Nainital: A group of astronomers from Argentina, Spain, Italy, the USA and India has discovered a binary supermassive black hole system in the gravitationally lensed blazar AO 0235+164 using extensive optical photometric observations carried out around the globe during the last 4 decades (1982 – 2019).
When the jet, composed of ionized matter travelling at nearly the speed of light, is pointed towards an observer, it is called a blazer. Blazars which are supermassive black holes (SMBH) feeding on gas in the heart of a very distant galaxy are among the most luminous and energetic objects in the Universe.
The blazar AO 0235+164 is unique as it is gravitationally lensed by intervening galaxies (a phenomenon by which light shining from far away is bent and pulled by the gravity of an object between its source and the observer).
The blazar AO 0235+164 is the first binary SMBH gravitationally lensed system, which will be a strong candidate of its kind for future detection of gravitational waves (GWs) using the pulsar timing array and future space-based GW detectors.
The astronomers discovered periodic double-peaked flaring events at an interval of around 8 years, and the separations between two peaks of these flares are around 2 years. Five such periodic patterns were detected, and it was predicted that the next such flaring event will occur between November 2022 and May 2025. To confirm the next periodic pattern, a global optical photometric monitoring campaign has been initiated under WEBT (Whole Earth Blazar Telescope) consortium. The observational campaign will be led by Dr Alok C. Gupta.
Dr Alok C. Gupta, a Senior Scientist from Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, an autonomous institution of the Department of Science and Technology (DST), Government of India, has participated in this study which has been recently published in the journal Monthly Notices of the Royal Astronomical Society (MNRAS). The study was led by Abhradeep Roy, a PhD student at the Department of High Energy Physics (DHEP), Tata Institute of Fundamental Research (TIFR), Mumbai. The other members of the Indian team include Prof. V. R. Chitnis, Dr Anshu Chatterjee and Dr Arkadipta Sarkar from TIFR, Mumbai.
The team detected five sets of double-peaked flaring activities during time ranges — January 1982 – October 1984, March 1989 – July 1993, April 1996 – March 2001, June 2006 – June 2009 and May 2014 – May 2017.
They expect the next such 2 years long flaring episode to happen between November 2022 and May 2025. An intensive multi-wavelength WEBT campaign will be conducted during this period to test the persistence of this apparent nearly-periodic oscillation (QPO) in AO 0235+164.
– global bihari bureau