Detection of the radial velocity curve of the B5-A0 supergiant companion star of Cir X-1?

In this Paper we report on phase resolved I-band optical spectroscopic and photometric observations of CirX-1 obtained with the Very Large Telescope. The spectra are dominated by Paschen absorption lines at nearly all orbital phases except near phase zero (coinciding with the X-ray dip) when the absorption lines are filled-in by broad Paschen emission lines. The radial velocity curve of the absorption lines corresponds to an eccentric orbit (e=0.45) whose period and time of periastron passage are consistent with the period and phase predicted by the most recent X-ray dip ephemeris. We found that the I-band magnitude decreases from 17.6 to ~16.8 near phase 0.9-1.0, this brightening coincides in phase with the X-ray dip. Even though it is likely that the absorption line spectrum is associated with the companion star of CirX-1, we cannot exclude the possibility that the spectrum originates in the accretion disc. However, if the spectrum belongs to the companion star, it must be a supergiant of spectral type B5-A0. If we assume that the compact object does not move through the companion star at periastron, the companion star mass is constrained to ~<10 Msun for a 1.4 Msun neutron star, whereas the inclination has to be ~> 13.7 degrees. Alternatively, the measured absorption lines and their radial velocity curve can be associated with the accretion disc surrounding a 1.4 Msun neutron star and its motion around the centre of mass. An absorption line spectrum from an accretion disc is typically found when our line-of-sight passes through the accretion disc rim implying a high inclination. However, from radio observations it was found that the angle between the line-of-sight and the jet axis is smaller than 5 degrees implying that the jet ploughs through the accretion disc in this scenario.Comment: 8 pages, 4 figures, 3 tables, accepted by MNRA

Further Constraints on Thermal Quiescent X-ray Emission from SAX J1808.4-3658

We observed SAX J1808.4-3658 (1808), the first accreting millisecond pulsar, in deep quiescence with XMM-Newton and (near-simultaneously) Gemini-South. The X-ray spectrum of 1808 is similar to that observed in quiescence in 2001 and 2006, describable by an absorbed power-law with photon index 1.74+-0.11 and unabsorbed X-ray luminosity L_X=7.9+-0.7*10^{31} ergs/s, for N_H=1.3*10^{21} cm^{-2}. Fitting all the quiescent XMM-Newton X-ray spectra with a power-law, we constrain any thermally emitting neutron star with a hydrogen atmosphere to have a temperature less than 30 eV and L_{NS}(0.01-10 keV)<6.2*10^{30} ergs/s. A thermal plasma model also gives an acceptable fit to the continuum. Adding a neutron star component to the plasma model produces less stringent constraints on the neutron star; a temperature of 36^{+4}_{-8} eV and L_{NS}(0.01-10 keV)=1.3^{+0.6}_{-0.8}*10^{31} ergs/s. In the framework of the current theory of neutron star heating and cooling, the constraints on the thermal luminosity of 1808 and 1H 1905+000 require strongly enhanced cooling in the cores of these neutron stars. We compile data from the literature on the mass transfer rates and quiescent thermal flux of the largest possible sample of transient neutron star LMXBs. We identify a thermal component in the quiescent spectrum of the accreting millisecond pulsar IGR J00291+5934, which is consistent with the standard cooling model. The contrast between the cooling rates of IGR J00291+5934 and 1808 suggests that 1808 may have a significantly larger mass. This can be interpreted as arising from differences in the binary evolution history or initial neutron star mass in these otherwise similar systems.Comment: ApJ in press, 7 pages, 2 color figure

Constraining the neutron star equation of state using quiescent low-mass X-ray binaries

Chandra or XMM-Newton observations of quiescent low-mass X-ray binaries can provide important constraints on the equation of state of neutron stars. The mass and radius of the neutron star can potentially be determined from fitting a neutron star atmosphere model to the observed X-ray spectrum. For a radius measurement it is of critical importance that the distance to the source is well constrained since the fractional uncertainty in the radius is at least as large as the fractional uncertainty in the distance. Uncertainties in modelling the neutron star atmosphere remain. At this stage it is not yet clear if the soft thermal component in the spectra of many quiescent X-ray binaries is variable on timescales too short to be accommodated by the cooling neutron star scenario. This can be tested with a long XMM-Newton observation of the neutron star X-ray transient CenX-4 in quiescence. With such an observation one can use the Reflection Grating Spectrometer spectrum to constrain the interstellar extinction to the source. This removes this parameter from the X-ray spectral fitting of the EPIC pn and MOS spectra and allows one to investigate whether the variability observed in the quiescent X-ray spectrum of this source is due to variations in the soft thermal spectral component or variations in the power law spectral component coupled with variations in N_H. This will test whether the soft thermal component can indeed be due to the hot thermal glow of the neutron star. Irrespective of the outcome of such a study, the observed cooling in quiescence in sources for which the crust is significantly out of thermal equilibrium with the core due to a prolonged outburst, such as KS 1731-260, seem excellent candidates for mass and radius determinations through modelling the observed X-rays with a neutron star atmosphere model.Comment: 7 pages, 3 figures, proceedings "40 years of pulsars" conferenc

