911 research outputs found
The tidal effects on the lithium abundance of binary systems with giant component
We analise the behavior of lithium abundance as a function of effective
temperature, projected rotational velocity, orbital period and eccentricity for
a sample of 68 binary systems with giant component and orbital period ranging
from about 10 to 6400 days. For these binary systems the Li abundances show a
gradual decrease with temperature, paralleling the well established result for
single giants. We have also observed a dependence of lithium content on
rotation. Binary systems with moderate to high rotation present also moderate
to high Li content. This study shows also that synchronized binary systems with
giant component seems to retain more of their original lithium than the
unsynchronized systems. For orbital periods lower than 100 to 250 days,
typically the period of synchronization for this kind of binary systems,
lithium depleted stars seems to be unusual. The suggestion is made that there
is an 'inhibited zone' in which synchronized binary systems with giant
component having lithium abundance lower than a threshold level should be
unusual.Comment: 6 pages, 3 Postscript figures, uses: aa.cls, psfig.st
High stakes and low bars: How international recognition shapes the conduct of civil wars
When rebel groups engage incumbent governments in war for control of the state, questions of international recognition arise. International recognition determines which combatants can draw on state assets, receive overt military aid, and borrow as sovereigns—all of which can have profound consequences for the military balance during civil war. How do third-party states and international organizations determine whom to treat as a state's official government during civil war? Data from the sixty-one center-seeking wars initiated from 1945 to 2014 indicate that military victory is not a prerequisite for recognition. Instead, states generally rely on a simple test: control of the capital city. Seizing the capital does not foreshadow military victory. Civil wars often continue for many years after rebels take control and receive recognition. While geopolitical and economic motives outweigh the capital control test in a small number of important cases, combatants appear to anticipate that holding the capital will be sufficient for recognition. This expectation generates perverse incentives. In effect, the international community rewards combatants for capturing or holding, by any means necessary, an area with high concentrations of critical infrastructure and civilians. In the majority of cases where rebels contest the capital, more than half of its infrastructure is damaged or the majority of civilians are displaced (or both), likely fueling long-term state weakness
The Extinction and Distance of Maffei 1
We have obtained low- and high-resolution spectra of the core of the
highly-reddened elliptical galaxy Maffei 1. From these data, we have obtained
the first measurement of the Mg2 index, and have measured the velocity
dispersion and radial velocity with improved accuracy. To evaluate the
extinction, a correlation between the Mg2 index and effective V-I colour has
been established for elliptical galaxies. Using a new method for correcting for
effective wavelength shifts, we find A_V = 4.67 +/- 0.19 mag, which is lower by
0.4 mag than previously thought. To establish the distance, the Fundamental
Plane for elliptical galaxies has been constructed in I. The velocity
dispersion of Maffei 1, measured to be 186.8 +/- 7.4 km/s, in combination with
modern wide-field photometry in I, leads to a distance of 2.92 +/- 0.37 Mpc.
The Dn-sigma relation, which is independently calibrated, gives 3.08 +/- 0.85
Mpc and 3.23 +/- 0.67 Mpc from photometry in B and K`, respectively. The
weighted mean of the three estimates is 3.01 +/- 0.30 Mpc. The distance and
luminosity make Maffei 1 the nearest giant elliptical galaxy. The radial
velocity of Maffei 1 is +66.4 +/- 5.0 km/s, significantly higher than the
accepted value of -10 km/s. The Hubble distance corresponding to the mean
velocity of Maffei 1, Maffei 2 and IC342 is 3.5 Mpc. Thus, it is unlikely that
Maffei 1 has had any influence on Local Group dynamics
How a turn to critical race theory can contribute to our understanding of 'race', racism and anti-racism in sport
As long as racism has been associated with sport there have been consistent, if not coordinated or coherent, struggles to confront its various forms. Critical race theory (CRT) is a framework established to challenge these racialized inequalities and racism in society and has some utility for anti-racism in sport. CRT's focus on social justice and transformation are two areas of convergence between critical race theorists and anti-racists. Of the many nuanced and pernicious forms of racism, one of the most obvious and commonly reported forms of racism in sport, racial abuse, has been described as a kind of dehumanizing process by Gardiner (2003), as those who are its target are simultaneously (re)constructed and objectified according to everyday myth and fantasy. However, this is one of the many forms of everyday racist experiences. Various forms of racism can be experienced in boardrooms, on television, in print, in the stands, on the sidelines and on the pitch. Many times racism is trivialized and put down as part of the game (Long et al., 2000), yet its impact is rarely the source of further exploration. This article will explore the conceptualization of 'race' and racism for a more effective anti-racism. Critical race theory will also be used to explore the ideas that underpin considerations of the severity of racist behaviour and the implications for anti-racism. © The Author(s) 2010
Disentangling protostellar evolutionary stages in clustered environments using Spitzer-IRS spectra and comprehensive SED modeling
When studying the evolutionary stages of protostars that form in clusters,
the role of any intracluster medium cannot be neglected. High foreground
extinction can lead to situations where young stellar objects (YSOs) appear to
be in earlier evolutionary stages than they actually are, particularly when
using simple criteria like spectral indices. To address this issue, we have
assembled detailed SED characterizations of a sample of 56 Spitzer-identified
candidate YSOs in the clusters NGC 2264 and IC 348. For these, we use spectra
obtained with the Infrared Spectrograph onboard the Spitzer Space Telescope and
ancillary multi-wavelength photometry. The primary aim is twofold: 1) to
discuss the role of spectral features, particularly those due to ices and
silicates, in determining a YSO's evolutionary stage, and 2) to perform
comprehensive modeling of spectral energy distributions (SEDs) enhanced by the
IRS data. The SEDs consist of ancillary optical-to-submillimeter
multi-wavelength data as well as an accurate description of the 9.7 micron
silicate feature and of the mid-infrared continuum derived from line-free parts
of the IRS spectra. We find that using this approach, we can distinguish
genuine protostars in the cluster from T Tauri stars masquerading as protostars
due to external foreground extinction. Our results underline the importance of
photometric data in the far-infrared/submillimeter wavelength range, at
sufficiently high angular resolution to more accurately classify cluster
members. Such observations are becoming possible now with the advent of the
Herschel Space Observatory.Comment: Accepted for publication in Ap
An Assessment of Dynamical Mass Constraints on Pre-Main Sequence Evolutionary Tracks
[abridged] We have assembled a database of stars having both masses
determined from measured orbital dynamics and sufficient spectral and
photometric information for their placement on a theoretical HR diagram. Our
sample consists of 115 low mass (M < 2.0 Msun) stars, 27 pre-main sequence and
88 main sequence. We use a variety of available pre-main sequence evolutionary
calculations to test the consistency of predicted stellar masses with
dynamically determined masses. Despite substantial improvements in model
physics over the past decade, large systematic discrepancies still exist
between empirical and theoretically derived masses. For main-sequence stars,
all models considered predict masses consistent with dynamical values above 1.2
Msun, some models predict consistent masses at solar or slightly lower masses,
and no models predict consistent masses below 0.5 Msun but rather all models
systematically under-predict such low masses by 5-20%. The failure at low
masses stems from the poor match of most models to the empirical main-sequence
below temperatures of 3800 K where molecules become the dominant source of
opacity and convection is the dominant mode of energy transport. For the
pre-main sequence sample we find similar trends. There is generally good
agreement between predicted and dynamical masses above 1.2 Msun for all models.
