soil samples were collected from seven sites in and around the metropolitan area of mexicocity. the locations were chosen as possible sources of fugitive dusts which contribute to suspended particulate matter in the atmosphere of mexico city. x-ray fluorescence (xrf) was used to determine the concentrations of several major elements (si, k, ca, ti, mn, and fe), as well as of other trace element...

We compute the X-ray spectra produced by non-static coronae atop accretion discs around black holes and neutron stars. The hot corona is radiatively coupled to the underlying disc (the reflector) and generates an X-ray spectrum which is sensitive to the bulk velocity of the coronal plasma, β = v/c. We show that an outflowing corona reproduces the hard-state spectrum of Cyg X-1 and similar objec...

We report here the results of the first Chandra X-Ray Observatory observations of the globular cluster M28 (NGC 6626). We detect 46 X-ray sources of which 12 lie within one core radius of the center. We show that the apparently extended X-ray core emission seen with the ROSAT HRI is due to the superposition of multiple discrete sources for which we determine the X-ray luminosity function down t...

We observed the gamma-ray pulsar Geminga with the FUV-MAMA and NUV-MAMA detectors of the Space Telescope Imaging Spectrometer to measure the Geminga’s spectrum and pulsations in the ultraviolet. The slope of the far-ultraviolet (FUV) spectrum is close to that of a Rayleigh-Jeans spectrum, suggesting that the FUV radiation is dominated by thermal emission from the neutron star (NS) surface. The ...

background: panoramic imaging is one of the most common imaging methods in dentistry. regarding the side-effects of ionizing radiation, it is necessary to survey different aspects and details of panoramic imaging. in this study, we compared the absorbed x-ray dose around two panoramic x-ray units: pm 2002 cc proline (planmeca, helsinki, finland) and cranex tome (soredex, helsinki, finland). mat...

We present a high-quality X-ray spectrum in the 3–53 keV rest-frame band of the radio-loud quasar 1508+5714, by far the brightest known X-ray source at z > 4. A simple power-law model with an absorption column density equal to the Galactic value in the direction of the source provides an excellent and fully adequate fit to the data; the measured power-law photon index Γ = 1.42 −0.10. Upper limi...

We present ROSAT PSPC and HRI observations of the dwarf irregular galaxy Holm-berg II (UGC4305). This is one of the most luminous dwarf galaxies (L x ∼ 10 40 erg s −1) detected in the ROSAT All-Sky Survey. The X-ray emission comes from a single unresolved point source, coincident with a large HII region which emits intense radio emission. The source is variable on both year and day timescales, ...

Sub-arcsecond resolution Chandra observations of η Car reveal a 40 × 70 ring or partial shell of X-ray emission surrounding an unresolved, bright, central source. The spectrum of the central source is strongly absorbed and can be fit with a high-temperature thermal continuum and emission lines. The surrounding shell is well outside the optical/IR bipolar nebula and is coincident with the Outer ...

We present the first optical validation of an X-ray Line-Emitting Object (XLEO) discovered in the XMM-Newton observation of the Chandra Deep Field South. The object is an AGN at zx ∼ 0.66. An optical spectrum of the source indeed confirms and refines (zo = 0.665) the redshift obtained from the X-ray line. The X-ray and optical properties of the source are presented and discussed. Subject headin...