X-Ray Astronomy: Why and How Emrah Kalemci Jörn Wilms Sabancı Universitesi University of Erlangen-Nuremberg Black Hole Universe Purpose of this lecture: Why do we do X-Ray Astronomy? • – Accretion on Black Holes – Diagnostic Possibilities How do we do X-Ray Astronomy? • – The need for Space – Balloons, Rockets, Satellites – Detection methods for X-rays and Gamma-rays Literature LONGAIR, M.S., 1992, High Energy Astrophysics, Vol. 1: Particles, Photons, and their Detection, Cambridge: Cambridge Univ. Press, 50e ∼ Good introduction to high energy astrophysics, the 1st volume deals extensively with high en- ergy procsses, the 2nd with stars and the Galaxy. The announced 3rd volume has never ap- peared. Unfortunately, everything is in SI units. TRÜMPER, J., HASINGER, G. (eds.), 2007, The Universe in X-rays, Heidelberg: Springer, 96.25e Recent book giving an overview of X-ray astronomy written by a group of experts (mainly) from Max Planck Institut für extraterrestrische Physik, the central institute in this area in Ger- many. BRADT, H., 2004, Astronomy Methods: A Physical Approach to Astronomical Observations, Cambridge: Cambridge Univ. Press, $50 Good general overview book on astronomical observations at all wavelengths. Introduction 2 Literature CHARLES, P., SEWARD, F., 1995, Exploring the X-ray Universe, Cambridge: Cambridge Univ. Press, out of print Summary of X-ray astronomy, roughly presenting the state of the early 1990s. SCHLEGEL, E.M., 2002, The restless universe, Oxford: Oxford Univ. Press, 32e Popular X-ray astronomy book summarizing results from XMM-Newton and Chandra. ASCHENBACH, B. et al., 1998, The invisible sky, New York: Copernicus Popular “table top” book summarizing the results of the ROSAT satellite, with many beautiful pictures. KNOLL, G.F., 2000, Radiation Detection and Measurement, 3rd edition, New York: Wiley, 126e The bible on radiation detection. If you want one book on detectors, this is it. Introduction 3 Part 1: Why is X-ray and Gamma-Ray Astronomy Interesting? Galactic X-ray binaries: Material flows from normal star via inner Lagrange point onto neutron star or black hole = Formation of a hot ( 107 K) accretion disk ⇒ ∼ = X-rays and gamma-rays. ⇒ M87: Image Credit & Copyright: Adam Block, Mt. Lemmon SkyCenter, U. Arizona Extragalactic Black Holes Credit: X-ray: NASA/CXC/MIT/H.Marshall et al. Radio: F.Zhou, F.Owen (NRAO), J.Biretta (STScI) Optical: NASA/STScI/UMBC/E.Perlman et al. (M87; Perlman et al., 2002) Many of the most extreme processes in the Universe produce broad band radiation. Redshift distribution on an accretion disk (Dauser et al. 2010; submitted) XMM−Newton EPIC−pn Suzaku−XIS 1.3 Ratio Emission lines from close to the black hole are strongly distorted by relativistic effects. 