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News and Public Affairs
Los Alamos National Laboratory

Contact:
Nancy Ambrosiano, nwa{at}lanl.gov, (505) 667-0471

May 26, 2003

03-069

XNM-Newton satellite uncovers diffuse X-ray emission and the first
accreting X-ray pulsar in Andromeda Galaxy

Part 2 of 2

A significant number of discrete X-ray sources detected in the survey
coincide with optically identified supernova remnants. When a massive
star explodes in a supernova, it expels a large amount of material
(often many times more than the mass of the Sun) at thousands of
kilometers per second. This high-speed gas then collides with the
interstellar medium, heating it up to millions of degrees, and the
heated gas can be detected by X-ray telescopes. 

Although point-like sources account for the most of the X-ray
luminosity of M31, there is another important source of X-rays within
this galaxy. Analyzing a recent, 15-hour-long XMM-Newton observation
of the northern disk regions of M31, the team of researchers
discovered a faint, extended, diffuse X-ray glow coming from the disk
of M31. 

The spectral properties of this emission component are quite distinct
from the typical emission from the point sources. This indicates that
most of the diffuse X-ray emission comes from a very hot,
million-degree gas concentrated in the spiral arms of Andromeda
Galaxy. The significance of the presence of this hot plasma goes far
beyond the case of M31, as this galaxy is often considered as the
prototype for the population of early-type galaxies, including our
own. And since our field of view across our own is often heavily
obscured, this is an important new insight into the substance within
the Milky Way's spiral arms.

The researchers plan to continue this survey, one that will
eventually cover a whole galaxy. "This will allow us to get a
complete X-ray picture of the Andromeda Galaxy, helping to highlight
similarities and differences between this galaxy and our own Milky
Way," said Trudolyubov. 

The international research team for this investigation includes
Sergey Trudolyubov, William Priedhorsky, Oleg Kotov and Konstantin
Borozdin of Los Alamos National Laboratory; Keith Mason of the
Mullard Space Science Laboratory, UK and France Cordova of the
University of California at Riverside. 

This announcement is based on observations obtained with XMM-Newton,
an ESA science mission with instruments and contributions directly
funded by ESA Member States and the United States through NASA.

For further information on the satellite and its mission, see
      http://sci.esa.int/xmm/

The results of these XMM-Newton observations appear in recent and
upcoming papers in The Astrophysical Journal.

A complete set of photos is available at
     http://www.nis.lanl.gov/~tsp/press_release_AAS_202_pictures.html

Los Alamos National Laboratory is operated by the University of
California for the National Nuclear Security Administration (NNSA) of
the U.S. Department of Energy and works in partnership with NNSA's
Sandia and Lawrence Livermore national laboratories to support NNSA
in its mission. 

Los Alamos enhances global security by ensuring the safety and
reliability of the U.S. nuclear stockpile, developing technologies to
reduce threats from weapons of mass destruction, and solving problems
related to energy, environment, infrastructure, health and national
security concerns.

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