126 research outputs found
High Resolution K-band Spectroscopy of MWC 480 and V1331 Cyg
We present high resolution (R=25,000-35,000) K-band spectroscopy of two young
stars, MWC 480 and V1331 Cyg. Earlier spectrally dispersed (R=230)
interferometric observations of MWC 480 indicated the presence of an excess
continuum emission interior to the dust sublimation radius, with a spectral
shape that was interpreted as evidence for hot water emission from the inner
disk of MWC 480. Our spectrum of V1331 Cyg reveals strong emission from CO and
hot water vapor, likely arising in a circumstellar disk. In comparison, our
spectrum of MWC 480 appears mostly featureless. We discuss possible ways in
which strong water emission from MWC 480 might go undetected in our data. If
strong water emission is in fact absent from the inner disk, as our data
suggest, the continuum excess interior to the dust sublimation radius that is
detected in the interferometric data must have another origin. We discuss
possible physical origins for the continuum excess.Comment: 29 pages, 5 figures, to appear in Ap
Spin down of protostars through gravitational torques
Young protostars embedded in circumstellar discs accrete from an angular
momentum-rich mass reservoir. Without some braking mechanism, all stars should
be spinning at or near break-up velocity. In this paper, we perform simulations
of the self-gravitational collapse of an isothermal cloud using the ORION
adaptive mesh refinement code and investigate the role that gravitational
torques might play in the spin-down of the dense central object. While magnetic
effects likely dominate for low mass stars, high mass and Population III stars
might be less well magnetised. We find that gravitational torques alone prevent
the central object from spinning up to more than half of its breakup velocity,
because higher rotation rates lead to bar-like deformations that enable
efficient angular momentum transfer to the surrounding medium. We also find
that the long-term spin evolution of the central object is dictated by the
properties of the surrounding disc. In particular, spiral modes with azimuthal
wavenumber couple more effectively to its spin than the lopsided
mode, which was found to inhibit spin evolution. We suggest that even in the
absence of magnetic fields, gravitational torques may provide an upper limit on
stellar spin, and that moderately massive circumstellar discs can cause
long-term spin down.Comment: 13 pages, 17 figures, 1 table. Accepted by MNRAS. Updated reference
Differential effects of tamoxifen and anastrozole on optic cup size in breast cancer survivors
Fairness as a Source of Hysteresis in Employment and Relative Wages
This paper analyses the inlfuence of norms of fairness on wage formation. Fairness is defined by \u27real-wage\u27 and \u27relative-wage\u27 norms that relate wage offers to workers\u27 own current wage and to the wages of other groups of workers, and, to avoil shirking, firms pay their wages. The wage norms change endogenously, and the result is hysteresis with respect to both employment and the distribution of wages. An extention of the model that allows \u27induced overeducation\u27 may help explain trends in wage inequality
Asteroseismology and Interferometry
Asteroseismology provides us with a unique opportunity to improve our
understanding of stellar structure and evolution. Recent developments,
including the first systematic studies of solar-like pulsators, have boosted
the impact of this field of research within Astrophysics and have led to a
significant increase in the size of the research community. In the present
paper we start by reviewing the basic observational and theoretical properties
of classical and solar-like pulsators and present results from some of the most
recent and outstanding studies of these stars. We centre our review on those
classes of pulsators for which interferometric studies are expected to provide
a significant input. We discuss current limitations to asteroseismic studies,
including difficulties in mode identification and in the accurate determination
of global parameters of pulsating stars, and, after a brief review of those
aspects of interferometry that are most relevant in this context, anticipate
how interferometric observations may contribute to overcome these limitations.
Moreover, we present results of recent pilot studies of pulsating stars
involving both asteroseismic and interferometric constraints and look into the
future, summarizing ongoing efforts concerning the development of future
instruments and satellite missions which are expected to have an impact in this
field of research.Comment: Version as published in The Astronomy and Astrophysics Review, Volume
14, Issue 3-4, pp. 217-36
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What Happened to the Bondholding Class? Public Debt, Power and the Top One Per Cent
In 1887 Henry Carter Adams produced a study demonstrating that the ownership of government bonds was heavily concentrated in the hands of a ‘bondholding class’ that lent to and, in Adams's view, controlled the government like dominant shareholders control a corporation. The interests of this bondholding class clashed with the interests of the masses, whose burdensome taxes financed the interest payments on government bonds. Since the late nineteenth century there has been plenty of debate about the ownership of the public debt. But the empirical evidence offered to support the various arguments has been scant. As a result, political economists have few answers to questions first raised by Adams over century ago: how has the pattern of public debt ownership changed? Can we still speak of a powerful ‘bondholding class’? Does public debt redistribute income from taxpayers to public creditors? This article develops a new framework to address these questions. Anchored within a ‘capital as power’ approach, the research indicates a staggering pattern of concentration in the ownership of US public debt in the hands of the top one per cent of US households over the past three decades. Accordingly, the bondholding class is still alive and well in contemporary US capitalism
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