Constraints on progenitors of Classical Novae in M31

1. Constraints on progenitors of Classical Novae in M31 Ákos Bogdán & Marat Gilfanov MPA, Garching 17th European White Dwarf Workshop 18/08/2010

2. Classical Novae in a nutshell • Thermonuclear runaway on the surface of white dwarfs • WD accretes material in close binary system • If critical mass (ΔM~10-5 Msun) accreted Nova • Increase in brightness: 6-19 mag 17th European White Dwarf Workshop Ákos Bogdán

3. Idea • Goal: constrain the nature of CN progenitors • Method: • - accretion of hydrogen-rich material releases energy • - if radiated at X-ray wavelengths contributes to total X-ray emission • - confront predicted X-ray luminosity with observations • Where: bulge of M31 • - well observed in X-rays (Chandra) • - CNe are well studied: ν=25 yr-1(Shafter & Irby 2001) 17th European White Dwarf Workshop Ákos Bogdán

4. Energy release from CN progenitors Energy release from one system Consider a white dwarf MWD=1Msun RWD=5000 km ΔM=5∙10-5 Msun (Yaron et al. 2005) ΔEaccr~3∙1046 erg Mdot=10-9 Msun/yr Δt =5∙104 yr Lbol~2∙1034 erg/s 17th European White Dwarf Workshop Ákos Bogdán

5. Energy release from CN progenitors Energy release from all progenitors NWD=(ΔM/Mdot)∙νCN ~ 105-106 Total number of progenitors: Total bolometric luminosity of progenitors: Comparable to total X-ray luminosity of the bulge of M31! 17th European White Dwarf Workshop Ákos Bogdán

6. Energy release from CN progenitors Spectrum of electromagnetic radiation depends on the type of the progenitor • Hard X-rays are released from: • Magnetic systems: • - polars, intermediate polars • - aim: constrain their contribution to the CN rate • Dwarf novae in quiescence: • - aim: constrain the fraction of mass accreted in quiescence 17th European White Dwarf Workshop Ákos Bogdán

7. The bulge of M31 in X-rays • Resolved sources • Low mass X-ray binaries • SN remnants, supersoft X-ray sources • L= 1035-1039 erg/s X-ray Optical Infrared • Unresolved emission • Multitude of faint discrete sources • Coronally active binaries • Cataclysmic variables • LCV,2-10keV=5.7∙1037 erg/s • Truly diffuse emission from hot gas 17th European White Dwarf Workshop Ákos Bogdán

8. Magnetic Cataclysmic Variables What fraction of CNe is prduced in mCVs? • Optically thin bremsstrahlung emission • kT ~ 23 keV  absorption correction insignificant (Landi et al. 2009, Brunschweiger et al. 2009) • Study the 2-10 keV energy range • Bolometric correction ~3.5 17th European White Dwarf Workshop Ákos Bogdán

9. Magnetic Cataclysmic Variables Upper limit on contribution of mCVs No more than ~10% of CNe are produced in mCV Bogdán & Gilfanov 2010 • Upper limit depends on MWD and Mdot • ≈85% of WDs are less massive than 0.85 Msun • Typical Mdot ≈ 2∙10-9 Msun/yr (Suleimanov et al. 2005) Realistic upper limit: ~2% 17th European White Dwarf Workshop Ákos Bogdán

10. Magnetic Cataclysmic Variables • But: in apparent contradiction with our results: • Aracujo-Betancor et al. (2005): Fraction of magnetic WDs in the Solar neighborhood is ≈1/5 • Ritter & Kolb catalogue (2009): ≈1/3 of CNe arise from mCVs Resolution: accretion rate in mCVs is much lower! In magnetic CVs: Mdot ~ 1.8∙10-9 Msun/yr (Suleimanov et al. 2005) In non-magnetic CVs: Mdot ~ 1.3∙10-8 Msun/yr(Puebla et al. 2007) 17th European White Dwarf Workshop Ákos Bogdán

11. Magnetic Cataclysmic Variables • Aracujo-Betancor (2005): Fraction of magnetic WDs in the Solar neighborhood is ≈1/5 Lower Mdot in mCVs Accretion of the same ΔM takes ~7 times longer in mCVs + If Mdot is smaller, ΔM is larger by factor of ~1.5-2 mCVs undergo CN outburst 10-20 times less frequently 17th European White Dwarf Workshop Ákos Bogdán

12. Magnetic Cataclysmic Variables • Ritter & Kolb catalogue (2009): ≈1/3 of CNe arise from mCVs Lower Mdot in mCVs Distance distribution of CNe in Milky Way Brighter CNe (Yaron 2005) CNe from mCVs can be observed from larger distance dCV≈2.2 kpc dmCV≈6.6 kpc 17th European White Dwarf Workshop Ákos Bogdán

13. Dwarf Novae • DNe show frequent outbursts due to thermal viscous disk instability • Bimodal spectral behaviour: • In quiescence: • Low Mdot (<10-10 Msun/yr) • Hard X-ray emission from optically-thin boundary layer • In outburst: • High Mdot (>10-10 Msun/yr) • UV and soft X-ray emission from optically-thick boundary layer In quiescence we observe hard X-rays In outburst soft emission is hidden 17th European White Dwarf Workshop Ákos Bogdán

14. Dwarf Novae What fraction of material is accreted in quiescence? • Assumptions: • ½ of CNe are produced in DNe (Ritter & Kolb 2009) • In quiescence: cooling flow model with kT=23 keV (Pandel et al. 2005) • Study the 2-10 keV energy range 17th European White Dwarf Workshop Ákos Bogdán

15. Dwarf Novae Upper limit on mass fraction accreted in quiescence No more than 10% accreted in quiescence Bogdán & Gilfanov 2010 • Upper limit depends on MWD and Mdot • Typical MWD=0.9 Msun • Typical Mdot ≈ 10-8 Msun/yr Realistic upper limit: ~3% 17th European White Dwarf Workshop Ákos Bogdán

16. Summary • No more than ~10% of CNe are produced in magnetic CVs (realistic upper limit ~2%) • No more than ~10% of the material is accreted in quiescence in DNe (realistic upper limit ~3%) • Results hold for other early-type galaxies • For details: Bogdán & Gilfanov, 2010, MNRAS 17th European White Dwarf Workshop Ákos Bogdán