Near the center of the Milky Way, astronomers have noticed a powerful variable source of polarized radio emission ASKAP J173608.2-321635. These flares are not accompanied by radiation in other ranges; therefore, it has not yet been possible to explain the nature of the source. It is reported in a new article accepted for publication in The Astrophysical Journal and available in the open preprint library arXiv.org.
The work was carried out by a large international team of scientists led by Ziteng Wang of the Sydney Institute of Astronomy. They spotted ASKAP J173608.2-321635 signals in observations from Australia's ASKAP radio telescope in late 2019 and early 2020. ASRAP registered 13 such outbreaks, but several attempts to examine the source with other instruments, already in the middle of last year, did not bring any results. Only in 2021, the ATCA radio telescopes (in Australia) and SA MeerKAT (in South Africa) confirmed the first observations and noticed new flares.
Historical searches revealed that ASKAP J173608.2-321635 had apparently not appeared before. Its flashes in the radio range last for weeks, after which they abruptly, in a matter of hours, fade out. They are distinguished by complex linear and circular polarization. This may indicate that the radiation on its way to us passes through gas and dust clouds penetrated by a powerful magnetic field, or the source itself is characterized by such fields.
However, the strangest thing was not the changeable nature of ASKAP J173608.2-321635, but the fact that this source does not emit at other wavelengths - neither in the infrared range, nor in the X-ray range. This means that it is unlikely to be associated with the activity of a star, a binary system, or even a neutron pulsar star. The authors also ruled out a gamma-ray burst and a supernova explosion. Perhaps we are dealing with an as yet unclear manifestation of one of these objects or with something completely new and still unknown.