Context: Recently, Researchers from the Indian Institute of Astrophysics (IIA), Bangalore, have conducted the first systematic study on the gamma-ray flux variability nature on different types of blazars.

• The research work based on characterizing the flux variability nature on month-like time scales in the high energy gamma-ray (100 MeV to 300 GeV) band for different types of blazars has been published in the journal Astronomy and Astrophysics.
• IIA is an autonomous institute of the Department of Science and Technology, Government of India.

Key Points

• Their study could provide clues to the processes happening close to the black hole, not visible through direct imaging. 
• At the center of most galaxies, there’s a massive black hole that can have mass of millions or even billions of Suns that accrete gas, dust, and stellar debris around it.  
• As these material falls towards the black hole, their gravitational energy gets converted to   light forming active galactic nuclei (AGN).   
• The results obtained from this particular piece of work will provide key inputs to the problem of finding the high energy gamma-ray production site in blazars.  
• Thus it will have direct relevance to the enhancement of the knowledge on blazars.  

About Blazars

• Blazars are the most luminous and energetic objects in the known universe were found to be emitters of gamma-rays in the 1990s.
• These are powerful sources of emission across the electromagnetic spectrum and are observed to be sources of high-energy gamma ray photons.
• It is only with the capability of Fermi Gamma-ray space telescope (launched in 2008) to scan the entire sky once in three hours one is able to probe the flux variability characteristics of blazars on a range of time scales.
• In July 2018, the IceCube Neutrino Observatory team traced a neutrino that hit its Antarctica-based detector in September 2017 to its point of origin in a blazar 3.7 billion light-years away. This was the first time that a neutrino detector was used to locate an object in space.

Origin of Blazars

• At the center of most galaxies, there’s a massive black hole that can have mass of millions or even billions of Suns that accrete gas, dust, and stellar debris around it.
• As these material falls towards the black hole, their gravitational energy gets converted to light forming Active Galactic Nuclei (AGN).
• A minority of AGN (~15%) emit collimated charged particles called jets travelling at speeds close to the speed of light.
• Blazars are AGN whose jets are aligned with the observer’s line of sight.
• Some blazars are thought to host binary black holes in them and could be potential targets for future gravitational-wave searches.

How this study will help the researchers?

• Bridging Gap: The knowledge on the flux variability nature in the high energy gamma-rays on a month like timescales is limited. The results of this work will thus fill the gap on the knowledge of the high energy flux variability nature of blazars.
• Locating Gamma Ray Emissions: One of the open problems in high energy astrophysics is to localize the site for the production of gamma-rays.
• Variability studies in the high energy gamma-ray band can help one to locate the high energy emission site and the high energy emission process.
• Exploration of Gamma Band of Electromagnetic Spectrum: Gamma-ray band is one of the bands of the electromagnetic spectrum on which there is limited knowledge on the flux variability of blazars.
• Thus, exploring this band of the electromagnetic spectrum will provide key inputs to constrain the high energy production site as well as the high energy emission processes. This is the key idea behind this work.
• The expertise of handling high energy data from celestial sources gained in this work will build capacity to interpret the gamma-ray data that will emerge from India's upcoming facility, the Major Atmospheric Cerenkov Experiment Telescope as well as from any X-ray missions by India in the future. 

About Major Atmospheric Cerenkov Experiment Telescope

• It is the India's largest and the world's highest gamma-ray telescope being established at Hanle, Ladakh.
• It is being built by the Electronics Corporation of India Limited (ECIL), Hyderabad for the Bhabha Atomic Research Centre (BARC).
• It is remotely operated and runs on Solar Power.
• It will help to explore the exciting energy range of the gamma-ray energy region in between satellites and the traditional Atmospheric Cerenkov experiments.
• The telescope is named after the Russian scientist Cerenkov who predicted that charged particles moving at high speeds in a medium, emit light.