Indian astronomers have tracked some of the blazars – rare and extreme type of galaxy cores producing massive amounts of electromagnetic energy – revealing new clues about the sources of X-ray emission in these extraterrestrial objects.
Blazars are the most energetic objects in the Universe. The research could help scientists understand the extreme physical conditions around these objects and provide insights into how active galaxies are powered, according to the Ministry of Science and Technology.
Blazars are active galaxies powered by Super Massive Black Holes (SMBHs) at their centers. As matter falls toward the black hole, enormous amounts of energy can be released, while powerful jets of relativistic particles are launched almost directly towards Earth.
This orientation can make blazars appear extraordinarily bright. A particularly extreme group of these objects, known as TeV blazars, produces very-high-energy gamma rays reaching teraelectron volt (TeV) energies. A TeV is equivalent to one trillion electron volts.
As the powerful jets from blazars are directed towards the Earth, their X-ray spectra are generally dominated by emission from the jet. This makes it difficult to identify radiation originating from other parts of the galaxy.
To overcome this difficulty, researchers from the Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, studied four classical TeV blazars using observations from NASA’s NICER and NuSTAR space telescopes. The researchers analysed their X-ray radiations to better understand the behaviour of these energetic galaxies.
According to the researchers, the spectra of some NICER and NuSTAR observations were analysed for the first time in this study, which had been published recently in The Astrophysical Journal, brought out by the American Astronomical Society.
They analysed 13 sets of X-ray observations of the four TeV blazars. NICER observed lower-energy X-rays, while NuSTAR covered a higher-energy range. Combining observations from the two telescopes gave a broader view of the X-ray emission from these energetic objects, the Ministry said.
Their findings suggest that the X-ray spectra of blazars are not simply dominated by a single source of radiation. When emission from their powerful jets weaken, radiation from the accretion flow may become detectable.
Observing blazars when they are both active and relatively quiet could therefore help astronomers understand how these two sources of radiation contribute. Apart from understanding the powering of active galaxies it can help comprehend the interaction of black holes with their surrounding environment, according to the Ministry.
