Modeling the Light Curve of V445 Puppis: Helium Nova on a Massiv

e White Dwarfs

Mariko KATO (Keio Univ., Japan)

collaboration withI. Hachisu (Univ. of Tokyo)S. Kiyota (VSOLJ)

Helium nova

predicted by Kato, Saio, & Hachisu (1989)

if WD accretes He

WD accretes H (H → He)

　Unstable He shell flash

He nova

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

.

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previous work: light curve analysis

Blackbody emission MWD > 1.33 Mo small distance < 1 kpc

for Av=0.78 Short recurrence period

< 100 yr

Kato & Hachisu (2003)

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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

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Optically Thick Wind Theory acceleration: deep inside the photosphere quasi-evolution: steady-state Solve equation of motion, continuity, diff

usion, energy conservation Evolution: sequence of steady-state solu

tions

Accurate Mass-loss rate, Tph etc.

Kato & Hachisu (1994) ApJ,437,802

The unique method to calculate nova light curve

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The Nova Model

WD

He

WD + He envelope

optically thick windacceleration: deep inside the photosphere

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

free-freeemission

Free-free emission of optically thin ejecta

Free-free emission

If Te and ionization degree are constant,

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Theoretical light curve

-- Free-free

-- Blackbody

HR diagram

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Free-free light curve ; a universal decline law of CN

Hachisu & Kato (2006) ApJS 167,59

V1500 Cyg

V1668 Cyg

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V1974 Cyg

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Light curve fitting of V445 Pup

MWD > 1.35 Mo

Dust formation

Ic

Vis

Best Fitted models : V445 Pup

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 %

Z=0.02, Y=1-C-O-Z

Candidate of type Ia supernova progenitor

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Preoutburst phaseNo 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

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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)

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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

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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 s

ec) Fe abundance: old disk population