"This is the weirdest supernova we’ve ever seen" - the star that refuses to die

[gary]

In a 9 Nov 2017 article in The Guardian, Science Editor Ian Sample reports
on the mysterious case of iPTF14hls, a star in Ursa Major that has
undergone a supernova power explosion multiple times since 1954.
The first star ever observed to have done so.

Originally Posted by Ian Sample, The Guardian

'Zombie star' amazes astronomers by surviving multiple supernovae.

Astronomers have spotted a “zombie star” that refused to die when massive explosions that are normally considered fatal rocked the heavenly body.

The star, which lies half a billion light years away in the constellation of the Great Bear, has exploded multiple times since 1954, but may finally be on its way to the cosmic graveyard.

It is the first time astronomers have seen the same star explode over and over. Until now stellar explosions, or supernovae, have been considered singular events, the dazzling death throes of stars that have burned up all their fuel.

“This is the weirdest supernova we’ve ever seen. It’s the first time we’ve seen multiple explosions in the same place,” said Iair Arcavi, an astronomer at Las Cumbres Observatory in California. There is no known theory that explains the observation.

The curious incident came to light after astronomers detected a supernova in September 2014 with the Intermediate Palomar Transient Factory (iPTF) telescope near San Diego. The exploding star seemed unremarkable at first, but observations four months later showed that rather than dimming over time as expected, the supernova had actually become brighter.

Originally Posted by Ian Sample, The Guardian

The astronomers ruled out the most common supernova theories, but found one that explained some of the star’s odd behaviour. According to the “pulsational pair-instability model”, stars with masses of at least 100 suns can explode multiple times before dying, with each blast sending vast amounts of material into space. Now and again, material rushing away from the star can catch up with older ejected material, producing bright flashes of light as it collides. “The theory doesn’t explain everything, but it’s the only one that comes close,” said Arcavi.

“One thing we can tell from the supernova is how long ago the star exploded,” he added. “The weird thing is that even two years later, it looked like a two-month-old supernova.” It is as if the star exploded in slow motion.

Originally Posted by Ian Sample, The Guardian

More recent observations of the star suggest that the 2014 explosion may be its last, according to details published in Nature. The astronomers have switched to larger instruments to watch the supernova fade and will soon look on with the Hubble space telescope. Before long, the centre of the supernova – where a black hole now lurks – should be visible. “We definitely plan to keep an eye on this one,” Arcavi said.

Stan Woosley, director of the Center for Supernova Research at the University of California, Santa Cruz, said understanding the supernova could throw light on the evolution of the most massive stars in the universe and the birth of certain kinds of black holes. “For now the supernova offers astronomers their greatest thrill: something they do not understand,” he said.

Originally Posted by Arcavi et.al. Nature

"Energetic eruptions leading to a peculiar hydrogen-rich explosion of a massive star"

Abstract
Every supernova so far observed has been considered to be the terminal explosion of a star.

Moreover, all supernovae with absorption lines in their spectra show those lines decreasing in velocity over time, as the ejecta expand and thin, revealing slower-moving material that was previously hidden.

In addition, every supernova that exhibits the absorption lines of hydrogen has one main light-curve peak, or a plateau in luminosity, lasting approximately 100 days before declining.

Here we report observations of iPTF14hls, an event that has spectra identical to a hydrogen-rich core-collapse supernova, but characteristics that differ extensively from those of known supernovae.

The light curve has at least five peaks and remains bright for more than 600 days; the absorption lines show little to no decrease in velocity; and the radius of the line-forming region is more than an order of magnitude bigger than the radius of the photosphere derived from the continuum emission.

These characteristics are consistent with a shell of several tens of solar masses ejected by the progenitor star at supernova-level energies a few hundred days before a terminal explosion.

Another possible eruption was recorded at the same position in 1954. Multiple energetic pre-supernova eruptions are expected to occur in stars of 95 to 130 solar masses, which experience the pulsational pair instability2,3,4,5.

That model, however, does not account for the continued presence of hydrogen, or the energetics observed here.

Another mechanism for the violent ejection of mass in massive stars may be required.

Article here :-
https://www.theguardian.com/science/...ple-supernovae

Abstract and paper in Nature (requires subscription) "Energetic eruptions leading to a peculiar hydrogen-rich explosion of a massive star" by Arcavi et. al. :-
https://www.nature.com/articles/nature24030

[xelasnave]

Thanks for posting that Gary and all the posts you do ..its great.

alex

[gary]

Originally Posted by xelasnave

Thanks for posting that Gary and all the posts you do ..its great.

alex

Thank you Alex. You are most welcome.

Sarah Kaplan is also writing about it in the Washington Post today :-
https://www.washingtonpost.com/news/...-and-surviving

and Amina Khan in the LA Times :-
http://www.latimes.com/science/scien...108-story.html

Originally Posted by Amina Khan, LA Times

Instead, scientists think this supernova may be a pulsational-pair instability supernova. In this scenario, the inside of a monster star with the mass of 100 suns becomes so hot that some of its energy turns into matter and antimatter. If that happens, the core becomes unstable, triggering an explosion that blows off the star’s outer layers, Arcavi said. If true, iPTF14hls would be the first example of this kind of supernova ever seen.

Stan Woosey has a draft Jan 2017 paper on "Pulsational Pair-Instability Supernovae" on arXiv here :-
https://arxiv.org/pdf/1608.08939.pdf

Perhaps he was on the money. I hadn't heard of the classification until today.
Some astronomers apparently theorize that the 1843 eruption of Eta Carinae A might be an example of a pulsational pair-instability supernovae.

This latest stars published brightness and light curve look phenomenal.

Whatever diet it is on is rich on energy!

Best Regards

Gary Kopff
Mount Kuring-Gai NSW

[xelasnave]

I am wondering about it being another star.

If a super nova happens I expect material would be blown into space and possibly caused mass to be added to a nearby star such to cause its mass to get to a collapse point.

Perhaps binaries.

I guess any idea seems more reasonable than just one behaving as the observations suggest.

Anyways I will follow up with my scope.

Alex

[Eratosthenes (Peter)]

"....An even earlier explosion appears to have happened in 1954 when a burst of light was detected from the same location. The group’s calculations show there is a 95 to 99% chance it was the same star."


95 to 99% chance

[xelasnave]

But a 5% chance it was a coincidence...someone said.

A double bunger is more newsworthy and other things.
Alex

[Dave2042 (Dave)]

It's a legitimate reason to be a bit skeptical.
That said, it's worth remembering that 95% is very certain by the standards of observational astrophysics. The high sigma levels that particle physics produces are entirely due to having a computerised accelerator doing gazillions of repetitions of the same experiment. A luxury astrophysics doesn't have.
Transporting the particle mindset to astrophysics is not really sensible.