1,180 research outputs found
Evidence for dust accumulation just outside the orbit of Venus
To contribute to the knowledge of dynamics of interplanetary dust we are
searching for structures in the spatial distribution of interplanetary dust
near the orbit of Venus. To this end we study the radial gradient of zodiacal
light brightness, as observed by the zodiacal light photometer on board the
Helios space probes on several orbits from 1975 to 1979. The cleanest data
result from Helios B (= Helios 2) launched in January 1976. With respect to the
general increase of zodiacal light brightness towards the Sun, the data show an
excess brightness of a few percent for positions of the Helios space probe just
outside the orbit of Venus. We consider this as evidence for a dust ring
associated with the orbit of Venus, somewhat similar to that found earlier
along the Earth's orbit.Comment: 7 pages, 8 figures, Astronomy&Astrophysics, accepte
Orbits and Masses in the multiple system LHS 1070
We present a study of the orbits of the triple system LHS1070, with the aim
to determine individual masses of its components.
Sixteen new relative astrometric positions of the three components in the K
band were obtained with NACO at the VLT, Omega CASS at the 3.5m telescope on
Calar Alto, and other high-spatial-resolution instruments. We combine them with
data from the literature and fit orbit models to the dataset. We derive an
improved fit for the orbit of LHS1070B and C around each other, and an estimate
for the orbit of B and C around A.
The orbits are nearly coplanar, with a misalignment angle of less than
10{\deg}. The masses of the three components are M_A = 0.13 - 0.16 Msun, M_B =
0.077+/-0.005 Msun, and M_C = 0.071+/-0.004 Msun. Therefore, LHS1070C is
certainly, and LHS1070B probably a brown dwarf. Comparison with theoretical
isochrones shows that LHS1070A is either fainter or more massive than expected.
One possible explanation would be that it is a binary. However, the close
companion reported previously could not be confirmed.Comment: 9 pages, 8 figures, accepted by Astronomy and Astrophysic
Approximation in
In order to extend the theory of well-bounded operators to include operators
with nonreal spectrum, Ashton and Doust introduced definitions for two new
algebras of functions defined on a nonempty compact subset of the
plane. These are the functions of bounded variation and the absolutely
continuous functions on . Proofs involving absolutely continuous
functions usually require that one first works with elements of a dense subset
and then take limits. In this paper we present some new theorems about
approximating absolutely continuous functions as well as providing missing
proofs for some important earlier results.Comment: 23 page
Knowledge About and Attitudes towards End of Life Care for Gay, Lesbian, Bisexual & Transgender People (Phase 2)
Increasing evidence suggests that many gay, lesbian, bisexual and transgender (GLBT) people are being denied their legal rights in their own end-of-life care and the end-of-life care of their partners and other important people in their lives. A study in the Northern Rivers region of NSW in 2009, which investigated end-of-life care issues for GLBT people and the use of legal mechanisms such as Advance Care Planning to support the rights of GLBT people at the end of life (Lienert T, Cartwright C, Beck K. 2010) found evidence of active discrimination and abuse of GLBT people. Building on the findings of the Phase 1 study, a second State-wide study funded by a grant from the Law and Justice Foundation of NSW was conducted in 2009-2010.Stage 1, which is the subject of this Report, is a state-wide hard copy and on-line survey and a series of in-depth interviews
NICMOS Images of the GG Tau Circumbinary Disk
We present deep, near-infrared images of the circumbinary disk surrounding
the pre-main-sequence binary star, GG Tau A, obtained with NICMOS aboard the
Hubble Space Telescope. The spatially resolved proto-planetary disk scatters
roughly 1.5% of the stellar flux, with a near-to-far side flux ratio of ~1.4,
independent of wavelength, and colors that are comparable to the central
source; all of these properties are significantly different from the earlier
ground-based observations. New Monte Carlo scattering simulations of the disk
emphasize that the general properties of the disk, such as disk flux, near side
to far side flux ratio and integrated colors, can be approximately reproduced
using ISM-like dust grains, without the presence of either circumstellar disks
or large dust grains, as had previously been suggested. A single parameter
phase function is fitted to the observed azimuthal variation in disk flux,
providing a lower limit on the median grain size of 0.23 micron. Our analysis,
in comparison to previous simulations, shows that the major limitation to the
study of grain growth in T Tauri disk systems through scattered light lies in
the uncertain ISM dust grain properties. Finally, we use the 9 year baseline of
astrometric measurements of the binary to solve the complete orbit, assuming
that the binary is coplanar with the circumbinary ring. We find that the
estimated 1 sigma range on disk inner edge to semi-major axis ratio, 3.2 <
Rin/a < 6.7, is larger than that estimated by previous SPH simulations of
binary-disk interactions.Comment: 40 pages, 8 postscript figures, accepted for publication in Ap
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