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The gravitationally lensed quasar Q2237+0305 in X-rays: ROSAT/HRI detection of the "Einstein Cross"
(1999)
We report the first detection of the gravitationally lensed quasar Q2237+0305 in X-rays. With a ROSAT/HRI exposure of 53 ksec taken in Nov./Dec. 1997, we found a count rate of 0.006 counts per second for the combined four images. This corresponds to an X-ray flux of 2.2*E(-13) erg/cm(2) /sec and an X-ray luminosity of 4.2*E(45) erg/sec (in the ROSAT energy window 0.1-2.4 keV). The ROSAT/HRI detector is not able to resolve spatially the four quasar images (maximum separation 1.8 arcsec). The analysis is based on about 330 source photons. The signal is consistent with no variability, but with low significance. This detection is promising in view of the upcoming X-ray missions with higher spatial/spectral resolution and/or collecting power (Chandra X-ray Observatory, XMM and ASTRO-E).
Si(1-x)Ge(x) laterally graded crystals as monochromators for X-Ray absorption spectroscopy studies
(1999)
Charakterisierung und Optimierung der Beugungseigenschaften von Si1_xGex Monochromatorkristallen
(1999)
Strukturfaktoränderungen von GaAs und ZnSe unter dem Einfluss eines äußeren elektrischen Feldes
(1999)
We consider a large population of globally coupled noisy phase oscillators. In the thermodynamic limit N this system exhibits a nonequilibrium phase transition, at which amacroscopic mean field appears. It is shown that for large but finite system size N the system can be described by the noisy Stuart-Landau equation, yielding scaling behavior of statistical characteristics of the macroscopic mean field with N. The predictions of the theory are checked numerically.
Q switch and longitudinal modes of a laser oscillator with a stimulated-Brillouin-scattering mirror
(1999)
We study a model describing a rotating linear rigid molicule interacting with a Bose-Einstein condensate. A generalization of the Landau criterion is established and gives the limit for which the molecule moves translationally and rotationally into the condensate without any friction. In particular, we show that the rotational energy released by the molecule is large enough to eject one atom out of the condensate. The detection of such an atom provides a direct measurement of the low-energy cross section of the scattering with the rotating molecule. Finally, increases of inertia and of centrifugal distortion of the molecule due to the surrounding condensate are estimated and compared with the experimental data obtained for a He4 droplet.
Broadband operation of a gain-switched Ti:sapphire laser for measurements with the coherence radar
(1999)