Binary Stars as the Source of the Far-UV Excess in Elliptical Galaxies

The discovery of an excess of light in the far-ultraviolet (UV) spectrum in elliptical galaxies was a major surprise in 1969. While it is now clear that this UV excess is caused by an old population of hot helium-burning stars without large hydrogen-rich envelopes rather than young stars, their origin has remained a mystery. Here we show that these stars most likely lost their envelopes because of binary interactions, similar to the hot subdwarf population in our own Galaxy. This has major implications for understanding the evolution of the UV excess and of elliptical galaxies in general. In particular, it implies that the UV excess is not a sign of age, as had been postulated previously, and predicts that it should not be strongly dependent on the metallicity of the population.Comment: Proceedings of Puerto Vallarta 07, "New Quests in Stellar Astrophysics. II. The Ultraviolet Properties of Evolved Stellar Populations", 6 pages, 2 figures. A much better version of Figure 1 can be obtained on reques

The role of non-gray model atmospheres in the evolution of low mass metal poor stars

Gray model atmospheres are generally considered a reasonable approximation to make upon stars of mass greater than about 0.6 M-circle dot. Here we show that non-gray atmospheres can significantly affect evolutionary models, with masses up to 0.9 M-circle dot. The effect of including a non-gray atmosphere is strongest in the pre-main and post-main Sequence. This may have implications for the ages of the oldest globular clusters

Textiles, connection and meaning

Why do some items of clothing remain safely housed in our wardrobes whilst others are quickly relegated to opportunity shops? This paper will investigate the practical, emotional and nostalgic connections people make with their possessions. This understanding will be used to suggest ways in which we can better design and promote textiles for the fashion market. Textiles for the body can be functional, fashionable, symbolic or a combination of the three. The method of ‘slow design’ will be used, as a vehicle to explore ways that ensure textiles meet the practical and emotional needs of consumers for the long term. Slow design follows a holistic approach where each stage of the design process is carefully considered. Bespoke, well-crafted design can be appreciated on a variety of levels increasing the bond between object and owner. A garment with cultural significance purchased whilst on holiday has an emotional advantage over a cheap poorly made garment purchased on a whim during lunch hour. The holiday purchase becomes a nostalgic reminder of travels, experiences and people. The cheap disposable garment has an immediate purpose, to protect, or to project an awareness and acceptance of fashion. Fast fashion is consumed in a similar way to fast food. Its job is to satisfy immediate needs, not to nourish long term. Opportunity shops are currently overwhelmed with cheap disposable fashion due to a continual wave of desire and disappointment. If designers can connect with people on multiple levels the desire for quantity over quality may be reversed and relieve the drain on resources

Exploring the human factors challenges of automated mining equipment

Over the past few years there has been an upsurge of interest in automated mining equipment, ranging from in-vehicle assistance systems (such as collision detection) through to visions of a fully automated and ‘people-less’ mine of the future. This project is aimed at understanding how new technologies can be developed in ways that take into account the human factors issues related to remote controlled/ automated mining equipment. In particular, this ongoing research is analysing the skills and cognitive capabilities that will be required to operate or maintain remote controlled equipment, where the focus is upon developing optimal interface designs to address performance gaps, rather than purely relying on operator training. Initially, the work includes conducting literature reviews, compiling an “active” database of existing and emerging technologies, and interviewing technology developers, regulators, managers and end-users. The interviews are ongoing at the time of writing and are still to be completed and fully analysed. Tentative analysis of the results of this work show several themes emerging. The work to date will be presented in the poster

Variability in the extreme helium star LSS 5121

We report a photometric and spectroscopic study of the hot extreme helium star LSS 5121. We found photometric variability, but no period was evident in its periodogram. This is consistent with the previous proposal, based on spectral line variations, that LSS 5121 is a non-radial pulsator similar to other hot extreme helium stars.Comment: 5 pages, 6 figure

Orbital Characteristics of the Subdwarf-B and F V Star Binary EC~20117-4014(=V4640 Sgr)

Among the competing evolution theories for subdwarf-B (sdB) stars is the binary evolution scenario. EC~20117-4014 (=V4640~Sgr) is a spectroscopic binary system consisting of a pulsating sdB star and a late F main-sequence companion (O'Donoghue et al. 1997), however the period and the orbit semi-major axes have not been precisely determined. This paper presents orbital characteristics of the EC 20117-4014 binary system using 20 years of photometric data. Periodic Observed minus Calculated (O-C) variations were detected in the two highest amplitude pulsations identified in the EC 20117-4014 power spectrum, indicating the binary system's precise orbital period (P = 792.3 days) and the light-travel time amplitude (A = 468.9 s). This binary shows no significant orbital eccentricity and the upper limit of the eccentricity is 0.025 (using 3 $\sigma$ as an upper limit). This upper limit of the eccentricity is the lowest among all wide sdB binaries with known orbital parameters. This analysis indicated that the sdB is likely to have lost its hydrogen envelope through stable Roche lobe overflow, thus supporting hypotheses for the origin of sdB stars. In addition to those results, the underlying pulsation period change obtained from the photometric data was $\dot{P}$ = 5.4 ($\pm$0.7) $\times$ $10^{-14}$ d d$^{-1}$, which shows that the sdB is just before the end of the core helium-burning phase