The correlation between the coronal X-ray temperature and the magnetic field strength in late-type stars is investigated, based on data primarily from the ROSAT PSPC. According to the observation, we divide the stars into three groups: single, binary and RS CVn stars. From the sample of single stars, we find a clear correlation of the coronal temperature with the magnetic field strength. We int...

We report the hard X-ray properties of the young Crab-like LMC pulsar PSR B0540-69, using archival RXTE PCA (2 – 60 keV) and RXTE HEXTE (15 – 250 keV) data. Making use of the very long effective exposure of 684 ks, we derived a very detailed master pulse profile for energies 2 – 20 keV. We confirm the broad single-pulse shape with a dip in the middle and with a significant fine structure to the...

There are several supernova remnants which contain unresolved X-ray sources close to their centers, presumably radio-quiet neutron stars. To prove that these objects are indeed neutron stars, to understand the origin of their X-ray radiation, and to explain why they are radio-quiet, one should know their periods and period derivatives. We searched for pulsations of the X-ray flux from the radio...

Different capsular serotypes of Streptococcus pneumoniae vary markedly in their ability to cause invasive infection, but the reasons why are not known. As immunity to S. pneumoniae infection is highly complement dependent, variations in sensitivity to complement between S. pneumoniae capsular serotypes could affect invasiveness. We have used 20 capsule-switched variants of strain TIGR4 to inves...

We analyze archival ROSAT HRI, ROSAT PSPC, and ASCA data of the X-ray faint early-type galaxy NGC 4697. The joint ROSAT PSPC + ASCA spectrum is fit by a two-component thermal model, a MEKAL model with kTMEKAL = 0.26 +0.04 −0.03 keV with low metallicity and a bremsstrahlung model with kTBREM = 5.2 +3.0 −1.6 keV. A similar model was found to fit the spectra of another faint early-type galaxy (NGC...

We present results and an analysis of a ROSAT/PSPC pointed observation of the galaxy cluster CL0939+472. This very rich and very distant cluster is known to contain an unusually high fraction of blue and E+A galaxies, and a lot of merging of galaxies is going on. The X-ray properties we find are also quite unusual. The luminosity in the ROSAT band (0.1-2.4 keV) is LX = (6:7 0:3) 1044erg/s, rath...

We present a combined analysis of the BeppoSAX and ROSAT PSPC observation of the cluster of galaxies A3562, a massive member of the core of the Shapley Supercluster. With a complex and interacting structure composed from two groups of galaxies and A3558 to the West, the surface brightness of A3562 shows excess in the sectors to East and South when compared with an azimuthally averaged model of ...

We present the ROSAT PSPC pointed and ROSAT All-Sky Survey (RASS) observations and the results of our low and high spectral resolution optical followup observations of the T Tauri stars (TTS) and X-ray selected T Tauri star candidates in the region of the high galactic latitude dark cloud MBM12 (L1453-L1454, L1457, L1458). Previous observations have revealed 3 “classical” T Tauri stars and 1 “w...

PKS1830-211 is an unusually radio−loud gravitationally lensed quasar. In the radio, the system appears as two compact, dominant features surrounded by relatively extended radio emission which forms an Einstein Ring. As the line of sight to it passes close to our Galactic center, PKS1830-211 has not been detected in wave-bands other than the radio and X-ray so far. Here we present X-ray data of ...