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Modeling the Light Curve of V445 Puppis: Helium Nova on a Massive White Dwarfs

Modeling the Light Curve of V445 Puppis: Helium Nova on a Massive White Dwarfs. Mariko KATO (Keio Univ., Japan) collaboration with I. Hachisu (Univ. of Tokyo) S. Kiyota (VSOLJ).

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Modeling the Light Curve of V445 Puppis: Helium Nova on a Massive White Dwarfs

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  1. Modeling the Light Curve of V445 Puppis: Helium Nova on a Massive White Dwarfs Mariko KATO (Keio Univ., Japan) collaboration with I. Hachisu (Univ. of Tokyo) S. Kiyota (VSOLJ)

  2. Helium novapredicted by Kato, Saio, & Hachisu (1989) if WD accretes He WD accretes H (H → He) Unstable He shell flash He nova

  3. V445 Pup (2000) . • no H lines • strong emission C, Na, Fe,Ti, Cr, Si, Mg, etc. • P Cyg profile • resemble classical slow nova => a nova • Iijima (2007) AAp, submitted

  4. previous work: light curve analysis Kato & Hachisu (2003) Blackbody emission • MWD > 1.33 Mo • small distance < 1 kpc for Av=0.78 • Short recurrence period < 100 yr

  5. New observational results Spectrum • Interstellar absorption lines Na I D velocity=16.0, 73.5 km/s  Distance >6.5 kpc • Av=1.8 Iijima & Nakanishi (2007) AAp, submitted Color index free-free emission

  6. Optically Thick Wind Theory acceleration: deep inside the photosphere • quasi-evolution: steady-state • Solve equation of motion, continuity, diffusion, energy conservation • Evolution: sequence of steady-state solutions Accurate Mass-loss rate, Tph etc. Kato & Hachisu (1994) ApJ,437,802 The unique method to calculate nova light curve

  7. optically thick wind acceleration: deep inside the photosphere The Nova Model WD + He envelope He free-free emission • Model parameter • WD mass : 1.35-1.38 Mo • radius of the burning zone • chemical composition : • Y=0.3-0.5, C+O=0.7-0.5 • Z=0.02 WD

  8. Free-free emission of optically thin ejecta Free-free emission If Te and ionization degree are constant,

  9. Theoretical light curve -- Free-free -- Blackbody HR diagram

  10. Free-free light curve ; a universal decline law of CN V1668 Cyg Hachisu & Kato (2006) ApJS 167,59 V1500 Cyg

  11. V1974 Cyg

  12. Light curve fitting of V445 Pup Ic MWD > 1.35 Mo Vis Dust formation

  13. Best Fitted models : V445 Pup Z=0.02, Y=1-C-O-Z WD mass Y C+O Distance accumulation 1.35 Mo 0.98 0.0 4.2-9 kpc 28-35 % 1.35 Mo 0.38 0.6 7.6 kpc 45 % 1.37 Mo 0.38 0.6 4.0-8.7kpc 49-59 % 1.377 Mo 0.38 0.6 2.8 kpc 58 % Candidate of type Ia supernova progenitor

  14. Preoutburst phase No hydrogen → He star companion Before the outburst 2000 ~14.5 mag 　（VSNET) After the outburst no object (V> 19 mag) since dust blackout The binary is still embedded in thick dust

  15. Accretion disk luminosity 1.37 Mo, i =70 accretion rate Mv mv (3kpc) mv(6kpc) 3.E-8 Mo/yr 3.2 17.4 18.9 1.E-7 Mo/yr 2.0 16.6 18.1 3.E-7 Mo/yr 1.2 15.8 17.3 Webbink et al. (1987)

  16. Helium star companion mv=14.5, Av=1.8, D=6kpc  Mv = -1.5 1450 Lo Tph 20,000 K 4000 Lo 30,000 K 11000 Lo 45,000 K • preoutburst brightness: consistent with an evolved He star He star evolution by Saio 1995

  17. For future observation: V445 Pup After the dust envelope diffuses away • Companion star Magnitude & Color → mass • Orbital period • Inclination • WD spin period( e.g. RS Oph, 1.35 Mo,35 sec) • Fe abundance: old disk population

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