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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

slide2

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

slide3

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

slide4

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

slide5

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

slide6

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

slide7

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

slide8

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

slide9

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

slide10

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

slide11

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

slide12

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

slide13

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

slide14

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

slide15

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

slide16

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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