Credit: RXTE ASM TEAM/MIT
Variations in the X-ray Sky
The All Sky Monitor (ASM) on board
X-ray Timing Explorer (RXTE) has been monitoring the X-ray
emission from relatively bright cosmic X-ray sources since the launch of
RXTE in February 1996. This monitoring represents the most detailed
look at the time variability of cosmic X-ray sources. Using the All-Sky
Monitor data, the ASM team has produced a movie showing in startling detail
the extreme variation of the X-ray sky. Sources appear and disappear, some
flicker mildly, others brighten wildly for a period of time and then fade
away. The quicktime movie above shows a segment of this movie highlighting
the X-ray antics of the Galactic "microquasar"
1915+105, visible on Aug 29, 1997 as a yellow circle on the left side
of the screen. As time goes on the intensity of the source (represented by
the size of the circle) and the energy of the emitted X-rays (represented
by the color of the circle) change erratically. However, if we could show
the movie in super-slow motion, we would see that the source pulses nearly
67 times every second. Note that the sources are displayed in Galactic
coordinates (in which the center of the Milky Way is at center of the
frame, and the disk of the Galaxy runs horizontally through the center).
Most of the X-ray sources fall in the plane of our Galaxy; the brightest
X-ray source, Scorpius X-1, is the large circle just above the Galactic
center. The full movie is astonishing and available at the ASM web site at the Massachussetts Institute of Technology.
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Page Author: Dr. Michael F. Corcoran
Last modified June 14, 2001