IV. Stratigraphie Die fazielle Einstufung fossilführender Sedimente

Ohne Zusammenfassung     

Analogous method for interpretation of gravitational anomalies

Summary From a corollary ofGreen's theorem is derived, that a thin layer of variable density can produce the same gravitational effect as a certain mass distribution below this layer. To this thin layer of variable density is analogous a sheet illuminated of variable intensity. The intensity of illumination is detected with a Philips LDR (light dependent resistor) cell. It is pointed out further that the method can be applied to determine the vertical gravity gradient too.

---

Zusammenfassung Aus einem Folgesatz des Green-Theorems wird abgeleitet, dass eine dünne Schicht mit veränderlicher Dichte die gleiche Gravitationswirkung verursacht wie eine bestimmte — unter dieser Schicht liegende — Massenverteilung. Zwischen dieser dünnen Schicht mit veränderlicher Dichte und einer beleuchteten Fläche mit veränderlicher Lichtstärke besteht eine Analogie. Die Intensität der Beleuchtung wird mit einer Philips-LDR-Zelle gemessen. Es wird weiter darauf hingewiesen, dass die Methode auch für Bestimmung des vertikalen Gravitationsgradienten anwendbar ist.

     

The structure of the 1–3 keV X-ray background

New infrared photometry of a sample of 39 stars in the open cluster NGC 752 is presented. These observations confirm the bimodality of the Main Sequence previously reported. We analyze the nature of this behaviour on the basis of the binary hypothesis.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain     

Chandra temperature and metallicity maps of the Perseus cluster core

We present temperature and metallicity maps of the Perseus cluster core obtained with the Chandra X-ray Observatory. We find an overall temperature rise from  ∼3.0 keV  in the core to  ∼5.5 keV  at 120 kpc and a metallicity profile that rises slowly from  ∼0.5  solar to  ∼0.6  solar inside 60 kpc, but drops to  ∼0.4  solar at 120 kpc. Spatially resolved spectroscopy in small cells shows that the temperature distribution in the Perseus cluster is not symmetrical. There is a wealth of structure in the temperature map on scales of  ∼10  arcsec (5.2 kpc) showingswirliness and a temperature rise that coincides with a sudden surface brightness drop in the X-ray image. We obtain a metallicity map of the Perseus cluster core and find that the spectra extracted from the two central X-ray holes as well as the western X-ray hole are best-fit by gas with higher temperature and higher metallicity than is found in the surroundings of the holes. A spectral deprojection analysis suggests, however, that this is due to a projection effect; for the northern X-ray hole we find tight limits on the presence of an isothermal component in the X-ray hole, ruling out volume-filling X-ray gas with temperatures below 11 keV at 3σ.