675 research outputs found
HD 85567: A Herbig B[e] star or an interacting B[e] binary
Context. HD 85567 is an enigmatic object exhibiting the B[e] phenomenon, i.e.
an infrared excess and forbidden emission lines in the optical. The object's
evolutionary status is uncertain and there are conflicting claims that it is
either a young stellar object or an evolved, interacting binary.
Aims. To elucidate the reason for the B[e] behaviour of HD 85567, we have
observed it with the VLTI and AMBER.
Methods. Our observations were conducted in the K-band with moderate spectral
resolution (R~1500, i.e. 200 km/s). The spectrum of HD 85567 exhibits Br gamma
and CO overtone bandhead emission. The interferometric data obtained consist of
spectrally dispersed visibilities, closure phases and differential phases
across these spectral features and the K-band continuum.
Results. The closure phase observations do not reveal evidence of asymmetry.
The apparent size of HD 85567 in the K-band was determined by fitting the
visibilities with a ring model. The best fitting radius, 0.8 +/- 0.3 AU, is
relatively small making HD 85567 undersized in comparison to the
size-luminosity relationship based on YSOs of low and intermediate luminosity.
This has previously been found to be the case for luminous YSOs, and it has
been proposed that this is due to the presence of an optically thick gaseous
disc. We demonstrate that the differential phase observations over the CO
bandhead emission are indeed consistent with the presence of a compact (~1 AU)
gaseous disc interior to the dust sublimation radius.
Conclusions. The observations reveal no sign of binarity. However, the data
do indicate the presence of a gaseous disc interior to the dust sublimation
radius. We conclude that the data are consistent with the hypothesis that HD
85567 is a YSO with an optically thick gaseous disc within a larger dust disc
that is being photo-evaporated from the outer edge.Comment: Accepted for publication in A &
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&
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
TB9: Newcastle Disease Virus Activity and Volume of Amniotic Allantoic Fluid in Chicken Embryos from Flocks with Different Vaccination Histories
Breeding hens of similar age, 9 to 11 months old, were selected from four flocks, each with a different vaccination history. One flock received no vaccinations, the second received spray and wing web Newcastle disease (ND) vaccine, the third was given three ND dust vaccinations, and the fourth received two dead ND viral vaccinations.https://digitalcommons.library.umaine.edu/aes_techbulletin/1191/thumbnail.jp
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&
THE RECOVERY OF FISSION PRODUCT RARE EARTH SULFATES FROM PUREX 1WW
Cerium- and 144 promethium-147, accompanied by rare earths resulting from fission or decay can be removed from Purex 1WW in>90% yield as an insoluble, crystalline sodium-rare earth double sulfate. Precipitation is initiated by a one-to-three hour equilibration at 90 deg C and centrifugation at 90 deg C to take advantage of the lower solubility of the double sulfate salt at a higher temperature. The sulfate concentration should be one molar and the solution pH at the time of precipitation should be 0.5 to 1.5. The addition of tartrate ion to complex the iron allows the use of a higher pH and sulfate concentration, gives a more complete separation from iron, and a quantitative recovery of the rare earths. The double sulfate precipitate can be dissolved in dilute nitric acid or converted to the carbonate and then dissolved to yield a solution for further processing. The double sulfate precipitation of the rare earths, with tartrate added, gives a good separation from impurities. One-cycle decontamination factors of 150 for Zr-Nb and 1100 for Ru-Rh have been achieved in laboratory tests. Tests in the Purex head-end equipment with up to twomegacurie batches of cerium have corroborated the laboratory results. Decontamination factors of 70 for iron, 10 for zirconium, 20 for niobium and 25 for ruthenium have been obtained. It was found wise to limit the batch size because decay heat leads to partial calcination in the centrifuge and to difficulty in redissolution. (auth
TB42: The Mycotoxic Effects of Fungi Isolated from Poultry Feed Ingredients: The Response of Ducklings and Performance of Commercial Broiler Chickens Fed Experimentally Infected Corn Diets
The present work, planned to investigate the possibility of mycotoxins occurring in feed ingredients fed to poultry in Maine, was designed with the following objectives: (1) to isolate fungi from poultry feed ingredients; (2) to grow the m separately on corn (the carbohydrate source of poultry rations) for later mixing into the diets; (3) to test the variously infected lots of this corn substrate for mycotoxicity by feeding ducklings, a bioindicator for toxins; (4) to determine the effects of aflatoxin and other mycotoxins from feed ingredients, on the performance of commercial broiler chickens; and (5) to appraise this response as a measure of toxicity of the fungi found in feed ingredients.https://digitalcommons.library.umaine.edu/aes_techbulletin/1159/thumbnail.jp
Tracers of Discs and Winds around Intermediate and High Mass Young Stellar Objects
We present a study of the kinematical properties of a small sample of nearby
near-infrared bright massive and intermediate mass young stellar objects using
emission lines sensitive to discs and winds. We show for the first time that
the broad (kms) symmetric line wings on the HI Brackett series
lines are due to Stark broadening or electron scattering, rather than pure
Doppler broadening due to high speed motion. The results are consistent with
the presence of a very dense circumstellar environment. In addition, many of
these lines show evidence for weak line self-absorption, suggestive of a wind
or disc-wind origin for that part of the absorbing material. The weakness of
the self-absorption suggests a large opening angle for such an outflow. We also
study the fluorescent 1.688m FeII line, which is sensitive to dense
material. We fitted a Keplerian disc model to this line, and find reasonable
fits in all bar one case, in agreement with previous finding for classical Be
stars that fluorescent iron transitions are reasonable disc tracers. Overall
the picture is one in which these stars still have accretion discs, with a very
dense inner circumstellar environment which may be tracing either the inner
regions of a disc, or of a stellar wind, and in which ionised outflow is also
present. The similarity with lower mass stars is striking, suggesting that at
least in this mass range they form in a similar fashion.Comment: 20 pages, 7 figures, accepted for publication in MNRA
Probing the properties of Be star discs with spectroastrometry and NLTE radiative transfer modelling: beta CMi
While the presence of discs around classical Be stars is well established,
their origin is still uncertain. To understand what processes result in the
creation of these discs and how angular momentum is transported within them,
their physical properties must be constrained. This requires comparing high
spatial and spectral resolution data with detailed radiative transfer
modelling. We present a high spectral resolution, R~80,000, sub milli-arcsecond
precision, spectroastrometric study of the circumstellar disc around the Be
star beta CMi. The data are confronted with three-dimensional, NLTE radiative
transfer calculations to directly constrain the properties of the disc.
Furthermore, we compare the data to disc models featuring two velocity laws;
Keperian, the prediction of the viscous disc model, and angular momentum
conserving rotation. It is shown that the observations of beta CMi can only be
reproduced using Keplerian rotation. The agreement between the model and the
observed SED, polarisation and spectroastrometric signature of beta CMi
confirms that the discs around Be stars are well modelled as viscous decretion
discs.Comment: Accepted for publication in MNRA
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