Two new pulsating DB Stars from the EC survey, EC 04207−4748 and EC 05221−4725

We report the discovery of pulsations in two DB stars found in the Edinburgh–Cape blue object survey. The light curve of EC 04207−4748 appears to be dominated by a strong variation at  2235 μHz  (447 s) and its first overtone near 4475 μHz (223 s). Two other peaks appear in the periodograms of all three data sets for this star; near  2370 μHz  (∼420 s) and  3000 μHz  (∼333 s), though these are less accurately defined. EC 05221−4725 is less easy to specify with the currently available data; it appears to have one coherent frequency near  1114 μHz  (898 s), but is obviously multiperiodic and probably has several more frequencies near the one clearly observed.     

A dark matter disc in three cosmological simulations of Milky Way mass galaxies

Making robust predictions for the phase-space distribution of dark matter at the solar neighbourhood is vital for dark matter direct-detection experiments. To date, almost all such predictions have been based on simulations that model the dark matter alone. Here, we use three cosmological hydrodynamic simulations of bright, disc-dominated galaxies to include the effects of baryonic matter self-consistently for the first time. We find that the addition of baryonic physics drastically alters the dark matter profile in the vicinity of the solar neighbourhood. A stellar/gas disc, already in place at high redshift, causes merging satellites to be dragged preferentially towards the disc plane where they are torn apart by tides. This results in an accreted dark matter disc that contributes ∼0.25–1.5 times the non-rotating halo density at the solar position. The dark disc, unlike dark matter streams, is an equilibrium structure that must exist in disc galaxies that form in a hierarchical cosmology. Its low rotation lag with respect to the Earth significantly boosts Weakly Interacting Massive Particle (WIMP) capture in the Earth and Sun, boosts the annual modulation signal and leads to distinct variations in the flux as a function of recoil energy that allow the WIMP mass to be determined.     

Two new large-separation gravitational lenses from SDSS

We present discovery images, together with follow-up imaging and spectroscopy, of two large-separation gravitational lenses found by our survey for wide arcs [the CAmbridge Sloan Survey Of Wide ARcs in the skY (CASSOWARY)]. The survey exploits the multicolour photometry of the Sloan Digital Sky Survey to find multiple blue components around red galaxies. CASSOWARY 2 (or 'the Cheshire Cat') is composed of two massive early-type galaxies at   z = 0.426  and 0.432, respectively, lensing two background sources, the first a star-forming galaxy at   z = 0.97  and the second a high -redshift galaxy  ( z > 1.4)  . There are at least three images of the former source and probably four or more of the latter, arranged in two giant arcs. The mass enclosed within the larger arc of radius ∼11 arcsec is  ∼33 × 10¹² M_⊙  . CASSOWARY 3 comprises an arc of three bright images of a   z = 0.725  source, lensed by a foreground elliptical at   z = 0.274  . The radius of the arc is ∼4 arcsec and the enclosed mass is  ∼2.5 × 10¹² M_⊙  . Together with earlier discoveries like the Cosmic Horseshoe and the 8 o'clock Arc, these new systems, with separations intermediate between the arcsecond-separation lenses of typical strong galaxy lensing and arcminute-separation cluster lenses, probe the very high end of the galaxy mass function.     

Catalogue of averaged stellar effective magnetic fields – II. Re-discussion of chemically peculiar A and B stars

This paper presents a catalogue and the method of determining averaged quadratic effective magnetic fields  〈 B _e〉  for 1212 main-sequence and giant stars, and 11 white dwarf stars. The catalogue includes stars that are members of several open clusters. We have compiled measurements of the longitudinal magnetic field for those stars, which were scattered in the existing literature. A new parameter, magnetization (MA), has been defined, and we present values of MA for stars of various spectral classes. Our sample includes a subset of 610 chemically peculiar early-type stars. We confirm the conclusion of our previous study that the number distribution of all chemically peculiar stars versus the averaged magnetic field strength is described by a decreasing exponential function. Relations of this type also hold for stars of all the analysed subclasses of chemical peculiarity. Magnetization tends to correlate with the effective temperature only at high MA, for He-weak and He-rich stars.     

HIDDRA: a highly independent data distribution and retrieval architecture for space observation missions

Institutions such as NASA, ESA or JAXA find solutions to distribute data from their missions to the scientific community, and their long term archives. This is a complex problem, as it includes a vast amount of data, several geographically distributed archives, heterogeneous architectures with heterogeneous networks, and users spread around the world. We propose a novel architecture that solves this problem aiming to fulfill the requirements of the final user. Our architecture is a modular system that provides a highly efficient parallel multiprotocol download engine, using a publisher/subscriber policy which helps the final user to obtain data of interest transparently. We have evaluated a first prototype, in collaboration with the ESAC centre in Villafranca del Castillo (Spain) that shows a high scalability and performance, opening a wide spectrum of opportunities.     

A jet production experiment using the high-repetition rate Astra laser

Plasma jets were produced using a high repetition rate laser by laser-ablation of coatings on the surface of conical impressions machined into solid blocks of an aluminium alloy. The ablating plasmas emerged into background gases generating shock waves. The jet-shock system was diagnosed using interferometry. The use of a high repetition rate laser allowed examination of a large number of combinations of jet materials, background gases and gas pressures.