XTE Guest Observer Facility
The X-ray Timing Explorer (XTE)
What does XTE offer?
The XTE orbit is at an altitude of 580 km with an inclination of about
23 degrees and a period of about 100 minutes. For many targets there may
be 15-30 minute gaps in coverage due to earth occultation and the
satellite's passage of the South Atlantic Anomaly regions of high
charged particle density. The gaps will be minimized by scheduling when
longer, uninterrupted data trains are important.
- If you want to explore fast and ultra-fast X-ray variability in
relatively bright sources, XTE should be unparalleled. The
effective area will give about 15,000 counts/s from the Crab nebula in
the energy range 2-200 keV. Events are tagged with microsecond
accuracy. Data modes can be chosen to optimize the selection of data
transmitted and achieve high rates of information retrieval.
- If you want simultaneous information across the 2-200 keV
band, XTE offers co-aligned 2-60 keV and 20-200 keV detectors which
all have a 1 degree peak to zero response. The energy resolution is 18%
at 6 keV, 10% at 20 keV, and 17% at 60 keV.
- If you want to look at AGN of various types (Seyferts, BL Lacs,
Quasars), at energies above 10 keV, XTE offers detectors with
background sufficiently low to detect 0.2 milliCrab sources.
- If you want X-ray data simultaneous or quasi-simultaneous with
radio, optical, UV, other X-ray, or gamma-ray observations, XTE can
point anywhere outside of 30 degrees to the sun and can be scheduled
to support other observations within a few days of the observation
(although planning ahead will, in general, be necessary).
- If you want to observe an unanticipated "target of
opportunity", the relatively flexible XTE observing program will accommodate scientifically compelling TOOs.
The three instruments on XTE are the Proportional Counter Array (PCA),
co-pointed with detectors on the High Energy X-Ray Timing Experiment
(HEXTE), and the All-Sky Monitor (ASM). HEXTE has half its area
co-pointed with the PCA, with the other half accumulating background
from nearby positions. Independently, the ASM steps around the sky
scanning 70% of it each satellite orbit, each of 3 detectors viewing a
10 degree by 90 degree swath for 100 seconds at a time through a coded
If you have a question about RXTE, please send email to one of our