Infrared astronomy

Spacecraft and astronomical observations of infrare

Modelling Epsilon Aurigae without solid particles

Three components can be expected to contribute to the emission of epsilon Aurigae. There is a primary F star. There is an opaque disk which occults it, and there is a gas stream which is observed to produce absorption lines. Evidence that the disk is not responsible for the gas stream lines comes both from the radial velocities, which are too small, and from the IR energy distribution out of eclipse, which shows free-free emission that would produce inadequate optical depth in electron scattering. The color temperature of the IR excess can give misleading indications of low temperature material. Free-free emission at 10,000 K between 10 and 20 microns has a color temperature of 350 K. Attempts to mold the system are discussed

Classical and fluctuation-induced electromagnetic interactions in micronscale systems: designer bonding, antibonding, and Casimir forces

Whether intentionally introduced to exert control over particles and macroscopic objects, such as for trapping or cooling, or whether arising from the quantum and thermal fluctuations of charges in otherwise neutral bodies, leading to unwanted stiction between nearby mechanical parts, electromagnetic interactions play a fundamental role in many naturally occurring processes and technologies. In this review, we survey recent progress in the understanding and experimental observation of optomechanical and quantum-fluctuation forces. Although both of these effects arise from exchange of electromagnetic momentum, their dramatically different origins, involving either real or virtual photons, lead to different physical manifestations and design principles. Specifically, we describe recent predictions and measurements of attractive and repulsive optomechanical forces, based on the bonding and antibonding interactions of evanescent waves, as well as predictions of modified and even repulsive Casimir forces between nanostructured bodies. Finally, we discuss the potential impact and interplay of these forces in emerging experimental regimes of micromechanical devices.Comment: Review to appear on the topical issue "Quantum and Hybrid Mechanical Systems" in Annalen der Physi

The Hot R Coronae Borealis Star DY Centauri is a Binary

The remarkable hot R Coronae Borealis (RCB) star DY Cen is revealed to be the first and only binary system to be found among the RCB stars and their likely relatives, including the extreme helium stars and the hydrogen-deficient carbon stars. Radial velocity determinations from 1982 to 2010 have shown that DY Cen is a single-lined spectroscopic binary in an eccentric orbit with a period of 39.67 days. It is also one of the hottest and most H-rich member of the class of RCB stars. The system may have evolved from a common envelope to its current form.Spanish Ministry of Economy and Competitiveness AYA-2011-27754McDonald Observator

Kinematics of subluminous O and B stars by surface helium abundance

The majority of hot subdwarf stars are low-mass core-helium-burning stars. Their atmospheres are generally helium deficient; however, a minority have extremely helium-rich surfaces. An additional fraction have an intermediate surface-helium abundance, occasionally accompanied by peculiar abundances of other elements. We have identified a sample of 88 hot subdwarfs including 38 helium-deficient, 27 intermediate-helium and 23 extreme-helium stars for which radial-velocity and proper-motion measurements, together with distances, allow a calculation of galactic space velocities. We have investigated the kinematics of these three groups to determine whether they belong to similar or different Galactic populations. The majority of helium-deficient subdwarfs in our sample show a kinematic distribution similar to that of thick disc stars. Helium-rich sdBs show a more diverse kinematic distribution. Although the majority are probably disc stars, a minority show a much higher velocity dispersion consistent with membership of a Galactic halo population. Several of the halo subdwarfs are members of the class of ‘heavy-metal’ subdwarfs discovered by Naslim et al

The ethnicity attainment gap among medical and biomedical science students: a qualitative study.

Background Black, Asian and Minority Ethnic (BAME) medical students and professionals frequently underachieve when compared with their White counterparts not only in the United Kingdom, but across the globe. There is no consensus for the definitive causes of this attainment gap, but suggestions contributing towards it include: increased feelings of isolation as a member of a minority culture or religion; a poorer higher education (HE) experience compared with White counterparts; and stereotype threat, whereby students underperform in exams from the stresses of fearing confirming to a negative-stereotype. Methods The aim of this study was to gather qualitative data on HE experiences of medical and biomedical science students to explore factors contributing to the attainment gap. Audio-recorded, semi-structured interviews and a novel approach for this research area of ethnically-homogenous student-led focus groups, were held with students and staff at a healthcare-based university in London, where lower attainment, slower rates of degree completion and lower levels of satisfaction with HE experience were identified in BAME students compared with White students. Thematic analysis was used to manage, summarize and analyse the data. Results Forty-one students and eight staff members were interviewed or took part in focus groups. The student data were best explained by two main themes: social factors and stereotyping, whilst staff data were also best explained by two main themes: social factors and student and staff behaviour. Social factors suggested ethnically-defined social networks and the informal transfer of knowledge impacted academic performance, isolating minority groups from useful academic information. BAME students may also be at a further disadvantage, being unable to attend social and academic functions for cultural or family reasons. Black students also mentioned changing their behaviour to combat negative stereotypes in a variety of contexts. Conclusions This study suggests that forms of discrimination, whether conscious or unconscious, may be negatively impacting the abilities of BAME students both in examinations and in coursework choice. It highlights the importance of social networks for the transfer of academic knowledge and the impact ethnicity may have on their formation, with issues around segregation and the sharing of information outside defined groups