Progenitor for Tycho's supernova was not hot and luminous

September 26, 2017, Max Planck Society
The remnant of Tycho’s supernova as seen in X-rays, showing the expanding shock wave. Credit: X-ray: NASA/CXC/Rutgers/K.Eriksen et al.; Optical: DSS

An international team of scientists from the Monash University (Melbourne, Australia), the Towson and Pittsburgh Universities (USA) and the Max Planck Institute for Astrophysics, has shed new light on the origins of the famous Tycho's supernova. The research, published in Nature Astronomy, debunks the common view that Tycho's supernova originated from a white dwarf, which had been slowly accreting matter from its companion in a binary system.

Type Ia supernovae (SNe Ia) serve as standard candles of modern observational cosmology; they also play a vital role in galactic chemical evolution. However, the origin of these gigantic cosmic explosions remains uncertain. Although there is a nearly universal consensus that SNe Ia are a result of the thermonuclear disruption of a white dwarf consisting of carbon and oxygen reaching the Chandrasekhar mass limit (about 1.4 times the mass of our Sun), the exact nature of their progenitors is still unknown. The white dwarf could have been gradually accumulating matter from a companion star thus reaching the Chandrasekhar mass limit, at which point the nuclear runaway began; or the nuclear explosion could have been triggered by the merger of two white dwarfs in a compact binary system. These two scenarios differ dramatically in the level of electromagnetic emission expected from the progenitor during millions of years prior to the explosion.

A white dwarf that is accreting material from the donor star becomes a source of copious X-ray and extreme UV photons – the canonical accretion scenario implies a hot and luminous progenitor that would ionize all surrounding gas within a radius of ~10–100 parsecs (up to about 300 light-years), the so called Strömgren sphere. After the white dwarf is disrupted in the , the source of ionizing emission disappears. However, it takes quite a long time for the interstellar gas to recombine and to become neutral again – an ionized nebula will continue to exist around the for about 100,000 years after the explosion. Thus, the detection of even small amounts of neutral gas in the vicinity of a supernova can help scientists to place tight constraints on the temperature and luminoisty of the progenitor.

Artist’s conception of a white dwarf slowly accreting matter from a companion star. Credit: David A. Hardy & PPARC

445 years ago, Tycho Brahe observed a stella nova ("new star") in the night sky. Brighter than Venus when it first appeared, it faded over the following year. Today, we know that Tycho had observed a nuclear disruption of a white dwarf – a type Ia supernova. Due to its history and relative proximity to Earth, Tycho's supernova is one of the most well-documented examples of a Type Ia supernova.

In particular, we know from optical observations that the supernova remnant today is expanding into the mostly neutral gas. Thus, using the remnant itself as a probe of its environment, scientists could exclude hot luminous progenitors that would have produced a Strömgren sphere larger than the radius of the present remnant (~3 parsecs). This conclusively rules out steadily nuclear-burning (supersoft X-ray sources), as well as disk emission from a Chandrasekhar-mass white dwarf accreting more than one solar mass in approximately 100 million years (recurrent novae). The lack of a surrounding Strömgren sphere is consistent with the merger of a double white dwarf binary, although other more exotic scenarios may be also possible.

Artist’s conception of a binary white dwarf system. Credit: Tod Strohmayer (GSFC), CXC, NASA, Illustration: Dana Berry (CXC)

Explore further: Evidence found of white dwarf remnant after supernova

More information: T. E. Woods et al. No hot and luminous progenitor for Tycho's supernova, Nature Astronomy (2017). DOI: 10.1038/s41550-017-0263-5

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4 comments

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rrwillsj
1 / 5 (2) Sep 26, 2017
If I am understanding this article as posted, collated with my (limited) knowledge of astrophysics, brings me to a couple of speculations.

That a major event, novae or super-nova may not be a terminal finality for a star. That, over periods of millions of years or a magnitude or two thereof, is it possible that many of these explosive events are cyclic?

While a portion of mass is blown away. Most of the stellar material would collapse back down into the originating star or it's partner? During these collapses transmuting light elements to heavier elements into the heaviest of naturally produced elements?

That the most massive stars, still existing after a super-nova, evolve into neutron stars? Would there be the possibility that the collision/combining of two such exotic stellar objects result in ...I'm not sure what to call such a titanic event.

What would be greater than a super-nova? Perhaps afflicting Space/Time to the extreme of creating a Black-Hole?
john berry_hobbes
1 / 5 (1) Sep 27, 2017

That a major event, novae or super-nova may not be a terminal finality for a star. That, over periods of millions of years or a magnitude or two thereof, is it possible that many of these explosive events are cyclic?


The accretive type are. There's no reason to think the collision model would be.


While a portion of mass is blown away. Most of the stellar material would collapse back down into the originating star or it's partner?


When white dwarfs collide, one of two things can happen: if the combined masses is greater than 140% of the Sun, the collision creates a supernova. In the other case, the white dwarfs will actually reignite nuclear fusion, creating a new star, eg. SDSS J010657.39–100003.3.

During these collapses transmuting light elements to heavier elements into the heaviest of naturally produced elements?


Only in the SN scenario. The rest can't happen or it wouldn't have been a white dwarf in the first place.
Da Schneib
not rated yet Sep 27, 2017
Well, here's some further information for you to ponder:
https://en.wikipe...iki/Nova
https://en.wikipe...upernova

This should give you a pretty good idea of the difference between novae and supernovae.
Da Schneib
not rated yet Sep 27, 2017
Interesting article. Pretty good evidence for the white dwarf collision scenario here. This is curious, because a companion star has been detected, Tycho G, a G2 similar to our sun. Because of this, previous to now this was believed to be an accretion supernova. Tycho G was discovered in 2004. I'll be interested to see how this shakes out.

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