Indian Scientists discover rare insights of how fluctuation in light curve in the jet of super-massive black holes may help explore emissions from them

Indian scientists have detected a rare moving blob (region of higher density) or fluctuation in the light curve of the jet of radiations and particles coming out from a supermassive black hole (SMBH) located at the centre of an active galaxy that can provide insight into the underlying emission process of the black hole.

Fluctuation in light curve in the jet of supermassive black holes may help explore emissions from them.

Super-massive black holes in the centres of some active galaxies create powerful jets of radiation and particles travelling close to the speed of light. Attracted by strong gravity, matter falls towards the central black hole as it feeds on the surrounding gas and dust, and as a result, they often outshine their host galaxies.

CTA 102 is a blazar subclass of active galaxy, and its center is SMBH situated at roughly 8 billion light-years away flared during 2016–17, and the emission observed during this flare was significantly higher than its average emission.

Dr. Alok C. Gupta and Dr. P. Kushwaha from Aryabhatta Research Institute of Observational Sciences (ARIES), an autonomous institute under the Department of Science & Technology, Government of India and collaborators Mr. A. Sarkar and Prof. V. R. Chitnis from Tata Institute of Fundamental Research (TIFR), Mumbai, and Prof. P. J. Wiita from The College of New Jersey, USA who gathered Gamma-ray data was from the NASA Fermi-LAT satellite and optical data from a large number of ground-based observatories from across the world of this flare.

Simultaneous quasi-periodic oscillations (QPOs) with a period of around 7.6 days were observed in the γ-ray and optical fluxes of CTA 102 during its high optical activity episode in 2016–2017.

The findings of the study have been recently published in the scientific journal ‘Astronomy & Astrophysics’. The best explanation for the detected QPO appears to be a region of enhanced emission (blob), moving helically inside the jet, which may help explore emission from black holes and the process behind it.

It may be noted that under the leadership of Dr. Gupta, the ARIES at Nainital has been doing this research over last one year on the optical properties of super-massive black-hole.

Through 153 nights, 17 scientists from 9 countries in Europe and Asia including researchers from ARIES had taken 2263 image frames and observed the changes in a very high energy gamma-ray emitting blazar ‘1ES 0806+524’ using seven optical telescopes in Europe and Asia.

A blazar is a feeding super-massive black-hole (SMBH) in the heart of a distant galaxy that produces a high-energy jet viewed face-on from Earth. Blazars are one of the most luminous and energetic objects in the known universe with a jet composed of ionized matter traveling at nearly the speed of light directed very nearly towards an observer.

Dr. Ashwani Pandey, guided by Dr. Alok C. Gupta from ARIES in their study published in the Astrophysical Journal, has provided the most extensive observations of this blazar, thereby chalking out the detailed optical properties of the blazar. The team studied in great details 1ES 0806+524’ flux, color, and spectral index variations within a day and long timescales of the blazer and explained the mechanism behind the variations.

They explained the large flares as the result of propagation of a shock in the relativistic jet that accelerates electrons to high energies followed by subsequent cooling. According to their study, the small amplitude changes can be understood to arise from small variations in the viewing angle, and hence in the Doppler factor, caused by either wiggling or helical jets or the motion of the most intense emitting region on a roughly helical trajectory within the jet. Variations on intra-day timescales can be explained by the turbulence expected in a relativistic plasma jet according to the study.

In this age of multi-wavelength (MW) time-domain astronomy in which the transient astronomical sources are of great interest due to their rapid change in flux and polarization. Simultaneous MW observation of a particular transient source on an extended period of time is important for understanding the emission mechanism in different electromagnetic (EM) bands. Blazars are among one of the most favourite astronomical transient objects because they emit radiation in the complete EM spectrum, and their flux and polarization are highly variable.