142 research outputs found
Marlow Moss (1889-1958)
Merged with duplicate record 10026.1/831 on 15.02.2017 by CS (TIS)This thesis is the first full-length academic study of Marlow Moss in English. The
methodology of this research has been to combine biographical, historical, and analytical
approaches, and the chapters (a literature review; a biographical account; an examination of
gender I identity issues; a European art historical perspective; a British art historical
perspective; and a critical analysis of Moss's oeuvre), function as thematic lenses through
which to view Moss. It could seem that Moss's historical position, a British artist working in
Europe and a European-influenced artist working in England, should have secured her a
more prominent role in the history of British Constructive Art. Moss's subsequent neglect
provokes questions about the construction of that history.
The impetus of this research has been the retrieval of a lost personality in British and
European Modernist Art. This thesis represents the most complete account of Moss's life and
work to date, and the most sustained examination of her aesthetic. Gathered in the
Catalogue Raisonne in appendix to this thesis are over a hundred recorded works by Moss,
with images whenever possible, with all currently available information and details of
provenance. Also accompanying this thesis are reproductions of photographs, of Moss and
of her works, hitherto inaccessible in private collections. This research has gathered and
collated extensive archival material, ranging from contemporary reviews of Moss exhibitions,
to all known manuscript material relating to Moss, including unpublished letters such as those
held in the Paule Vezelay Collection of the Tale Archives, which remain un-catalogued at the
time of writing.
Moss's relationship with Mondrian, the focus of much previous research, is addressed and
clarified in this thesis. The significance of Moss's connections to Paris, the Academie
Moderne and Leger, and Abstraction-Creation, and her relationship to her contemporaries,
particularly Georges Vantongerloo and Max Bill, are traced. Her position in British art history
is mapped, with particular attention to her exhibitions in London during the fifties. Beyond
establishing Moss's absence from art historical narratives, and examining the circumstances
of her neglect, this thesis primarily seeks to retrieve the position she did occupy, by exploring
her working aesthetic and situating it within a specific historical and theoretical context. This
context includes Moss's sexuality and the questions it raises for a critical evaluation of her
achievement. Although both feminist and Queer Theorist paradigms are pertinent to this
research, and are indeed included in this study, Moss is found to problematise existent
theoretical categories. Moss's neglect may thus be explained by her lack of fit with prevalent
historical and theoretical approaches to Constructivism, to British Modernism, and to the
gendering of arts practice
Mass fluxes for O stars
The theory of moving reversing layers for hot stars is updated to include an
extensive line list, a radiative boundary condition from static model
atmospheres, line transfer by scattering, and continuation to supersonic
velocities. A Monte Carlo technique determines the theory's eigenvalue J, the
mass flux, and the derived J's are in good agreement with the wind models of
Pauldrach et al. (2001). The solutions' sensitivity to the photospheric
microturbulent velocity reveals that this parameter has a throttling effect on
J: turbulent line-broadening in the quasi-static layers reduces the radiation
force available to accelerate matter through the sonic point. If photospheric
turbulence approaches sonic velocities, this mechanism reduces mass loss rates
by factors > 3, which would partly account for the reduced rates found
observationally for clumpy winds.Comment: Accepted by A&A; 9 pages, 4 figure
2D Simulations of the Line-Driven Instability in Hot-Star Winds: II. Approximations for the 2D Radiation Force
We present initial attempts to include the multi-dimensional nature of
radiation transport in hydrodynamical simulations of the small-scale structure
that arises from the line-driven instability in hot-star winds. Compared to
previous 1D or 2D models that assume a purely radial radiation force, we seek
additionally to treat the lateral momentum and transport of diffuse
line-radiation, initially here within a 2D context. A key incentive is to study
the damping effect of the associated diffuse line-drag on the dynamical
properties of the flow, focusing particularly on whether this might prevent
lateral break-up of shell structures at scales near the lateral Sobolev angle
of ca. . We first explore nonlinear simulations that cast the
lateral diffuse force in the simple, local form of a parallel viscosity.
Second, to account for the lateral mixing of radiation associated with the
radial driving, we next explore models in which the radial force is azimuthally
smoothed over a chosen scale. Third, to account for both the lateral line-drag
and the lateral mixing in a more self-consistent way, we explore further a
method first proposed by Owocki (1999), which uses a restricted 3-ray approach
that combines a radial ray with two oblique rays set to have an impact
parameter within the stellar core. From numerical simulations,
we find that, compared to equivalent 1-ray simulations, the high-resolution
3-ray models show systematically a much higher lateral coherence.... (Full
abstract in paper)Comment: Accepted by A&A, 12 pages, 7 figures, 3 only shown in version
available at http://www.mpa-garching.mpg.de/~luc/2778.ps.g
Is macroturbulent broadening in OB Supergiants related to pulsations?
