A compressed cloud in the Vela supernova remnant

To elucidate the nature of the interstellar medium in the vicinity of the Vela supernova remnants (SNR) an extensive study with the International Ultraviolet Explorer of interstellar absorption lines toward 35 stars in the vicinity of the Vela SNR was undertaken. Observations of interstellar absorption, in particular of CI, towards one of these stars, HD 72350 (type B4 III), is of particular interest

High resolution CCD spectra of stars in globular clusters. Part 2: Metals and CNO in M71

Palomar coude CCD spectra of resolution 0.3 and 0.6 has been used to redetermine abundances in five stars of the relatively metal rich globular cluster M71. The (Fe/H) value is restricted to the limits of -0.6 to -1.0. The largest source of uncertainty is a systematic difference in f-values between those derived via the Holweger-Muller (1974) solar model and the Bell et al. (1976) solar model. If we use absolute f-values measured by the Oxford group (Blackwell et al. 1982) we find Fe/H to lie in the range of -0.6 to -0.75, i.e., as given by using the Bell et al. solar model. The relative abundances of the light elements, i.e., Na through Ca and probably including Ti show an average excess relative to iron of 0.4 dex. The effect of this difference on metal indices derived from broad- and narrow- band photometry is discussed. For three stars we find O/H = -0.6 using absolute f-values. For CN an analysis of individual rotational lines of the 2-0 band of the red system yields lines in the (C/H,N/H) plane that are consistent with either an original C/Fe = N/Fe = 0 or a modest increase in N relative to C due to CN burning and mixing. A search for C-13N was not successful and an uncertain lower limit of C-12/C-13 near 10 was obtained

BF Cyg during ITS current outburst

We are intensively monitoring the current outburst on BF Cyg, both spectroscopically (high and low resolution modes) and photometrically (so far 450 BVRCRIC measurements have been collected). The outburst is photometrically reminiscent of the major event BF Cyg experienced in 1890 when it rose by 4 mag in the blue. In this contribution we present the data and describe the plans to investigate this object

Spatial and Temporal Variations in Interstellar Absorption toward HD 72127AB

New optical spectra of Ca II and Na I toward HD 72127AB provide additional evidence for both spatial and temporal variations in the complex interstellar absorption along the two sight lines; archival UV spectra yield information on the abundances, depletions, and physical conditions in the gas toward HD 72127A. Similarities in the strengths of various tracers of interstellar material in the two lines of sight suggest that the total hydrogen column densities [N(H) ~ 2.5 x 10^{20} cm^{-2}] and the depletions and ionization in the main components at low LSR velocities also are similar. Toward HD 72127A, the main components are relatively cool (T < 900 K), but with depletions resembling those found in warm, diffuse disc clouds; the generally weaker components at higher velocities have much milder depletions, more like those found in halo clouds. Several trace neutral species -- Ca I, Cr I, and Fe I -- are much stronger toward HD 72127B, however. The column density of Cr I, for example, is about 30 times the value determined toward zeta Oph (the only previous detection of that species in the ISM). Dielectronic recombination in warmer gas (T > 5000 K) may be largely responsible for the enhanced abundances of those trace neutral species toward HD 72127B. If the main components toward HD 72127AB are associated with material in the Vela SNR, the differences in abundances and physical conditions occur on scales of about 1100 AU.Comment: 13 pages, 4 figures, accepted to MNRA

Nucleosynthesis of light element isotopes in evolved stars experiencing extended mixing

We present computations of nucleosynthesis in red giants and asymptotic giant branch stars of Population I experiencing extended mixing. The assumed physical cause for mass transport is the buoyancy of magnetized structures, according to recent suggestions. The peculiar property of such a mechanism is to allow for both fast and slow mixing phenomena, as required for reproducing the spread in Li abundances displayed by red giants and as discussed in an accompanying paper. We explore here the effects of this kind of mass transport on CNO and intermediatemass nuclei and compare the results with the available evidence from evolved red giants and from the isotopic composition of presolar grains of AGB origin. It is found that a good general accord exists between predictions and measurements; in this framework we also show which type of observational data best constrains the various parameters. We conclude that magnetic buoyancy, allowing for mixing at rather different speeds, can be an interesting scenario to explore for explaining together the abundances of CNO nuclei and of Li.Comment: 8 pages, 7 figures, proceeding of 'The Origin of the Elements Heavier than Fe' September 24-28, 2008, Torino, Italy. PASA (accepted for publication

