2,911 research outputs found
Apsidal advance in SS 433?
Context. The Galactic microquasar SS 433 launches oppositely directed jets at
speeds approximately a quarter of the speed of light. Both the speed and
direction of the jets exhibit small fluctuations. A component of the speed
variation has 13 day periodicity and the orbital phase at which its maximum
speed occurs has advanced approximately 90 degrees in 25 years. Aims. To
examine the possibility that these variations are associated with a mildly
eccentric orbit and conditions necessary to achieve this apsidal advance.
Methods. The advance of the orbital phase for maximum speed is taken to be
advance of the apses of the putative elliptical orbit. It is compared with
calculations of the effects of tides induced in the companion and also with
gravitational perturbations from the circumbinary disc. These calculations are
made in the light of recent results on the SS 433 system. Results. The 13 day
periodicity in the speed of the jets of SS 433 might be attributed to a mildly
elliptical orbit, through periodic approaches of the donor and the compact
object. Advance of the apses of such an elliptical orbit due to tidal effects
induced in a normal companion looks to be to small; if caused by the
circumbinary disc the mass of the inner regions of that disc is ~ 0.15 solar
masses.Comment: 2 pages, no figures To appear in A & A. No significant changes from
original version poste
Modeling Multi-Wavelength Stellar Astrometry. II. Determining Absolute Inclinations, Gravity Darkening Coefficients, and Spot Parameters of Single Stars with SIM Lite
We present a novel technique to determine the absolute inclination of single
stars using multi-wavelength sub-milliarcsecond astrometry. The technique
exploits the effect of gravity darkening, which causes a wavelength-dependent
astrometric displacement parallel to a star's projected rotation axis. We find
this effect is clearly detectable using SIM Lite for various giant stars and
rapid rotators, and present detailed models for multiple systems using the
REFLUX code. We also explore the multi-wavelength astrometric reflex motion
induced by spots on single stars. We find that it should be possible to
determine spot size, relative temperature, and some positional information for
both giant and nearby main-sequence stars utilizing multi-wavelength SIM Lite
data. This data will be extremely useful in stellar and exoplanet astrophysics,
as well as supporting the primary SIM Lite mission through proper
multi-wavelength calibration of the giant star astrometric reference frame, and
reduction of noise introduced by starspots when searching for extrasolar
planets.Comment: 8 pages, 7 figures, 4 tables. Accepted for publication in the
Astrophysical Journa
Imaging Findings in Two Cases of Fluoroquinolone-Induced Achilles Tendinopathy
AbstractTendonitis and tendon rupture are rare but recognized complications of fluoroquinolone therapy. Most reports of this problem have appeared in the rheumatology and pharmacology literature, and this topic has received little attention in the radiologic literature. We report two cases of fluoroquinolone-induced tendinopathy and describe their magnetic resonance (MR) and sonographic findings. Although Achilles tendinopathy is generally the result of repetitive injury, it is useful to keep other causes in mind. MR or sonographic findings of Achilles tendinopathy in a patient without history of antecedent trauma should prompt the radiologist to consider fluoroquinolone treatment as a possible causative agent
Cluster randomised triAl of PSA testing for Prostate cancer (CAP) Study: 15 year Statistical Analysis Plan:Version 1.0 13th January 2021
Developmental and Degenerative Cardiac Defects in the Taiwanese Mouse Model of Severe Spinal Muscular Atrophy
We would like to acknowledge the Microscopy and Histology Core Facility at the University of Aberdeen, Kevin Mackenzie, Debbie Wilkinson, Gillian Milne and Lucy Wight, for the use of their facilities. G.K.M. was funded by a research award from RGA awarded to S.H.P. E.S. was funded by a University of Aberdeen Elphinstone PhD Studentship and a research award from the Euan Macdonald Centre for Motor Neurone Disease Research. H.K.S. was funded by a Euan Macdonald Centre for Motor Neurone Disease Research PhD Studentship. S.H.P. is funded by Tenovus (Scotland), SMA Trust and Prinses Beatrix Spierfonds. T.H.G. is funded by SMA Trust (UK SMA Research Consortium Award), Muscular Dystrophy UK, and Anatomical Society (PhD Studentship).Peer reviewedPostprin
CAP: Cluster randomised triAl of PSA testing for Prostate cancer Statistical Analysis Plan:version 1.3 16/12/2014
CAP: Cluster randomised triAl of PSA testing for Prostate cancer Statistical Analysis Plan:version 1.5 26/07/2016
Aetiology of shame and its association with adolescent depression and anxiety: results from a prospective twin and sibling study
On a new observable for measuring the Lense-Thirring effect with Satellite Laser Ranging
In this paper we present a rather extensive error budget for the difference
of the perigees of a pair of supplementary SLR satellites aimed to the
detection of the Lense-Thirring effect.Comment: LaTex2e, 14 pages, 1 table, no figures. Some changes and additions to
the abstract, Introduction and Conclusions. References updated, typos
corrected. Equation corrected. To appear in General Relativity and
Gravitatio
KIC 4247791: A SB4 system with two eclipsing binaries (2EBs)
KIC 4247791 is an eclipsing binary observed by the Kepler satellite mission.
We wish to determine the nature of its components and in particular the origin
of a shallow dip in its Kepler light curve that previous investigations have
been unable to explain in a unique way. We analyze newly obtained
high-resolution spectra of the star using synthetic spectra based on atmosphere
models, derive the radial velocities of the stellar components from
cross-correlation with a synthetic template, and calculate the orbital
solution. We use the JKTEBOP program to model the Kepler light curve of KIC
4247791. We find KIC 4247791 to be a SB4 star. The radial velocity variations
of its four components can be explained by two separate eclipsing binaries. In
contradiction to previous photometric findings, we show that the observed
composite spectrum as well as the derived masses of all four of its components
correspond to spectral type F. The observed small dip in the light curve is not
caused by a transit-like phenomenon but by the eclipses of the second binary
system. We find evidence that KIC 4247791 might belong to the very rare
hierarchical SB4 systems with two eclipsing binaries.Comment: 6 pages, 8 figures, 2 table
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