December 17, 2013
Swift Data Reveals 100K New Cosmic X-Ray Source Locations
redOrbit Staff & Wire Reports - Your Universe Online
By analyzing data collected by NASA’s Swift robotic spacecraft, astronomers from the University of Leicester have reportedly discovered the location of nearly 100,000 previously unknown cosmic X-ray sources.
The research team studied eight years’ worth of observations collected during the Swift Gamma-Ray Burst Mission to compile a catalog of major celestial X-ray sources – a list that includes more than 150,000 high-energy stars and galaxies and appears in the latest edition of The Astrophysical Journal.
“In addition to providing the positions of almost a hundred thousand previously unknown X-ray sources, the team have also analyzed the X-ray variability and X-ray colors of the sources in order to help to understand the origin of their emission, and to help in the classification of rare and exotic objects,” the university said in a statement Monday. “All of the data, including light curves and spectra are available online.”
The Swift satellite was originally launched back in November 2004, and since then it has been studying the immensely powerful stellar explosions, which date back to the earliest days of the universe. The study authors have called it one of the most productive observatories, ever since its launch.
Over the past eight years, Swift has helped revolutionize gamma ray burst (GRB) research thanks largely to its powerful X-ray telescope, which was built at the UK university. In addition to finding the afterglows of these gamma-ray bursts, the telescope can also detect several other types of x-ray sources located within its field of view.
“In order to be able to respond quickly to the rapidly fading GRBs, Swift is uniquely agile and autonomous, able to point within a minute or so at a new target,” the university said. “Because of its science remit and this unusual ability, the Swift XRT has observed a much larger fraction of the sky than the larger European and US X-ray observatories. For this reason it has found a vast number of extra sources in spite of its much lower cost.”
“Most of the newly discovered X-ray sources are expected to signal the presence of super-massive black holes in the centers of large galaxies many millions of light-years from earth, but the catalogue also contains transient objects (short-lived bursts of X-ray emission) which may come from stellar flares or supernovae,” the university said.
X-rays are emitted by stars and galaxies because the electrons that they contain travel at exceptionally high speeds, either because they are extremely hot or because they are accelerated by powerful magnetic fields. Gravity is typically the underlying cause. Gas can be compressed and heated as it falls onto black holes, neutron stars and white dwarfs, the researchers said, or when it becomes trapped in the magnetic fields of stars.
“The unique way Swift works has allowed us to produce not just another catalogue of X-ray objects, but one with a real insight into how celestial X-ray emission varies with time. Astronomers will use this for years ahead when trying to understand the new things they see,” said first author Dr. Phil Evans of the University of Leicester’s Department of Physics and Astronomy.
“Catalogues of stars and galaxies form the bedrock of the work of astronomers,” added Professor Julian Osborne, leader of the Swift team at the university. “The culmination of great effort, they are a valuable resource for understanding the Universe, and frequently go on to be used in ways which could not be imagined when they are made.”