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Astrophysics from Space Lecture 11: High-energy astronomy

Astrophysics from Space Lecture 11: High-energy astronomy. Prof. Dr. M. Baes (UGent) Prof. Dr. C. Waelkens (KUL) Academic year 2013-2014. High-energy spectrum. High-energy spectrum: hard UV radiation X-rays gamma-rays Radiation with λ < 10 -12 m

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Astrophysics from Space Lecture 11: High-energy astronomy

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  1. Astrophysics from Space Lecture 11: High-energy astronomy Prof. Dr. M. Baes (UGent) Prof. Dr. C. Waelkens (KUL) Academic year 2013-2014

  2. High-energy spectrum • High-energy spectrum: • hard UV radiation • X-rays • gamma-rays • Radiation with λ < 10-12m • Usually high-energy radiation is characterized by energy instead of wavelength/frequency • e.g. soft X-rays: 0.2-10 keV

  3. The X-ray and gamma-ray atmosphere Atmosphere completely opaque for high-energy photons E < 60 keV: photoelectric effect 60 keV < E < 100 MeV: inelastic Compton scattering E > 10 MeV: production of electron-positron pairs

  4. High-energy astronomy • High-energy astronomy seems to be limited to space, but there are alternatives… • balloon missions • Čerenkov telescopes

  5. Grazing-incidence telescopes No materials are reflective at X-ray wavelengths. Solution: grazing-incidence telescopes.

  6. High-energy detectors Soft X-rays: CCDs and microcalorimeters (bolometers). Hard X-rays and gamma-rays: scintillation counters.Directional information is provided by coded aperture masks (accuracy of several arcmin).

  7. High-energy missions: the early years 1949: first X-ray observations from space detect the Sun. 1961: Explorer-XI first gamma-ray mission (22 cosmic gamma rays) 1962: First astronomical X-ray source detected (Sco X-1), plus detection of X-ray background. 1960s-1970s: many X-ray/gamma-ray missions (often by-product)

  8. HEAO-1 • 1977: launch of NASA’s High Energy Astrophysical Observatory 1 (HEAO-1) • catalogue of approx. 850 point sources • comprehensive measurement of X-ray background • first time variability studies on ms time scale

  9. Einstein (HEAO-2) Late 1960s: NASA starts to work on Large Orbiting X-ray Telescope (LOXT) 1970: LOXT approved 1973: LOXT program abruptly cancelled due to cost overruns on the Viking program Final result: Einstein or HEAO-2 (launched 1978)

  10. Einstein (HEAO-2) legacy • Enormous improvement compared to previous X-ray missions (despite downsizing) • sensitivity: x 100 • FOV: much bigger • first imaging capabilities • Also important: legacy beyond the (small) X-ray community. • X-rays are relevant • new operational format (guest program, quick data reduction pipeline)

  11. Röntgensatellit (ROSAT) • 1975: proposed by MPE1983: approved and booked for launch on Space Shuttle 1987: Challenger… • 1990: launched on Delta rocket • Revolutionary aspects • huge telescope: 4 nested Wolter telescopes with 84 cm diameter • high spatial resolution (< 5 arcsec) • very sensitive all-sky survey: 60 000 sources !

  12. Compton (CGRO) • 1991: launched as part of NASA’s Great Observatories • Heaviest payload to be launched to space (17 tons) • 2000: de-orbited (NASA’s first…) • Legacy • huge coverage(20 keV – 30 GeV) • all instruments 10 times moresensitive than previous missions • 400 gamma-ray sources • 2500 GRB’s • Still, not the same fame as the three other Great Observatories(gamma-rays less sexy…)

  13. Chandra and XMM-Newton Chandra: NASA missionXMM-Newton: ESA mission Both operational in soft X-raysBoth launched in 1999Both still operational

  14. Chandra and XMM-Newton • Chandra strengths • very narrow PSF (0.5” vs 15”) • better at high-resolution imaging • better point-source sensitivity • XMM-Newton strengths • huge collecting area (4650 cm2vs 555 cm2) • more efficient detectors • larger FOV • better extended-source and spectroscopic sensitivity Chandra ACIS-I XMM-Newton EPIC pn XMM-Newton EPIC MOS1 XMM-Newton EPIC MOS2

  15. INTEGRAL • Most recent ESA high-energy mission, key mission in Horizon 2000 program. • Launched in 2002, operational until at least Dec 2014. • Key features • design borrow from XMM • truly international mission (participation from USA, Russia, Czech republic and Poland) • simultaneous observations from optical to gamma-rays

  16. Fermi Most recent NASA high-energy mission, launched in 2008. Formerly known as GLAST. Tailored to very high energies (up to 300 GeV).

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