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

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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

Energy release from all progenitors

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NWD=(ΔM/Mdot)∙νCN ~ 105-106

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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

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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

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Magnetic Cataclysmic Variables

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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

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

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Dwarf Novae

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In quiescence we observe hard X-raysIn outburst soft emission is hidden

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Dwarf Novae

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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

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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

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Summary

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