The source of mysterious recurring radio signals from space has been identified

there A mysterious phenomenon in it Strong radio signals Reach out periodically spaceBut its source is still completely unknown. These phenomena are known as “long period radio transients” (LPTs), and are observed as… Radio bursts Which is repeated at intervals ranging from several minutes to several hours. Only about ten examples have been discovered inside milky wayTheir physical nature remained a mystery for a long time.

Previous research has suggested that candidates for the source of LPTs include: Neutron stars Known as “magnetars”, they rotate very slowly and are composed of binary systems White dwarfs With accompanying stars. However, the magnetar hypothesis faces the problem of contradicting existing theoretical models.

On the other hand, while some cases suggesting a connection to white dwarf binaries have been reported, there have been no cases where it has been directly confirmed that the accretion process actually occurred.

Against this background, an international research team led by the University of Sydney in Australia conducted a sky survey using the “Australian Square Kilometer Array (ASKAP)” radio telescope and determined the true nature of a mysterious object called “ASKAP J174508.9-505149”. These results are observational It is said to be the strongest evidence to date pointing to LPT as one of the sources of this phenomenon.

“For the first time we have identified the origin of these signals.” He said Kofi Rose, PhD student at the University of Sydney School of Physics and the Commonwealth Scientific and Industrial Research Organization (CSIRO), said in a press release. “We were able to show that the source of one of these transient elements comes from a white dwarf pulling material from a companion star.”

A white dwarf and a companion star

Rose and his research team confirmed through spectroscopic observations that ASKAP J1745-5051 shows hydrogen emission lines (Balmer series) and helium emission lines (HeI and HeII). In particular, the strong HeII emission line is known to be a distinct optical property of “magnetic catastrophic variables”.

Cataclysmic variables is a general term for nearby binary systems in which a white dwarf accretes matter from a companion star. Among these cases, those in which the white dwarf has a strong magnetic field and gas accretes along magnetic field lines are called “magnetocataclysmic variables.”

Furthermore, analysis of the radial velocities of the Balmer series emission lines showed that the orbital period of this binary system is about 1.368 hours, which has been confirmed to match the repetition period of the radio pulses, about 1.345 hours. Furthermore, based on the orbital period, the companion star’s mass was estimated to be about 0.096 times that of the Sun, and its radius was about 0.13 times that of the Sun, indicating that it corresponds to an M6-class red dwarf.

In other words, ASKAP J1745-5051 is a binary system in which a white dwarf and a red dwarf orbit each other at an extremely close distance. A white dwarf is the remains of a high-density star that has reached the end of its life. Although its size is approximately the size of the Earth, its mass is equivalent to the mass of the Sun. Its companion, the red dwarf, is larger but less dense, with a mass of only about one-tenth that of the Sun. The two stars orbit each other in a short period of just over one hour.