X-ray Multi-Mirror Satellite Research Articles

Million-Degree Plasma Pervading the Extended Orion Nebula

Most stars form as members of large associations within dense, very cold (10 to 100 kelvin) molecular clouds. The nearby giant molecular cloud in Orion hosts several thousand stars of ages less than a few million years, many of which are located in or around the famous Orion Nebula, a prominent gas structure illuminated and ionized by a small group of massive stars (the Trapezium). We present x-ray observations obtained with the X-ray Multi-Mirror satellite XMM-Newton, revealing that a hot plasma with a temperature of 1.7 to 2.1 million kelvin pervades the southwest extension of the nebula. The plasma flows into the adjacent interstellar medium. This x-ray outflow phenomenon must be widespread throughout our Galaxy.

A classical nova, V2487 Oph 1998, seen in x-rays before and after its explosion.

Classical nova explosions are very energetic and frequent phenomena caused by explosive hydrogen burning on top of an accreting white dwarf. Observations of the recent nova V2487 Oph 1998 by the X-ray Multi-Mirror satellite (XMM-Newton) provide evidence that accretion (probably on a magnetic white dwarf) was reestablished as early as 2.7 years after the explosion. In addition, positional correlation with a source previously discovered by the Röntgen Satellite (ROSAT) in 1990 suggests that the site of a nova explosion had been seen in x-rays before the outburst.

Simulations of observations with the Optical Monitor of the X-ray Multi-Mirror Satellite

This paper addresses the question of the observations to be performed with the Optical Monitor (OM) of the X-ray Multi-Mirror Satellite (XMM) under several aspects. First, we discuss XMM-OM's photometric system and its colour transformations towards the standard UBV system. Second, we establish a set of procedures to determine the temperature and the amount of interstellar absorption affecting the observed stars. Last, we address the possibility of isolating quasars in multidimensional colour diagrams based on the XMM-OM filter set.

On the perspectives of using XMM to study fundamental parameters of early-type stars

Although substantial progress has been achieved since the discovery of X-ray emission from early-type stars with the EINSTEIN satellite, several crucial aspects of this phenomenon are still not fully understood. Considerable breakthroughs in this field are expected from observations with the X-ray Multi-Mirror satellite (XMM) due for launch in early 2000. XMM is the second cornerstone mission of the ESA Horizon 2000 science programme (see Lumb et al. 1996 and references therein for an overall description of the satellite). XMM offers a large effective area over a wide range of energies and its instrumentation provides simultaneously non-dispersive spectroscopic imaging (EPIC - European Photon Imaging Camera), medium-resolution dispersive spectroscopy (RGS - Reflection Grating Spectrometer) and optical-UV imaging (OM - Optical Monitor).

The pn-CCD as focal plane detector for the XMM satellite mission

The X-ray Multi Mirror (XMM) satellite mission is one of the major European Space Agency (ESA) space missions scheduled for launch by the end of this decade. Its goal is to observe the x-ray-emitting sky in the 100 eV to 15 keV photon energy range with high spectral and spatial resolution. XMM's scientific instruments consist mainly of three independent Wolter telescopes each having an imaging charge-coupled-device (CCD) detector in the focal plane. Two of the three telescopes are equipped with CCDs based on the conventional MOS-CCD technology. The third is equipped with pn-CCDs, a new developement of the semiconductor laboratory of the Max-Planck-Institut fur extraterrestrische Physik. The pn-CCD has several features such as full detector depletion, parallel readout and good radiation hardness due to the replacement of the MOS structures with pn-diode electrodes. The design of the pn-CCD detector for XMM is shown and measurements with pn-CCD prototype units are presented.

EXAFS and XANES: New Astrophysical Tools to Study the Solid State Structure of Interstellar Grains

I show that new information about the compositions and crystal structures of interstellar grains can be derived from measurements of extended X-ray absorption fine structure (EXAFS) above the absorption edges in the spectra of highly extincted and bright X-ray stars. It will be also possible to probe the long-range crystal structures of solid grains by analyzing extended X-ray absorption-edge profiles modified by X-ray absorption near edge structure (XANES). I show that recently developed high-resolution (E/ΔE ≈ 1000) X-ray spectrometers (e.g., the High-Energy Transmission Grating Spectrometer on the Advanced X-Ray Astrophysics Facility [AXAF] or the Reflection Grating Spectrometer on the X-Ray Multi-Mirror satellite [XMM]) will be able to measure these features.

First results with the pn-CCD detector system for the XMM satellite mission

The pn-CCD is a novel CCD type which is developed for fast X-ray imaging and spectroscopy for the X-ray Multi Mirror (XMM) satellite mission. Each 200 × 64 pixel large pn-CCD unit with a sensitive area of 3 × 1 cm 2 is a fully depleted detector. Full depletion allows for high photon detection efficiency (> 90% in the energy range of 500 eV-10 keV), for a small input capacitance necessary for low noise signal measurements and for backward illumination. For good time resolution and low noise performance each of the 64 CCD channels is terminated with an integrated input-JFET for signal amplification. With the use of the CMOS Amplifier and Multiplexing Chip (CAMEX64B) it is possible to read out the 64 CCD channels in parallel before they are multiplexed and sent to an ADC. For the first time the system of a 64 channel pn-CCD together with CAMEX64B readout, ADC conversion and data acquisition and storage has been brought into operation. First images of an 55Fe X-ray source are presented and discussed.