Scientists spot brightest flare in blazar paving way for understanding galaxy mergers

The blazar called PG 1553+113 which is a primary candidate for a binary supermassive black hole system has lately intrigued scientists because of its repetitive gamma-ray emissions which are quasi-periodic. A group of astronomers from around the world, who studied it for 76 nights at a stretch, spotted its brightest flare. Analysis of this flare has helped them trace the dominant emission mechanism of this blazer paving the way towards understanding the process of galaxy mergers in the early universe.

Galaxies merge frequently throughout cosmic times. Whenever two galaxies harbour supermassive black hole (SMBH) at their centers, the formation of a binary SMBH is inevitable. SMBHs, cannot be spatially spotted with current techniques. Therefore, to search them, scientists have to rely on indirect methods. One of these indirect search strategies is based on the detection of periodicity in the source. A few recent candidates displaying quasi-periodic light curve variability have emerged from large-sky surveys and long-term monitoring programs. PG 1553+113 is one of them which enters outburst and produces very high energy emission.

Researchers from Raman Research Institute (RRI) an autonomous institute of the Department of Science & Technology (DST), Government of India along with collaborators from all over the world captured this flare using the 1.3 m JC Bhattacharya telescope (JCBT), Kavalur, India. Subsequently they monitored the Blazar for 76 nights using nine different telescopes around the globe. They studied the multiband flux and spectral variability of the blazar PG 1553+113 on diverse timescales.

The astronomers estimated the periodicity, radius, size of the emission region, the magnetic field strength, and the electron energy for the blazar. Besides, having recorded the flare, they have found that the accelerated particles cool off by synchrotron radiation (popularly known as synchrotron cooling) and is the dominant emission mechanism. The research was published in the journal “Astronomy & Astrophysics”.

These findings which can help explore the binary black hole nature of PG 1553+113 can facilitate understanding the process of galaxy mergers in the early universe and also provide interesting targets for observation of multi-messengers like light, neutrinos, and gravity waves which help us in studying the cosmos.