Diffuse X-ray background measurements in the energy range 2–18 keV

Rocket measurements, of the diffuse X-ray background in the energy range 2–18 keV, conducted from Thumba Equatorial Rocket Launching Station (TERLS), India, are presented. The estimates of the cosmic background are derived by the method which employs the Earth and its atmosphere as a shutter to intercept the celestial X-rays. The results are shown to be consistent with a power law photon spectrum.13.6 _–3.3 ^+4.3 E ^{–1.73±0.15} photons/cm²-sec-keV-ster the spectrum being much flatter than that observed at higher energies.     

Eliminating Virtual Impactors with the Very Large Telescope: An ESO Program with the FORS2 Camera

We have used the ESO Very Large Telescope (VLT) to perform as trometric observations of Near Earth Asteroids (NEAs) having remote collision possibilities with the Earth. The observations were made for those objects which became too faint to be observed elsewhere. Using the 4 hours allocated in the semester April–September 2003, 5 faint NEAs were observed. As a result, no NEA that could impact the Earth was lost.     

Radiative Equilibrium Model of 51 Peg B

Earth, Moon, and Planets -     

Post-collisional volcanism in a sinking slab setting—crustal anatectic origin of pyroxene-andesite magma, Caldear Volcanic Group, Neogene Alborán volcanic province, southeastern Spain

Caldear Volcanic Group (CVG), a stratigraphically well defined, calc-alkaline rock complex within S^a de Gata in the eastern part of the Alpine Betic mountain chain, S Spain, consists of three distinct formations: Hernández pyroxene andesites, Bujo hornblende-bearing pyroxene andesites and Viuda hornblende-bearing pyroxene dacites–rhyolites. The letter rock formation may have developed through crystal fractionation of mainly plagioclase and pyroxenes, however there is no direct relation between two formations. CVG has a domainal structure with a northeastern domain where Hernández formation is overlain by Bujo formation while Viuda formation is absent, and a southwestern domain where Viuda formation forms the only fractionate after Hernández formation. Hernández parent magma is thought generated through crustal anatexis by dehydration melting of a predominantly amphibolitic source rock complex which was formed by metamorphism from c. 500 Ma volcano-sedimentary parent material. The domainal structure of CVG is explained by compositional variation within this protogenetic complex. Single crystal U–Pb ages of c. 500 Ma to 1800 Ma for inherited zircon support the presence of clastic material of Proterozoic derivation within the original volcano-sedimentary complex. Regional study of syn-collisional rock formations (Alpine nappe complexes) indicate that the collisional tectonic stage in the Betic-Rif orogenic belt took place rather early (25–30 Ma?) and was followed by a stage of rapid regional rock uplift, fast cooling (c. 500°C/my) and extensional tectonics in the period 22–17 Ma. This later tectonic stage was set into motion by slab break-off which set the stage for a high temperature regime in the overlying lithosphere, providing the framework for the crustal melting and magma production responsible for the calc-alkaline rocks of Alborán volcanic province. Miocene zircon with ages ranging from c. 17 to 11 Ma indicate a rather protracted magmatic development prior to eruption at c. 11 Ma. Post-collisional character of Caldear Volcanic Group thus seems well established.     

Some special restricted four-body problems—II. From Caledonia to Copenhagen

Special analytical solutions are determined for restricted, coplanar, four-body equal mass problems, including the Caledonian problem, where the masses M_i = M for i = 1,2,3,4. Most of these solutions are shown to reduce to the Lagrange solutions of the Copenhagen problem of three bodies by reducing two of the masses (m_i = m for i = 1,2) in the four-body equal mass problem to zero while maintaining their equality of mass. In so doing, families of special solutions to the four-body problem are shown to exist for any value of the mass ratio μ = m/M.