Peculiar Helium Nova V445 Puppis

Vitaly Goranskij, Sternberg Astronomical Institute, Moscow University, Russia

also participated or presented their observations

Peter Kroll, Sonneberg Observatory, GermanyElena Barsukova, Special Astrophysical Observatory,

Russian Academy of SciencesAlon Retter, Tel Aviv, Israel

Albert Jones, Nelson, New Zealand

We used also VSNET observations

as event of merging of white dwarf with a nucleus of an evolved star

Light curves of V445 Pup

Sonneberg & Moscow eye estimates

Takamizawa, VSNET

The outburst in 2000

Pre- and post-outburst observations in the B band

R band light curves in outburst and later

Last measured remnant’s magnitudes:

B = 20.5 +/- 0.2V= 19.5 +/- 0.1Rc = 19.1 +/-0.2Ic = 20.1 +/-0.2

E(B-V) = 0.51

Spectra of V445 Pup in the outburstIijima & Nakanishi, AsAp V482, 865, 2008

Hydrogen lines are absent in the spectrum

Sonneberg and Moscow photographic photometry of the precursor of V445 Pup

The precursor is evidently variable

*Heliocentric Julian dates are given without first two digits 24…

Photographic plates were digitized with a scanner or a digital camera. Digitized images were reduced using 16 comparison stars, and characteristic curves were approximated with a quadratic or cubic expression. Error bars are RMS of approximation.

Periodogram analysis of the light curve

Phase dispersion minimization method by Lafler & Kinman (1965)

Discrete Fourier transform by Deeming (1975)

Spectrum of window

The precursor of V445 Pup is a periodic variable, and a binary system

There are many aliases due to short duration visibility at night (the star has low declination).

Light curves extracted with PDM method

*Heliocentric Julian dates are given without first two digits 24…

Light curves extracted with Discrete Fourier Transform method

This period is one of two extracted by PDM method

These sets of day aliases have reverse (mirror) phase localization

B band light curves

Periodic light variation of V445 Pup progenitor

Contains some contradicted points.

Does not like the light variation of the hot spot of an inclined accretion disk.

Resembles a reflection effect on the surface of a donor star in the low-mass X-ray binaries, but no signs of burning on the surface of WD were seen before the outburst. And the outburst was beginning of such a burning.

Possible common envelope evolved binary with a WD inside before the outburst. Non uniform surface brightness of common envelope.

Additional facts

Dust formation after outburst (Lynch et al., 2001; Ashok and Banerjee, 2003).

Dust emission disappeared in 2005 November (Lynch et al., 2005).

Blue colors in the optical bands and I band excess absence in 2008.

The remnant is now 300 times fainter than progenitor in B band.

Evidently, donor was an evolved star.

And it was accreted on the massive white dwarf in the merging event. This caused a helium flash on the surface of the dwarf which destroyed the common envelope and probably the donor remnant itself. We do not see it in the light curve.

CONCLUSION