Wednesday 24 June 2015

Possible identity for mysteriously bright x-ray-emitting objects

Science Focus

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A new study may have discovered the nature of a class of objects that have been mysterious for decades. The objects in question are Ultraluminous X-ray sources (ULXs), which are named for their incredible brightness at those wavelengths.

ULXs are understood to be black holes (though some are known to be pulsars, we're not sure what percentage), but their properties challenge our understandings of these objects. Many of the black holes seem to be taking in matter (accreting) faster than their Eddington limits, which describes how much matter can be ingested in a given time. At that accretion rate, the light produced by the friction of the infalling material should push new material away, slowing the process down.

Since it’s not known how much mass the ULX black holes have, models have proposed a variety of scenarios. It could be that the ULXs are mostly intermediate-mass black holes (black holes with masses between 100 and 100,000 times the mass of the Sun), which have higher Eddington limits. Or maybe they’re stellar-mass black holes (black holes that formed out of a collapsed star) that are accreting faster than their Eddington limit by some unknown mechanism.

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 » see original post http://feeds.arstechnica.com/~r/arstechnica/science/~3/u8bikk3iHhU/
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