The spectrum of O and B Supergiants is known to be affected by an important
extra line-broadening (usually called macroturbulence) that adds to stellar
rotation. Recent analysis of high resolution spectra has shown that the
interpretation of this line-broadening as a consequence of large-scale
turbulent motions would imply highly super-sonic velocity fields, making this
scenario quite improbable. Stellar oscillations have been proposed as a likely
alternative explanation. We present first encouraging results of an
observational project aimed at investigating the broadening in
O and B Supergiants, and its possible connection with spectroscopic variability
phenomena and stellar oscillations: a) all the studied B Supergiants show line
profile variations, quantified by means of the first () and third velocity
() moments of the lines, b) there is a strong correlation between the
peak-to-peak amplitudes of the and variability and the size of
the extra-broadening.Comment: 4 pages, 2 figures, 1 table. Proceeding of the IV Helas International
Conference: "Seismological challeges for stellar structure". Editors:Teodoro
Roca Cort\'es, Pere Pall\'e and Sebasti\'an Jim\'enez Reye
A fiasco of volcanic proportions? Eyjafjallajökull and the closure of European airspace
The unprecedented and recurrent closure of much of UK and northern European airspace from 14 April 2010, following the eruption of Icelandâs Eyjafjallajökull volcano, caused the cancellation of 108,000 flights, disrupted the travel plans of 10.5 million passengers, and cost the airline industry in excess of $1.7bn in lost revenue (Eurocontrol, 2010). The airspace closures highlighted the inherent riskiness of aviation and destabilised dominant cultural discourses of the âsuperiorityâ and capability of aviation technology. It also brought issues of risk acceptability and our socio-economic reliance on air travel into sharp relief. This paper explores how the political and media framing of the response to the airspace closures as a human âpolicy fiascoâ served to obfuscate the inherent dangers of aviation and âget Europe flyingâ again. Thus, this paper contends that this particular fiasco was ânecessaryâ in that it served to highlight the fragility of air travel and the vulnerabilities of the mobile citizen
Tracing colliding winds in the UV line orbital variability of gamma-ray binaries
Gamma-ray binaries emit most of their radiated power beyond ~10 MeV. The
non-thermal emission is thought to arise from the interaction of the
relativistic wind of a rotation-powered pulsar with the stellar wind of its
massive (O or Be) companion star. A powerful pulsar creates an extended cavity,
filled with relativistic electrons, in the radiatively-driven wind of the
massive star. As a result, the observed P Cyg profiles of UV resonant lines
from the stellar wind should be different from those of single massive stars.
We propose to use UV emission lines to detect and constrain the colliding wind
region in gamma-ray binaries. We compute the expected orbital variability of P
Cyg profiles depending upon the interaction geometry (set by the ratio of
momentum fluxes from the winds) and the line-of-sight to the system. We predict
little or no variability for the case of LS 5039 and PSR B1259-63, in agreement
with currently available HST observations of LS 5039. However, variability
between superior and inferior conjunction is expected in the case of LS I+61
303.Comment: Accepted for publication in MNRA
Low mass loss rates in O-type stars: Spectral signatures of dense clumps in the wind of two Galactic O4 stars
We have analyzed the far-UV spectrum of two Galactic O4 stars, the O4If+
supergiant HD190429A and the O4V((f)) dwarf HD96715, using archival FUSE and
IUE data. We have conducted a quantitative analysis based on the two NLTE model
atmosphere and wind codes, TLUSTY and CMFGEN. We have derived the stellar and
wind parameters and the surface composition of the two stars. The surface of
HD190429A has a composition typical of an evolved O supergiant (N-rich, C and
O-poor), while HD96715 exhibits surface N enhancement similar to the enrichment
found in SMC O dwarfs and attributed to rotationally-induced mixing. We find
that homogeneous wind models could not match the observed profile of O V1371
and require very low phosphorus abundance to fit the P V1118-1128 resonance
lines. However, we are able to match the O V and P V lines using clumped wind
models. We find that N IV1718 is also sensitive to wind clumping. For both
stars, we have calculated clumped wind models that match well all these lines
from different species and that remain consistent with Halpha data. These fits
therefore provide a coherent and thus much stronger evidence of wind clumping
in O stars than earlier claims. We find that the wind of these two stars is
highly clumped, as expressed by very small volume filling factors, namely
f=0.04 for HD190429A and f=0.02 for HD96715. In agreement with our analysis of
SMC stars, clumping starts deep in the wind, just above the sonic point. The
most crucial consequence of our analysis is that the mass loss rates of O stars
need to be revised downward significantly, by a factor of 3 and more.
