Detection of large-scale X-ray bubbles in the Milky Way halo.

The halo of the Milky Way provides a laboratory to study the properties of the shocked hot gas that is predicted by models of galaxy formation. There is observational evidence of energy injection into the halo from past activity in the nucleus of the Milky Way; however, the origin of this energy (star formation or supermassive-black-hole activity) is uncertain, and the causal connection between nuclear structures and large-scale features has not been established unequivocally. Here we report soft-X-ray-emitting bubbles that extend approximately 14 kiloparsecs above and below the Galactic centre and include a structure in the southern sky analogous to the North Polar Spur.

Large area x-ray collimator-the zone plate approach.

One question of particular interest in the measurement of x-ray imaging optics for space telescopes concerns the characteristics of the point spread function (PSF) in orbit and the focal length for an infinite source distance. In order to measure such a PSF, a parallel x-ray beam with a diameter of several centimeters to meters is required. For this purpose a large area transmission x-ray zone plate (ZP) for collimating x-ray beams has been designed, built, and tested.

Toward the diffraction limit with transmissive x-ray lenses in astronomy.

We develop an analytical approach to refractive, blazed diffractive, and achromatic x-ray lenses of scalable dimensions for energies from 1 to 20 keV. Based on the parabolic wave equation, their wideband imaging properties are compared and optimized for a given spectral range. Low-Z lens materials for massive cores and rugged alternatives, such as polycarbonate or Si for flat Fresnel components, are investigated with respect to their suitability for diffraction-limited high-energy astronomy.

Efficient Fresnel x-ray optics made simple.

A practical design for upcoming spaceborne x-ray telescopes with ultrahigh angular resolution is proposed. Particular attention is directed to technological simplicity and robust as well as cheap components. Based on dispersion corrected Fresnel lenses, an optimized arrangement will be identified with respect to the instrumental sensitivity for a given focal spot size.

High-Resolution Spectroscopy of the X-Ray-photoionized Wind in Cygnus X-3 with the Chandra High-Energy Transmission Grating Spectrometer.

We present a preliminary analysis of the 1-10 keV spectrum of the massive X-ray binary Cygnus X-3, obtained with the high-energy transmission grating spectrometer on the Chandra X-Ray Observatory. The source reveals a richly detailed discrete emission spectrum, with clear signatures of photoionization-driven excitation. Among the spectroscopic novelties in the data are the first astrophysical detections of a number of He-like "triplets" (Si, S, Ar) with emission-line ratios characteristic of photoionization equilibrium, fully resolved narrow radiative recombination continua of Mg, Si, and S, the presence of the H-like Fe Balmer series, and a clear detection of an approximately 800 km s-1 large-scale velocity field as well as an approximately 1500 km s-1 FWHM Doppler broadening in the source.

First Light Measurements of Capella with the Low-Energy Transmission Grating Spectrometer aboard the Chandra X-Ray Observatory.

We present the first X-ray spectrum obtained by the Low-Energy Transmission Grating Spectrometer (LETGS) aboard the Chandra X-Ray Observatory. The spectrum is of Capella and covers a wavelength range of 5-175 Å (2.5-0.

Recognition of damage in polarizing transmission-grating facets.

An optical setup was built for microscopic damage inspection on transmission-grating facets composed of a gold-wire structure. Contrast improvement was achieved by exploiting the polarizing properties of these gratings in the near-infrared region. Spatial filtering yields an additional contrast enhancement and reduces unwanted signals caused by the periodic support structure.

Polarimetry of transmission gratings.

We have investigated the polarizing properties of gold wire gratings in the resonance domain. The partial polarizing properties of 1-μm period gratings in the near IR are then used to orient the wire structure of transmission grating facets parallel to each other by means of an alignment polarimeter technique. The absolute alignment accuracy for these gratings is limited by the influence of the support structure on the orientation of the polarization ellipse.

A Lunar Occultation of the Dust-Scattering Halo Around GX 5-1 Observed with ROSAT.

The x-ray source GX 5-1 in the galactic bulge has been observed with the position-sensitive proportional counter onboard the Röntgen satellite (ROSAT) during and after a lunar occultation. Extended emission around the source was unambiguously discovered while the central source was behind the lunar rim. This emission is interpreted as a dust-scattering halo around GX 5-1 that has a fractional intensity of 28 percent, implying a grain column density between GX 5-1 and Earth of approximately 3 x 10(10) per square centimeter.

Characterization of x-ray transmission gratings.

Self-supporting transmission gratings with periods of 1 microm or below are used in combination with grazing-incidence telescopes in celestial x-ray astronomy. They can be produced with sizes up to only a few cm(2); therefore, several hundreds or even thousands of individual elements are needed in order to cover the aperture of a telescope. This large number leads to the problem of characterization of the gratings regarding their x-ray performance.

Fabrication of transmission gratings for use in cosmic x-ray and XUV astronomy.

The manufacturing process of open transmission gratings with high efficiency and high line density is described. This process is developed by Dr. Johannes Heidenhain GmbH in cooperation with the Max- Planck-Institut and involves two steps, the mechanical ruling of the original master and the photochemical replication of the individual grating facets.

Transmission grating efficiencies for wavelengths between 5.4 A and 44.8 A.

Diffraction efficiencies of 44.8-5.4-A x rays by a free-standing gold transmission grating of 1.