Discovery of a new ultra-luminous X-ray source in Andromeda
Date: 11 December 2012
Copyright: ESA/XMM-Newton/MPE
This movie shows the Andromeda galaxy (also known as M31) as seen in X-rays with ESA's XMM-Newton space observatory (shown here in red, green, blue and white, according to the energy of the different sources). This X-ray view is combined with an image of Andromeda taken with ESA's Herschel space observatory at far-infrared wavelengths (shown here in grey).
A series of observations taken with XMM-Newton in 2012 illustrate the discovery of a new source, XMMU J004243.6+412519.
In the image for 7 January 2012, the new source is not yet visible. The source was first detected on 15 January 2012 and it can be seen in the upper part of the frame. About ten days after its discovery, XMMU J004243.6+412519 underwent a dramatic brightness boost, which can be seen in the images from 21 January and 31 January 2012.
With a luminosity in excess of 1039 erg/s, XMMU J004243.6+412519 was classified as an ultra-luminous X-ray source, or ULX. This is only the second ULX known in the Andromeda galaxy. The source then became fainter, as shown in the last two images of the sequence, from 28 July and 8 August 2012. Note that the field of view in these latter two images is slightly different to the earlier images.
XMMU J004243.6+412519 is an X-ray binary which consists of a stellar-mass black hole that is accreting matter from a low-mass companion star. The source's dramatic boost in X-rays indicates a transition to an accretion rate close to the black hole's Eddington limit, or even above it.
Other X-ray sources visible in the images are: novae - binary systems comprising a white dwarf accreting material from a companion star; X-ray binaries - binary systems hosting a neutron star or a black hole accreting material from a companion star; and supernova remnants.