Some of the sources in the 4XMM catalog (colored points) and some of the 4XMM products, including a flare from a star (top left), a very variable star (top middle) and the brightness of the star with energy (bottom left) showing a star in the process of being formed.
To celebrate twenty years since the launch of the European Space Agency's X-ray observatory, XMM-Newton, a new catalogue of all of the X-ray sources detected with this satellite has been released. XMM-Newton was launched from Kourou in French Guyana at 14:32 UT on 10th December 1999. Following a flawless launch, the observatory started to take data in January 2000. The European consortium, the XMM-Newton Survey Science Centre (XMM-SSC) has created a new catalogue of all the detections since launch, using the most up to date calibration and software. This new version is called 4XMM and comprises two versions called 4XMM-DR9 and 4XMM-DR9s.
IFCA through its Galaxies and AGNs group is part of the XMM-SSC consortium since its creation.
XMM-Newton has recorded a total of 810795 X-ray detections using individual observations. Most of these detections are serendipitous and are often of unknown but diverse nature. These detections are listed in the catalogue 4XMM-DR9. Some regions of the sky have been observed many times, so this amounts to 550124 unique celestial objects. Some objects were observed repeatedly up to 69 times.
But what are the objects that XMM-Newton observes? Whilst the nature of many of the sources is still to be revealed, the majority of the objects are supermassive black holes which are between a million and ten billion times the mass of our Sun, each one in the centre of its own galaxy. XMM-Newton records the matter swirling around these invisible objects, until the moment it reaches the event horizon, the limit of no return, where not even light can escape the gravitational pull of the black hole. Other objects contained in the catalogue include stars, large groups of galaxies called clusters of galaxies, comets and stars exploding as supernovae at the ends of their lives.
"Thanks to the wealth of data provided in the catalogues, along with complimentary images and other new products such as information from other wavelengths, astronomers can identify new and exotic objects that are expected to be found in our Universe", enthuses the director of the XMM-SSC, Natalie Webb at the Astrophysics and Planetary Science Institute of Research, Toulouse, France.
The complementary catalogue, 4XMM-DR9s, was created from overlapping observations. Specially designed software allows yet fainter sources to be detected in sky regions observed more than once, increasing the number of detections and uncovering long-term variability on repeatedly observed objects.
"4XMM-DR9s allows objects to be followed over a time span of almost twenty years, which can give us a great insight into their nature", says Iris Traulsen of the Leibniz Institute for Astrophysics in Potsdam (AIP), Germany, and lead author of the accompanying paper presenting 4XMM-DR9s to the scientific community.
These catalogues will allow astronomers to study highly energetic objects that are often invisible to humans in 1174 square degrees of sky (about 6000 times the area of the full Moon). Studying these objects will help us understand how black holes and galaxies grow and help to identify how the Universe is structured.
The XMM-SSC is a consortium of the following institutions:
Instituto de Física de Cantabria, Santander, Spain
Institut de Recherche en Astrophysique et Planétologie, Toulouse, France
Observatoire Astronomique de Strasbourg, France
Département d'Astrophysique, CEA/DRF/IRFU, Saclay, France
Leibniz-Institut für Astrophysik Potsdam (AIP), Germany
Max-Planck Institut für extraterrestrische Physik, Garching, Germany
University of Leicester, United Kingdom
Mullard Space Science Laboratory, University College London, United Kingdom
The papers describing the catalogue are:
'The XMM-Newton serendipitous survey IX. The fourth XMM-Newton serendipitous source catalogue' N. A. Webb et al., submitted
The XMM-Newton serendipitous survey X. Long-term variability in the second source catalogue from overlapping XMM-Newton observations, I.Traulsen et al., submitted