7,640 research outputs found
AMBER and CRIRES observations of the binary sgB[e] star HD 327083: evidence of a gaseous disc traced by CO bandhead emission
HD 327083 is a sgB[e] star that forms a binary system with an orbital
semi-major axis of ~1.7 AU. Our previous observations using the VLTI and AMBER
in the medium resolution K-band mode spatially resolved the environment of HD
327083. The continuum visibilities obtained indicate the presence of a
circumbinary disc. CO bandhead emission was also observed. However, due to the
limited spectral resolution of the previous observations, the kinematic
structure of the emitting material was not constrained. In this paper, we
address this and probe the source of the CO emission with high spectral
resolution and spatial precision. We have observed HD 327083 with high spectral
resolution (25 & 6 km/s) using AMBER and CRIRES. The observations are compared
to kinematical models to constrain the source of the emission. It is shown that
the CO bandhead emission can be reproduced using a model of a Keplerian disc
with an inclination and size consistent with our previous VLTI observations.
The model is compared to AMBER differential phase measurements, which have a
precision as high as 30-micro-arcseconds. A differential phase signal
corresponding to 0.15 milli-arcseconds (~5 sigma) is seen over the bandhead
emission, which is in excellent agreement with the model that fits the CRIRES
observations. In comparison, a model of an equatorial outflow, as envisaged in
the standard sgB[e] scenario, does not reproduce the observations well. The
excellent agreement between the disc model and observations in the spatial and
spectral domains is compelling evidence that the CO bandhead emission of HD
327083 originates in a circumbinary Keplerian disc. In contrast, the model of
an equatorial outflow cannot reproduce the observations well. This suggests
that the standard sgB[e] scenario is not applicable to HD 327083, which
supports the hypothesis that the B[e] behaviour of HD 327083 is due to binarity
(ABRIDGED).Comment: Accepted for publication in A&
M Theory As A Matrix Model: A Conjecture
We suggest and motivate a precise equivalence between uncompactified eleven
dimensional M-theory and the N = infinity limit of the supersymmetric matrix
quantum mechanics describing D0-branes. The evidence for the conjecture
consists of several correspondences between the two theories. As a consequence
of supersymmetry the simple matrix model is rich enough to describe the
properties of the entire Fock space of massless well separated particles of the
supergravity theory. In one particular kinematic situation the leading large
distance interaction of these particles is exactly described by supergravity .
The model appears to be a nonperturbative realization of the holographic
principle. The membrane states required by M-theory are contained as
excitations of the matrix model. The membrane world volume is a noncommutative
geometry embedded in a noncommutative spacetime.Comment: Typo and tex error corrected. 41 pages, harvma
Probing discs around massive young stellar objects with CO first overtone emission
We present high resolution (R~50,000) spectroastrometry over the CO 1st
overtone bandhead of a sample of seven intermediate/massive young stellar
objects. These are primarily drawn from the red MSX source (RMS) survey, a
systematic search for young massive stars which has returned a large, well
selected sample of such objects. The mean luminosity of the sample is
approximately 5 times 10^4 L_\odot, indicating the objects typically have a
mass of ~15 solar masses. We fit the observed bandhead profiles with a model of
a circumstellar disc, and find good agreement between the models and
observations for all but one object. We compare the high angular precision
(0.2-0.8 mas) spectroastrometric data to the spatial distribution of the
emitting material in the best-fitting models. No spatial signatures of discs
are detected, which is entirely consistent with the properties of the
best-fitting models. Therefore, the observations suggest that the CO bandhead
emission of massive young stellar objects originates in small-scale disks, in
agreement with previous work. This provides further evidence that massive stars
form via disc accretion, as suggested by recent simulations.Comment: Accepted for publication in MNRA
VLTI/AMBER observations of the binary B[e] supergiant HD 327083
HD 327083 is a luminous B type star which exhibits emission lines and an
infrared excess and is therefore classified as a supergiant B[e] star. In
addition, the star is the primary of a close binary system. It is not clear
whether the B[e] behaviour of HD 327083 is related to its binarity or its
evolutionary state. Here we address this issue by studying its circumstellar
environment with high spatial resolution. To this end, we have observed HD
327083 with the VLTI and AMBER in the medium resolution K-band setting. 13CO
bandhead emission is detected, confirming HD 327083 is a post-main sequence
object. The observations spatially resolve the source of the NIR continuum and
the Br-gamma and CO line emission. In addition, differential phase measurements
allow us to probe the origin of the observed Br-gamma emission with sub-mas
precision. Using geometrical models, we find that the visibilities and closure
phases suggest that the close binary system is surrounded by a circum-binary
disk. We also find that in the case of the binary HD 327083, the relative sizes
of the continuum and Br-gamma emitting regions are different to those of a
single supergiant B[e] star where the standard dual outflow scenario is thought
to apply. These findings are consistent with the hypothesis that the mass loss
of HD 327083 is related to its binary nature.Comment: Accepted in A&
Docetaxel (Taxotere): an active agent in metastatic urothelial cancer; results of a phase II study in non-chemotherapy-pretreated patients.
The semisynthetic taxoid docetaxel was investigated in a phase II study in non-chemotherapy pretreated patients with metastatic urothelial cell cancer. Thirty patients (median age 61, range 45-72) were treated with docetaxel 100 mg m(-2) administered as a 1-h infusion every 3 weeks. Of 29 evaluable patients, four achieved a complete response and five a partial response, for an overall response rate of 31%. The median duration of response was 6 months (range 4-51+). A total of 104 cycles were administered. The median number of cycles given was three (range 1-9). Toxic effects of docetaxel mainly consisted of neutropenia, which, however, rarely caused infectious complications (5%). Fluid retention or neuropathy necessitated treatment cessation in two patients. We conclude that docetaxel is an effective agent in urothelial cell cancer, and should be further tested in combination chemotherapy
A mid-IR interferometric survey with MIDI/VLTI: resolving the second-generation protoplanetary disks around post-AGB binaries
We present a mid-IR interferometric survey of the circumstellar environment
of a specific class of post-Asymptotic Giant Branch (post-AGB) binaries. For
this class the presence of a compact dusty disk has been postulated on the
basis of various spatially unresolved measurements. Our interferometric survey
was performed with the MIDI instrument on the VLTI. In total 19 different
systems were observed using variable baseline configurations. Combining all the
visibilities at a single wavelength at 10.7 micron, we fitted two parametric
models to the data: a uniform disk (UD) and a ring model mimicking a
temperature gradient. We compared our observables of the whole sample, with
synthetic data computed from a grid of radiative transfer models of passively
irradiated disks in hydrostatic equilibrium. These models are computed with a
Monte Carlo code that has been widely applied to describe the structure of
protoplanetary disks around young stellar objects (YSO). The spatially resolved
observations show that the majority of our targets cluster closely together in
the distance-independent size-colour diagram, and have extremely compact N-band
emission regions. The typical uniform disk diameter of the N-band emission
region is about 40 mass which corresponds to a typical brightness temperature
of 400-600~K. The resolved objects display very similar characteristics in the
interferometric observables and in the spectral energy distributions.
Therefore, the physical properties of the disks around our targets must be
similar. The grid of protoplanetary disk models covers very well the observed
objects. Much like for young stars, the spatially resolved N-band emission
region is determined by the hot inner rim of the disk. Continued comparisons
between post-AGB and protoplanetary disks will help to understand grain growth
and disk evolution processes,Comment: 30 pages, 21 figures, in press in Astronomy and Astrophysic
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