Stellar Hydrodynamics in Radiative Regions

We present an analysis of the response of a radiative region to waves generated by a convective region of the star; this wave treatment of the classical problem of ``overshooting'' gives extra mixing relative to the treatment traditionally used in stellar evolutionary codes. The interface between convectively stable and unstable regions is dynamic and nonspherical, so that the nonturbulent material is driven into motion, even in the absence of ``penetrative overshoot.'' These motions may be described by the theory of nonspherical stellar pulsations, and are related to motion measured by helioseismology. Multi-dimensional numerical simulations of convective flow show puzzling features which we explain by this simplified physical model. Gravity waves generated at the interface are dissipated, resulting in slow circulation and mixing seen outside the formal convection zone. The approach may be extended to deal with rotation and composition gradients. Tests of this description in the stellar evolution code TYCHO produce carbon stars on the asymptotic giant branch (AGB), an isochrone age for the Hyades and three young clusters with lithium depletion ages from brown dwarfs, and lithium and beryllium depletion consistent with observations of the Hyades and Pleiades, all without tuning parameters. The insight into the different contributions of rotational and hydrodynamic mixing processes could have important implications for realistic simulation of supernovae and other questions in stellar evolution.Comment: 27 pages, 5 figures, accepted to the Astrophysical Journa

Re-theorising the core: a ‘globalized’ business elite in Santiago, Chile

World systems theory continues to be a widely adopted approach in theorisations of the contemporary world economy. An important epistemological component to world systems theory is the metaphor of core-periphery. Recent work within the approach has sought to transcend earlier criticisms of regional conceptions of cores, peripheries and semi-peripheries by an increasing sensitivity to local differences and an increasing emphasis on Wallerstein's original idea of core-periphery as process, operating at all scales in the contemporary world system. However, this paper argues that the core-periphery metaphor currently used by world systems theorists is founded around a restrictively narrow spatial epistemology. Such a narrow epistemology implements the core-periphery metaphor only as something which produces territorial outcomes in the physical world. This paper contends that recent work within the social services, concerned with the globalization debate and issues of spatial epistemology, should inform world systems theory in producing a reformulated spatial understanding of the core-periphery metaphor, embodying a wider conception of space to include abstract social spaces. This argument is developed in the notion that the world economy must also be understood as having a ‘social core’: a transnational diasporic business elite exercising decision-making power over the capitalist world system. The contention is grounded in the presentation of research into a case study of such a ‘globalized’ business elite in the capital city of Chile, Santiago

The ethical challenge of Touraine's 'living together'

In Can We Live Together? Alain Touraine combines a consummate analysis of crucial social tensions in contemporary societies with a strong normative appeal for a new emancipatory 'Subject' capable of overcoming the twin threats of atomisation or authoritarianism. He calls for a move from 'politics to ethics' and then from ethics back to politics to enable the new Subject to make a reality out of the goals of democracy and solidarity. However, he has little to say about the nature of such an ethics. This article argues that this lacuna could usefully be filled by adopting a form of radical humanism found in the work of Erich Fromm. It defies convention in the social sciences by operating from an explicit view of the 'is' and the 'ought' of common human nature, specifying reason, love and productive work as the qualities to be realised if we are to move closer to human solidarity. Although there remain significant philosophical and political differences between the two positions, particularly on the role to be played by 'the nation', their juxtaposition opens new lines of inquiry in the field of cosmopolitan ethics

Studying the Pulsation of Mira Variables in the Ultraviolet

We present results from an empirical study of the Mg II h & k emission lines of selected Mira variable stars, using spectra from the International Ultraviolet Explorer (IUE). The stars all exhibit similar Mg II behavior during the course of their pulsation cycles. The Mg II flux always peaks after optical maximum near pulsation phase 0.2-0.5, although the Mg II flux can vary greatly from one cycle to the next. The lines are highly blueshifted, with the magnitude of the blueshift decreasing with phase. The widths of the Mg II lines are also phase-dependent, decreasing from about 70 km/s to 40 km/s between phase 0.2 and 0.6. We also study other UV emission lines apparent in the IUE spectra, most of them Fe II lines. These lines are much narrower and not nearly as blueshifted as the Mg II lines. They exhibit the same phase-dependent flux behavior as Mg II, but they do not show similar velocity or width variations.Comment: 26 pages, 12 figures; AASTEX v5.0 plus EPSF extensions in mkfig.sty; to appear in Ap