1.0 1.1 1.2 Measurement of the line shape al- lows determination of the param- 0.9 4.0 5.0 6.0 7.0 eters of the black hole and the ac- observed Energy [keV] cretion flow. MCG 6-30-15 − XMM-Newton and Suzaku (Miniutti et al., 2007) .V : `Q].7 1H:C ]V` ]VH 10V • R`:7 ^@V R @V_7 8JV`$V 1H :JR ]VJV `: 1J$ ^ JI T 8 JI_7 – + VCC:` : IQ ].V`V 5 1.1 V R1:`` 5 JV% `QJ :` :JR GC:H@ .QCV 5 :H 10V $:C:H 1H J%HCV15 1J `:RHC% V` .Q $: 5 =V 5 3<4 :` V`$CQ1 8 4C:H@ .QCV C1JV VI1 1QJ VC: ]Q1V`1J$ 1 JVG%C: :JR : =V *G1 :@ <:75 Q0VIGV` .7 ]:HV : `QJQI75 .V : `Q].7 1H:C ]V` ]VH 10V • 3:II:R`:7 ^] @V_7 – V% `QJ :` 5 GC:H@ .QCV 5 $:II:R`:7 G%` 5 J%HCVQR 7J .V 1 8 4V]]QR+:6 RV VH 1QJ Q` .V .Q $:C:67 Q` : 3<48 *G1 :@ <:75 Q0VIGV` Part 2: Tools of the Trade: Satellites Charles & Seward, Fig. 1.12 Earth’s atmosphere is opaque for all types of EM radiation except for optical light and radio. 3 Major contributor at higher energies: photoabsorption ( E− ), esp. from Oxygen (edge at 500 eV). ∝ ∼ = If one wants to look at the sky in other wavebands, one has to go to space! ⇒ ':CCQQJ1J$7 AC1IG :GQ0V @I 8 V :GCV 11JR V`7 .1J ^8 HI_ G% `QJ$ I: V`1:C V`7 C:`$V V`7 R1``1H%C * *G1 :@ <:75 Q0VIGV` Q%JR1J$`QH@V 7 I%1H@5 CQ1 HQ :HHV Q %]]V` : IQ ].V`V 11 . `V% :GCV ^JQ :C1:7 *_ 1J `%IVJ 8 <Q : V 11 . : `16VR ]V`1QR :CCQ11J$ ]Q1J VR QG V`0: 1QJ ^11 .Q% %]V`G :HH%`:H7_8 CV]VJR1J$ QJ 1V1$. 5 H:J $Q %] Q @I :JR :7 .V`V `Q` .%JR`VR Q` VHQJR 8 *G1 :@ <:75 Q0VIGV` 80VJ .Q%$. `QH@V :JR G:CCQJ :`V IQ C7 % VR `Q` V 1J$ JV1 CV VH Q` :JR VCV HQ]V VH.JQCQ$1V 5 :JR V 1J$ V_%1]IVJ GV`Q`V : : VCC1 V C:%JH.5 8 ]VH1:CC7 `QH@V ]C:7VR : 0V`7 1I]Q` :J `QCV 1J .V G1` . :JR RV0VCQ]IVJ Q` R`:7 : `QJQI7 1J :JR * <8 31QHHQJ1 $Q .V QGVC -`1<V `Q` .V -1QJVV`1J$ 1Q`@ ^1JHC%R1J$ R1 HQ0V`7 Q` +HQ R5 .V G`1$. V R`:7 Q%`HV 1J .V @78 AQ%` V 7 Q` <1H@ <Q . H.1CR8 *G1 :@ <:75 Q0VIGV` & *G1 :@ <:75 Q0VIGV` .V`V :`V : `QJQI7 : VCC1 V - !Q C7 ,"8* *G1 :@ <:75 Q0VIGV` "<4#+ #83<, 11$.C7 VHHVJ `1H Q`G1 5 H1VJ 1`1H QJC78 *G1 :@ <:75 Q0VIGV` .7 CQ1 V:` . Q`G1 - 1Q .:`I`%C `:R1: 1QJ GVC V61 7 : @I ^ @I .1H@_ :JR : @I ^ @I .1H@_8 4VCQ1 @I 1 Q@ `Q` : VCC1 V 8 ]`QGCVI 11 . `:R1: 1QJ GVC 7 1 .1J .V GVC 0V`7 .1$. G:H@$`Q%JR5 VJV`$V 1H ]:` 1HCV :``VH VI1HQJR%H Q` RV VH Q` 5 :JR RV$`:RV VCVH `QJ1H H1`H%1 8 GQ0V .V GVC 5 HQ I1H `:7 G:H@$`Q%JR .1$.8 8: 7 `Q` I:JV%0V`1J$5 H.V:] :JR V: 7 Q ]C:HV 1J Q Q`G1 ^QJV ].: V C:%JH._ .7 JQ CQ1 V:` . Q`G1 ● ,:`$V VHC1] V R%V Q V:` .8 #I]Q 1GCV `Q` HQJ 1J%Q% HQ0V`:$V ^8``1H1VJH7 R Q_8 *G1 :@ <:75 Q0VIGV` 8HHVJ `1H Q`G1 7 • !%H. GV V` V``1H1VJH7 :JR HQ0V`:$V8 • 11$.V` Q0V`:CC G:H@$`Q%JR • 11$.V` V6]Q %`V Q `:R1: 1QJ GVC • :$V C:%JH.8 *G1 :@ <:75 Q0VIGV` 86]VJ 10V ]VH1:CQ`G1 • `:1CV`7 `:1C V:` .8 + :7 HQQC5 `V_%1`V I%H. CV C1_%1R 1VC1%I8 +V]:`: V 8 L7V:`8 • :$`:J$V]Q1J + :7 : %J :GCV C:$`:J$V ]Q1J , ^C1@V %J QG V`01J$ +"1"_ Q` , ^C1@V !