Constraints on progenitors of classical novae in m31
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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. Classical Novae in a nutshell. Thermonuclear runaway on the surface of white dwarfs WD accretes material in close binary system

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Constraints on progenitors of classical novae in m31
Constraints on progenitors of Classical Novae in M31

Ákos Bogdán & Marat Gilfanov

MPA, Garching

17th European White Dwarf Workshop

18/08/2010


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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