Evidence found of white dwarf remnant after supernova

August 18, 2017 by Bob Yirka, Phys.org report
Image of the accretion disk: A snapshot of the binary star system before the violent supernova explosion blew it to pieces. Credit: Copyright Russell Kightley

An international team of space scientists has found evidence of what they believe is a remnant of a type Iax supernova—a white dwarf moving in a way that suggests it was blown across part of the universe by the power of a thermonuclear explosion. In their paper published in the journal Science, the team describes their study of the star and why they believe it is the remains of an Iax supernova.

Most scientists agree that supernovae occur when a white dwarf pulls a certain amount of the outer layer from a nearby star until it reaches a tipping point—when that happens, a occurs, obliterating the white dwarf—at least, most of the time. This so-called normal type of supernova is classified as Ia. But some theories suggest that the explosion is sometimes not strong enough to completely obliterate the white dwarf—some of it is left behind and pushed through space at a very high speed due to the energy of the explosion. Such supernovae are labeled Iax, but until now, none had ever actually been observed. In this new effort, the research team describes a white dwarf that appears to have all the markings of a supernova Iax remnant.

The star, called LP 40-365, was actually first spotted back in 2013—it drew attention because it was traveling so fast. The researchers found that the star was spinning faster than expected and that it had a mixed composition, which suggested that it very likely once had a companion star.

The progenitor of LP40-365 could be a binary star system like the one shown in this animation. Here, an ultra-massive and compact dead star called a white dwarf (shown as a small white star) is accreting matter from its giant companion (the larger red star). The material escapes from the giant and forms an accretion disk around the white dwarf. Once enough material is accreted onto the white dwarf, a violent thermonuclear runaway tears it apart and destroys the entire system. The giant star and the surviving fragment of the white dwarf are flung into space at tremendous speeds. The surviving white dwarf shrapnel hurtles towards our region of the Galaxy, where its radiation is detected by ground based telescopes. Credit: Copyright Russell Kightley

The researchers also note that in most cases, stars that move faster than normal are doing so because they were flung across their galaxy after traveling too close to its center. But the trajectory of LP 40-365 showed that it had not approached the center of its galaxy.

The team suggests the evidence indicates that the white dwarf is most likely the remnant of a supernova—one that occurred between 5 and 50 million years ago. The team and likely others will continue to study the star to add further proof to their assumption. They believe it will help in better understanding what happens prior to a , regardless of type.

00.0sec: Initial binary star outside the disk of the Milky Way galaxy. A massive white dwarf accreting material through an accretion disk from its red giant companion star. The stars orbit around the center of mass of the binary system. 14.6sec: The white dwarf reaches the Chandrasekhar mass limit and explodes as a bright Type Ia supernova. However, the explosion is not perfect; a fraction of the white dwarf shoots out like a shrapnel to the left. The binary system disrupts. 18.0sec: The supernova explosion again, at an edge-on view. The shrapnel comes at the viewer and passes by. 20.0sec: After passing by, the remnant flies off towards the disk of the Milky Way towards the spiral arm with the Solar System. 24.0sec: The fast moving remnant from the solar neighborhood as it passes by the stars in our galactic arm, including the Sun. The remnant gets in the reach of our telescopes. Credit: Copyright Sardonicus Pax

Explore further: Search for stellar survivor of a supernova explosion

More information: S. Vennes et al. An unusual white dwarf star may be a surviving remnant of a subluminous Type Ia supernova, Science (2017). DOI: 10.1126/science.aam8378

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11 comments

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Jeffhans1
5 / 5 (2) Aug 18, 2017
I can't wait for the day when all of the stars have been studied well enough that we can rewind the galaxy and virtually watch the journey of this star along with simulating the explosion that launched it on its path.
katesisco
1 / 5 (3) Aug 18, 2017
Maybe the idea that stars are twinned is a bit off? Maybe it is that they 'bubble off' matter that is a spherical balls continuously over time? That these 'gas balls' are the first step in the companion formation? Maybe they are attached with an umbilical when being created and drift off after the sun has relieved itself of this excess gas? Maybe away from the birth mother sun they magnetically compact to have a core? This gas ball with a core may encounter other cosmic bodies which produce plasma arcing between them? Maybe even have a 3-body encounter? One of which could be an iron meteorite which is shattered coating the plasma sphere with iron dust and dusting the other planet with surface iron?
Does that sound possible? Even likely? Perhaps the creation of our Moon?
Zenmaster
1.5 / 5 (4) Aug 18, 2017
Or the white dwarf was a product of the explosion, not having existed prior.
Nik_2213
5 / 5 (3) Aug 18, 2017
Zen, do you propose the white dwarf accreted from S/N debris, rather than derived from core of the binary's faster evolving member ? Please show working...
Da Schneib
5 / 5 (3) Aug 18, 2017
How can a supernova produce a white dwarf? I also, @Zen, would like to see some "working."
IronhorseA
5 / 5 (2) Aug 18, 2017
Perhaps zen is thinking that the white dwarf they found is the core of the companion star that the white dwarf that went supernova was cannibalizing. Not sure if the companion star could withstand the blast long enough to be ejected.
Da Schneib
5 / 5 (1) Aug 18, 2017
@Ironhorse, we'd need to see a mathematical physics proof that such an event could happen. And yes we could really figure out if it's plausible.

If you want to present novel astrophysical hypotheses do the "working." Let's see the math.
RealScience
5 / 5 (4) Aug 18, 2017
People should be welcome to politely present novel hypotheses, as Ironhorse has done, without doing the math. It is when people repeatedly INSIST on some hypothesis, without even bothering to do the math, that it gets annoying.

It is actually a reasonable hypothesis: Fast moving stars have been explained by one star of a tight binary sheds enough mass through a supernova explosion to let the other star free.

However In this case "The researchers found that the star was spinning faster than expected and that it had a mixed composition, which suggested that it very likely once had a companion star.", and the supernova would be a bigger, and hence shorter-lived star, and hence not a companion feeding the white dwarf.

To make the hypothesis work it would have had to have been more than two stars, something like two close white dwarfs being fed from one red-giant companion, and one white dwarf goes over the limit first, goes supernova, and sets the other white dwarf free.
Da Schneib
5 / 5 (3) Aug 19, 2017
I'm good with a plausible explanation, @RealSci. Just speculating without any supporting evidence looks too much like the cranks we get around here a lot in case you haven't noticed. I don't include @Ironhorse in that, but I'd encourage a more thoughtful post with some support if we're going to speculate. Maybe the speculations will be wrong; I respect @Ironhorse enough to expect s/he'll be OK with being right or wrong, and learn something either way.
RealScience
5 / 5 (3) Aug 19, 2017
I cannot think of any prolific poster here who has never been wrong in a post (myself included).

The cranks are indeed annoying, but what makes them so annoying is the endless repetition of arrogant posts that are dismissive toward others. A crank's posts being wrong merely amplifies the crime.

Without those attributes the implausibility of a poster's speculation is more amusing than annoying. For example, katesisco's speculation above is so far off that it is amusing, and because it is polite I personally don't find it annoying. However if katesisco were to insist that mainstream scientists were idiots because they failed to agree with his/her brilliant insight, his/her posts would become annoying.
Da Schneib
5 / 5 (2) Aug 21, 2017
@Real, agreed. Just being fussy I guess.

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