-_8 VVR :R=% IVJ V0V`7 R:7 R JQ `:R1: 1QJ GVC 5 Q V``1H1VJH78 *G1 :@ <:75 Q0VIGV` XMM-Newton (ESA): launched 10 Dec. 1999 INTEGRAL (ESA): launched 17 Oct 2002 Currently active missions: X-ray Multiple-Mirror Mission (XMM-Newton; ESA), Chandra (USA), International Gamma-Ray Laboratory (INTEGRAL; ESA), Swift (USA), Rossi X-ray Timing Explorer (RXTE) (USA), High Energy Transient Explorer (HETE-2; USA), Fermi (aka GLAST ; USA), High Energy Solar Spectroscopic Imager Spacecraft (RHESSI; USA), Suzaku (Japan, USA), AGILE (Italy). Planned missions: ASTROSAT (India), Spectrum-X-Gamma (Russia/Germany/France), Astro-H (Japan/USA), NuSTAR (USA), GEMS (USA), IXO (USA/ESA/Japan) We’re living in the “golden age” of X-ray and gamma-ray astronomy. R`:7 VCV HQ]V A.:JR`: T %]V`G :J$%C:` !!RV1 QJ5 C:`$V `V QC% 1QJ5 VJV`$7 `V QC% 1QJ8 HQCCVH 1J$ :`V:8 +11` 5 `: `V ]QJ V* *G1 :@ <:75 Q0VIGV` Part 3: Tools of the Trade: Detectors Introduction There are two steps in the X-ray detection process: 1. Collection of X-rays (“imaging”) Wolter telescopes (soft X-rays up to 15 keV) • ∼ Coded Mask telescopes (above that) • Or just use a collimator 2. Detection of X-rays Non-imaging detectors • Detectors capable of detecting photons from a source, but without any spatial resolution = Require, e.g., collimators to limit field of view or use these to form individual pixels. ⇒ Example: Proportional Counters, Scintillators Imaging detectors • Detectors with a spatial resolution, typically used in the IR, optical, UV or for soft X-rays. Gen- erally behind some type of focusing optics. Example: Charge coupled devices (CCDs), Position Sensitive Proportional Counters X-rays: Detection 1 Step 1: Collecting X-rays Imaging Cassegrain telescope, after Wikipedia Reminder: Optical or radio telescopes are usually reflectors: primary mirror secondary mirror detector → → Main characteristics of a telescope: collecting area (i.e., open area of telescope, πd2/4, where d: telescope diameter) • ∼ for small telescopes: angular resolution, • λ θ = 1.22 (1) d but do not forget the seeing! Wolter Telescopes 2 Imaging Optical telescopes are based on principle that reflection “just works” with metal- lic surfaces. For X-rays, things are more complicated. Snell’s law of refraction: α n sin α1 n2 1 1 = = n (2) sin α2 n1 θ where n index of refraction, and α1,2 angle wrt. 1 surface normal. If n 1: Total internal reflection ≫ Total reflection occurs for α2 = 90◦, i.e. for n < n 2 α sin α1 c = n cos θc = n (3) 1 2 , ⇐⇒ with the critical angle θ = π/2 α . c − 1,c Clearly, total reflection is only possible for n < 1 Light in glass at glass/air interface: n = 1/1.6 = θ 50 = principle behind optical fibers.