ESA Space Science | XMM-Newton | 2016 Apr 28
ESA’s XMM-Newton has discovered gas streaming away at a quarter of the speed of light from very bright X-ray binaries in two nearby galaxies.
[img3="Powerful Winds from an Ultra-Luminous X-ray Binary (Credit: ESA/C. Carreau)"]http://www.esa.int/var/esa/storage/imag ... mage_2.jpg[/img3][hr][/hr]At X-ray wavelengths, the celestial sky is dominated by two types of astronomical objects: supermassive black holes, sitting at the centres of large galaxies and ferociously devouring the material around them, and binary systems, consisting of a stellar remnant – a white dwarf, neutron star or black hole – feeding on gas from a companion star.
In both cases, the gas forms a swirling disc around the compact and very dense central object: friction in the disc causes the gas to heat up and emit light at many wavelengths, with a peak in X-rays. ...
But an intermediate class of objects was discovered in the 1980s and is still not well understood. Ten to a hundred times brighter than ordinary X-ray binaries, these sources are nevertheless too faint to be linked to accreting supermassive black holes, and in any case, are usually found far from the centre of their host galaxy. ...
Ciro and his colleagues delved into the XMM-Newton archives and collected several days’ worth of observations of three ultra-luminous X-ray sources, all hosted in nearby galaxies located less than 22 million light-years from our Milky Way. ...
In all three sources, the scientists were able to identify X-ray emission from gas in the outer portions of the disc surrounding the central compact object, slowly flowing towards it.
But two of the three sources – known as NGC 1313 X-1 and NGC 5408 X-1 – also show clear signs of X-rays being absorbed by gas that is streaming away from the central source at an extremely rapid 70 000 km/s – almost a quarter of the speed of light. ...
Resolved atomic lines reveal outflows in two ultraluminous X-ray sources - Ciro Pinto, Matthew J. Middleton, Andrew C. Fabian
- Nature (online 27 Apr 2016) DOI: 10.1038/nature17417