MACHO Photometry of Two LMC Be X-ray Transients, EXO 0531-66 and H 0544-665

Long-term variations are well-known in Be X-ray binaries, and are attributed to non-orbital changes in the structure of the Be circumstellar (equatorial) disc. However, the timescales involved are so long (tens of days, to years) that systematic studies have been very restricted. The ~8 year MACHO monitoring of the Large Magellanic Cloud (LMC) therefore presents an ideal opportunity to undertake such studies of Be X-ray systems that lie within the monitored fields. Here we present MACHO observations of two LMC Be X-ray transients, EXO 0531-66 and H 0544-665, the light curves of which show substantial (~0.5 mag) long-term variations. However, our analysis shows little evidence for any periodic phenomena in the light curves of either source. We find an upper limit for detection of a short (1-100 d) periodicity in the V- and R-band light curves of EXO 0531-66 of 0.041 mag and 0.047 mag semi-amplitude, respectively. The upper limits for the V- and R-band data of H 0544-665 are 0.054 mag and 0.075 mag semi-amplitude, respectively. Both EXO 0531-66 and H 0544-665 become redder as they brighten, possibly due to variations in the structure of the equatorial disc around the Be star. Spectra of both sources show H$\alpha$ emission; for EXO 0531-66 we find the emission varies over time, thereby confirming its optical identification.Comment: 8 pages, 7 figures, accepted for publication in MNRA

Bridging the gap between academia and industry:a social media case study

The social media operating environment is every changing, as such it is difficult for students to develop up to date theoretical knowledge and practitioner skills. Through a Management Knowledge Transfer Project (mKTP) with a new social media start-up company, a team of academics were able to create a real-time case study, offering business and marketing students tailored workshops and weekly interactions with industry, contributing to the development of the social media service. The academics followed the Theory – Application- Implication (TAI) framework

Refusing to Endorse. A must Explanation for Pejoratives.

In her analysis of pejoratives, Eva Picardi rejects a too sharp separation between descriptive and expressive content. I reconstruct some of her arguments, endorsing Eva’s criticism of Williamson’s analysis of Dummett and developing a suggestion by Manuel Garcia Carpintero on a speech act analysis of pejoratives. Eva’s main concern is accounting for our instinctive refusal to endorse an assertion containing pejoratives because it suggests a picture of reality we do not share. Her stance might be further developed claiming that uses of pejoratives not only suggest, but also promote a wrong picture of reality. Our refusal to endorse implies rejecting not only a wrong picture of reality but also a call for participation to what that picture promotes

Galliformes science and species extinctions: what we know and what we need to know

Extinciones de especies de Galliformes y conocimientos científicos: lo que sabemos y lo que necesitamos saber A principios de 2010, las 193 partes que habían firmado el Convenio sobre la Diversidad Biológica reconocieron que no habían cumplido el objetivo que ellas mismas habían fijado en 1992 de reducir de forma significativa las extinciones de especies en 2010. Al final del año establecieron un objetivo nuevo y más ambicioso que consistía en evitar las extinciones de especies en 2020. Lograr dicho objetivo requerirá una utilización mucho más eficiente de los recursos y la investigación tiene un papel fundamental en hacer que esto ocurra. Existen 290 especies de Galliformes, de las cuales el 26% se considera en peligro de extinción, en comparación con el 12% del total de las 10.000 especies de aves. Al mismo tiempo, hay numerosos estudios publicados sobre el grupo que abarcan décadas para algunas especies. Por consiguiente, es oportuno analizar si es posible aumentar la eficiencia y las repercusiones a escala mundial de la investigación sobre aves de caza, de forma que, con la planificación meticulosa que conlleva más orientación estratégica e intercambio de experiencias, los biólogos especializados en este tipo de aves puedan desempeñar una función destacada en la consecución del objetivo de 2020 para las especies aprobado por el Convenio sobre la Diversidad Biológica. Los ámbitos específicos que necesitan este planteamiento de intercambio de experiencias son la estimación de la población y la evaluación de las amenazas, el análisis de la explotación y la determinación de la base ecológica de las intervenciones que hayan obtenido buenos resultados

