The VLT-FLAMES Tarantula survey: XX. The nature of the X-ray bright emission-line star VFTS 399

Context: The stellar population of the 30 Doradus star-forming region in the Large Magellanic Cloud contains a subset of apparently single, rapidly rotating O-type stars. The physical processes leading to the formation of this cohort are currently uncertain. 

Aims: One member of this group, the late O-type star VFTS 399, is found to be unexpectedly X-ray bright for its bolometric luminosity-in this study we aim to determine its physical nature and the cause of this behaviour. 

Methods: To accomplish this we performed a time-resolved analysis of optical, infrared and X-ray observations. 

Results: We found VFTS 399 to be an aperiodic photometric variable with an apparent near-IR excess. Its optical spectrum demonstrates complex emission profiles in the lower Balmer series and select He i lines-taken together these suggest an OeBe classification. The highly variable X-ray luminosity is too great to be produced by a single star, while the hard, non-thermal nature suggests the presence of an accreting relativistic companion. Finally, the detection of periodic modulation of the X-ray lightcurve is most naturally explained under the assumption that the accretor is a neutron star. 

Conclusions: VFTS 399 appears to be the first high-mass X-ray binary identified within 30 Dor, sharing many observational characteristics with classical Be X-ray binaries. Comparison of the current properties of VFTS 399 to binary-evolution models suggests a progenitor mass 25 M_⊙ for the putative neutron star, which may host a magnetic field comparable in strength to those of magnetars. VFTS 399 is now the second member of the cohort of rapidly rotating "single" O-type stars in 30 Dor to show evidence of binary interaction resulting in spin-up, suggesting that this may be a viable evolutionary pathway for the formation of a subset of this stellar population.

Rotational velocities of single and binary O-type stars in the Tarantula Nebula

Rotation is a key parameter in the evolution of massive stars, affecting their evolution, chemical yields, ionizing photon budget, and final fate. We determined the projected rotational velocity, υ e sin i, of ~330 O-type objects, i.e. ~210 spectroscopic single stars and ~110 primaries in binary systems, in the Tarantula nebula or 30 Doradus (30 Dor) region. The observations were taken using VLT/FLAMES and constitute the largest homogeneous dataset of multi-epoch spectroscopy of O-type stars currently available. The most distinctive feature of the υ e sin i distributions of the presumed-single stars and primaries in 30 Dor is a low-velocity peak at around 100 km s^-1. Stellar winds are not expected to have spun-down the bulk of the stars significantly since their arrival on the main sequence and therefore the peak in the single star sample is likely to represent the outcome of the formation process. Whereas the spin distribution of presumed-single stars shows a well developed tail of stars rotating more rapidly than 300 km s^-1, the sample of primaries does not feature such a high-velocity tail. The tail of the presumed-single star distribution is attributed for the most part - and could potentially be completely due - to spun-up binary products that appear as single stars or that have merged. This would be consistent with the lack of such post-interaction products in the binary sample, that is expected to be dominated by pre-interaction systems. The peak in this distribution is broader and is shifted toward somewhat higher spin rates compared to the distribution of presumed-single stars. Systems displaying large radial velocity variations, typical for short period systems, appear mostly responsible for these differences.

The VLT-FLAMES Tarantula Survey:V. the peculiar B[e]-like supergiant, VFTS698, in 30 Doradus

Aims. We present an analysis of a peculiar supergiant B-type star (VFTS698/Melnick 2/Parker 1797) in the 30 Doradus region of the Large Magellanic Cloud which exhibits characteristics similar to the broad class of B[e] stars. Methods. We analyse optical spectra from the VLT-FLAMES survey, together with archival optical and infrared photometry and X-ray imaging to characterise the system. Results. We find radial velocity variations of around 400 km s ^-1 in the high excitation Si iv, N iii and He ii spectra, and photometric variability of ∼0.6 mag with a period of 12.7 d. In addition, we detect long-term photometric variations of ∼0.25 mag, which may be due to a longer-term variability with a period of ∼400 d. Conclusions. We conclude that VFTS698 is likely an interacting binary comprising an early B-type star secondary orbiting a veiled, more massive companion. Spectral evidence suggests a mid-to-late B-type primary, but this may originate from an optically-thick accretion disc directly surrounding the primary. © 2012 ESO.

L & D: The Challenges, New Approaches

This report aims to help L&D practitioners consider how they can best respond to changes in the external environment in order to improve the effectiveness of their learning practice, and in turn enhance organisational performance. It also has wider relevance for those wishing to explore the impact of the key drivers of change. It is hoped that the report sparks insight and action, to encourage more organisations to align their L&D practice to future requirements.

Exploring Intrinsic Gender Identity Using Second Life

Virtual Worlds (VWs) provide an environment to understand and explore notions of gender and identity, particularly given the ability for users to experiment with gender in online worlds. Our study analyses gender identity using the virtual space of Second Life (SL) to explore experiences and responses to gender in an avatar. We introduced 46 novice users to the VW of SL in order to see if real life gender influenced their choices of avatar. Participants selected the gender of their original avatar and once they were used to SL, they were then asked to change the gender of that avatar. We used mixed methods research consisting of paper based questionnaires (n=34) and focus groups (n=46) conducted in SL. Nearly all participants chose an initial avatar that reflected their real-life gender with females (n=22) reporting higher levels of identification with this initial avatar. Females were significantly more concerned with the gender-specific appearance of their initial avatar. On swapping gender, females reported higher levels of discomfort and many changed back before 7 minutes. Males (n=24) did not report significant discomfort with their changed-gender avatar and did not revert back to their original avatar as quickly. Our findings suggest that female participants in this study tended to reinforce gender binaries through such things as clothing, hairstyles and behaviors of their avatars. Male participants were less likely to experience discomfort through changing the gender of their avatar (with the males noting they still perceived an avatar with a female appearance as male).

