Anomalous reversible torque in layered superconducting Bi2Sr2CaCu2x single crystal

Magnetic anisotropy of layered superconducting Bi2Sr2CaCu2O x single crystal was investigated by the torque metlod in the reversible regime. The torque was analyzed in the model taking into account 2D layered structure. Considered model gives the better fit to the data wlen the magnetic fieJd is applied near (a, b) plane. Obtained results establish to 6 x 10 3 value of the superconducting effective mass anisotropy coefficient ε

Milliarcsecond structure of water maser emission in two young high-mass stellar objects associated with methanol masers

The 22.2 GHz water masers are often associated with the 6.7 GHz methanol masers but owing to the different excitation conditions they likely probe independent spatial and kinematic regions around the powering young massive star. We compared the emission of these two maser species on milliarcsecond scales to determine in which structures the masers arise and to test a disc-outflow scenario where the methanol emission arises in a circumstellar disc while the water emission comes from an outflow. We obtained high-angular and spectral resolution 22.2 GHz water maser observations of the two sources G31.581+00.077 and G33.641-00.228 using the EVN. In both objects the water maser spots form complex and filamentary structures of sizes 18-160 AU. The emission towards the source G31.581+00.077 comes from two distinct regions of which one is related to the methanol maser source of ring-like shape. In both targets the main axis of methanol distribution is orthogonal to the water maser distribution. Most of water masers appear to trace shocks on a working surface between an outflow/jet and a dense envelope. Some spots are possibly related to the disc-wind interface which is as close as 100-150 AU to the regions of methanol emission.Comment: 10 pages, accepted to Astronomy and Astrophysic

Spin Waves in the Ferromagnetic Ground State of the Kagome Staircase System Co3V2O8

Inelastic neutron scattering measurements were performed on single crystal Co3V2O8 wherein magnetic cobalt ions reside on distinct spine and cross-tie sites within kagome staircase planes. This system displays a rich magnetic phase diagram which culminates in a ferromagnetic ground state below Tc~6 K. We have studied the low-lying magnetic excitations in this phase within the kagome plane. Despite the complexity of the system at higher temperatures, linear spin-wave theory describes most of the quantitative detail of the inelastic neutron measurements. Our results show two spin-wave branches, the higher energy of which displays finite spin-wave lifetimes well below Tc, and negligible magnetic exchange coupling between Co moments on the spine sites.Comment: 4 pages and 4 figure

Ring shaped 6.7 GHz methanol maser emission around a young high-mass star

We report on EVN imaging of the 6.7 GHz methanol maser emission from the candidate high-mass protostar G23.657-0.127. The masers originate in a nearly circular ring of 127 mas radius and 12 mas width. The ring structure points at a central exciting object which characteristics are typical for a young massive star; its bolometric luminosity is estimated to be <3.2*10^4 L_sun and <1.2*10^5 L_sun for near (5.1 kpc) and far (10.5 kpc) kinematic distances, respectively. However, the spatial geometry of the underlying maser region remains ambiguous. We consider scenarios in which the methanol masers originate in a spherical bubble or in a rotating disc seen nearly face-on.Comment: 4 pages, 4 figures, accepted by Astronomy and Astrophysics Letter

VLA observations of water masers towards 6.7 GHz methanol maser sources

22 GHz water and 6.7 GHz methanol masers are usually thought as signposts of early stages of high-mass star formation but little is known about their associations and the physical environments they occur in. The aim was to obtain accurate positions and morphologies of the water maser emission and relate them to the methanol maser emission recently mapped with Very Long Baseline Interferometry. A sample of 31 methanol maser sources was searched for 22 GHz water masers using the VLA and observed in the 6.7 GHz methanol maser line with the 32 m Torun dish simultaneously. Water maser clusters were detected towards 27 sites finding 15 new sources. The detection rate of water maser emission associated with methanol sources was as high as 71%. In a large number of objects (18/21) the structure of water maser is well aligned with that of the extended emission at 4.5 $\mu$m confirming the origin of water emission from outflows. The sources with methanol emission with ring-like morphologies, which likely trace a circumstellar disk/torus, either do not show associated water masers or the distribution of water maser spots is orthogonal to the major axis of the ring. The two maser species are generally powered by the same high-mass young stellar object but probe different parts of its environment. The morphology of water and methanol maser emission in a minority of sources is consistent with a scenario that 6.7 GHz methanol masers trace a disc/torus around a protostar while the associated 22 GHz water masers arise in outflows. The majority of sources in which methanol maser emission is associated with the water maser appears to trace outflows. The two types of associations might be related to different evolutionary phases.Comment: accepted by Astronomy & Astrophysic

The nature of the methanol maser ring G23.657-00.127

Methanol masers are associated with young high-mass stars and are an important tool for investigating the process of massive star formation. The recently discovered methanol maser ring in G23.657-00.127 provides an excellent ``laboratory'' for a detailed study of the nature and physical origin of methanol maser emission, as well as parallax and proper motion measurements. Multi-epoch observations of the 12.2 GHz methanol maser line from the ring were conducted using the Very Long Baseline Array. Interferometric observations with milliarcsecond resolution enabled us to track single maser spots in great detail over a period of 2 years. We have determined the trigonometric parallax of G23.657-00.127 to be 0.313+/-0.039 mas, giving a distance of 3.19{+0.46}{-0.35} kpc. The proper motion of the source indicates that it is moving with the same circular velocity as the LSR, but it shows a large peculiar motion of about 35 km/s toward the Galactic center.Comment: 6 pages, 3 figures, accepted for publication in A&