X-ray Binary Circinus X-1
The youngest member of an important class of objects has been found using
data from NASA's Chandra X-ray Observatory and the Australia Compact Telescope
Array. A composite image shows the X-rays in blue and radio emission in purple,
which have been overlaid on an optical field of view from the Digitized Sky
Survey. This discovery, described
in the press release, allows scientists to study a critical phase after a
supernova and the birth of a neutron star.
Systems known as "X-ray binaries" are some of the brightest X-ray sources in
the sky. They consist of either an ultra-dense star packed with neutrons ---
a.k.a., a "neutron star" --- or a black hole that is paired with a normal star
like the sun. As these two objects orbit one another, the neutron star or black
hole pulls material from the companion star onto it.
A new study shows that the X-ray binary called Circinus X-1 is less than
4,600 years old, making it the youngest ever seen. Astronomers have detected
hundreds of X-ray binaries throughout the Milky Way and other nearby galaxies.
However, these older X-ray binaries only reveal information about what happens
later in the evolution of these systems.
Astronomers were able to determine the age of Circinus X-1 by examining
material around the orbiting pair. While the source itself has been known for
decades, the neutron star is usually so bright that the glare from its X-ray
light overwhelms any faint emission surrounding it. The new Chandra data were
obtained while the neutron star was in a very faint state, which meant it was
dim enough for astronomers to detect the faint afterglow created by the
supernova explosion plowing through the surrounding interstellar gas. This,
combined with characteristics of the radio emission, allowed the researchers to
pinpoint the age of the supernova remnant. In turn, this information reveals the
age of the neutron star since they were formed at the same time.
These results have been published in the December 4th issue of The
Astrophysical Journal. In addition to those mentioned above, the other authors
on this paper are Peter Jonker of the SRON Netherlands Institute for Space
Research, Niel Brandt of Penn State University, Daniel Emilio Calvelo-Santos of
the University of Southampton, Tasso Tzioumis of the Australia Telescope
National Facility, Michael Nowak and Norbert Schultz of the Kavli Institute/MIT,
Rudy Wijnands and Michiel van der Klis of the University of Amsterdam.
Image credit: X-ray: NASA/CXC/Univ. of Wisconsin-Madison/S. Heinz et al;
Optical: DSS; Radio: CSIRO/ATNF/ATCA
NASA
Guillermo Gonzalo Sánchez Achutegui
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