constraints on progenitors of classical novae in m31 Ákos bogdán & marat gilfanov mpa,...
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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
• 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
• 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
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
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
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
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
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
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
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
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
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
17th European White Dwarf Workshop
Distance distribution of CNe in Milky Way
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
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
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
• 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
17th European White Dwarf Workshop
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