Past and current X-ray observatories

Table 1: Observatories and instruments that have been important for studies of X-ray reflection from black hole sources. Note that some of these observatories possess other instruments/detectors that we have not listed since they are not of direct relevance to iron line studies. Instrument abbreviations: ACIS=AXAF Charged Coupled Imaging Spectrometer; EPIC=European Photon Imaging Camera; GIS=Gas Imaging Spectrometer; GS=Gas Scintillation Proportional Counter; HETG=High Energy Transmission Grating; HEXTE=High Energy X-ray Timing Experiment; LAC=Large Area Proportional Counter; LECS=Low Energy Concentrator Spectrometer; ME=Medium Energy Proportional Counter; MECS=Medium Energy Concentrator Spectrometer; PCA=Proportional Counter Array; PDS=Phoswich Detection System; SIS=Solid-State Imaging Spectrometer.

Observatory Instrument Area Band pass Resolution

$$^2 E/\Delta E$$ (lifetime) (keV)

EXOSAT (ESA) GS 100 2-20 10

May 1983-Apr. 1986 ME 1600 1-50 10

Ginga (Japan) LAC 4000 1.5-37 10 Feb. 1987-Nov. 1991

$$+ 2\times 50$$ GIS 0.8-11 10

$$2\times 100$$ Feb. 1993-Mar. 2001 SIS 0.5-10 50

RXTE (NASA) PCA 6500 2-60 10

$$2\times 800$$ Dec. 1995-present HEXTE 15-250 -

BeppoSAX (IT+NL) LECS 22 @ 0.28keV 0.1-10 8

Apr. 1996-Apr.2002 MECS 150 @ 6keV 1.3-10 8

PDS 600 @ 80keV 15-300 -

Chandra (NASA) ACIS 340 @ 1keV 0.2-10 50

Jul. 1999-present HETG 59 @ 1keV 0.4-10 200

$$2\times 920$$ XMM-Newton (ESA) EPIC-MOS 0.2-12 50

Dec. 1999-present EPIC-PN 1220 @ 1keV 0.2-12 50

Table 1 lists the capabilities of the major X-ray observatories relevant to the present discussion. Before the launch of ASCA, the most important observatories for iron line studies were the European's EXOSAT and Japan's Ginga satellites. As we will discuss in the following sections, these observatories provided the first clear evidence for iron fluorescence and X-ray reflection in accreting black hole sources [189,200,201,202]. However, we had to await the major increase in spectral resolution brought about by the launch of ASCA before the relativistic effects could truly be explored.

The fourth Japanese X-ray satellite, initially called Astro-D, was renamed to ASCA¹¹ shortly after launch in February 1993 ASCA had two major innovations which revolutionized the study of many astrophysical X-ray sources. It was the first observatory to possess (four) focusing X-ray telescopes that worked up to 10keV (previous focusing X-ray telescopes only operated in the soft X-ray band). But, most importantly, ASCA had X-ray sensitive CCDs placed at the focal plane of two of these telescopes, giving X-ray spectra with an energy resolution $E/\Delta E \approx 50$. This allowed, for the first time, X-ray line widths to be resolved, as well as details of broader features to be discerned. Many of the results of AGN studies discussed below were obtained via ASCA observations. NASA and ESA also had a significant contribution to the ASCA project.

The two premier X-ray observatories currently operating are the Chandra X-ray Observatory (NASA) and XMM-Newton (ESA). Before discussing future planned missions, we briefly describe these two observatories in a little more detail.