The first high-resolution observations of 37.7-, 38.3- and 38.5-GHz methanol masers

We have used the Australia Telescope Compact Array (ATCA) to undertake the first high angular resolution observations of 37.7-GHz ($7_{-2} - 8_{-1}E$) methanol masers towards a sample of eleven high-mass star formation regions which host strong 6.7-GHz methanol masers. The 37.7-GHz methanol sites are coincident to within the astrometric uncertainty (0.4 arcseconds) with the 6.7-GHz methanol masers associated with the same star formation region. However, spatial and spectral comparison of the 6.7- and 37.7-GHz maser emission within individual sources shows that the 37.7-GHz masers are less often, or to a lesser degree co-spatial than are the 12.2-GHz and 6.7-GHz masers. We also made sensitive, high angular resolution observations of the 38.3- and 38.5-GHz class II methanol transitions ($6_{2} - 5_{3}A^{-}$ and $6_{2} - 5_{3}A^{+}$, respectively) and the 36.2-GHz ($4_{-1} - 3_{0}E$) class I methanol transition towards the same sample of eleven sources. The 37.7-, 38.3- and 38.5-GHz methanol masers are unresolved in the current observations, which implies a lower limit on the brightness temperature of the strongest masers of more than $10^6$K. We detected the 38.3-GHz methanol transition towards 7 sources, 5 of which are new detections and detected the 38.5-GHz transition towards 6 sources, 4 of which are new detections. We detected 36.2-GHz class I methanol masers towards all eleven sources, 6 of these are new detections for this transition, of which 4 sources do not have previously reported class I methanol masers from any transition.Comment: Accepted for publication in MNRAS, 34 pages, 20 figure

Maser action in methanol transitions

We report the detection with the ATCA of 6.7 GHz methanol emission towards OMC-1. The source has a size between 40'' and 90'', is located to the south-east of Ori-KL and may coincide in position with the 25 GHz masers. The source may be an example of an interesting case recently predicted in theory where the transitions of traditionally different methanol maser classes show maser activity simultaneously. In addition, results of recent search for methanol masers from the 25 and 104.3 GHz transitions are reported.Comment: To appear in the Proceedings of the 2004 European Workshop: "Dense Molecular Gas around Protostars and in Galactic Nuclei", Eds. Y.Hagiwara, W.A.Baan, H.J. van Langevelde, 2004, a special issue of ApSS, Kluwer; author list has been corrected, text is unchange

Arc Magmas from Slab to Eruption: The Case of Kliuchevskoy Volcano

Arc magmas are generated by a number of mantle and crustal processes. Our multidisciplinary, long-term research is aimed at deciphering these processes for a single arc volcano, Kliuchevskoy volcano in Kamchatka. Some key results of the study follow: 1) Modeling of trace element and H2O contents in melt inclusions suggests that the primary magmas originate via hydrous flux-melting of the mantle wedge at temperatures close to the dry peridotite solidus. The role of decompression melting is minor or absent at Kliuchevskoy and other arc volcanoes built on relatively thick crust. 2) Geochemistry of high-Mg olivine suggests that primary Kliuchevskoy magmas have substantial contribution from olivine-free pyroxenite (up to 30 %), which could be formed by reaction of slab melts (or supercritical fluids) with mantle wedge peridotite. 3) Parental Kliuchevskoy melts start to crystallize as deep as the Moho boundary, and the erupted magmas reflect multistage and complex processes of crystallization, magma mixing and crustal assimilation. None of the Kliuchevskoy rocks analyzed thus far represent true primary melt compositions. 4) The Kliuchevskoy Holocene eruptive history is not steady-state in terms of eruption rate and geochemistry. There are two millenial cycles with major and trace element and OSr- Nd-Pb and U-series isotope compositions of the magmas changing gradually from more to less affected by crustal (?) assimilation. The onset of the cycles correlates with periods of enhanced volcanic activity in Kamchatka, suggesting that the extent of magma-crust interaction is inversely related to magma production rate and thus magma flux from the mantle

Molecular beam epitaxy of metamorphic buffer for InGaAs/InP photodetectors with high photosensitivity in the range of 2.2–2.6 um

The present work is concerned with finding optimal technological conditions for the synthesis of heterostructures with a metamorphic buffer for InGaAs/InP photodetectors in the wavelength range of 2.2–2.6 um using molecular beam epitaxy. Three choices of buffer structure differing in design and growth parameters were proposed. The internal structure of the grown samples was investigated by X-ray diffraction and transmission electron microscopy. Experimental data analysis has shown that the greatest degree of elastic strain relaxation in the InGaAs active layer was achieved in the sample where the metamorphic buffer formation ended with a consecutive increase and decrease in temperature. The said buffer also had InAs/InAlAs superlattice inserts. The dislocation density in this sample turned out to be minimal out of three, which allowed us to conclude that the described heterostructure configuration appears to be the most appropriate for manufacturing of short wavelength infrared range pin-photodetectors with high photosensitivity

Evidence for Archean hydrous deep-mantle reservoir provided by Abitibi komatiites

Archean komatiites result from melting under extreme conditions of the Earth’s mantle. Their chemical compositions evoke very high eruption temperatures, up to 1600°C, providing clues to still higher temperatures in their mantle source [1]. This message is clouded, however, by uncertainty about the water content in komatiite magmas. One school holds that komatiites were essentially dry and originated in mantle plumes [2] while the other argues that these magmas contained several percent of water, which drastically reduced their eruption temperature and links them to subduction processes [3]