For many years astronomers have been trying to understand the similarities between stellar-mass sized Galactic black hole systems and the supermassive black holes in active galactic nuclei (AGN).In particular, do they vary fundamentally in the same way, but perhaps with any characteristic timescales being scaled up in proportion to the mass of the black hole. If so, the researchers proposed, we could determine how AGN should behave on cosmological timescales by studying the brighter and much faster galactic systems.
Professor Ian McHardy, from the University of Southampton, heads up the research team whose findings are published today (along with colleagues Drs Elmar Koerding and Christian Knigge and Professor Rob Fender, and Dr Phil Uttley, currently working at the University of Amsterdam). Their observations were made using data from NASA’s Rossi X-ray Timing Explorer and XMM Newton’s X-ray Observatory.
Professor McHardy comments, "By studying the way in which the X-ray emission from black hole systems varies, we found that the accretion or ‘feeding’ process - where the black hole is pulling in material from its surroundings - is the same in black holes of all sizes and that AGN are just scaled-up Galactic black holes. We also found that the way in which the X-ray emission varies is strongly correlated with the width of optical emission lines from black hole systems."
He adds, "These observations have important implications for our understanding of the different types of AGN, as classified by the width of their emission lines. Thus narrow line Seyfert galaxies, which are often discussed as being unusual, are no different to other AGN; they just have a smaller ratio of mass to accretion rate."
The research shows that the characteristic timescale changes linearly with black hole mass, but inversely with the accretion rate (when measured relative to the maximum possible accretion rate). This result means that the accretion process is the same in black holes of all sizes. By measuring the characteristic timescale and the accretion rate, the team argues this simple relationship can help determine black hole masses where other methods are very difficult, for example in obscured AGN or in the much sought after intermediate mass black holes.
Professor McHardy continues: "Accretion of matter into a black hole produces strong X-ray emission from very close to the black hole itself. So, studying the way in which the X-ray emission varies with time, known as the X-ray lightcurves, provides one of the best ways of understanding the behaviour of black holes.
It has been known for over two decades that characteristic timescales can be seen in the X-ray lightcurves of Galactic black hole systems. The timescales are short (second) and so can be found in short observations. However to find the equivalent timescales in AGN is much harder as we must observe for months or years."
Igniting a solar flare in the corona with lower-atmosphere kindling
29.03.2017 | New Jersey Institute of Technology
NASA spacecraft investigate clues in radiation belts
28.03.2017 | NASA/Goddard Space Flight Center
The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.
To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...
Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.
The results will be published on March 22 in the journal „Astronomy & Astrophysics“.
Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...
Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.
Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...
In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.
Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...
20.03.2017 | Event News
14.03.2017 | Event News
07.03.2017 | Event News
29.03.2017 | Materials Sciences
29.03.2017 | Physics and Astronomy
29.03.2017 | Earth Sciences