9C: a survey of radio sources at 15 GHz with the Ryle Telescope

The fields chosen for the first observations of the cosmic microwave background with the Very Small Array have been surveyed with the Ryle Telescope at 15 GHz. We have covered three regions around RA  00^h 20^m Dec. +30°  , RA  09^h 40^m Dec. +32°  and RA  15^h 40^m Dec. +43° (J2000.0)  , an area of  520 deg²  . There are 465 sources above the current completeness limit of  ≈25 mJy  , although a total of  ≈760  sources have been detected, some as faint as 10 mJy. This paper describes our techniques for observation and data analysis; it also includes source counts and some discussion of spectra and variability. Preliminary source lists are presented.     

Upper Cretaceous pelagic red beds,implications for paleoclimate and pale oc eanography

Members of IGCP 463, Upper Cretaceous Oceanic Red Beds: Response to Ocean/Climate Global Change (CORBs) held their second workshop near the Black Sea in Bartin, Turkey. In addition to discussion of results and plans, the participants examined exposures of pelagic red beds in northern Turkev.     

The RHESSI Spacecraft Instrument Data Processing Unit

The Ramaty High-Energy Spectroscopic Imager (RHESSI) spacecraft is a NASA Small Explorer (SMEX) class mission. RHESSI is designed to image solar X-rays and gamma rays with high-energy resolution. The Instrument Data Processing Unit (IDPU) serves as the central RHESSI instrument on-board data-processing element. It controls and monitors the instrument operations, and provides a flexible telemetry collection and formatting system. The system responds autonomously to optimize science data collection over a wide dynamic range of conditions, handling up to 40 Mbps of telemetry during solar flares. This paper presents an overview of the IDPU hardware and software design.     

Sketch-based Identification of Bench and Terrace Slope Breaks in the Laramie Basin, Wyoming

This study presents a semi‐automated approach to support the identification of fluvial landform slope breaks in the Laramie Basin, southeastern Wyoming. The landforms in question form the edges of terraces and benches and tend to be subtle and varied depending on where they appear in the landscape. Because of this variation combined with DEM error, conventional raster filtering methods were unable to readily identify the benches with any consistency. In an effort to automate the collection of benches, a two stage, sketch‐based algorithm was designed to detect bench edges on a semi‐automated basis and was integrated into a commercial GIS environment for testing and execution. The approach of tailoring an algorithm to detect a particular feature proved viable and, in fact, more consistent in many cases than heads‐up digitizing. However, feature complexity appears to be a significant driver in the accuracy of the algorithmic approach with the unlikely finding that more complex features are more accurately identified than less complex features. This research demonstrates that user cognition, DEM resolution, algorithm functionality and landform characteristics are thus all important and interrelated factors requiring consideration when implementing approaches to topographic feature identification.     

Measurement of the Sunyaev–Zel'dovich increment in massive galaxy clusters

We have detected the Sunyaev–Zel'dovich (SZ) increment at 850 μm in two galaxy clusters (Cl 0016+16 and MS 1054.4−0321) using the Submillimetre Common User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope. Fits to the isothermal β model yield a central Compton y parameter of  (2.2 ± 0.7) × 10⁻⁴  and a central 850-μm flux of  Δ I ₀= 2.2 ± 0.7 mJy beam⁻¹  in Cl 0016. This can be combined with decrement measurements to infer   y = (2.38 ±^0.36_0.34) × 10⁻⁴  and   v _pec= 400±¹⁹⁰⁰₁₄₀₀ km s⁻¹  . In MS 1054 we find a peak 850-μm flux of  Δ I ₀= 2.0 ± 1.0 mJy beam⁻¹  and   y = (2.0 ± 1.0) × 10⁻⁴  . To be successful such measurements require large chop throws and non-standard data analysis techniques. In particular, the 450-μm data are used to remove atmospheric variations in the 850-μm data. An explicit annular model is fit to the SCUBA difference data in order to extract the radial profile, and separately fit to the model differences to minimize the effect of correlations induced by our scanning strategy. We have demonstrated that with sufficient care, SCUBA can be used to measure the SZ increment in massive, compact galaxy clusters.     

X-ray emissions from two-temperature accretion flows within a dipole magnetic funnel

We investigate the hydrodynamics of accretion channelled by a dipolar magnetic field (funnel flows). We consider situations in which the electrons and ions in the flow cannot maintain thermal equilibrium [two-temperature (2T) effects] due to strong radiative loss, and determine the effects on the keV X-ray properties of the systems. We apply this model to investigate the accretion shocks of white dwarfs in magnetic cataclysmic variables (mCVs). We have found that the incorporation of 2T effects could harden the keV X-rays. Also, the dipolar model yields harder X-ray spectra than the standard planar model if white dwarf is sufficiently massive  (≳1 M_⊙)  . When fitting observed keV X-ray spectra of mCVs, the inclusion of 2T hydrodynamics and a dipolar accretion geometry lowers estimates for white dwarf masses when compared with masses inferred from models excluding these effects. We find mass reductions ≲9 per cent in the most massive cases.