A team of astronomers observing the Small Magellanic Cloud, a companion galaxy to the Milky Way, captured an extremely bright X-ray burst and discovered a rare binary system consisting of a Be-type star and a white dwarf. Previously, researchers had observed such a bright event only once.

The Magellanic Clouds, the Milky Way’s two largest satellite galaxies, have been interacting with each other and with our Galaxy for seven billion years. The Large Magellanic Cloud is about ten times larger than the Small Magellanic Cloud, but a group of astronomers led by scientists from the University of Pennsylvania (USA) observed a bright X-ray burst coming from the source CXOU J005245.0-. 722844.

Thus, the authors of the scientific study presented in the journal Monthly Notices of the Royal Astronomical Society, They were able to detect a rare binary system consisting of a white dwarf and a Be-type star.

Be stars are very hot, massive luminaries. Due to their enormous rotation speed, disks of gas are formed around them that can interact with the companion in the binary system. This interaction results in various astronomical phenomena, including X-ray flares.

Neutron stars or black holes are usually companions in such systems, but in this case, as astronomers detected, a white dwarf has become a companion. This is the seventh known case of such a pair; This makes the discovery particularly valuable for understanding the evolution of stars and binary systems.

Using the X-ray Orbital Observatory Swift, astronomers recorded a flash that lasted less than 16 days. The event exceeded the Eddington limit, which is the threshold for the strength of electromagnetic radiation emitted from a star’s interior and where the pressure of this radiation is sufficient to compensate for the weight of the star’s shells. In other words, according to him, the star is in balance; It does not contract and expands. Exceeding the limit causes light to leak out of the outer layers, leading to loss of matter.

After analyzing the spectrum, the team discovered that the radiation source was typical for white dwarfs: Thermonuclear explosions were observed on the surface of these stars, which occur when a sufficient amount of accumulating material accumulates.

Astronomers then made additional observations in the optical and ultraviolet ranges using the OGLE and ATLAS telescopes and found a brief increase in the star’s brightness coinciding with the X-ray burst. The obtained data provided new evidence that the flare is associated with thermonuclear processes on the surface of the white dwarf.

The researchers also found that a few years before the explosion, the system’s orbital period shortened from 17.55 days to 17.14 days. This indicates dynamic changes in the system associated with the accretion of material on the white dwarf before the explosion: as its mass grew, the rotation of the body naturally slowed down.

Astronomers have previously observed such a flare, caused by a thermonuclear explosion on a white dwarf paired with a Be star in the MAXI J0158-744 system. These extremely rare events make it possible to study accumulation and eruption processes under extreme conditions. The discovery also helps explain the origin of ultraluminous X-ray sources observed in other galaxies.

The team plans to continue observing CXOU J005245.0-722844 to understand how often such explosions occur and what mechanisms cause them. According to the authors of the scientific paper, further research will help study the evolution of stars and develop models of the cosmic catastrophic events that form and transform galaxies.