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Constraints on progenitors of Classical Novae in M31 Ákos Bogdán & Marat Gilfanov MPA, Garching 17 th European White Dwarf Workshop 18/08/2010
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Thermonuclear runaway on the surface of white dwarfs WD accretes material in close binary system If critical mass (ΔM~10 -5 M sun ) accreted Nova Increase in brightness: 6-19 mag Classical Novae in a nutshell Ákos Bogdán 17 th European White Dwarf Workshop
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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) Idea Ákos Bogdán 17 th European White Dwarf Workshop
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Energy release from one system Energy release from CN progenitors Ákos Bogdán 17 th European White Dwarf Workshop M WD =1M sun R WD =5000 km ΔM=5∙10 -5 M sun (Yaron et al. 2005) ΔE accr ~3∙10 46 erg Mdot=10 -9 M sun /yr Δt =5∙10 4 yr L bol ~2∙10 34 erg/s Consider a white dwarf
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Energy release from all progenitors Ákos Bogdán N WD =(ΔM/Mdot)∙ν CN ~ 10 5 -10 6 17 th European White Dwarf Workshop Total number of progenitors: Total bolometric luminosity of progenitors: Comparable to total X- ray luminosity of the bulge of M31! Energy release from CN progenitors
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Spectrum of electromagnetic radiation depends on the type of the progenitor Ákos Bogdán 17 th European White Dwarf Workshop 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 Energy release from CN progenitors
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The bulge of M31 in X-rays Resolved sources Low mass X-ray binaries SN remnants, supersoft X-ray sources L= 10 35 -10 39 erg/s Unresolved emission Multitude of faint discrete sources - Coronally active binaries - Cataclysmic variables L CV,2-10keV =5.7∙10 37 erg/s Truly diffuse emission from hot gas Ákos Bogdán X-ray Optical Infrared 17 th European White Dwarf Workshop
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Ákos Bogdán 17 th European White Dwarf Workshop 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
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Ákos Bogdán 17 th European White Dwarf Workshop No more than ~10% of CNe are produced in mCV Upper limit depends on M WD and Mdot ≈ 85% of WDs are less massive than 0.85 M sun Typical Mdot ≈ 2∙10 -9 M sun /yr (Suleimanov et al. 2005) Realistic upper limit: ~2% Bogdán & Gilfanov 2010 Upper limit on contribution of mCVs Magnetic Cataclysmic Variables
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But: in apparent contradiction with our results: 1. 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 Ákos Bogdán 17 th European White Dwarf Workshop Resolution: accretion rate in mCVs is much lower! In magnetic CVs: Mdot ~ 1.8∙10 -9 M sun /yr (Suleimanov et al. 2005) In non-magnetic CVs: Mdot ~ 1.3∙10 -8 M sun /yr (Puebla et al. 2007) Magnetic Cataclysmic Variables
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Ákos Bogdán 1.Aracujo-Betancor (2005): Fraction of magnetic WDs in the Solar neighborhood is ≈1/5 Accretion of the same ΔM takes ~7 times longer in mCVs Lower Mdot in mCVs + If Mdot is smaller, ΔM is larger by factor of ~1.5-2 mCVs undergo CN outburst 10-20 times less frequently 17 th European White Dwarf Workshop Magnetic Cataclysmic Variables
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Ákos Bogdán 2. Ritter & Kolb catalogue (2009): ≈1/3 of CNe arise from mCVs Brighter CNe (Yaron 2005) CNe from mCVs can be observed from larger distance Lower Mdot in mCVs Magnetic Cataclysmic Variables d CV ≈2.2 kpc d mCV ≈6.6 kpc 17 th European White Dwarf Workshop Distance distribution of CNe in Milky Way
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DNe show frequent outbursts due to thermal viscous disk instability Bimodal spectral behaviour: In quiescence: Low Mdot (<10 -10 M sun /yr) Hard X-ray emission from optically-thin boundary layer In outburst: High Mdot (>10 -10 M sun /yr) UV and soft X-ray emission from optically-thick boundary layer Ákos Bogdán Dwarf Novae 17 th European White Dwarf Workshop In quiescence we observe hard X-rays In outburst soft emission is hidden
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Ákos Bogdán Dwarf Novae 17 th European White Dwarf Workshop 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
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Ákos Bogdán No more than 10% accreted in quiescence Upper limit depends on M WD and Mdot Typical M WD =0.9 M sun Typical Mdot ≈ 10 -8 M sun /yr Realistic upper limit: ~3% Bogdán & Gilfanov 2010 Upper limit on mass fraction accreted in quiescence 17 th European White Dwarf Workshop Dwarf Novae
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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 Bogdán & Gilfanov, 2010, MNRAS For details: Bogdán & Gilfanov, 2010, MNRAS Ákos Bogdán Summary 17 th European White Dwarf Workshop
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