FUSE/Lyman grant

A variety of options for a short wavelength spectrometer for the Lyman telescope has been studied, and the optimum configuration for this instrument identified. In this spectrometer option study it is assumed (consistent with performance goals outlined by the project) that the instrument, whose prime spectral domain is 900-12000A, will incorporate a grazing incidence telescope which will maintain good collecting efficiency down to 100A. In particular it is assumed that the telescope will have an effective focal length of 10 meters, an image quality of 1.5", and will provide a diverging f/10 beam. Designs compatible with this telescope are analyzed, and it is determined that a two-element grazing incidence spectrometer using as its first optic an ellipsoid to re-focus the beam and a varied line-space plane diffraction grating to disperse the light is the best overall design. This spectrometer could be fed by a small pick-off mirror located just behind the prime focus of the telescope and would clear the light path when not in use. A test of the diffraction efficiency of a low blaze angle grating is undertaken, which is the only technical uncertainty in the spectrometer design

Complete fabrication of rocket payload hardware Final report

Aerobee payload and other instrumentation for studies in galactic X ray astronom

Completion of design and fabrication of a rocket payload for search of the Southern Hemisphere sky for galactic X-ray sources Final report

Design and fabrication of rocket payload for search for galactic X ray source

Limits on intergalactic helium from the 3C 273 X-ray spectrum

An X-ray spectrum of the quasi-stellar object 3C 273 in the interval 0.25 to 10 KeV was obtained by sounding rocket observations. The best-fit power law spectrum has photon index n= 1.3 with no photoelectric absorption. An upper limit on the X-ray optical depth to 3C 273 was calculated from the data, permitting upper limits to be set on the absolute abundance of helium in the intergalactic medium

Shopping for food: lessons from a London borough

Purpose – This paper aims to measure access to food in an inner London borough. Design/methodology/approach – There were six phases, which included designing food baskets, consultation with local residents and a shop survey. Recognising the cultural make-up of the borough food baskets and menus were developed for four key communities, namely: White British, Black Caribbean, Turkish, and Black African. Three areas were identified for the study and shopping hubs identified with a 500-metre radius from a central parade of shops. Findings – The findings paint an intricate web of interactions ranging from availability in shops to accessibility and affordability being key issues for some groups. It was found that in the areas studied there was availability of some key healthy items, namely fresh fruit and vegetables, but other items such as: fresh meat and poultry, fish, lower fat dairy foods, high fibre pasta and brown rice were not available. Access was found to be defined, by local people, as more extensive than just physical distance to/from shops – for many shopping was made more difficult by having to use taxis and inconvenient buses. Small shops were important in delivering healthy food options to communities in areas of deprivation and were judged to offer a better range and more appropriate food than the branches of the major supermarket chains. Research limitations/implications – The importance of monitoring the impact of shops and shop closures on healthy food availability is emphasised. From a policy perspective the findings suggest that approaches based on individual agency need to be balanced with upstream public health nutrition approaches in order to influence the options available. Originality/value – The paper is arguably the first to examine and dissect the issue of food availability and accessibility in the inner London borough in question, especially in the light of its proposed redevelopment for the London Olympics in 2012

A pulsing X-ray source in Circinus

Spectrum of pulsing X ray source observed in Circinu

The SERENDIP 2 SETI project: Current status

Over the past 30 years, interest in extraterrestrial intelligence has progressed from philosophical discussion to rigorous scientific endeavors attempting to make contact. Since it is impossible to assess the probability of success and the amount of telescope time needed for detection, Search for Extraterrestrial Intelligence (SETI) Projects are plagued with the problem of attaining the large amounts of time needed on the world's precious few large radio telescopes. To circumvent this problem, the Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations (SERENDIP) instrument operates autonomously in a piggyback mode utilizing whatever observing plan is chosen by the primary observer. In this way, large quantities of high-quality data can be collected in a cost-effective and unobtrusive manner. During normal operations, SERENDIP logs statistically significant events for further offline analysis. Due to the large number of terrestrial and near-space transmitters on earth, a major element of the SERENDIP project involves identifying and rejecting spurious signals from these sources. Another major element of the SERENDIP Project (as well as most other SETI efforts) is detecting extraterrestrial intelligence (ETI) signals. Events selected as candidate ETI signals are studied further in a targeted search program which utilizes between 24 to 48 hours of dedicated telescope time each year

OGO-6 gas-surface energy transfer experiment

The kinetic energy flux of the upper atmosphere was analyzed using OGO-6 data. Energy transfer between 10 microwatts/sq cm and 0.1 W/sq cm was measured by short-term frequency changes of temperature-sensitive quartz crystals used in the energy transfer probe. The condition of the surfaces was continuously monitored by a quartz crystal microbalance to determine the effect surface contamination had on energy accommodation. Results are given on the computer analysis and laboratory tests performed to optimize the operation of the energy transfer probe. Data are also given on the bombardment of OGO-6 surfaces by high energy particles. The thermoelectrically-cooled quartz crystal microbalance is described in terms of its development and applications

Radiation mechanisms and geometry of Cygnus X-1 in the soft state

We present X-ray/gamma-ray spectra of Cyg X-1 observed during the transition from the hard to the soft state and in the soft state by ASCA, RXTE and OSSE in 1996 May and June. The spectra consist of a dominant soft component below ~2 keV and a power-law-like continuum extending to at least ~800 keV. We interpret them as emission from an optically-thick, cold accretion disc and from an optically-thin, non-thermal corona above the disc. A fraction f ~ 0.6 of total available power is dissipated in the corona. We model the soft component by multi-colour blackbody disc emission taking into account the torque-free inner-boundary condition. If the disc extends down to the minimum stable orbit, the ASCA/RXTE data yield the most probable black hole mass of about 10 solar masses and an accretion rate about 0.5 L_E/c^2, locating Cyg X-1 in the soft state in the upper part of the stable, gas-pressure dominated, accretion-disc solution branch. The spectrum of the corona is well modelled by repeated Compton scattering of seed photons from the disc off electrons with a hybrid, thermal/non-thermal distribution. The electron distribution can be characterized by a Maxwellian with an equilibrium temperature of kT ~ 30--50 keV and a Thomson optical depth of ~0.3 and a quasi-power-law tail. The compactness of the corona is between 2 and 7, and a presence of a significant population of electron-positron pairs is ruled out. We find strong signatures of Compton reflection from a cold and ionized medium, presumably an accretion disc, with an apparent reflector solid angle ~0.5--0.7. The reflected continuum is accompanied by a broad iron K-alpha line.Comment: 18 pages, 12 figures, 2 landscape tables in a separate file. Accepted to MNRA

The extreme ultraviolet excess emission in five clusters of galaxies revisited

Evidence for excess extreme ultraviolet (EUV) emission over a tail of X-ray gas bremsstrahlung emission has been building up recently, but in some cases remains controversial, mostly due to the moderate quality of the EUV data. In order to improve the signal to noise ratio in the EUV, we have performed the wavelet analysis and image reconstructions for five clusters of galaxies observed both at EUV and X-ray energies with the EUVE and ROSAT satellites respectively. The profiles of the EUV and X-ray reconstructed images all differ at a very large confidence level and an EUV excess over a thermal bremsstrahlung tail is detected in all five clusters (Abell 1795, Abell 2199, Abell 4059, Coma and Virgo) up to large radii. These results, coupled with recent XMM-Newton observations, suggest that the EUV excess is probably non thermal in origin.Comment: accepted for publication in Astronomy & Astrophysics, final versio