Stellar Wind Accretion in GX301-2: Evidence for a High-density Stream

The X-ray binary system GX301-2 consists of a neutron star in an eccentric orbit accreting from the massive early-type star WRAY 977. It has previously been shown that the X-ray orbital light curve is consistent with existence of a gas stream flowing out from Wray 977 in addition to its strong stellar wind. Here, X-ray monitoring observations by the Rossi X-ray Timing Explorer (RXTE)/ All-Sky-Monitor (ASM) and pointed observations by the RXTE/ Proportional Counter Array (PCA) over the past decade are analyzed. We analyze both the flux and column density dependence on orbital phase. The wind and stream dynamics are calculated for various system inclinations, companion rotation rates and wind velocities, as well as parametrized by the stream width and density. These calculations are used as inputs to determine both the expected accretion luminosity and the column density along the line-of-sight to the neutron star. The model luminosity and column density are compared to observed flux and column density vs. orbital phase, to constrain the properties of the stellar wind and the gas stream. We find that the change between bright and medium intensity levels is primarily due to decreased mass loss in the stellar wind, but the change between medium and dim intensity levels is primarily due to decreased stream density. The mass-loss rate in the stream exceeds that in the stellar wind by a factor of 2.5. The quality of the model fits is significantly better for lower inclinations, favoring a mass for WRAY 977 of 53 to 62 Msun.Comment: 19 pages, 6 figure

Radio Spectrum and Distance of the SNR HB9

New images are presented of the supernova remnant (SNR) HB9 based on 408 MHz and 1420 MHz continuum emission and HI-line emission data of the Canadian Galactic Plane Survey (CGPS) by the Dominion Radio Astrophysical Observatory (DRAO). Two methods of spectral index analysis for HB9 are presented and compared: one removes compact sources at both frequencies but is limited to the resolution of the 408 MHz image; the other removes compact sources only in the 1420 MHz image so is effective at higher spatial resolution. The second allows more detailed spectral index variation studies than the first. The two T-T plot methods and new integrated flux densities give spectral index (S_{\nu}\propto\nu^{-alpha}) for the whole of HB9 of 0.48+-0.03; and 0.47+-0.06, respectively. These are lower than previous spectral index for HB9 (alpha=0.61). Spatial variations of spectral index are derived using the second method and yield a steeper spectral index for interior regions than for the rim. This can be explained by a standard curved interstellar electron energy spectrum combined with lower interior magnetic field compared to that near the outer shock, which results in a larger proportion of steep spectrum emission for lines-of-sight through the central body of the SNR. HI observations show structures probably associated with the SNR in the radial velocity range -3 to -9 km/s and suggest a distance of 0.8+-0.4 kpc for the SNR. This is consistent with the distance to the radio pulsar 0458+46, offset from the center of HB9 by 23'. However the pulsar spindown and kinematic ages are significantly greater than estimates of the SNR age: the Sedov age for HB9 is 6600 yr and the evaporative cloud model yields ages of 4000-7,000 yr.Comment: 8 pages, 6 figures, 1 table, accepted by A&

Dundee Discussion Papers in Economics 197:'Make-or-buy' in international oligopoly and the role of competitive pressure

We study how competitive pressure influences the make-or-buy decision that oligopolistic firms face between producing an intermediate component in-house or purchasing it from a domestic supplier. We model outsourcing as a bilateral relationship in which the supplier undertakes relationship-specific investments. A home and foreign firm compete in the home market. Firms’ mode of operation decision depends on cost and strategic considerations. Competitive pressure increases firms’ incentive to outsource. Consumer gains from trade liberalisation are enhanced when it leads to less outsourcing

The HI absorption distance of HESS J1943+213 favours its extragalactic nature

The H.E.S.S. collaboration (Abramowski et al. 2011) dicovered a new TeV point-like source HESS J1943+213 in the Galactic plane and suggested three possible low-energy-band counterparts: a $\gamma$-ray binary, a pulsar wind nebula (PWN), or a BL Lacertae object. We measure the distance to the radio counterpart G57.76-1.29 of HESS J1943+213. We analyze Very Large Array observations to obtain a reliable HI absorption spectrum.The resulting distance limit is $\ge$ 16 kpc. This distance strongly supports that HESS J1943+213 is an extragalactic source, consistent with the preferred counterpart of the HESS collaboration.Comment: 3 figures, 2 pages, A&A accepte

Musicians in Space

Musicians in space (MiS) is a practice-based research project investigating the impact of spatialization on the performance of free improvised music (FiM). It draws heavily on Christopher Small’s idea of musicking to contextualize the argument that in the fifty year history of FiM, improvisers have failed to fully explore possible alternatives to the formal separation and static positioning of the audience and performer. While the conventional performance situation is seen as being integral to the pageantry of the performative experience, I argue that the fixity of the spatial and social arrangement has done little to support the allencompassing and heterarchical aspirations that had once been a noted rallying cry of the free improviser. The thesis traces a journey through a series of live performances involving experienced free improvisers, on the UK and European improvised music scene, and incorporates the voices of over 70 participants. The thesis establishes a separation between hierarchical and heterarchical forms of musicking, where the former emphasizes the convergence of more unifying and fixed ideals associated with the construction and organisation of a musical process, while the later celebrates a more decentralized, polysemic, and self-organizing musicking practice. This categorization is used throughout this research to support a greater degree of understanding of the particular characteristics of FiM within the broader context of music-making. MiS, in essence, simply invites all the participants the option to modify their spatial relationship to the musicking process in order to expand their listening and playing experiences. It was found that this single change, in the approach to performance, greatly influenced many aspects of the FiM process, providing new insights into ways of engaging and listening for both the improviser and the listener. It afforded the improviser new opportunities to connect musically with the ensemble, while elevating the profile of the audience member from a focused listener to a visible participant and active collaborator in the process. This document attempts to establish a clear impression of what was uncovered by this research, while also celebrating the impossibility of capturing in words the complexity of an improvisation experience. It does this by incorporating a range of different forms of writing and a collection of personal depictions of a number of performances and improvising participants. This document also includes links to multi-perspective audio and visual footage of all the performances. This can be found at: http://www.dafmusic.com/Musicians_in_Space/mis_projectbrief.html

R&D Spillovers and the Case for Industrial Policy in an Open Economy

In this paper we consider the case for subsidies towards firms which generate R&D spillovers in open economies. We show that many expected results are overturned in the presence of strategic behaviour by firms. Local R&D spillovers to other domestic firms may justify an R&D tax rather than a subsidy; R&D cooperation by local firms over-internalises the externality and also justifies an R&D tax; and international spillovers which benefit foreign firms may justify a subsidy, even though the government cares only about the profits of home firms.