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. Unstable He shell flash
Helium nova predicted 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 > 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, 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. The Nova Model WD + He envelope WD He Model parameter
optically thick wind
acceleration:
deep inside the photosphere
WD + He envelope
free-free
emission
Model parameter
WD mass : Mo
radius of the burning zone
chemical composition :
　　Y= , C+O=
　　Z=0.02 WD He

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

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

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 PupIc
Vis
MWD > 1.35 Mo
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 kpc %
1.35 Mo kpc %
1.37 Mo kpc %
1.377 Mo kpc %
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
Webbink et al. (1987)
1.37 Mo, i =70
accretion rate Mv mv (3kpc) 　 mv(6kpc)
3.E-8 Mo/yr
1.E-7 Mo/yr
3.E-7 Mo/yr

16. He star evolution by Saio 1995
Helium star companion
mv=14.5, Av=1.8, D=6kpc
 Mv = -1.5
1450 Lo Tph 20,000 K
4000 Lo ,000 K
11000 Lo ,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