Supernova X-ray

A team of scientists at the University of Chicago led by Indian American Vikram Dwarkadas, the study co-author and UChicago research associate professor, has detected the first X-rays from mystery supernovas. (Jean Lachat/UChicago photo)

A research team led by scientists at the University of Chicago including Vikram Dwarkadas has published a report of its findings that have the possibility of learning more about a certain time of supernova, or explosion of a star.

The study, published Aug. 23 in the Monthly Notices of the Royal Astronomical Society, may have found the first X-rays coming from a specific type of supernova – a type of explosion that allows for scientists to discern that we live in an expanding universe.

The Dwarkadas-led team examined a type Ia, or one-a, supernova, which is popular with astronomers because it burns at a specific brightness that allows researchers to calculate how far away it is from Earth.

But a few years ago, scientists began to find type Ia supernovas with a strange optical signature that suggested they carried a very dense cloak of circumstellar material surrounding them.

Such dense material is normally only seen from a different type of supernova called type II, and is created when massive stars start to lose mass.

The ejected mass collects around the star; then, when the star collapses, the explosion sends a shockwave hurtling at supersonic speeds into this dense material, producing a shower of X-rays. Thus, we regularly see X-rays from type II supernovas, but they have never been seen from type Ia supernovas.

“Although other type Ias with circumstellar material were thought to have similarly high densities, we have never before detected them with X-rays,” research associate professor at University of Chicago’s Department of Astronomy and Astrophysics and study co-author Dwarkadas said in a statement.

The scientists made two sets of observations using recordings from NASA’s Chandra X-ray Observatory.

The first set was made about a year and a half after the supernova exploded and another 200 days later. The team detected a small number of X-rays indicating a supernova surrounded by an accumulation of matter that measured a million times denser than previously thought.

“This certainly appears to be a Ia supernova with substantial circumstellar material, and it looks as though it’s very dense,” the Indian American scientist added. “What we saw suggests a density about a million times higher what we thought was the maximum around Ias.”

It’s thought that white dwarfs don’t lose mass before they explode. The usual explanation for the circumstellar material is that it would have come from a companion star in the system, but the amount of mass suggested by this measurement was very large, Dwarkadas said, which is far larger than one could expect from most companion stars.

“Even the most massive stars do not have such high mass-loss rates on a regular basis,” he said. “This once again raises the question of how exactly these strange supernovas form. If it’s truly a Ia, that’s a very interesting development because we have no idea why it would have so much circumstellar material around it,” he added.

More studies to look for X-rays, and even radio waves coming off these anomalies, could open a new window to understanding such supernovas and how they form, the authors said.

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