The feeding patterns of black holes offer insight into their size, researchers report. A new study revealed that the flickering in the brightness observed in actively feeding supermassive black holes is related to their mass.
Supermassive black holes are millions to billions of times more massive than the sun and usually reside at the center of massive galaxies. When dormant and not feeding on the gas and stars surrounding them, SMBHs emit very little light; the only way astronomers can detect them is through their gravitational influences on stars and gas in their vicinity. However, in the early universe, when SMBHs were rapidly growing, they were actively feeding – or accreting – materials at intensive rates and emitting an enormous amount of radiation – sometimes outshining the entire galaxy in which they reside, the researchers said.
The new study, led by the University of Illinois Urbana-Champaign astronomy graduate student Colin Burke and professor Yue Shen, uncovered a definitive relationship between the mass of actively feeding SMBHs and the characteristic timescale in the light-flickering pattern. The findings are published in the journal Science.
The observed light from an accreting SMBH is not constant. Due to physical processes that are not yet understood, it displays a ubiquitous flickering over timescales ranging from hours to decades. “There have been many studies that explored possible relations of the observed flickering and the mass of the SMBH, but the results have been inconclusive and sometimes controversial,” Burke said.
The team compiled a large data set of actively feeding SMBHs to study the variability pattern of flickering. They identified a characteristic timescale, over which the pattern changes, that tightly correlates with the mass of the SMBH. The researchers then compared the results with accreting white dwarfs, the remnants of stars like our sun, and found that the same timescale-mass relation holds, even though white dwarfs are millions to billions times less massive than SMBHs.
The light flickers are random fluctuations in a