ASCA Science Highlights: Supernova Remnants
Follow the links to images and plotsMassive stars (Type II) and some white dwarf binaries (Type I) end their lives in a catastrophic supernova explosion. The outer layers of the dying star is expelled at tremendous speeds in such an explosion. When the high-speed gas collides with the interstellar matter, it is heated to X-ray temperatures: this is how a supernova remnant (SNR) is born. At the same time, most massive stars should leave a hot, rotating neutron star as well.
- Some of the most spectacular ASCA spectra have been obtained on the diffuse emission from SNRs. W49B is a good example. ASCA data also allow the construction of images of SNRs in specific emission lines, for example those of Tycho: this gives a good way to study the variation of conditions across the SNRs.
- SNRs in the Large Magellanic Clouds (LMC) are particularly attractive targets, because they provide a sample of SNRs at roughly the same distance, and without the obscuration that SNRs in the Galactic plane suffer. The ASCA X-ray spectra of the LMC SNRs have been used to distinguish between Type I and Type II supernovae.
- ASCA observations of SN1006 appear to be the first direct observational evidence for cosmic ray acceleration by SNRs (also read the press release on this subject). Scientists are finding similar non-thermal components in other SNRs, including G347.5-0.5.
- ASCA observations are shedding some light on another puzzle in the study of SNRs: why are there so few SNR-neutron star associations known? It appears that, at least in some cases, scientists simply did not have the right tools to discover the neutron star in an SNR -- until ASCA. The high energy (>3 keV) imaging capability of ASCA was essential in the discovery of several associations including the point-like source in RCW 103. Sometimes, the timing capability of ASCA has been used to reveal that the central source is a pulsar, such as in Kes 73. Read more about this subject in the press release.
This page created by Dr. Koji Mukai (USRA) at the U.S. ASCA Guest Observer Facility.
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