We present numerical simulations of the gaseous coronae in elliptical galaxies. These models consist of a modified King profile for the luminous portion of the galaxy and an isothermal dark halo. We include evolving stellar mass loss from planetary nebulae, and type I and II supernovae. Our models show that elliptical galaxies are likely to produce strong galactic winds at early times with x-ray luminosities of 1042 — 1044 ergs s-1 and temperatures of 10 keV. Galaxies can lose approximately 10-30% of their initial luminous mass in the wind which has an oxygen-to-iron ratio twice the solar value. Since elliptical galaxies are a principle component of rich clusters and compact groups this early wind phase affects the metallicity and temperature of the intracluster medium.

The correlation of Mgas/Mstellar with the intracluster gas temperature in clusters of galaxies has implications for the efficiency of galaxy formation and predicts trends for the heavy element abundances in these systems.

The luminous material in clusters of galaxies falls primarily into two forms — the visible galaxies and the X-ray emitting intracluster medium. The hot intracluster medium is the major observed baryonic component of clusters with a mass equal to or greater than that of the stellar matter. In this paper we discuss changes in the efficiency of galaxy formation for different clusters and the origin of the intracluster medium.

We perform the numerical hydrodynamical calculation of cluster cooling flow including the mass deposition process and examine evolution of cooling flow. We take two mass deposition models. In one model, mass deposition occurs in large extent. In other model, mass deposition occurs only in central region. In any model, diagnostics of X-ray surface brightness do not agree with observation in any evolutional phases.

In this paper we discuss the cluster of galaxies 1E0839.9+2938, serendipitously discovered at x-ray wavelengths. The collected data imply that this is an example of cooling flow cluster.

High-resolution X-ray spectroscopy has the potential to reveal a number of interesting features of active galactic nuclei, primarily, though not exclusively, through the measurement of absorption lines. After a brief review of the principal problems of AGN research, selected potential high-resolution observations are discussed with a view toward assessing their scientific value and the degree of resolution they will require. Two classes of observations pertaining directly to AGNs are discussed: Fe Kα spectroscopy relevant to the dynamical and thermal character of the emission line zones; and measurement of resonance line absorption by highly-ionized species in BL Lac objects, which should tell us about entrainment of interstellar material by relativistic jets. A third class of potentially important observations uses AGNs as background light sources in order to directly measure the distance to clusters of galaxies.

A model for the origin of the cosmic X-ray background (hereafter XRB) is presented. The component of the background left after subtraction of the known classes of sources is explained by emission from a population of black hole sources at the redshift of z ~ 4-5. The model is presented in more detail elsewhere (Zdziarski 1988). Here, we summarize its most important results.

A model is proposed for the origin of the diffuse cosmic x-ray background whereby it is primarily due to the contribution of low luminosity active galactic nuclei which are increasingly self-absorbed at low luminosities. Strong self-absorption for low luminosity objects allows the observed background spectrum to be flatter in the ~2-20 keV band than the asymptotic spectrum, assumed to have mean index γ ~ -0.7 up to a high energy cutoff at ~125 keV. The model can account for the spectral shape and intensity of the background spectrum, as well as its possible fluctuations, if the AGN undergo modest density evolution and the bulk of the CXB arises from AGNs at redshifts z ~ 1-3. The model can be tested with AXAF observations of low luminosity AGNs at 5-10 keV and sensitive new hard x-ray observations.

Following a brief discussion of the possibilities offered by X-ray spectroscopy at various values of resolving power (E/ΔE), the spectroscopic capabilities of a number of future missions are presented. The possible roles of Charge Coupled Devices (CCD’s), Microcalorimeters, Diffraction Grating and Bragg Crystal Spectrometers are then evaluated.

The scientific payload of ROSAT consists of a 83 cm X-ray telescope (6 – 100 Å) and a 60 cm XUV-telescope (60 – 300 Å) which are looking parallel. An important objective of the mission is to perform the first all-sky survey with imaging X-ray telescopes providing an improvement in sensitivity by several orders of magnitude compared with previous surveys. A large number of new X-ray sources (~ 105) is expected to be discovered and located with an accuracy of 1 arcmin or better, depending on source strength. The sources discovered will represent almost all types of astronomical objects, ranging from nearby normal stars to distant quasars.

