OH(1720 MHz) Masers As Signposts of Molecular Shocks

We present observations of molecular gas made with the 15-m James Clark Maxwell Telescope toward the sites of OH(1720 MHz) masers in three supernova remnants: W28, W44 and 3C391. Maps made in the 12CO J=3-2 line reveal that the OH masers are preferentially located along the edges of thin filaments or clumps of molecular gas. There is a strong correlation between the morphology of the molecular gas and the relativistic gas traced by synchrotron emission at centimeter wavelengths. Broad CO line widths (dV=30-50 km/s) are seen along these gaseous ridges, while narrow lines are seen off the ridges. The ratio of H2CO line strengths is used to determine temperatures in the broad-line gas of 80 K, and the 13CO J=3-2 column density suggests densities of 10^4-10^5 cm{-3}. These observations support the hypothesis that the OH(1720 MHz) masers originate in post-shock gas, heated by the passage of a supernova remnant shock through dense molecular gas. From the observational constraints on the density, velocity and magnetic field we examine the physical properties of the shock and discuss the shock-production of OH. These OH(1720 MHz) masers are useful ``signposts'', which point to the most promising locations to study supernova remnant/molecular cloud interactions.Comment: ApJ (in press

Orbital correlations in the pseudo-cubic \emph{O} and rhombohedral R{R}-phases of LaMnO3_3

The local and intermediate structure of stoichiometric LaMnO$_3$ has been studied in the pseudocubic and rhombohedral phases at high temperatures (300 to 1150 K). Neutron powder diffraction data were collected and a combined Rietveld and high real space resolution atomic pair distribution function analysis carried out. The nature of the Jahn-Teller (JT) transition around 750 K is confirmed to be orbital order to disorder. In the high temperature orthorhombic ($O$) and rhombohedral ($R$) phases the MnO$_6$ octahedra are still fully distorted locally. The data suggest the presence of local orbitally ordered clusters of diameter $\sim 16$ \AA ($\sim$four MnO$_6$ octahedra) implying strong nearest neighbor JT anti-ferrodistortive coupling.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Le

Material studies related to lunar surface exploration. Volume 4 - Preliminary studies for the design of engineering probes Final report, 6 Mar. 1967 - 30 Jun. 1968

Preliminary design of engineering probes for studying lunar surface material propertie