An international team of astronomers has detected a bright, slow-moving nuclear transition event using NASA’s Swift spacecraft. The source of the newly discovered transition, named Swift J221951-484240, has yet to be determined.

Nuclear astrophysics is key to understanding supernova explosions and especially the synthesis of chemical elements that arose after the Big Bang. Therefore, the detection and study of nuclear transitions may be important to advance our knowledge in this area.

Recently, a team of astronomers led by Sam Oates of the University of Birmingham, England, followed Swift’s gravitational wave, known as S190930t, to find its electromagnetic equivalent. As a result, they identified Swift J221951-484240 (or J221951 for short) with the Swift Ultraviolet/Optical Telescope (UVOT).

“J221951 was discovered while observing the gravitational phenomenon: S190930t…. Source looks nuclear compared to our ACS images [удосконалена камера для оглядів космічного телескопа Хаббл] with DES images [Dark Energy Survey]Made in 2014,” the researchers explained.

J221951 was detected at 0.52 spectroscopic redshift and excluded its association with S190930t. At its peak, J221951 was 1-3 orders of magnitude brighter than archive values ​​across all ultraviolet, optical, and infrared wavelengths. The transient reached a maximum absolute magnitude of -23 and a peak bolometric luminosity of 1.1 quartet million ergs/sec.

The total energy emitted by J221951 is estimated to be about 26 sexdecillion ergs. According to the astronomers, this result, together with the absence of broad absorption lines in the optical spectrum, excludes the J221951 supernova explosion scenario.

Archival photometric data for J221951 shows slow growth before a peak near the date of discovery. In addition, the new optical spectra of this transition process are blue and relatively obscure. Therefore, based on all the results, Oates’ team classified J221951 as a bright and slowly evolving blue transition.

In trying to determine the origin of J221951, the paper’s authors consider the two most plausible hypotheses, because the transient has characteristics consistent with a tidal disruption event (TDE) and an active galactic core (AGN) ignition.

“The ancestor of J221951 is unknown. Optical and UV spectra show properties similar to both TDEs and AGNs. In general, their spectral, temporal and economic properties and energies are closest in nature to ASASSN-15lh and ASASSN-18jd. ASASSN-15lh, ASASSN -18jd, and J221951 belong to an increasing population of bright blue transitions, termed ambiguous nuclear transitions, whose ancestry is not well constrained but may be due to TDEs or AGN activity.”

They added that further observations of the late evolution of J221951 will be crucial to figuring out which hypothesis is correct. Source