The infrared counterpart of the Z source GX5-1

We have obtained UKIRT infrared observations of the field of the bright Galactic Z source GX5-1. From an astrometric plate solution tied to Tycho-ACT standards we have obtained accurate positions for the stars in our field which, combined with an accurate radio position, have allowed us to identify the probable infrared counterpart of GX5-1. Narrow-band photometry marginally suggests excess Br-gamma emission in the counterpart, supporting its association with an accretion-disc source. No significant variability is observed in a limited number of observations. We compare the H and K magnitudes with those of other Z sources, and briefly discuss possible sources of infrared emission in these systems.Comment: 5 pages, 2 figures, accepted by MNRA

An investigation into factors impacting on exports from South Africa to the Southern African Development Community (SADC)

Manufacturers face vigorous competition in local and export markets and need to have a genuine competitive advantage in order to grow. The South African government has recognised the importance of developing national manufacturing capacity as a means of increasing employment and reducing poverty. To this end, the government provides substantial support to both the manufacturing and exporting sectors. The government also negotiated the Southern African Development Community (SADC) agreement which leverages competitive advantages for South African manufacturers exporting into the region. However, since the ratification of the SADC agreement in 2008, there has been no perceptible increase in export activity to the region when compared to other markets. This research study was conducted to determine why this is the case and what factors are influencing the process. A structured literature review was undertaken to encapsulate export barriers, the role of the South African government in the export process, and the SADC agreement. The findings of the reviewed literature form the basis of the survey that led to the compilation of the research primary data. The results indicate that export barriers do not pose a major obstacle to trade into the SADC region. The role that the South African government holds was less conclusive with some successes noted, but on the whole the impact is not meaningfully positive. The SADC agreement and the dynamics prevailing in the free trade area do have a positive impact on exports to the region. The level of awareness with regard to the government support initiatives appears to be low.RésuméLes fabricants font face à une vive concurrence sur les marchés locaux et d’exportation et ont besoin d’avoir un véritable avantage concurrentiel pour se développer. Le gouvernement sud-africain a reconnu l’importance de renforcer les capacités nationales de production comme un moyen d’accroître l’emploi et réduire la pauvreté . À cette fin, le gouvernement apporte un soutien important à la fois la fabrication et secteurs exportateurs. Le gouvernement a également négocié l’accord Southern African Development Community (SADC ), qui s’appuie sur des avantages concurrentiels pour les fabricants sud-africains exportateurs dans la région. Cependant , depuis la ratification de l’accord de la SADC en 2008 , il a eu aucune augmentation perceptible de l’activité d’exportation de la région par rapport à d’autres marchés. Cette étude a été menée afin de déterminer pourquoi c’est le cas et quels sont les facteurs qui influencent le processus . Une revue de la littérature structurée a été entreprise pour encapsuler les obstacles à l’exportation , le rôle du gouvernement sud-africain dans le processus d’exportation , et l’accord de la SADC . Les résultats de la littérature examinée forment la base de l’enquête qui a conduit à la compilation des données primaires de la recherche . Les résultats indiquent que les barrières à l’exportation ne constituent pas un obstacle majeur au commerce dans la région de la SADC . Le rôle que le gouvernement sud-africain détient était moins concluante avec quelques réussites constatées, mais dans l’ensemble l’impact n’est pas significative positive. L’accord de la SADC et la dynamique qui prévaut dans la zone de libre-échange ont un impact positif sur les exportations de la région . Le niveau de sensibilisation à l’égard des initiatives de soutien du gouvernement semble être faibl

Formalisation of Dynamic Properties of Multi-Issue Negotiation

This document contains a number of formal dynamic properties that are relevant for multi-issue negotiation

Planting a misdiagnosis of Alzheimer's disease in a person's mind

Objective: There is an extensive corpus of knowledge about how misinformation may distort autobiographical memories. A diagnostic error can be conceptualised as a form of misinformation. Methods: The authors discuss the case of a 58-year-old woman who was given a misdiagnosis of Alzheimer's disease. Results: The patient was deeply convinced that the diagnosis was correct, even when she was confronted with contradictory evidence. Conclusion: A diagnosis is not a neutral piece of information. It profoundly affects the lives of patients. The consequences of a misdiagnosis may be similar to persistent false memories