As the “V” in the designation of V445 Puppis indicates, this star was a variable star located in the constellation of Puppis. It was a fairly ordinary periodic variable, although with a rather complex light curve, but still showing a distinct periodicity of about fifteen and a half hours. It wasn’t especially bright, yet something seemed to tug at my memory regarding the star’s name as I scanned through articles to write on. Just over a year ago, Nancy wrote a post on V445 Puppis stating it’s a supernova just waiting to happen. A new article challenges this claim.
In December of 2000, V445 Puppis underwent an unusual nova. It was first noticed on December 30th, but archival records showed the eruption began in early November of that year and reached a peak brightness on November 29th. The system was known to be a binary star system with a shared envelope in which the primary star was a white dwarf and thus, a nova was the most readily available explanation.
However, this wasn’t a normal nova. Spectroscopic observations early the next year showed the ejecta lacked the helium emission seen in classical novae in which hydrogen piles up on a white dwarf surface until it undergoes fusion into helium. Instead, astronomers saw lines of iron, calcium, carbon, sodium, and oxygen expanding at nearly 1,000 km/sec. This fit better with a proposed type of explosion where, instead of hydrogen collecting on the dwarf’s surface, it was helium and the eruption seen was a helium flash in which it was helium that underwent fusion. Slowly the star faded, and debris from the eruption cooled to form dust. Today, the star itself is completely obscured in the visible portion of the spectrum.
The 2009 paper by Woudt, Steeghs, and Karowska that Nancy cited, suggested accretion might continue until the white dwarf passed the Chandrasekhar limit and exploded as a type Ia supernova. However, the authors of the new paper, led by V. P. Goranskij at Moscow University, say that this 2000 detonation has effectively ruled out that possibility because an explosion of that magnitude would likely destroy the envelope of the donor star. Their evidence for this is the very same structure Woudt noted in his paper (shown above).
While the structure looks to be bipolar in nature, other observations have suggested that there is an additional component along the line of sight and that the structure is more of a doughnut shape. In this case, the total amount of material lost is higher than originally anticipated and must have come from from the envelope of the companion star. Additionally, observations in wavelengths able to pierce the dust have been unable to resolve a strong stellar source which suggests that the donor star’s envelope has been largely blown away as well. Additionally, this large and rapid loss of mass from the system may have broken the gravitational bond between the two stars and allowed the giant star to be ejected from the system, which would also preclude the possibility of a supernova in the future.
The conclusion is that V445 Puppis is not a candidate for a supernova of any type in the future. It’s own premature fireworks have likely destroyed whatever chance it may have had for an even grander show in the future.
Fascinating ! They have witnessed the birth of a Planetary Nebula, perhaps from a star or stellar object binary. Too bad they don’t understand this fact ! (I guess they can only see what they are looking for.)
Researching older photos and data of the variable phenomena may lead to understanding how the variability led to the mirror-image biconical cone structures forming. Good luck guys !
That is actually unfortunate. A close up of a SNIa would be good on a number of fronts.
LC
Looks like a classic bipolar jet and accretion disk to these eyes. Doughnut shaped?
V445 Puppis are among th so-called pre-Asymptotic Giant Branch (pre-AGB) stars, approximately between 5M≻ and 11M⊙s.
These common kind of objects are generally describe as Bipolar Planetary Nebulae. It is presumed that the gaseous shells surrounds will only feature prominently in particular areas, which in turn, become formed shapes of unusual structures of the nebula shell. They can sometimes be either asymmetric, symmetric or mirrored. Uncertain mechanisms still exist for these strange structures, but many theorists now suspect these phenomena are strongly influenced by either the activity on the star, fast stellar rotation, and display other secondary effects such as magnetic fields, or being associated as close binary systems.
In evolutionary terms, these observed structures are related to the initial conditions of envelope ejection by the more or less pedestrian stellar winds. They are influenced, among many other other reasons, to magnetic fields, stellar rotation, binaries, etc. Consequently this theory means that all expelled gas tends to flow in preferential directions; mostly along the poles, perpendicular to the rotational axis of motion. Although this may seem very complicated superficially it is fundamentally simple. This produces the observed pipe-like effect.
Simplistically, if the surrounding nebula originates as some spherical, evenly spaced symmetrical bubble, then the evolutionary process for the nebulosity can be basically just be expressed as an increasing ballooning bubble expanding at the rate of the expansion velocity of the shell. As the bubble enlarges in time, the material of the shell joined with the expanding shock front, increasing in size but reducing the mean shell thickness.
Furthermore, the expelled shell from the central star now favours certain directions and differences in thickness, producing some maxima along the equatorial axis and another minima at both opposing poles. As the energetic charged particles strike the expanding three-dimensional circumstellar shell(s), the irregularities of the internal pressure combined with the dispersal of the matter from the AGB phase, cause significant polar thinning. In stages, the shell stays intact, but as it enlarges, the polar regions of the envelope simultaneously weaken, then tear it apart.
Suddenly the once restricted internal winds break through doing so first at each pole, tearing a small hole of the shell’s membrane. In these cases, the visual consequences on the observed shell are astonishing. The simple bubble structure metamorphoses into these far more complex objects. Then, and quickly, the impeded outflow of the inner shell is freed. Travelling at about 1,000 km.s^-1, with temperatures of 10^7 K to 10^9 K, the highly ionised gases suddenly escapes to produce ferocious hypersonic winds. These winds will ultimately destroy the neat spherical symmetry of the bubble, forming the familiar generalised bipolar shape.
Slowly at first, the edges of the broken shell are pushed aside, then stretched into hollow shapes similar to wine glasses with its open opposing holes at either end. This evolves further to look more like drawn champagne flutes or pipes.
An overall generalised scenario is dependant on the properties of the PNN which will play far more significant role in determining the shape and evolution of the luminous shell(s). I.e. Mass, rotation, magnetic field strength, the central star’s UV-energy output, composition of the gases in the denser nebulous atmosphere, (super)wind strengths, etc.
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Really. This object from the very start was unlikely to go supernova. I.e the star explodes before it gets to the AGB and age into a red giant. Also the white dwarf also has a dense atmosphere, and this is likely the cause of the phenomena.