Below 1.2 Msun and down to 0.3 Msun (the lowest mass testable) most
evolutionary models systematically under-predict the dynamically determined
masses by 10-30% on average with the Lyon group models (e.g. Baraffe et al.
1998) predicting marginally consistent masses *in the mean* though with large
scatter.Comment: accepted for publication in ApJ (2004
Incidence of symptomatic venous thromboembolism in oncologic patients undergoing lower-extremity endoprosthetic arthroplasty
“Not a good look”: impossible dilemmas for young women negotiating the culture of intoxication in the United Kingdom.
This paper investigates young women's alcohol consumption in the United Kingdom within a widespread culture of intoxication in relation to recent debates about postfeminism and contemporary femininity. Young women are faced with an “impossible dilemma,” arising from the contradiction between a hedonistic discourse of alcohol consumption and postfeminist discourse around attaining and maintaining the “right” form of hypersexual heterosexual femininity. Drawing on a recent interview study with 24 young white working-class and middle-class women in the South-West of England, we explore how young women inhabit the dilemmas of contemporary femininity in youth drinking cultures, striving to achieve the “right” form of hypersexual femininity and an “optimum” level of drunkenness
Structure of the outer layers of cool standard stars
Context: Among late-type red giants, an interesting change occurs in the
structure of the outer atmospheric layers as one moves to later spectral types
in the Hertzsprung-Russell diagram: a chromosphere is always present, but the
coronal emission diminishes and a cool massive wind steps in.
Aims: Where most studies have focussed on short-wavelength observations, this
article explores the influence of the chromosphere and the wind on
long-wavelength photometric measurements.
Methods: The observational spectral energy distributions are compared with
the theoretical predictions of the MARCS atmosphere models for a sample of 9 K-
and M-giants. The discrepancies found are explained using basic models for flux
emission originating from a chromosphere or an ionized wind.
Results: For 7 out of 9 sample stars, a clear flux excess is detected at
(sub)millimeter and/or centimeter wavelengths. The precise start of the excess
depends upon the star under consideration. The flux at wavelengths shorter than
about 1 mm is most likely dominated by an optically thick chromosphere, where
an optically thick ionized wind is the main flux contributor at longer
wavelengths.
Conclusions: Although the optical to mid-infrared spectrum of the studied K-
and M-giants is well represented by a radiative equilibrium atmospheric model,
the presence of a chromosphere and/or ionized stellar wind at higher altitudes
dominates the spectrum in the (sub)millimeter and centimeter wavelength ranges.
The presence of a flux excess also has implications on the role of these stars
as fiducial spectrophotometric calibrators in the (sub)millimeter and
centimeter wavelength range.Comment: 13 pages, 6 figures, 7 pages of online material, submitted to A&
Herschel-ATLAS: VISTA VIKING near-IR counterparts in the Phase 1 GAMA 9h data
We identify near-infrared Ks band counterparts to Herschel-ATLAS sub-mm
sources, using a preliminary object catalogue from the VISTA VIKING survey. The
sub-mm sources are selected from the H-ATLAS Phase 1 catalogue of the GAMA 9h
field, which includes all objects detected at 250, 350 or 500 um with the SPIRE
instrument. We apply and discuss a likelihood ratio (LR) method for VIKING
candidates within a search radius of 10" of the 22,000 SPIRE sources with a 5
sigma detection at 250 um. We find that 11,294(51%) of the SPIRE sources have a
best VIKING counterpart with a reliability , and the false
identification rate of these is estimated to be 4.2%. We expect to miss ~5% of
true VIKING counterparts. There is evidence from Z-J and J-Ks colours that the
reliable counterparts to SPIRE galaxies are marginally redder than the field
population. We obtain photometric redshifts for ~68% of all (non-stellar)
VIKING candidates with a median redshift of 0.405. Comparing to the results of
the optical identifications supplied with the Phase I catalogue, we find that
the use of medium-deep near-infrared data improves the identification rate of
reliable counterparts from 36% to 51%.Comment: 20 pages, 20 figures, 3 tables, accepted by MNRA
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