Strategies for protecting intellectual property when using CUDA applications on graphics processing units

Recent advances in the massively parallel computational abilities of graphical processing units (GPUs) have increased their use for general purpose computation, as companies look to take advantage of big data processing techniques. This has given rise to the potential for malicious software targeting GPUs, which is of interest to forensic investigators examining the operation of software. The ability to carry out reverse-engineering of software is of great importance within the security and forensics elds, particularly when investigating malicious software or carrying out forensic analysis following a successful security breach. Due to the complexity of the Nvidia CUDA (Compute Uni ed Device Architecture) framework, it is not clear how best to approach the reverse engineering of a piece of CUDA software. We carry out a review of the di erent binary output formats which may be encountered from the CUDA compiler, and their implications on reverse engineering. We then demonstrate the process of carrying out disassembly of an example CUDA application, to establish the various techniques available to forensic investigators carrying out black-box disassembly and reverse engineering of CUDA binaries. We show that the Nvidia compiler, using default settings, leaks useful information. Finally, we demonstrate techniques to better protect intellectual property in CUDA algorithm implementations from reverse engineering.

Nine for ones in nine: a schizophrenic cyborg love story.

By appropriating the images of the schizophrenic and the cyborg from Deleuze and Guattari, and from Donna Haraway respectively, this paper seeks to discuss the relationship between human and computer, composer and performer in a way that undermines and subverts the normal binaries commonly employed, and even implied in the descriptions of these relationships in this paper. “Nine for ones in nine”, despite employing the use of the OpenMusic software in its composition, retains a degree of choice and indeterminacy for the performers; despite employing the use of precise just harmony in its design and intent, the work depends upon the imprecision of human control rather than ceding to the precision of a synthesiser. Given the vast possibilities opened up to composers by the use of computers to calculate and create sound, why then do composers continue to employ performers in the realisation of their designs, and rely on sometimes hundreds of years-old technology to articulate them in real time? The very social and imprecise aspect of the act of performance is key to the messy, compromised, and complicit product that scores such as Nine for ones in nine aim to produce.

Methodology is content: Indigenous Australian approaches to research through practice

An Indigenous Australian approach to research through practice is premised on building relationality. Indigenous Australian methodological approaches operate in their own right, and at the same time they accept existing binaries and ambiguities, as they are not linear in their worldview and epistemology. The methodological approaches to research are the content of the research and vice versa. These are inseparable in an Indigenous world-view. Motivation for this work: It can reconfigure the above. The methodological approach is through:Practice- Indigenist materialismEthics/pre-ethics and building relationality with peoples and communities

Effects of spin on high-energy radiation from accreting black holes

Observations of jets in X-ray binaries show a correlation between radio power and black hole spin. This correlation, if confirmed, points toward the idea that relativistic jets may be powered by the rotational energy of black holes. In order to examine this further, we perform general relativistic radiative transport calculations on magnetically arrested accretion flows, which are known to produce powerful jets via the Blandfordâ Znajek (BZ) mechanism. We find that the X-ray and γ-ray emission strongly depend on spin and inclination angle. Surprisingly, the high-energy power does not show the same dependence on spin as the BZ jet power, but instead can be understood as a redshift effect. In particular, photons observed perpendicular to the spin axis suffer little net redshift until originating from close to the horizon. Such observers see deeper into the hot, dense, highly magnetized inner disk region. This effect is largest for rapidly rotating black holes due to a combination of frame dragging and decreasing horizon radius. While the X-ray emission is dominated by the near horizon region, the near-infrared (NIR) radiation originates at larger radii. Therefore, the ratio of X-ray to NIR power is an observational signature of black hole spin.

Íntimamente distantes: diferencia social en las intimidades del servicio doméstico

En este trabajo de investigación cualitativa exploro las formas en que la desigualdad social se proyecta en las intimidades del servicio doméstico. Me intereso por analizar las experiencias y trayectorias de vida de tres mujeres que trabajan como empleadas domésticas en Bogotá, en torno a las tensiones que implican las diferencias sociales entre patronos y empleadas. Por un lado, propongo considerar las experiencias de los procesos de violencias en las trayectorias de estas mujeres como aspectos que marcan de forma contundente la distancia social entre ellas y sus empleadores. Por otra parte, abordo discusiones analíticas en torno a las definiciones de intimidad para comprender las contradicciones, ambigüedades y ejercicios de poder que configuran diferentes situaciones de intimidad en estas relaciones de servicio doméstico. El argumento central de este texto sostiene que en el servicio doméstico se dan múltiples configuraciones de intimidad que están entretejidas por las diferentes formas en que se marcan las diferencias sociales entre las empleadas y los empleadores. Las relaciones de servicio doméstico difieren entre sí en función de las formas de acceder y transferir informaciones privadas entre las empleadas y los patrones, así como según los modos en que se establecen vínculos de confianza y afecto entre ellos. De igual manera, expongo cómo operan las intimidades ilícitas “compartidas” e “individuales” en el marco de la “intimidad pública” de los hogares para los que trabajan las empleadas domésticas.