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HIGH ENERGY ASTROPHYSICS

HIGH ENERGY ASTROPHYSICS. F.J. Castander M. Hernanz J. Isern IEEC/CSIC. I Emission & Absorption of X and  Rays. X-ray band: 0.01   (nm)  10 3x10 16   (HZ)  3x10 19 0.1  E (keV)  100.  -ray band:  (nm)  0.01  (HZ)  3x10 19 E (keV)  100. Balloons. Airplanes.

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HIGH ENERGY ASTROPHYSICS

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  1. HIGH ENERGY ASTROPHYSICS F.J. Castander M. Hernanz J. Isern IEEC/CSIC

  2. I Emission & AbsorptionofX and  Rays X-ray band: 0.01   (nm)  10 3x1016   (HZ)  3x1019 0.1  E (keV)  100 -ray band:  (nm)  0.01  (HZ)  3x1019 E (keV)  100

  3. Balloons Airplanes Rockets & satellites flying at h  200 km are necessary to detect X-rays. High energy Gamma rays can be detected with balloons

  4. INTEGRAL

  5. INTEGRAL

  6. History of X-Ray Astronomy • 1949: NRL, first x-ray view of the Sun. LX = 1025 erg/s = 10-6 Lopt (Friedman et al) • 1962: Rocket flight to search for emission from the Moon. Detection of the first extra-solar source: Sco X-1, LX = 1037 ergs/s = 600 Lo (Giacconi) Major Missions

  7. UHURU Dec 1970- Mar 1973 2-20 keV Two proportional counters

  8. Celestial sphere as seen by UHURU

  9. HEAO-2 (Einstein) Nov 1978- Apr 1981 First imaging telescope 0.1 - 3 keV

  10. EXOSAT (ESA): May 1983 - Apr 1986 0.05 - 50 keV Highly eccentric orbit FOV 2o Cas A for diferent lines Si, S, Fe

  11. AGN in the Perseus cluster

  12. ROSAT Jun 1990-Feb 1999 0.1 -2.4 keV 0.006-0.2 keV (UV)

  13. ASCA Advanced Satellite for Cosmology & Astrophysics Feb 1993-March 2001 0.4 -10 keV Space resolution 0.5’ @ 1 keV

  14. Rossi X-ray timing Explorer Dec 1995 2-250 keV Very large collecting are and all sky monitor Proportional counters Ability to follow temporal variations in the range 0f 10-6 to 106 s

  15. Chandra Jul 1999 0.1-10 keV grazing incidence mirrors (340 cm2 @ 1 keV) E/dE = 20-50 @ 1-6 keV Spatial resolution < 1arcsec Cas A. Central source?

  16. XMM-Newton Dec 1999 0.1 - 15 keV Grazing incidence mirrors ( 922 cm2 @ 1 keV) Spatial resolution 6” E/dE =20-50 @ 1- 6 keV

  17. XEUS X-ray Evolving Universe Spectrometer 0.05 - 30 keV 6 m2 effective @ 1 keV (200 times more effective than XMM) Final mirror 30 m2

  18. It is quite difficult to observe gamma-rays. Besides the necessity to work outside the atmosphere, there is a severe background problem. The flux above 100 MeV from the strongest cosmic source is about 10-5 - 10-6 photons cm-2 while the background produced by the interaction of cosmic rays in the detector and in the atmosphere is 105 times larger!

  19. VELA satellites They discovered the GRBs: the biggest challenge of modern astrophysics!

  20. COS-B First detailed map of the Milky Way revealing the first high-energy source catalogue with 24 objects. Aug 1975- Apr 1982 2 keV - 5 GeV

  21. HEAO-3 Discovery of 26Al in the Galaxy Sep 1979 - May 1981 50 keV - 10 MeV Field of view 30o

  22. GRANAT First high resolution images, 13’, of the sky regions in the hard X-ray/soft gamma-ray range 30 - 1000 keV 1989 - 1997

  23. Compton Gamma-Ray Observatory Apr 1991 - Jun 2000 30 keV - 30 GeV Four instruments: BATSE, EGRET, COMPTEL, The first true observatory: Isotropic distribution of GRBs High energy map of the Galaxy

  24. 26Al distribution obtained by COMPTEL

  25. 511 keV image of the GC OSSE

  26. SAX Apr 1996 - Apr 2002 0.1 - 300 keV Proportional counters X-ray afterglow of the GRB 970229

  27. INTEGRAL Oct 2002 15 keV - 10 MeV SPI, IBIS, JEM-X OM IBIS

  28. SPI

  29. Galactic plane survey INTEGRAL strategy

  30. Gamma lens: MAX/Claire

  31. Radiative processes • Charles & Seward, “Exploring the X-ray Universe”, Cambridge University Press (1995) • Longair,”High Energy Astrophysics”, Vol 1, Cambridge University Press (1992) • ….., Vol 2, Cambridge University Press (1994) • Rybicki & Lightman, “Radiative processes in astrophysics”, Wiley Interscience (1979) • Schönfelder, “The Universe in Gamma Rays”, Springer (2001)

  32. Main sources of X and  rays Continuum emission T=2x106 K E

  33. Thermal bremsstrahlung (braking radiation) T = 2x108 K

  34. Synchrotron radiation (magnetic bremstrahlung) Particles accelerated by a magnetic field radiate. For nonrelativistic velocities the radiation is called cyclotron. The frequency of radiation depends on the electron energy, the magnetic field and the direction of motion relative to the field. In the astrophysical cases of interest, the velocity of electrons is isotropic and the spectrum only depends on B and on the spectral energy of electrons. If they follow a power law, the radiation also exhibits a power law spectrum:

  35. Inverse Compton scattering Compton collision between relativistic electrons and low energy photons The scattered photon frequency is given by: h’  2 h. For en electron of E = 5 x109 eV ( = 104) h = 1 eV; h’ = 100 MeV h = 2.5x10-4 eV; h’ = 25 keV

  36. Transitions involving bound electrons in atoms or ions The K line of Fe has 6 KeV

  37. Nuclear transitions Other important transitions are the first excited states 4.438 MeV (12C*) 6.129 MeV (16O*)

  38. Annihilation Annihilation of particles and antiparticles produce gamma rays and viceversa. The most common process is the annihilation of electrons and positrons with a mass of 511 keV each. This process can occur in two steps: # Direct annihilation that produce two photons of 511 keV each # Formation of positronium, a bound atomic like system, with two different states depending on the orientation of the spin. The parallel spin state forms a triplet that decays, by momentum conservation into three photons that share the total energy. The spectrum peaks at the maximum energy, 511 keV, and extends in a continuous way towards lower energies

  39. Absorption processes Photoelectric absorption or photoionization: Atomic electrons are removed from tehir nuclei. Dominant below 100 keV Compton scattering: Electrons are hit by photons and absorb part of the enrgy. Dominant in the 0.1 - 4 MeV region Pair creation: In the presence of nuclei, gamma rays can produce pairs of particles and antiparticles Bound-Bound transitions

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