1,238 research outputs found
Water vapor and silicon monoxide maser observations in the protoplanetary nebula OH 231.8+4
OH 231.8+4.2 is a well studied preplanetary nebula (pPN) around a binary
stellar system that shows a remarkable bipolar outflow. To study the structure
and kinematics of the inner 10-80 AU nebular regions we performed
high-resolution observations of the HO 6--5 and SiO
=2, =1--0 maser emissions with the Very Long Baseline Array. The absolute
position of both emission distributions were recovered using the phase
referencing technique, and accurately registered in HST optical images. HO
maser clumps are found to be distributed in two areas of 20 mas in size
spatially displaced by 60 milli-arcseconds along an axis oriented nearly
north-south. SiO masers are tentatively found to be placed between the two
HO maser emitting regions, probably indicating the position of the Mira
component of the system. The SiO maser emission traces an inner equatorial
component with a diameter of 12 AU, probably a disk rotating around the M-type
star. Outwards, we detect in the HO data a pair of polar caps, separated by
80 AU. We believe that the inner regions of the nebula probably have been
altered by the presence of the companion, leading to an equator-to-pole density
contrast that may explain the lack of HO masers and strong SiO maser
emission in the denser, equatorial regions.Comment: 5 pages, 1 figure, A&A accepte
Recent developments in the eikonal description of the breakup of exotic nuclei
The study of exotic nuclear structures, such as halo nuclei, is usually
performed through nuclear reactions. An accurate reaction model coupled to a
realistic description of the projectile is needed to correctly interpret
experimental data. In this contribution, we briefly summarise the assumptions
made within the modelling of reactions involving halo nuclei. We describe
briefly the Continuum-Discretised Coupled Channel method (CDCC) and the
Dynamical Eikonal Approximation (DEA) in particular and present a comparison
between them for the breakup of 15C on Pb at 68AMeV. We show the problem faced
by the models based on the eikonal approximation at low energy and detail a
correction that enables their extension down to lower beam energies. A new
reaction observable is also presented. It consists of the ratio between angular
distributions for two different processes, such as elastic scattering and
breakup. This ratio is completely independent of the reaction mechanism and
hence is more sensitive to the projectile structure than usual reaction
observables, which makes it a very powerful tool to study exotic structures far
from stability.Comment: Contribution to the proceedings of the XXI International School on
Nuclear Physics and Applications & the International Symposium on Exotic
Nuclei, dedicated to the 60th Anniversary of the JINR (Dubna) (Varna,
Bulgaria, 6-12 September 2015), 7 pages, 4 figure
Relative astrometry of the J=1-0, v=1 and v=2 SiO masers towards R Leonis Minoris using VERA
Oxygen-rich Asymptotic Giant Branch (AGB) stars are intense emitters of SiO
and HO maser lines at 43 (J=1-0, v=1 and 2) and 22 GHz, respectively. VLBI
observations of the maser emission provides a unique tool to sample the
innermost layers of the circumstellar envelopes in AGB stars. Nevertheless, the
difficulties in achieving astrometrically aligned v=1 and v=2 SiO maser maps
have traditionally prevented a unique interpretation of the observations in
terms of physical underlying conditions, which depend on the nature of the SiO
pumping mechanism.
We have carried out observations of the SiO and HO maser emission towards
RLMi, using the astrometric capabilities of VERA. Due to the too-weak emission
of the reference calibrator we had to develop a special method to accurately
relate the coordinates for both transitions. We present relative
astrometrically aligned v=1 and v=2 J=1-0 SiO maser maps, at multiple epochs,
and discuss the astrophysical results. The incorporation of astrometric
information into the maps of SiO masers challenges the weak points in the
current theoretical models, which will need further refinements to address the
observations results.Comment: 17 pages, 8 figure
Relationships between fat depots and body condition score or tail fatness in Rasa Aragonesa breed
The relationships between body fat depots and body condition score (BCS) were determined in 52 adult
Rasa Aragonesa ewes aged 10 (s.d. 2) years and ranging in BCS from 1-5 to 4•5. BCS of each ewe was
assessed by three people. the repeatability within individual being 90"/0 and between individuals 80%.
The ewes were weighed before slaughter. After slaughter the omental mesenteric kidney and pelvic fat
were separated and weighed. The fat of the left side of the carcass was separated into subcutaneous and
intermuscular depots. The relationship between live weight and BCS was semilogarithmic and those
between fat depots and BCS were logarithmic. Regression analysis was also used to describe the
relationships between the various fat depots and BCS or live weight Of the variation in total fat weight.
proportionately 0•90 was accounted for by variations in BCS while 0•84 was accounted for by variations
in live weight. For individual fat depots proportionately 0•86 to 0•90 of the variation was accounted for
by variation in BCS and 0•69 to 0-79 by variation in live weight. BCS was a better predictor than live
weight of the weight of both total body fat and the individual fat depots.
A curvilinear regression between BCS and live weight showed that the increases in live weight for a
unit change in BCS was 7, 10, 12 and 16 kg for each one point increase ill BCS from 1 to 5
respectively.
The tail fat depot (tail fatness score) •Was assessed in the same ewes by score on a three-point scale.
Of the variation in the weight of individual fat depots proportionately 0•79 to 0•86 was accounted for
by variation in tail fatness score. Thus the tail fatness score could be used as an additional method of
assessing body condition in the Aragonesa breed
A note on the use of a lumbar joint as a predictor of body fat depots in Aragonesa ewes with different body confition scores
The lumbar joint, which is handled to assess body condition scores, was taken from 52 adult Rasa Aragonesa ewes with body condition scores between 1·5 and 4·5 and dissected into muscle, bone, subcutaneous and intermuscular fat. The subcutaneous fat in the lumbar joint was highly correlated with total fat in the body (r=0·97), confirming the value of this region for assessing body condition in Rasa Aragonesa ewes
Astrometry of circumstellar masers
The circumstellar masers around evolved stars offer an interesting
possibility to measure stellar parameters through VLBI astrometry. In this
paper the application of this technique is discussed, including the accuracy
and the uncertainties of the method. The different maser species (OH, H_2O,
SiO) have slightly different characteristics and applications. This paper does
not concern astrometry of maser spots to study the kinematics of the envelope,
but concentrates on attempting to measure the motion of the underlying star.Comment: 8 pages, 2 figures, to appear in "Mass-losing Stars and their
Circumstellar Matter", eds Y. Nakada & M. Honma, Kluwer ASSL serie
- …