After completion of the sky survey which will take half a year, the instruments will be used for detailed investigations of selected sources with respect to spatial structures, spectra and time variability. In this pointing mode, which will be open for guest observers, ROSAT is expected to provide substantial improvements over the imaging instruments of the Einstein observatory.

High resolution spectroscopy will be an important diagnostic tool in future X-ray astronomy. SPEKTROSAT, the follow-up mission to ROSAT will be equipped with a transmission grating spectrometer with a spectral resolution of 0.2 Å over the wavelength range between 6 Å and 300 Å. Third order aberations are minimized by a mounting of the grating elements according to the Rowland-torus geometry. The ROSAT mirror system will be slightly changed by a redesign of the optical stops in order to reduce the field of view. The Focal Instrumentation has to be modified for a better match with the spectroscopic requirements. Since SPEKTROSAT is almost identical to ROSAT, this concept offers a large amount of science at relatively low costs. Its limiting line sensitivity will be about 20 times better than that of the EINSTEIN-OGS.

The SAX satellite is forseen for launch at the end of 1992 to study the X-ray emission from galactic and extra-galactic sources in the energy range 0.1-200 keV. The payload consists of four concentrator/spectrometer systems (3 units 1-10keV, 1 unit 0.1-10keV), a high pressure gas scintillation proportional counter (3-120keV), a phoswich scintillation counter (15-200keV), and two wide field cameras (2-30keV). Together these instruments will perform the following:-

1. - Broad band spectroscopy (E/ΔE=12) in the energy range 0.1-10 keV with imaging resolution of 1 arcmin

2. - Continuum and cyclotron line spectroscopy (E/ΔE=5-20) in the wide energy range 3-200 keV

3. - Variability studies of bright source energy spectra on time scales from milliseconds to days and months

4. - Systematic long term source variability studies in selected regions of the sky down to a source intensity of 1 mCrab.

The SPECTRUM RÖNTGEN-GAMMA mission is being developed by the Babakin Center (BC) together with the Space Research Institute (IKI) of the Academy of Sciences, USSR and is scheduled for launch in 1993. Mission objectives include broad and narrow band imaging spectroscopy over a wide range of energies from the EUV through gamma rays with particular emphasis on the study of extragalactic objects. The Danish Space Research Institute (DSRI) BC and IKI share the responsibility for the preparation of the XSPECT system. Two thin foil telescopes which are conical shell approximations to Wolter 1 geometry, each with an aperture of 60 cm and a focal length of 8 m, are designed to have a half-power width of less than 2 arcmin and will have collecting areas of 1700 and 1200 cm at 2 and 8 keV, respectively. Images and spectra will be recorded with position sensitive proportional counters with good spectral resolution. An objective Bragg crystal panel, placed in front of one of the telescopes, will make high resolution spectroscopic studies (E/ΔE ~103) of point- and extended sources. Other instruments are under consideration.

The Joint European X-Ray Telescope, JET-X, is one of the core instruments of the scientific payload of the USSR SPECTRUM-X astrophysics mission due for launch in 1993. The JET-X instrument concept is described and its scientific performance and capability discussed.

We present a new design for high resolution spectroscopy from 80 to 400 Å. This design employs grazing incidence optics and variable line-spaced gratings to achieve high resolution. Unlike some previously proposed EUV echelles, this design employs straight groove planar gratings, which are a well-proven, easily manufactured design. The instrument delivers a peak resolution of λ/Δλ = 7500 and a peak effective area of 3 cm2.

