X-ray Echoes Map a Black Hole’s Disk
Some 3.9 billion years ago in the heart of a distant galaxy, the tidal pull of a monster black
hole shredded a star that wandered too close. X-rays produced in this event first reached
Earth on March 28,
2011, when they were detected by
NASA's
Swift satellite.
Within days, scientists concluded that the outburst, now known as
Swift J1644+57, represented both the tidal disruption of a star and the sudden flare-up of a previously inactive black hole.
Now astronomers using archival observations from Swift, the
European Space Agency's XMM-Newton observatory and the Japan-led
Suzaku satellite have identified the reflections of X-ray flares erupting during the event. Led by
Erin Kara, a postdoctoral researcher at NASA'
s Goddard Space Flight Center in
Greenbelt, Maryland, and the
University of Maryland, College Park, the team has used these light echoes, or reverberations, to map the flow of gas near a newly awakened black hole for the first time.
Swift J1644+57 is one of only three tidal disruptions that have produced high-energy X-rays, and to date it remains the only event caught at the peak of this emission. While astronomers don't yet understand what causes flares near the black hole, when one occurs they can detect its echo a couple of minutes later as its light washes over structures in the developing accretion disk. The technique, called X-ray reverberation mapping, has been used before to explore stable disks around black holes, but this is time it has been applied to a newly formed disk produced by a tidal disruption.
Swift J1644+57's accretion disk was thicker, more turbulent and more chaotic than stable disks, which have had time to settle down into an orderly routine. One surprise is that high-energy X-rays arise from the innermost regions of the disk instead of a narrow jet of accelerated particles, as originally thought.
The researchers estimate the black hole has a mass about a million times that of the sun. They expect future improvements in understanding and modeling accretion flows will allow them to measure the black hole's spin using this data.
Music:"
The Orion Arm" and "
Particle Acceleration," both from
Killer Tracks.
Credit:
NASA/Goddard/
Scott Wiessenger
Read more:
http://www.nasa.gov/feature/goddard/2016/x-ray-echoes-of-a-shredded-star-provide-close-up-of-killer-black-hole
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