Accounting for wind clumping is essential when determining the wind properties
of O stars. Our study therefore calls for a fundamental revision in our
understanding of mass loss and of O-type star winds. (abridged)Comment: To appear in Astronomy & Astrophysics; 16 pages; accepted version
after minor revisio
Predictions for mass-loss rates and terminal wind velocities of massive O-type stars
Mass loss forms an important aspect of the evolution of massive stars, as
well as for the enrichment of the surrounding ISM. Our goal is to predict
accurate mass-loss rates and terminal wind velocities. These quantities can be
compared to empirical values, thereby testing radiation-driven wind models. One
specific issue is that of the "weak-wind problem", where empirically derived
mass-loss rates fall orders of magnitude short of predicted values. We employ
an established Monte Carlo model and a recently suggested new line acceleration
formalism to solve the wind dynamics consistently. We provide a new grid of
mass-loss rates and terminal wind velocities of O stars, and compare the values
to empirical results. Our models fail to provide mass-loss rates for
main-sequence stars below a luminosity of log(L/Lsun) = 5.2, where we run into
a fundamental limit. At luminosities below this critical value there is
insufficient momentum transferred in the region below the sonic point to
kick-start the acceleration. This problem occurs at the location of the onset
of the weak-wind problem. For O dwarfs, the boundary between being able to
start a wind, and failing to do so, is at spectral type O6/O6.5. The direct
cause of this failure is a combination of the lower luminosity and a lack of Fe
V lines at the wind base. This might indicate that another mechanism is
required to provide the necessary driving to initiate the wind. For stars more
luminous than log(L/Lsun) = 5.2, our new mass-loss rates are in excellent
agreement with the mass-loss prescription by Vink et al. 2000. This implies
that the main assumption entering the method of the Vink et al. prescriptions -
i.e. that the momentum equation is not explicitly solved for - does not
compromise the reliability of the Vink et al. results for this part of
parameter space (Abridged).Comment: 10 pages, 10 figures, Astronomy & Astrophysics (in press
Implications of the metallicity dependence of Wolf-Rayet winds
Aims: Recent theoretical predictions for the winds of Wolf-Rayet stars
indicate that their mass-loss rates scale with the initial stellar metallicity
in the local Universe.We aim to investigate how this predicted dependence
affects the models of Wolf-Rayet stars and their progeny in different chemical
environments. Methods: We compute models of stellar structure and evolution for
Wolf-Rayet stars for different initial metallicities, and investigate how the
scaling of the Wolf-Rayet mass-loss rates affects the final masses, the
lifetimes of the WN and WC subtypes, and how the ratio of the two populations
vary with metallicity. Results: We find significant effects of metallicity
dependent mass-loss rates for Wolf-Rayet stars. For models that include the
scaling of the mass-loss rate with initial metallicity, all WR stars become
neutron stars rather than black holes at twice the solar metallicity; at lower
, black holes have larger masses. We also show that our models that include
the mass-loss metallicity scaling closely reproduce the observed decrease of
the relative population of WC over WN stars at low metallicities.Comment: 8 pages, 9 figures, accepted by Astronomy & Astrophysic
Modelling the orbital modulation of ultraviolet resonance lines in high-mass X-ray binaries
The stellar-wind structure in high-mass X-ray binaries (HMXBs) is
investigated through modelling of their ultraviolet (UV) resonance lines. For
the OB supergiants in two systems, Vela X-1 and 4U1700-37, high-resolution UV
spectra are available; for Cyg X-1, SMC X-1, and LMC X-4 low-resolution spectra
are used. In order to account for the non-monotonic velocity structure of the
stellar wind, a modified version of the Sobolev Exact Integration (SEI) method
by Lamers et al. (1987) is applied. The orbital modulation of the UV resonance
lines provides information on the size of the Stroemgren zone surrounding the
X-ray source. The amplitude of the observed orbital modulation (known as the
Hatchett-McCray effect), however, also depends on the density- and velocity
structure of the ambient wind. Model profiles are presented that illustrate the
effect on the appearance of the HM effect by varying stellar-wind parameters.
The q parameter of Hatchett & McCray (1977), as well as other parameters
describing the supergiant's wind structure, are derived for the 5 systems. The
X-ray luminosity needed to create the observed size of the Stroemgren zone is
consistent with the observed X-ray flux. The derived wind parameters are
compared to those determined in single OB supergiants of similar spectral type.
Our models naturally explain the observed absence of the HM effect in
4U1700-37. The orbital modulation in Vela X-1 indicates that besides the
Stroemgren zone other structures are present in the stellar wind (such as a
photo-ionization wake). The ratio of the wind velocity and the escape velocity
is found to be lower in OB supergiants in HMXBs than in single OB supergiants
of the same effective temperature.Comment: 29 pages, good quality figures 11, 12, 13, A2 & B1 available upon
request from JvL. Accepted for publication in Astronomy & Astrophysic
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