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Bill Steigerwald                    March 24, 2003
NASA Goddard Space Flight Center, Greenbelt, Md.
301 286 5017

Release 03-33

NEW CLASS OF HOT-TEMPERED BLACK HOLES BUCKS TRENDS

NASA scientists have found two smoking-gun features of an 
intermediate-mass black hole that suggest these newly identified 
objects are fundamentally different from other types of black holes, 
running hotter than expected.

The observation further establishes these objects as a new class of 
black hole, yet offers a perplexing twist: Intermediate-mass black 
holes do not appear to suck in matter the same way as their larger 
and smaller cousins do.

Drs. Tod Strohmayer and Richard Mushotzky of NASA Goddard Space 
Flight Center in Greenbelt, Md., present these findings today at a 
press conference at the meeting of the High Energy Astrophysics 
Division of the American Astronomical Society at Mt. Tremblant, 
Quebec. The observation was made with the European Space Agency's 
XMM-Newton satellite and NASA's Rossi X-ray Timing Explorer.

"We have been neatly assembling pieces of the black-hole puzzle over 
the years," said Strohmayer. "Now we have new pieces, some of which 
are familiar and others which don't seem to fit. A picture may emerge 
in which intermediate-mass black holes are a different beast 
altogether."

Black holes are objects so dense and have a gravitational potential 
so heightened that nothing, not even light, can escape the pull if it 
ventures too close. Although the black holes themselves are 
invisible, the region surrounding them glow furiously as matter pours 
in.

Stellar black holes are the remains of massive stars that have 
imploded, left with the mass of up to about ten suns. Supermassive 
black holes contain the mass of millions to billions of suns confined 
to a region about the size of our Solar System. Scientists suspect 
that intermediate black holes contain the mass of about 500 to 10,000 
suns. Stellar and supermassive black holes exhibit similar features, 
only scaled accordingly. Intermediate-mass black holes might buck 
this trend, Strohmayer said.

Scientists call intermediate-mass black holes ultra-luminous X-ray 
sources (ULXs). While they are clearly extremely bright sources of 
X-ray radiation, these objects could be smaller black holes with all 
of their energy (or, light) beamed in our direction, like a 
flashlight shined directly into the eyes. This would make them appear 
intrinsically brighter (and more massive) than they really are.

Strohmayer and Mushotzky's observation strongly rules out the beaming 
model for one of the brightest ULXs in galaxy M82. The scientists 
uncovered, for the first time, a type of flickering in this ULX's X 
rays called quasiperiodic oscillations (QPOs). The oscillations 
likely arise from gas whipping around the black hole in a tight and 
frenzied orbit  the collective, periodic motion of material in what 
is known as a black hole accretion disk. It is unlikely that light 
from an entire accretion disk would be beamed, Strohmayer said.

The scientists also detected the first "broad iron line" from a ULX. 
This refers to a pattern of X-ray light from iron atoms stretched by 
extreme gravity, a telltale sign of black hole shenanigans afoot, as 
Einstein predicted. The one-two punch of a QPO and broad iron line 
suggests that this ULX in M82 is a non-beamed black hole at least 50 
times more massive than a stellar black hole.

What the scientists cannot explain, however, is why the M82 ULX 
accretion disk is so hot. Theory predicts that smaller black holes 
have hotter accretion disks, particularly in the inner ring closest 
to the black hole. This is because material can swirl faster and more 
closely around a stellar size black hole compared to a supermassive 
black hole. Yet, according to XMM-Newton data, the intermediate-sized 
black hole in M82 has an accretion disk hotter than those found 
around stellar black holes.

"Something new and exotic may be taking place in this object to heat 
the accretion disk to such high temperatures," said Strohmayer. "The 
nature of these objects is one of the most interesting conundrums in 
high energy astrophysics."

XMM-Newton was launched from French Guiana in December 1999 and 
carries three advanced X-ray telescopes. NASA Goddard hosts the XMM 
U.S. guest visitor support center. NASA Goddard operates the Rossi 
Explorer, which was launched in 1995.

For animation, refer to the directory at:
http://universe.gsfc.nasa.gov/press/ulx/

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