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XMM - advanced X-ray Astronomy school I. Georgantopoulos NATIONAL OBSERVATORY OF ATHENS Talks Overview [AGN are mainly addressed] Overview XMM Formation of jets in AGN (Vlahakis) X-ray emission from jets (Mastichiadis) Radio quiet AGN, I, II (Corral) Scripts for data analysis (Ranalli) XMM data analysis, the SAS package (Corral) X-ray spectra and XSPEC (Corral) The 3XMM source catalog X-rays: an Introduction X-rays : 60 Angstrom or Ε = h v keV 0.2keV up to 100 The most energetic phenomenae in the Universe Temperatures 1-100 million degrees High temperatures because of large gravitational potentials (black holes and clusters of galaxies). Contents Brief History of X-ray Astronomy Instrumentation and the X-ray missions Capabilities XMM The first X-ray observations 1949 Sun (solar corona, gas 106 K) SOHO image of the sun.This is not a 1949 observation !! Why observe in X-rays ? WIEN’s LAW Wavelength inversely prop. Temperature λmax= 3x107 / T Energetic phenomenae, temperatures of million degrees (very large gravitational potentials: BH, clusters of galaxies) Birth of X-ray astronomy 1962. Trying to observe the moon. Not detected instead Sco-X1 and the X-ray background Giacconi (Nobel 2003) 1962 measurement X-ray Moon as pictured by rosat in 1990 1960 1970 1979/1990 1993 1999 First X-ray satellite UHURU (1970), First imaging Einstein (1979), First imaging of hard X-rays (2-10 keV) ASCA (1993) XMM XMM has 3 telescopes. The first telescope focuses the light on the PN CCD detector. In the other two telescopes the light is split between the MOS CCD detectors and the RGS grating spectrograph. XMM components The 3 Telescopes Detectors X-ray Telescopes -- Wolter type telescopes where the X-rays are scaterred on two tubes. Nested tubes to increase the telescope area Grazing angle Max grazing angle: θc ∝ E-1 √Z Spatial Resolution The XMM spatial resolution is 16 arcsec Half-Power-Diameter (this is the light from a point source will be spread in (almost) a Gaussian with the above dimensions). Although the spatial resolution in all telescopes is dictated by Airy’s law which says that for a given telescope diameter, the resolution (decreases) gets better with decreasing wavelength. However, two effects play a crucial role in X-rays: a) micro-roughness (how well are the mirrors polished) b) the mirror alignments Telescope Area compare with Keck 785.000 cm2 (160 larger) An example of an X-ray image Limitations: XMM view of the tycho SNR 1. PSF degrades off-axis 2. Vignetting 3. Background Sensitivity We detect sources down to a given signal-to-noise ratio (SNR) SNR= S x t / SQRT (BKG x t ) Hence the flux limit goes with the square root of the exposure time: In the above: t= exposure time S= source counts per sec BKG= background counts (noise) per sec Sensitivity: spatial resolution The sensitivity has to do with the spatial resolution of the telescope and secondly with the size of the telescope Signal-to-noise ratio = Net counts / SQRT (BKG) Chandra: 50% light in 1 arcsec XMM 50% light 16arcsec background (BKG) in XMM 256 larger SQRT (256)= 16 tikes fainter More on XMM optics The size of the PSF increases with increasing off-axis angle. This effect is energy dependent. X-ray detectors: CCD Do not give only images but also low resolution spectra ( ΔE/E~ 6 % spectral resolution ONLY for moderately bright sources) The idea is that the more the energetic the photon the more the electrons that are produced Works if there are not many photons ( 1/ 3sec) Otherwise pile-up (a situation in which no spectra can be obtained) data cubes (event files) 4-dimensions x-y (Image) Energy (spectrum) Time (Light curve) More complex requests eg image 2-4 keV, Light curve 6-7 keV CCD spectra why a black hole ? Spectroscopy/Gratings Grating spectroscopy (λ/Δλ~1000) Chandra vs. XMM Chandra (NASA) XMM (ESA) a. 5000 cm2 @ 1keV (largest telescope) b. moderate spatial resolution 6 arcsec FWHM c. CCDs d. Gratings at low energies a. Highest spatial resolution ever achieved 1 arcsec (~optical astronomy) b. 1000 cm2 c. CCDs d. Grating at both high and low energies Bibliography ‘X-ray spectroscopy in Astrophysics’ (van Paradijs, Bleeker eds) Springer ‘The Universe in X-rays’ (Truemper et al. eds) Springer Exploring the X-ray Universe, ‘Cambridge Univ. Press’, Seward