Extreme X-rays may be signature of lame black hole

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Last summer, we reported on an extremely bright object that may have been an intermediate mass black hole. The existence of black holes this size has been hotly debated, in part because we've never observed one. The object, 2XMM J011028.1-460421 or (moreconveniently) HLX-1, is a source of ultraluminous X-rays near thespiral galaxy ESO243-49. Newly reported results, appearing in an upcoming edition of The Astrophysical Journal, confirm that HLX-1 is over 100 times brighter than typical objects inits class, and a factor of 10 times more luminous than its nearestpeer.

The prior work could not conclusively rule out the possibility that the X-rays were produced by a foreground star or background galaxy. With new observations made using the European Southern Observatory's Very Large Telescopein Chile, the researchers were able to obtain an optical spectrum ofHLX-1.  With this spectrum, it was possible to calculate aprecise distance between HLX-1 and Earth. 

Using some more advanced techniques, it was possible to separate the light from HLX-1 and the light generated by ESO243-49. The analysis proved that HLX-1 is indeed part of ESO243-49, and not one of the alternatives, like a supermassive black hole in the center of a distantgalaxy, or a source in our own galaxy. Given its location, the previous brightnesscalculations are correct. 

While still not conclusive, these newfindings strengthen the case that HLX-1 is an intermediate mass blackhole. According to Sean Farrell, one of the authors, "This [the result] is very difficult to explain without the presence of an intermediate mass black hole of between ~500 and 10,000 times the mass of the Sun. HLX-1 is therefore (so far!) weathering the scrutiny of the international astronomy community." The team has secured time on the Hubble Space Telescope to take thehighest resolution images of the host galaxy to date in the hopes of learningmore about this intriguing object.

The Astrophysical Journal, 2010. DOI: upcoming

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