Donald Savage
Headquarters, Washington, DC                    January 27, 1999
(Phone:  202/358-1727)

Tim Tyson
Marshall Space Flight Center, Huntsville, AL
(Phone:  256/544-0994)

Bill Steigerwald
Goddard Space Flight Center, Greenbelt, MD
(Phone:  301/286-5017)

RELEASE:  99-8

GAMMA RAY BURST IMAGED FOR FIRST TIME

       Astronomers racing the clock managed to take the first-ever 
optical images of one of the most powerful explosions in the 
Universe -- a gamma ray burst -- as it was occurring on Saturday, 
Jan. 23, 1999.  Gamma ray bursts produce more energy in a very 
short period than the rest of the entire Universe combined.

       Because such bursts occur with no warning and typically 
last for just a few seconds, quick detection by orbiting 
spacecraft and instant notification to astronomers are critical in 
order to catch the bursts in the act.  

       The gamma-ray-burst detectors of the Burst and Transient 
Source Experiment (BATSE) onboard NASA's orbiting Compton Gamma 
Ray Observatory detected the beginning of a bright gamma ray 
burst.  As the burst was still in progress, computers determined a 
rough location and radioed the position to the Gamma Ray Burst 
Coordinates Network (GCN), based at NASA's Goddard Space Flight 
Center, Greenbelt, MD.  The position was immediately forwarded via 
the GCN to astronomers at ground based observatories throughout 
the world.

       Just 22 seconds later the Robotic Optical Transient Search 
Experiment (ROTSE) in Los Alamos, NM, operated by a team led by 
Dr. Carl Akerlof of the University of Michigan, was in position 
and took images of the patch of sky where the burst was reported.  
Their equipment is assembled from 35 mm camera lenses and parts 
culled from the amateur astronomy market.  The first picture 
showed a brightening new star within the sky region where the 
burst was reported. 

       Five seconds later, the burst achieved peak brightness, 
reaching 9th magnitude, about 16 times fainter than the human eye 
can see, but easily visible in an amateur telescope.  Within eight 
minutes of the initial detection, the burst had faded by a factor 
of 100 below its maximum brightness.  "I was amazed," Akerlov 
said.  "At best, we expected something really dim optically, at 
the limit of our sensitivity.  Instead we found a whopper."

       "If this burst had originated in the Milky Way Galaxy, it 
would have lit up the night sky," said Dr. Alan Bunner, Director 
of NASA's Structure and Evolution of the Universe science theme at 
NASA Headquarters.

       The event was also recorded by instruments aboard the 
Italian-Dutch BeppoSAX satellite, which obtained a much more 
accurate position for the burst within a few hours of its onset.   
It was this more precise location information that the ROTSE team 
used to find the burst in their images.

       "This is the Holy Grail for the Gamma Ray Burst Coordinates 
Network," said Dr. Scott Barthelmy, the astronomer at Goddard, who 
developed and runs the network.  "Optical telescopes had seen the 
afterglow of a burst, but never the burst itself.  This 
observation will help us understand the physical processes behind 
the bursting."

       Within three hours of the gamma ray burst, a team of 
astronomers led by Dr. Stephan Odewahn, and Profs. Shri Kulkarni 
and George Djorgovski of the California Institute of Technology 
used the 60-inch Mt. Palomar telescope to find a fading optical 
counterpart to this gamma ray burst, helped by the precise 
localization provided by BeppoSAX.

       The next night, a joint team led by Dr. D. Kelson of the 
Carnegie Institution of Washington, using the Keck II 10-meter 
telescope located at Mauna Kea, HI, found that the distance to the 
burst is about nine billion light years, more than half way to the 
edge of the observable Universe. 

       Astronomers are not certain what produces gamma ray bursts, 
but possible causes include the mergers of two neutron stars, two 
black holes, or a neutron star and a black hole, or the explosion 
of a so-called hypernova.  A hypernova is a theorized type of 
supernova or exploding star.

       "The optical emission was about 10,000 times brighter than 
ever observed, something you could see with a pair of good 
binoculars," said Dr. Neil Gehrels, Project Scientist of the 
Compton Observatory.  "Theorists will have a field day trying to 
explain this phenomenon."

       Dr. Gehrels said the simultaneous observation of the burst 
in optical and gamma ray energies might open the door to a whole 
new generation of instruments like ROTSE, which is a fully 
automated telescope that can respond to information about 
transient celestial sources instantly.  Orbiting telescopes detect 
several hundred gamma ray bursts each year.

       The ROTSE project is designed and operated by a 
collaboration of astrophysicists from the University of Michigan 
and the Department of Energy's Los Alamos and Lawrence Livermore 
National Laboratories.  The Principal Investigator for BATSE is 
Dr. Gerald Fishman at NASA's Marshall Space Flight Center, 
Huntsville, AL.  The National Science Foundation provided funding 
for observations at Keck II.

                              - end -