Limits on I-band microvariability of the Galactic Bulge Miras

We search for microvariability in a sample of 485 Mira variables with high quality I-band light curves from the second generation Optical Gravitational Lensing Experiment (OGLE-II). Rapid variations with amplitudes in the ~0.2-1.1 mag range lasting hours to days were discovered in Hipparcos data by de Laverny et al. (1998). Our search is primarily sensitive to events with time-scales of about 1 day, but retains a few percent efficiency (per object) for detecting unresolved microvariability events as short as 2 hours. We do not detect any candidate events. Assuming that the distribution of the event time profiles is identical to that from the Hipparcos light curves we derive the 95% confidence level upper limit of 0.038 per year per star for the rate of such events (1 per 26 years per average object of the ensemble). The high event rates of the order of 1 per year per star implied by the Hipparcos study in the H_P band are excluded with high confidence by the OGLE-II data in the I band. Our non-detection could still be explained by much redder spectral response of the I filter compared to the H_P band or by population differences between the bulge and the solar neighborhood. In any case, the OGLE-II I-band data provide the first limit on the rate of the postulated microvariability events in Mira stars and offer new quantitative constraints on their properties. Similar limits are obtained for other pulse shapes and a range of the assumed time-scales and size-frequency distributions.Comment: Accepted for publication in Ap

Optical Follow-up of New SMC Wing Be/X-ray Binaries

We investigate the optical counterparts of recently discovered Be/X-ray binaries in the Small Magellanic Cloud. In total four sources, SXP101, SXP700, SXP348 and SXP65.8 were detected during the Chandra Survey of the Wing of the SMC. SXP700 and SXP65.8 were previously unknown. Many optical ground based telescopes have been utilised in the optical follow-up, providing coverage in both the red and blue bands. This has led to the classification of all of the counterparts as Be stars and confirms that three lie within the Galactic spectral distribution of known Be/X-ray binaries. SXP101 lies outside this distribution becoming the latest spectral type known. Monitoring of the Halpha emission line suggests that all the sources bar SXP700 have highly variable circumstellar disks, possibly a result of their comparatively short orbital periods. Phase resolved X-ray spectroscopy has also been performed on SXP65.8, revealing that the emission is indeed harder during the passage of the X-ray beam through the line of sight.Comment: 9 pages, 9 figures, 2 tables, accepted for publication in MNRA

The early and late-time spectral and temporal evolution of GRB 050716

We report on a comprehensive set of observations of Gamma Ray Burst 050716, detected by the Swift satellite and subsequently followed-up rapidly in X-ray, optical and near infra-red wavebands. The prompt emission is typical of long-duration bursts, with two peaks in a time interval of T90 = 68 seconds (15 - 350 keV). The prompt emission continues at lower flux levels in the X-ray band, where several smaller flares can be seen, on top of a decaying light curve that exhibits an apparent break around 220 seconds post trigger. This temporal break is roughly coincident with a spectral break. The latter can be related to the extrapolated evolution of the break energy in the prompt gamma-ray emission, and is possibly the manifestation of the peak flux break frequency of the internal shock passing through the observing band. A possible 3 sigma change in the X-ray absorption column is also seen during this time. The late-time afterglow behaviour is relatively standard, with an electron distribution power-law index of p = 2 there is no noticable temporal break out to at least 10 days. The broad-band optical/nIR to X-ray spectrum indicates a redshift of z ~> 2 for this burst, with a host-galaxy extinction value of E(B-V) ~ 0.7 that prefers an SMC-like extinction curve.Comment: Accepted to MNRAS. 8 pages, 5 figure

Probing the Pulsar Wind Nebula of PSR B0355+54

We present XMM-Newton and Chandra X-ray observations of the middle-aged radio pulsar PSR B0355+54. Our X-ray observations reveal emission not only from the pulsar itself, but also from a compact diffuse component extending ~50'' in the opposite direction to the pulsar's proper motion. There is also evidence for the presence of fainter diffuse emission extending ~5' from the point source. The compact diffuse feature is well-fitted with a power-law, the index of which is consistent with the values found for other pulsar wind nebulae. The morphology of the diffuse component is similar to the ram-pressure confined pulsar wind nebulae detected for other sources. The X-ray emission from the pulsar itself is described well by a thermal plus power-law fit, with the thermal emission most likely originating in a hot polar cap.Comment: 9 pages (uses emulateapj.cls), 8 figures, 2 tables, accepted for publication in Ap