A team of astronomers has observed a new phenomenon in the aftermath of SN 2012au, an extremely energetic supernova discovered on March 14, 2012 in the barred spiral galaxy NGC 4790.
Unlike most supernovae that fade away, SN 2012au continues to shine today thanks to a powerful new pulsar. Image credit: NASA / ESA / J. DePasquale, STScI.
As large stars explode, their interiors collapse down to a point at which all their particles become neutrons.
If the resulting neutron star has a magnetic field and rotates fast enough, it may develop into a pulsar wind nebula. This is most likely what happened to SN 2012au.
“We know that supernova explosions produce these types of rapidly rotating neutron stars, but we never saw direct evidence of it at this unique time frame,” said Purdue University researcher Dr. Dan Milisavljevic.
“This is a key moment when the pulsar wind nebula is bright enough to act like a light bulb illuminating the explosion’s outer ejecta.”
SN 2012au was already known to be extraordinary — and weird — in many ways.
Although the explosion wasn’t bright enough to be termed a superluminous supernova, it was extremely energetic and long-lasting, and dimmed in a similarly slow light curve.
Dr. Milisavljevic and colleagues predict that if astronomers continue to monitor the sites of extremely bright supernovae, they might see similar transformations.
“If there truly is a pulsar or magnetar wind nebula at the center of the exploded star, it could push from the inside out and even accelerate the gas,” Dr. Milisavljevic said.
“If we return to some of these events a few years later and take careful measurements, we might observe the oxygen-rich gas racing away from the explosion even faster.”
Superluminous supernovae are potential sources of gravitational waves and black holes, and astronomers think they might be related to other kinds of explosions, like gamma-ray bursts and fast radio bursts.
Astronomers want to understand the fundamental physics behind them, but they’re difficult to observe because they’re relatively rare and happen so far from Earth. Only the next generation of telescopes will have the ability to observe these events in such detail.
“This is a fundamental process in the Universe. We wouldn’t be here unless this was happening,” Dr. Milisavljevic said.
“Many of the elements essential to life come from supernova explosions. I think it’s crucial for us, as citizens of the Universe, to understand this process.”
The results were published in the Astrophysical Journal Letters.
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Dan Milisavljevic et al. 2018. Evidence for a Pulsar Wind Nebula in the Type Ib Peculiar Supernova SN 2012au. ApJL 864, L36; doi: 10.3847/2041-8213/aadd4e
