Scientists have recorded transient rhythmic oscillations in gamma radiation from blazar Markarian 501. This detection will improve our understanding of the energy processes occurring in space.
Blazars, classified as members of a large group of galaxies with active nuclei (AGN), are considered the most numerous extragalactic sources of gamma radiation. They are characterized by relativistic jets that are directed almost exactly to the Earth. Blazars are perceived as high-energy engines, which play the role of natural laboratories for studying particle acceleration, relativistic plasma processes, magnetic field dynamics, and black hole physics.
Markarian 501 is 456 million light years distant. This is a blazar or BL Lac source whose spectrum extends to the highest energy gamma rays. Before us is one of the closest blazars glowing in the X-ray image, and one of the earliest extragalactic sources found in the TeV band.
Weighted z-transformation of the γ-ray emission curve for blazar Mrk 501. The left shows the distribution of the color power of the WWZ in the time period plane, and the right shows the time-averaged power (blue curve) as a function of the period. The purple and red curves show the contours of the local value of 90% and 99% During the last decade, the object was monitored with the Fermi gamma-ray telescope. Recently, scientists analyzed data from observations collected from August 2008 to June 2018, and were able to record the rhythmic fluctuations in the gamma radiation of Blazar. That is, the researchers noticed a powerful signal of quasiperiodic oscillations (QPO) at intervals of 332 days. Modulation of the gamma-ray flux has gradually faded out over recent years.
Scientists stressed that the gamma ray QPO in Mrk 501 lasted for almost 7 cycles, until it weakened. Not many QPO gamma rays show more than 5 cycles, so the case with Mrk 501 may be one of the few examples when a relatively high frequency is demonstrated with a period of less than a year.
The study put forward several hypotheses that can serve as a driving force for such rhythmic oscillations. There are several scenarios, including supermassive binary black holes, jet precession, and an accretion disk precessing under the action of gravitational torque. Scientists believe that it is necessary to continue to study the object in order to determine the most plausible theory of the origin of oscillations in the blazar.
