New Method Developed to Measure UV Sources and Brightest Ultraviolet/Optical Flare Ever Observed
Researchers from the Purple Mountain Observatory (PMO) of the Chinese Academy of Sciences and the Italian National Institute for Astrophysics have made a groundbreaking discovery in the field of astrophysics. They have developed a new method to measure ultraviolet (UV) sources using the Swift/UVOT satellite and have identified the brightest ultraviolet/optical flare ever observed, known as GRB 220101A.
The findings, which challenge prior understandings of ultraviolet/optical bursts, were recently published in the journal Nature Astronomy. Gamma-ray bursts (GRBs) are considered the most violent explosions in the universe. They emit prompt radiation primarily in the soft gamma-ray band, which lasts for a short time. This prompt emission is then followed by X-ray, optical, and radio afterglow emissions that can last for weeks or even years.
In 2008, GRB 080319B set the record for the brightest ultraviolet/optical emission in the universe. It was so bright that it could be seen with the naked eye in a dark location. However, GRB 220101A has now broken that record. On New Year’s Day 2022, the Swift satellite detected this new burst, which had a high redshift of 4.618. The observed optical photons suffered from significant absorption due to the high redshift, resulting in an intrinsic radiation flux approximately 100 times higher than the observed value.
The researchers conducted a detailed photometric analysis of the burst and found a rapid evolution of the flux. The UVOT telescope used in the study was already moderately saturated at the peak time of the flare. The team proposed a processing method for the UVOT data based on the telescope’s point spread function, confirming its reliability in providing accurate flux measurements.
After accounting for proper distance and absorption corrections, the researchers determined that the ultraviolet/optical emission of GRB 220101A reached an absolute magnitude of -39.4. This makes it the only known source to date with a brightness surpassing -39. Furthermore, the luminosity of GRB 220101A is estimated to be approximately 400 quadrillion times that of the Sun, breaking the 14-year record held by GRB 080319B.
This discovery not only signifies a new astrophysical process but also highlights the diversity of physical origins of super-bright optical-ultraviolet bursts. It challenges previous understandings and opens up new avenues for research in the field of astrophysics.
Looking ahead, the China-France Space Variable Objects Monitor (SVOM) satellite, set to launch in early 2024, is expected to detect even higher redshift ultraviolet/optical flares. This will provide further insights into these astrophysical phenomena and contribute to a deeper understanding of the universe.
The research article titled “An optical-ultraviolet flare with an absolute AB magnitude of -39.4 detected in GRB 220101A” was authored by Zhi-Ping Jin, Hao Zhou, Yun Wang, Jin-Jun Geng, Stefano Covino, Xue-Feng Wu, Xiang Li, Yi-Zhong Fan, Da-Ming Wei, and Jian-Yan Wei. It was published on June 26, 2023, in Nature Astronomy.
Reference: “An optical-ultraviolet flare with absolute AB magnitude of −39.4 detected in GRB 220101A” by Zhi-Ping Jin, Hao Zhou, Yun Wang, Jin-Jun Geng, Stefano Covino, Xue-Feng Wu, Xiang Li, Yi- Zhong Fan, Da-Ming Wei and Jian-Yan Wei, 26 June 2023, Nature Astronomy.
DOI: 10.1038/s41550-023-02005-w