淫妻社

Sarah Dalessi, a graduate student in the UAH College of Science, holding a model of NASA鈥檚 Fermi Gamma-ray Space Telescope.

Russ Nelson / UAH

Sarah Dalessi, a fifth-year student in the College of Science at 淫妻社 (UAH), a part of The University of Alabama System, is the lead author of detailing the discovery of the fastest gamma-ray burst (GRB) ever recorded. GRB 230307A is a gamma-ray burst in the ultrarelativistic category, meaning the velocity of the GRB鈥檚 jet, a focused beam of high-energy particles and photons, came within 99.99998 percent of the speed of light 鈥� 186,000 miles per second 鈥� making it the fastest GRB ever observed. The observation was made possible with data from the Fermi Gamma-ray Burst Monitor, one of two instruments on NASA鈥檚 Fermi Gamma-ray Space Telescope.

鈥淭he Lorentz factor is the measure of speed of the jet here, and 1,600 is the highest we ever measured,鈥� explains Dr. Peter Veres, an assistant professor who works in the UAH Center for Space Plasma and Aeronomic Research (CSPAR) and is co-author on the study.

The Lorentz factor measures the relativistic velocity of the ejected fireball, providing insights into the GRB's energy, luminosity and the surrounding environment. GRB jets are thought to have Lorentz factors ranging from about 100 to 1,000, with typical values around 300.

An illustration of a gamma-ray burst erupting from a dense environment around a collapsing massive star.

Courtesy NASA, ESA and M. Kornmesser

Dalessi began working with the team in 2021. The group is a collaborative effort between NASA and the at UAH, which acts as the operations center, and the in Germany. The team also recently discovered the brightest GRB ever observed.

The Fermi observatory launched in 2008 to study the highest-energy light, or gamma rays, from violent cosmic phenomena in the universe's most extreme environments.

鈥淧art of my responsibilities on the team is to be what is called a 鈥楤urst Advocate,鈥欌�� Dalessi explains. 鈥淲hich means I have a number of shifts per month where I am responsible for processing and classifying incoming triggers from the satellite. It was during one of my shifts when I got the trigger notification for GRB 230307A, and right away, I knew that this was an extraordinarily bright event, perhaps the second or third brightest GRB ever. To be a part of such a unique discovery is not something I ever planned or dreamed of.鈥�

鈥淕RB 230307A is the second brightest gamma-ray burst observed in over 50 years,鈥� Veres adds.

The research also produced new insights through observations of a phenomenon called a 鈥渒ilonova,鈥� an optical signal, brightest after about a day, that accompanies mergers of neutron stars. A kilonova can provide information about the source of the GRB and the creation of the heaviest elements in the universe.

鈥淭he mergers of compact binary objects, such as those involving two neutron stars, serve as almost a cosmic kitchen for heavy elements,鈥� Dalessi notes. 鈥淒uring the merger, there is an abundance of neutron-rich matter that is expelled, and then is decompressed in space and can generate rare heavy elements such as gold and platinum.鈥�

Follow-up observations of the kilonova remnant of GRB 230307A by researchers in the Netherlands and the United Kingdom using NASA鈥檚 James Webb Space Telescope showed evidence of the rare heavy element tellurium.

Dalessi says one of the highlights of her experience as part of the GBM team has been working alongside NASA scientists at Marshall Space Flight Center, also in Huntsville.

鈥淎 main part of the reason that I chose to attend UAH was that I knew the Space Science Department had opportunities for students to work with NASA collaborators,鈥� the student says. 鈥淲orking with Dr. Michelle Hui has been the absolute best part of my graduate school experience. I am forever grateful to the GBM team for putting their faith in me and letting me take the lead on such a project. To have such a wealth of knowledge freely available any time I had questions or needed guidance has been such a gift.鈥�

Looking to the future of gamma-ray burst research, the UAH graduate says there are many potential avenues to explore.

鈥淭he most significant is finding another long GRB resulting from a merger,鈥� Dalessi says. 鈥淭his could involve either detecting a new trigger or identifying possible candidates. Currently, it is not possible to fully confirm the origin of GRBs without additional observations, so I am interested in identifying any signatures in the prompt emission that could signal a long burst is potentially from a merger.鈥