UChicago scientists, including an Indian-American detect first X-rays from mystery supernovas

Vikram Dwarkadas, research associate professor in the Department of Astronomy and Astrophysics. (Photo by Jean Lachat, courtesy U Chicago)

A team of scientists at the University of Chicago, including Professor Vikram Dwarkadas, appear to have found the first X-rays coming from type Ia supernovas. Their findings, co-authored by Dwarkadas, research associate professor in the Department of Astronomy and Astrophysics, are published in the Aug. 23 issue of the Monthly Notices of the Royal Astronomical Society.

Type Ia supernovas, created when a white dwarf star in a two-star system experiences a thermonuclear explosion, are a favorite of scientists because they burn at a specific brightness which allows them to calculate how far away they are from Earth. That makes it possible to measure distances in the universe as a while. A few years ago, scientists began to find type Ia supernovas that appeared to carry a very dense cloak of circumstellar material which is normally only seen from a type II supernova. To date X-rays are regularly observed from type II supernovas their dense material produced these rays when a star collapsed and sent shockwaves at supersonic speeds into the dense materials around type II supernovas.

However, X-Rays have never been seen from type Ia supernovas. Which is why the UChicago-led team’s detection of X-ray photons from the supernova 2012ca recorded by the Chandra X-ray Observatory, may be a breakthrough.

“Although other type Ia’s with circumstellar material were thought to have similarly high densities based on their optical spectra, we have never before detected them with X-rays,” Dwarkadas is quoted saying in a press release. The amounts of X-rays they found were small but present, according to the research team — 33 photons in the first observation a year and a half after the supernova exploded, and ten in another about 200 days later.

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

“Even the most massive stars do not have such high mass-loss rates on a regular basis,” he said in the press release. “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,” Dwarkadas contended.




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