Searching for Neutrinos from Record Bright Gamma-Ray Bursts
NASA’s Fermi space telescope observed one of the closest and brightest gamma-ray bursts ever in October of 2022. A data analysis from the neutrino telescope IceCube has set new limits for neutrinos coming from gamma-ray bursts.
The observations were carried out by an international team of five PhD students, including Nora Valtonen-Mattila from Uppsala University, and allows for new insights about the composition of gamma ray bursts, as well as what powers the explosions.
In October 2022, NASA's Fermi space telescope detected one of the closest and brightest gamma-ray bursts ever recorded, known as GRB221009A. The burst was observed in the constellation Sagitta, located 2.4 billion light-years from Earth. Gamma-ray bursts are the most energetic explosions in the universe, emitting as much energy in seconds as the Sun will do throughout its lifetime. They are believed to be linked to distant supernovae.
Neutrinos, which are among the most elusive particles in the universe, have long been considered a possible product of gamma-ray bursts. Despite being a billion times more common than the particles that make up all matter in our environment, neutrinos are very small and almost massless, making them difficult to detect. To search for neutrinos from GRB221009A, the international PhD team performed complementary data analyses on data collected by IceCube during the gamma-ray burst, covering a range of energies from mega electron volts (106 eV) to peta electron volts (1015 eV). Nora Valtonen-Mattila focused on analyzing data at the lowest energies, at the mega electron volt level.
According to the results, the team was able to set new limits for the neutrinos coming from gamma-ray bursts, providing new insights into the composition of these events and what powers the explosions. However, detecting low-energy neutrinos was a challenging task due to their similarity to detector noise, as Nora Valtonen-Mattila explained:
"Because neutrinos with low energies are difficult to distinguish from the detector noise, it was an interesting challenge to design a search to find them.".
From the study, which was published in The Astrophysical Journal Letters, no significant neutrino flux could be deduced, but the results showed new limit values for neutrino fluxes from gamma-ray bursts.
“Even though we could not observe neutrinos above the expected background value for the IceCube detector, we can still use the results from the study to gain insight into the processes that give rise to gamma-ray bursts. The search for neutrinos gives us a unique insight into these extremely bright phenomena”, says Nora Valtonen-Mattila.
R. Abbasi et al (2023) Limits on Neutrino Emission from GRB 221009A from MeV to PeV Using the IceCube Neutrino Observatory, The Astrophysical Journal Letters, DOI: 10.3847/2041-8213/acc077.
Nora Valtonen-Mattila, PhD Student at the Department of Physics and Astronomy, phone: 073-9588592, email: email@example.com.
Erin O'Sullivan, Associate Professor at the Department of Physics and Astronomy, phone: 076-145 90 91, firstname.lastname@example.org.
English translation: Johan Wall