WASHINGTON (Dec. 7, 2022) – The recent discovery of a long gamma-ray burst (GRB) triggered by the collision of two neutron stars challenged the scientific consensus on the cause of that cosmic phenomenon. Brendan O’Connor, a sixth-year PhD student in the George Washington University Department of Physics, is among the scientists who observed this momentous event and interpreted its significance. O’Connor served as principal investigator (PI) of an International Gemini Observatory program that studied this unique explosion, known as GRB 211211A, and helped distinguish this particular event from other GRBs.
Long GRBs last up to a minute and were thought to be caused by supernovae, the explosion of a massive star. Short GRBs last less than two seconds and are associated with kilonovae caused by the merger of two dense bodies in outer space, such as neutron stars and black holes. O’Connor gathered critical data on the host galaxy environment of GRB 211211A, which indicated that this particular explosion occurred just one billion light years away, far closer to Earth than most other GRBs.
O’Connor observed that the burst happened far from the center of its host galaxy and in a low-density environment, which is not typical for supernovae. He took into account the distance, environment, and brightness of the explosion and deduced that the burst was caused by the collision of two neutron stars, an event that was previously believed to only cause short GRBs. GRB 211211A is the first long GRB known to have been caused by the merger of two compact objects. It is also the first GRB of its kind to display kilonova emission, which is the signature heavy elements, such as gold and platinum, synthesized during the merger. The discovery of a kilonova provided the smoking-gun evidence that GRB 211211A was produced during a merger.
In addition to being a doctoral student at GW, O’Connor is also a graduate research assistant at NASA’s Goddard Space Flight Center.
FROM THE EXPERTS
“GRB 211211A was a very unexpected, but extremely fortunate revelation. We were extremely lucky that the explosion occurred so nearby, as the proximity to Earth allowed us to study the event in exquisite detail. Only with this fantastic dataset were we able to unveil the signatures of a kilonova imposed on top of the gamma-ray burst emission.” – Brendan O’Connor, PhD student, George Washington University
“We started with two gamma-ray burst classes thirty years ago, where collapsars produced the long GRBs and mergers the short ones. But in our field, we know that paradigms change. Now it appears we have a long GRB from what appears to be a merger of two neutron stars, which is a puzzle we need to solve. Nature just served us a curveball and we need to understand the consequences.” – Chryssa Kouveliotou, professor of astrophysics and Department of Physics chair, George Washington University
O’Connor co-authored the article “A long gamma-ray burst from a merger of compact objects,” which was published in Nature on December 7, 2022.