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GRB 991216:
Chandra Helps Put The Pieces Together On Gamma-Ray Bursts
This composite image shows the
X-ray spectrum and CCD image of the gamma-ray burst
(GRB) known as GRB991216. An international team
used Chandra to observe iron emission lines from
ejected material surrounding GRB991216, the first time
emission lines associated with GRBs have been
unambiguously detected and their properties precisely
measured at X-ray wavelengths. These data strengthens
that GRBs are the result of a "hypernova," a gigantic
star collapsing on itself under its own weight.
While GRB afterglows have been studied in the optical,
radio, and X-ray regimes for some time, high precision
X-ray observations were needed to detect the dense,
massive medium that would exist if the scenario of a
massive progenitor were true. With Chandra, the
scientists believe they are seeing the iron emission
that is predicted if the surrounding medium becomes
heavily ionized and recombination takes place after
being hit with the radiation produced by the GRB and
its afterglow.
Chandra observed GRB991216 on December 18, 1999, using
the High Energy Grating Spectrometer (HETG) in
conjunction with the Advanced CCD Imaging Spectrometer
(ACIS) for 3.4 hours.
| Fast Facts for GRB 991216: |
| Credit |
NASA/CNR/L.Piro et al. |
| Category |
Miscellaneous Objects |
| Constellation |
Pisces |
| Observation Dates |
December 18, 1999
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| Observation Time |
3 hours |
| Instrument |
HETG |
| Distance Estimate |
About 8 billion light years |
| Release Date |
November 03, 2000 |
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