Black hole size revealed by its eating pattern

Date:
August 12, 2021
Source:
University of Illinois at Urbana-Champaign, News Bureau
Summary:
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.



FULL STORY ========================================================================== [Black hole illustration | Credit: (c) hallowedland / stock.adobe.com]
Black hole illustration (stock image).

Credit: (c) hallowedland / stock.adobe.com [Black hole illustration |
Credit: (c) hallowedland / stock.adobe.com] Black hole illustration
(stock image).

Credit: (c) hallowedland / stock.adobe.com Close 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 black hole's feeding
process, the researchers said. Astronomers can quantify this flickering
pattern by measuring the power of the variability as a function of
timescales. For accreting SMBHs, the variability pattern changes from
short timescales to long timescales. This transition of variability
pattern happens at a characteristic timescale that is longer for more
massive black holes.



==========================================================================
The team compared black hole feeding to our eating or drinking activity by equating this transition to a human belch. Babies frequently burp while drinking milk, while adults can hold in the burp for a more extended
amount of time. Black holes kind of do the same thing while feeding,
they said.

"These results suggest that the processes driving the flickering during accretion are universal, whether the central object is a supermassive
black hole or a much more lightweight white dwarf," Shen said.

"The firm establishment of a connection between the observed light flicker
and fundamental properties of the accretor will certainly help us better understand accretion processes," said Yan-Fei Jiang, a researcher at
the Flatiron Institute and study co-author.

Astrophysical black holes come in a broad spectrum of mass and size. In
between the population of stellar-mass black holes, which weigh less
than several tens of times the mass of the sun, and SMBHs, there is
a population of black holes called intermediate-mass black holes that
weigh between about 100 and 100,000 times the mass of the sun.

IMBHs are expected to form in large numbers through the history of
the universe, and they may provide the seeds necessary to grow into
SMBHs later.

However, observationally this population of IMBHs is surprisingly elusive.

There is only one indisputably confirmed IMBH that weighs about 150 times
the mass of the sun. But that IMBH was serendipitously discovered by the gravitational wave radiation from the coalescence of two less-massive
black holes.



==========================================================================
"Now that there is a correlation between the flickering pattern and the
mass of the central accreting object, we can use it to predict what the flickering signal from an IMBH might look like," Burke said.

Astronomers worldwide are waiting for the official kickoff of an era
of massive surveys that monitor the dynamic and variable sky. The Vera
C. Rubin Observatory in Chile's Legacy Survey of Space and Time will
survey the sky over a decade and collect light flickering data for
billions of objects, starting in late 2023.

"Mining the LSST data set to search for flickering patterns that are
consistent with accreting IMBHs has the potential to discover and fully understand this long-sought mysterious population of black holes,"
said co-author Xin Liu, an astronomy professor at the U. of I.

This study is a collaboration with astronomy and physics professor
Charles Gammie and astronomy postdoctoral researcher Qian Yang, the
Illinois Center for Advanced Study of the Universe, and researchers at the University of California, Santa Barbara; the University of St. Andrews,
U.K.; the Flatiron Institute; the University of Southampton, U.K.;
the United States Naval Academy; and the University of Durham, U.K.

Burke, Shen and Liu also are affiliated with the Center for Astrophysical Surveys at the National Center for Supercomputing Applications at
Illinois.

The National Science Foundation, the Science and Technology Facilities
Council and the Illinois Graduate Survey Science Fellowship supported
this research.

========================================================================== Story Source: Materials provided by University_of_Illinois_at_Urbana-Champaign,_News_Bureau.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. 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, Qian Yang. A characteristic optical variability
time scale in astrophysical accretion disks. Science, 2021 DOI:
10.1126/science.abg9933 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210812145033.htm

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