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Massive Flash from Birth of a Black Hole Testing Long-Held Theories About the Universe

 

  Grb050709_hst


A massive comsic blast, the rare birth of a black hole in the constellation Leo, labeled GRB 130427A by astrophysicists, is testing some long-held assumptions about the nature of the universe. Scientists recorded energy levels for gamma rays that are higher than what some researchers thought theoretically possible. This revelation may require physicists to modify existing theories about radiation. The astronomer s used the RAPTOR system is a network of small robotic observatories that scan the skies for optical anomalies such as flashes emanating from a star in its death throes as it collapses and becomes a black hole.

“This was the burst of the century,” said Los Alamos co-author James Wren. “It’s the biggest, brightest one to happen in at least 20 years, and maybe even longer than that.”

“Los Alamos’ RAPTOR telescopes in New Mexico and Hawaii received a very bright cosmic birth announcement for a black hole on April 27,” said astrophysicist Tom Vestrand (shown below), lead author of a paper in the journal Science that highlights the unusual event.

 

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The RAPTOR (RAPid Telescopes for Optical Response) system is a network of small robotic observatories that scan the skies for optical anomalies such as flashes emanating from a star in its death throes as it collapses and becomes a black hole—an object so dense that not even light can escape its gravity field. This birth announcement arrived from the constellation Leo in the form of an exceptionally bright flash of visible light that accompanied a powerful burst of cosmic gamma-ray emissions.

What made such an extremely rare event even more spectacular for scientists, however, is that, in addition to the RAPTOR sighting, it was witnessed by an armada of instruments—including gamma-ray and X-ray detectors aboard NASA’s Fermi, NuSTAR and Swift satellites. While the NASA instruments recorded some of the highest-energy gamma-ray bursts ever measured from such an event, RAPTOR noticed that the massive and violent transformation of a star into a black hole yielded a lingering “afterglow” that faded in lock-step with the highest energy gamma-rays.

“This afterglow is interesting to see,” said paper co-author Przemek Wozniak of Los Alamos’s Intelligence and Space Research Division. “We normally see a flash associated with the beginning of an event, analogous to the bright flash that you would see coinciding with the explosion of a firecracker. This afterglow may be somewhat analogous to the embers that you might be able to see lingering after your firecracker has exploded. It is the link between the optical phenomenon and the gamma-rays that we haven’t seen before, and that’s what makes this display extremely exciting.”

All things considered, the event was among the brightest and most energetic of its type ever witnessed.

“This was a Rosetta-Stone event that illuminates so many things—literally,” Vestrand said. “We were very fortunate to have all of the NASA and ground-based instruments seeing it at the same time. We had all the assets in place to collect a very detailed data set. These are data that astrophysicists will be looking at for a long time to come because we have a detailed record of the event as it unfolded.”

The Chandra image at the top of the page depicts a gamma-ray burst that was discovered on 9 July, 2005 by NASA's High-Energy Transient Explorer. The burst radiated an enormous amount of energy in gamma-rays for half a second, then faded away. Three days later, Chandra's detection of the X-ray afterglow (inset) established its position with high accuracy.

A Hubble Space Telescope image showed that the burst occurred in the outskirts of a spiral galaxy about 2 billion light years from Earth. This location is outside the star-forming regions of the galaxy and evidence that the burst was not produced by the explosion of an extremely massive star. The most likely explanation for GRB 050709 is that it was produced by a collision of two neutron stars, or a neutron star and a black hole. Such a collision would result in the formation of a black hole (or a larger black hole), and could generate a beam of high-energy particles that could account for the powerful gamma-ray pulse as well as observed radio, optical and X-ray afterglows.

This gamma-ray burst is one of a class of short-duration bursts that now appear to have a different origin from the more powerful, long-duration gamma-ray bursts that last more than two seconds. Long-duration bursts have been connected to black holes formed in the explosion of extremely massive stars, or hypernovas.

The Daily Galaxy via Los Alams National Laboratory

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