The expected in-orbit performance of the three spectrometers included on the Extreme Ultraviolet Explorer (EUVE) astronomical satellite is presented. Recent calibrations of the gratings, mirrors and detectors using monochromatic and continuum EUV light sources allow the calculation of the spectral resolution and throughput of the instrument. An effective area range of 0.2 to 2.8 cm2 is achieved over the wavelength range 70-600Å with a peak spectral resolution λ/Δλ (FWHM) of ~ 360 assuming a spacecraft pointing knowledge of 10 arc seconds (FWHM). For a 40,000 sec observation, the average 3σ sensitivity to a monochromatic line source is 3 × 103 photons cm-2 sec-1. Simulated observations of known classes of EUV sources such as hot white dwarfs and cataclysmic variables are also presented.

There are two transmission grating spectrometers and one Bragg crystal spectrometer being developed for the Advanced X-ray Astrophysics Facility (MIT is building the crystal spectrometer and one of the grating spectrometers; the Laboratory for Space Research in Utrecht is responsible for the other grating spectrometer). The gratings divide the AXAF energy band (80 eV – 10 keV) into three regions (the MIT instrument contains gratings with two different periods) and attain resolving powers for point sources between 100 and 1800. The gratings are composed of arrays of small facets mounted on plates which can be inserted immediately behind the AXAF telescope. The dispersed spectra from the grating arrays are read out by one of the AXAF imaging instruments.

The Bragg Crystal Spectrometer (BCS) is a focal plane instrument. One of eight selectable curved diffractors intercepts the AXAF X-ray beam as it diverges beyond the focal point X-rays that satisfy Bragg’s law are reflected from the crystal which, because of its curvature, re-focuses the beam onto an imaging detector. Narrow spectral regions are scanned by rocking the crystal over a range ~0.1 to 1°. Nearly the entire AXAF energy range can be studied by selecting the appropriate crystal and rotating it to the proper Bragg angle. The BCS achieves the highest spectral resolutions of the AXAF spectrometers: for 500 eV < E < 1600 eV, the FWHM of a narrow line (ΔE) is ≲ 1 eV.

Spectroscopy is traditionally characterized by the sacrifice of quantum efficiency for high spectral resolution. Since X-ray astronomy is a photon-limited discipline, the choice between high resolution for very few sources versus much lower resolution for many more has not always been an easy one. The development of new thermal detectors offers the opportunity to “have one’s cake and eat it, too.”

In our x-ray calorimetry effort, we have developed several techniques which may be helpful to other groups working in this field. We are studying several different monolithic and composite calorimeter designs. In our readout configuration, the preamplifier circuit employs negative voltage feedback which allows us to accurately measure the temporal profile of the thermal pulse produced by an x-ray absorbed in a micro-calorimeter. Rise times of less than two microseconds have been observed in monolithic devices operating at .3 K. Furthermore, the feedback preamplifier can be configured for either positive or negative electro-thermal feedback. This preamplifier system is followed by an analog pulse shaping amplifier with a frequency response that can be adjusted to yield the maximum signal to noise ratio for a given thermal response of the calorimeter. In addition, we have developed several diagnostic procedures which have been useful in determining the operating and noise characteristics of our devices. These include an infrared light-emitting diode which flashes a discrete amount of energy on to the calorimeter, and a capacitively coupled test input to the preamplifier which allows us to directly determine the total noise in the thermal detection system. Finally, we are developing an adiabatic demagnetization refrigerator with a temperature control system that is designed to stabilize the 0.1 K cold stage to better than 8 μK. This is required for a resistive thermal detector with resolving power of 1000.

We have been developing X-ray calorimeters that have high spectral resolution and high quantum efficiency. For an X-ray calorimeter working at 0.1 K, the energy resolution ideally can be as good as one eV for a practical detector. A detector with a resolution of 17 eV FWHM at 6 keV has been constructed. We expect to be able to improve this by a factor of two or more. With X-ray calorimeters flown on a sounding rocket, we should be able to observe soft X-ray line emission from the interstellar medium over the energy range 0.07 to 1 keV. Here we present a preliminary design for an X-ray calorimeter rocket experiment and the spectrum which might be observed from an equilibrium plasma. For later X-ray calorimeter sounding rocket experiments, we plan to add an aluminum foil mirror with collecting area of about 400 cm2 to observe line features from bright supernova remnants.