New X-ray Signals from Blazars to Help Understand Energy Processes of Active Galaxies
Researchers fromARIES have discovered that the accretion disk also contributes to X-ray emissions during low-activity states after studying four powerful blazars.
Astronomers have gained significant new insights into the sources of X-ray emissions through the study of 'blazars', some of the most energetic celestial bodies in the universe. This research could be instrumental in understanding the process that powers active galaxies and the extreme physical conditions surrounding them.
Blazars are active galaxies powered by supermassive black holes (SMBH) located at their centers. As matter falls toward the black hole, massive amounts of energy are released, and powerful jets of relativistic particles are projected almost directly toward Earth, making these objects appear exceptionally bright. This group includes 'TeV blazars', which produce high-energy gamma rays reaching tera-electron volts.
Researchers from the Aryabhatta Research Institute of Observational Sciences (ARIES), an autonomous institute under the Department of Science and Technology (DST) located in Nainital, studied four classical blazars: Mrk 421, Mrk 501, PG 1553+113, and PKS 2155-304. Researchers Riya Bhowmik and Alok C. Gupta analyzed 13 sets of X-ray observations obtained from NASA's NICER and NuSTAR space telescopes. While NICER studied low-energy X-rays, NuSTAR focused on the high-energy range.
During the study, it was found that in some observations of Mrk 421 and Mrk 501, an additional component appeared at low X-ray energies when they were in a medium to low activity state. This indicates that during periods of low activity, emissions from the accretion disk surrounding the black hole contributed to the X-ray spectrum alongside the jet. While such evidence had been found for Mrk 421 previously, this is the first potential signal for Mrk 501, which requires further observations for confirmation.
Meanwhile, observations of the other two blazars, PG 1553+113 and PKS 2155-304, were found to be consistent with standard models. The study, published in 'The Astrophysical Journal', clarifies that the X-ray spectrum of a blazar is not dominated by a single radiation source. When the jet emission is weak, the contribution of the accretion flow can be detected. This will help in understanding the interactions between black holes and their environments in the future.
