Unique supernova explosion

Date:
September 10, 2020
Source:
Florida State University
Summary:
Astronomers have discovered a supernova that could help uncover
the origins of the group of supernovae this star belongs to.



FULL STORY ========================================================================== One-hundred million light years away from Earth, an unusual supernova
is exploding.


==========================================================================
That exploding star -- which is known as "supernova LSQ14fmg" -- was
the faraway object discovered by a 37-member international research
team led by Florida State University Assistant Professor of Physics
Eric Hsiao. Their research, which was published in the Astrophysical
Journal, helped uncover the origins of the group of supernovae this star belongs to.

This supernova's characteristics -- it gets brighter extremely slowly,
and it is also one of the brightest explosions in its class -- are unlike
any other.

"This was a truly unique and strange event, and our explanation for it
is equally interesting," said Hsiao, the paper's lead author.

The exploding star is what is known as a Type Ia supernova, and more specifically, a member of the "super-Chandrasekhar" group.

Stars go through a sort of life cycle, and these supernovae are the
exploding finale of some stars with low mass. They are so powerful that
they shape the evolution of galaxies, and so bright that we can observe
them from Earth even halfway across the observable universe.



==========================================================================
An image of the "Blue Snowball" planetary nebula taken with the Florida
State University Observatory. The supernova LSQ14fmg exploded in a system similar to this, with a central star losing a copious amount of mass
through a stellar wind. When the mass loss abruptly stopped, it created
a ring of material surrounding the star. Courtesy of Eric Hsiao Type
Ia supernovae were crucial tools for discovering what's known as dark
energy, which is the name given to the unknown energy that causes the
current accelerated expansion of the universe. Despite their importance, astronomers knew little about the origins of these supernova explosions,
other than that they are the thermonuclear explosions of white dwarf
stars.

But the research team knew that the light from a Type Ia supernova rises
and falls over the course of weeks, powered by the radioactive decay
of nickel produced in the explosion. A supernova of that type would
get brighter as the nickel becomes more exposed, then fainter as the
supernova cools and the nickel decays to cobalt and to iron.

After collecting data with telescopes in Chile and Spain, the research
team saw that the supernova was hitting some material surrounding it,
which caused more light to be released along with the light from the
decaying nickel. They also saw evidence that carbon monoxide was being produced. Those observations led to their conclusion -- the supernova
was exploding inside what had been an asymptotic giant branch (AGB)
star on the way to becoming a planetary nebula.

"Seeing how the observation of this interesting event agrees with the
theory is very exciting," said Jing Lu, an FSU doctoral candidate and
a co-author of the paper.

They theorized that the explosion was triggered by the merger of the
core of the AGB star and another white dwarf star orbiting within
it. The central star was losing a copious amount of mass through a
stellar wind before the mass loss was turned off abruptly and created
a ring of material surrounding the star.

Soon after the supernova exploded, it impacted a ring of material often
seen in planetary nebulae and produced the extra light and the slow
brightening observed.

"This is the first strong observational proof that a Type Ia supernova
can explode in a post-AGB or proto-planetary-nebula system and is an
important step in understanding the origins of Type Ia supernovae," Hsiao
said. "These supernovae can be particularly troublesome because they can
mix into the sample of normal supernovae used to study dark energy. This research gives us a better understanding of the possible origins of Type
Ia supernovae and will help to improve future dark energy research."

========================================================================== Story Source: Materials provided by Florida_State_University. Original
written by Bill Wellock. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. E. Y. Hsiao, P. Hoeflich, C. Ashall, J. Lu, C. Contreras,
C. R. Burns, M.

M. Phillips, L. Galbany, J. P. Anderson, C. Baltay, E. Baron, S.

Castello'n, S. Davis, Wendy L. Freedman, C. Gall, C. Gonzalez, M. L.

Graham, M. Hamuy, T. W.-S. Holoien, E. Karamehmetoglu,
K. Krisciunas, S.

Kumar, H. Kuncarayakti, N. Morrell, T. J. Moriya, P. E. Nugent, S.

Perlmutter, S. E. Persson, A. L. Piro, D. Rabinowitz, M. Roth, M.

Shahbandeh, B. J. Shappee, M. D. Stritzinger, N. B. Suntzeff,
F. Taddia, S. A. Uddin. Carnegie Supernova Project II: The Slowest
Rising Type Ia Supernova LSQ14fmg and Clues to the Origin of
Super-Chandrasekhar/03fg- like Events. The Astrophysical Journal,
2020; 900 (2): 140 DOI: 10.3847/ 1538-4357/abaf4c ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200910130416.htm

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