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Artist’s impression of an internal accretion flow and jet from a supermassive black hole as it actively feeds on, say, a star it has recently torn apart. Image: ESO / L. Calçada
Flickering light emitted from astrophysical accretion discs can reveal mass of supermassive black hole (SMBH) at their center, according to a new study. The results provide a new method to characterize SMBH masses using optical observations and help limit the poorly understood processes that occur in accretion disks.
Accretion discs – made up of gas, dust and plasma – surround the SMBHs located in the center of active galaxies. As the material from the accretion disk falls toward the black hole, it heats up, emitting an enormous amount of radiation, including ultraviolet and optical light.
While these disks are much smaller than their host galaxy – roughly the size of the Solar System – they can often outperform everything else in the galaxy. However, accretion discs flicker for unknown reasons, causing their brightness to fluctuate over a wide range of time scales.
Colin Burke and colleagues report that a characteristic timescale measured from the optical variability of accretion disks correlates with the masses of SMBH they surround. The authors measured the optical variability of 67 well-observed active galaxies to determine the timescale over which the fluctuations became noticeably smaller, known as the “damping” timescale (typically several hundred days). ). They find that this damping timescale is related to SMBH mass over the entire range of SMBH masses seen in active galaxies and may even extend to smaller accretion disks around other objects.
“One of the most interesting aspects of Burke’s study et al. is that he extends his discoveries to much less massive objects, such as white dwarf stars, which emit radiation via a similar accretion disk mechanism and can be thought of as miniature accretion SMBHs, ”write Paulina Lira and Patricia Arevalo in a related perspective.
To learn more about this discovery, read Mysterious Flickering Decoded: Supermassive Black Hole Size Revealed by Its Feeding Pattern.
Reference: “A characteristic optical variability timescale in astrophysical accretion discs” by Colin J. Burke, Yue Shen, Omer Blaes, Charles F. Gammie, Keith Horne, Yan-Fei Jiang, Xin Liu, Ian M. McHardy, Christopher W. Morgan, Simone Scaringi and Qian Yang, August 12, 2021, Science.
DOI: 10.1126 / science.abg9933
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