Northwestern led international team reevaluates what is possible within our universe

The study, “A cool and inflated progenitor candidate for the Type Ib supernova 2019yvr at 2.6 yr before explosion,” was published in the Monthly Notices of the Royal Astronomical Society on May 5th, 2021.

This international research team was led by Northwestern’s Charles Kilpatrick, a postdoctoral fellow who works with Professor Wen-fai Fong on gravitational wave events, gamma-ray bursts, and other related time-domain phenomena at the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA).

Kilpatrick and his team utilized NASA’s Hubble Space Telescope to examine a curious yellow massive star many years before it exploded into a supernova. Typically, these stars are shrouded in hydrogen, which conceals the star’s hot, blue interior. However, the team found this star defied the norm and lacked this crucial hydrogen layer when it exploded.

“If a star explodes without hydrogen, it should be extremely blue — really, really hot. It’s almost impossible for a star to be this cool without having hydrogen in its outer layer. We looked at every single stellar model that could explain a star like this, and every single model requires that the star had hydrogen, which, from its supernova, we know it did not. It stretches what’s physically possible,” shared Charles Kilpatrick.

The team hypothesized that before the star’s death it may have shed its hydrogen layer or lost it to a nearby companion star due to a clue found several months after the explosion.

“This star’s discovery provides some of the most direct evidence ever found that stars experience catastrophic eruptions, which cause them to lose mass before an explosion. If the star was having these eruptions, then it likely expelled its hydrogen several decades before it exploded.”

Charles Kilpatrick

Read more about this study in the Northwestern Now article: “‘Oddball supernova’ appears strangely cool before exploding.”

Learn more about Charles Kilpatrick and his research on his CIERA page.