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Constraints on progenitors of Constraints on progenitors of Classical Novae in M31Classical Novae in M31
Ákos Bogdán & Marat Ákos Bogdán & Marat GilfanovGilfanov
MPA, GarchingMPA, Garching
17th 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 Msun) accreted Nova• Increase in brightness: 6-19 mag
Classical Novae in a nutshell
Ákos Bogdán 17th 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 17th European White Dwarf Workshop
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Energy release from one system
Energy release from CN progenitors
Ákos Bogdán 17th European White Dwarf Workshop
MWD=1Msun
RWD=5000 kmΔM=5∙10-5 Msun (Yaron et al.
2005)
ΔEaccr~3∙1046 erg
Mdot=10-9 Msun/yrΔt =5∙104 yr
Lbol~2∙1034 erg/s
Consider a white dwarf
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Energy release from all progenitors
Ákos Bogdán
NWD=(ΔM/Mdot)∙νCN ~ 105-106
17th 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 17th 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= 1035-1039 erg/s
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 Ákos Bogdán
X-rayOptical
Infrared
17th European White Dwarf Workshop
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Ákos Bogdán 17th European White Dwarf Workshop
Magnetic Cataclysmic VariablesWhat 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 17th European White Dwarf Workshop
No more than ~10% of CNe are produced in mCV
• 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%
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
2. Ritter & Kolb catalogue (2009): ≈1/3 of CNe arise from mCVs
Ákos Bogdán 17th European White Dwarf Workshop
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)
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
17th 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
dCV≈2.2 kpcdmCV≈6.6 kpc
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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 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
Ákos Bogdán
Dwarf Novae
17th European White Dwarf Workshop
In quiescence we observe hard X-raysIn outburst soft emission is hidden
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Ákos Bogdán
Dwarf Novae
17th 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 MWD and Mdot• Typical MWD=0.9 Msun
• Typical Mdot ≈ 10-8 Msun/yr
Realistic upper limit: ~3%
Bogdán & Gilfanov 2010
Upper limit on mass fraction accreted in
quiescence
17th 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
• For details: Bogdán & Gilfanov, 2010, MNRAS Bogdán & Gilfanov, 2010, MNRAS
Ákos Bogdán
Summary
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