is the best facility that has ever been available. STIS Snapshot was limited by S/N and spectral resolution.

• Quadruple the number of WD masses; ~ 50 rotation rates, Vsini; double the number of reliable surface temperatures (~ 50), double the number of CV WDs with photospheric abundances.

• Increase the number of Post-TTMT Systems by a factor of 2 – 3. What is their Period distribution?

The overall result of our Large GO will be a ‘Transformational Knowledge’ of compact binary evolution and accretion physics