52,504 research outputs found
Disc atmospheres and winds in X-ray binaries
We review the current status of studies of disc atmospheres and winds in low
mass X-ray binaries. We discuss the possible wind launching mechanisms and
compare the predictions of the models with the existent observations. We
conclude that a combination of thermal and radiative pressure (the latter being
relevant at high luminosities) can explain the current observations of
atmospheres and winds in both neutron star and black hole binaries. Moreover,
these winds and atmospheres could contribute significantly to the broad iron
emission line observed in these systems.Comment: Accepted for publication in Acta Polytechnica. Invited review talk at
the Vulcano Workshop 2012: "Frontier Objects in Astrophysics and Particle
Physics
A new div-curl result. Applications to the homogenization of elliptic systems and to the weak continuity of the Jacobian
In this paper a new div-curl result is established in an open set of
, , for the product of two sequences of vector-valued
functions which are bounded respectively in and
, with , and whose respectively
divergence and curl are compact in suitable spaces. We also assume that the
product converges weakly in . The key ingredient of the proof
is a compactness result for bounded sequences in , based on
the imbedding of into ( the
unit sphere of ) through a suitable selection of annuli on which
the gradients are not too high, in the spirit of De Giorgi and Manfredi. The
div-curl result is applied to the homogenization of equi-coercive systems whose
coefficients are equi-bounded in for some
\rho\textgreater{}{N-1\over 2} if N\textgreater{}2, or in if
. It also allows us to prove a weak continuity result for the Jacobian for
bounded sequences in satisfying an alternative assumption
to the -strong estimate of Brezis and Nguyen. Two examples show the
sharpness of the results
Northern European retired residents in nine southern European areas: characteristics, motivations and adjustment
During the last two decades, northern European retirement residence in the southern European sunbelt has grown strongly and its forms have rapidly changed, but standard demographic and social statistical sources provide no information about the flows, the migrants or their increasingly mobile and complex residential patterns. Considerable primary research has however recently been undertaken into the causes, conditions, experiences and consequences of international retirement migration (IRM) by investigators from Germany, Spain, Switzerland and the United Kingdom. Many collaborated when designing their studies and instruments, and all have subsequently worked together in a European Science Foundation Scientific Network.
This paper compares the findings of six systematic social surveys in (to be more precise than the title) eight regions of southern Europe and the Canary Islands: all that have tackled similar research questions with similar methods and instruments. It presents interpretations of several comparative tables compiled from their original data, with a focus on the socio-economic backgrounds, motivations and behaviour of the various migrant groups and their relationship with the host and home countries. The paper presents new findings about the typical and variant forms of IRM, and additional understanding of the heterogeneity of the retirees of different nations and in the several regions
Involved, Invisible, Ignored: The Experiences of Lesbian, Gay, Bisexual and Transgender Parents and Their Children in Our Nation's K-12 Schools
Current estimates suggest there are upwards of 7 million lesbian, gay, bisexual and transgender (LGBT) parents with dependent children in the United States, and it is likely that these numbers have been increasing over recent years. Yet little is known about the life experiences of this population of families in general and even less is know about the experiences of these families when interacting with their children's schools.This national study conducted by GLSEN in partnership with the Family Equality Council and COLAGE (Children of Lesbians and Gays Everywhere), examines and highlights the school experiences of LGBT-headed families using results from surveys of LGBT parents of children in K-12 schools and of secondary students who have LGBT parents.The study examines the family-school relationship, including family-school communication, parental involvement in school activities, parent-child discussions about school, parental role in educating school staff about LGBT families and the quality of treatment by school staff and by other members of the school community
A search for brown-dwarf like secondaries in cataclysmic variables
We present VTL/ISAAC infrared spectroscopy of a sample of short orbital
period cataclysmic variables which are candidates for harboring substellar
companions. We have detected the KI and NaI absorption lines of the companion
star in VY Aqr. The overall spectral distribution in this system is best fit
with a M9.5 type dwarf spectra, implying a distance of pc. VY Aqr
seems to fall far from the theoretical distribution of secondary star
temperatures around the orbital period minimum. Fitting of the IR spectral
energy distribution (SED) was performed by comparing the observed spectrum with
late-type templates. The application of such a spectral fitting procedure
suggests that the continuum shape in the 1.1-2.5 m spectral region in
short orbital period cataclysmic variables may be an useful indicator of the
companion spectral type. The SED fitting for RZ Leo and CU Vel suggests M5 type
dwarf companions, and distances of 340 110 and 150 50 pc,
respectively. These systems may be placed in the upper evolution branch for
short period cataclysmic variables.Comment: accepted for publication in MNRAS, 6 pages, 7 figure
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