 X-ray
Astronomy
Chandra
XMM
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In the high-energy domain of the electromagnetic spectrum of X-rays and
gamma-rays, we observe emission from cosmic sources which is characterized
by unusually-intense and violent energy production rates often from events
that occur at the end of the stellar lifetimes. X-rays in the 0.1 to 100 keV
range are produced from hot plasma, heating processes being e.g. infall of matter
onto compact stars such as white dwarfs and neutron stars, or violent explosions
into dilute interstellar or intergalactic gas. Characterisitic lines from
highly-ionized atoms in the 0.1 to 7 keV range provide diagostics on the state
and dynamics of cosmic gas, often in otherwise hardly accessible regions, such
as event horizon regions around black holes or intergalactic gas at intermediate
redshifts. Continuum emission in this
energy range is mostly thermal, with synchrotron emission being important for
special sources such as supernova remnants and gamma-ray bursts. The energy
regime of nuclear line radiation lies in the 70 to 8000 keV range, where
radioactivity produces unique spectral lines which allow the study of
nucleosynthesis sources and interstellar mixing. Annihilation of positrons
adds another new and puzzling spectral-line type at 511 keV. All cosmic
emission seen at energies above about 100 keV is non-thermal in origin.
Above about 100 keV up to 100 GeV, continuum emission from relativistic
particles (cosmic rays) dominates the emission, through Bremsstrahlung,
Inverse-Compton Emission, and Pion emission. This is the domain where
relativistic particle acceleration in different types of sources such as
pulsars and supernova remnants is studied, but also the propagation of cosmic
rays throughout our Galaxy.
Prominent cosmic sources studied in the X- and gamma-ray range are Active
Galaxies and Blazar Jets, accreting binary systems, supernova remnants,
rapidly-spinning neutron stars, and stellar explosions such as supernovae,
gamma-ray bursts, novae, and X-ray bursters. But also normal stars and galaxies
can be studied with modern X-ray telescopes. And even comets and planets in
the solar system are seen in X-rays. Astrophysical processes being
studied are gravitational energy release near and on compact stars,
radiation processes in high-field magnetospheres, the physics of cosmic
plasma jets, cosmic nucleosynthesis sources, and relativistic particle
acceleration as well as its propagation. Astrophysical themes are the late
stages of stellar evolution and their remnants, cosmic evolution of elemental
abundances, and the evolution of galaxies.
Instruments employed are grazing-incidence X-ray focusing telescopes, coded
mask and Compton telescopes, and pair tracking chambers, all operated on
satellites in space. Currently-active missions with MPE participation are Chandra,
XMM-Newton, INTEGRAL, and FERMI. In preparation is the eROSITA mission,
other mission concepts are being pursued.
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γ-ray
Astronomy
INTEGRAL
Fermi
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MPE
High-Energy Astrophysics
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