18,916 research outputs found
13 Years of Timing of PSR B1259-63
This paper summarizes the results of 13 years of timing observations of a
unique binary pulsar, PSR B125963, which has a massive B2e star companion.
The data span encompasses four complete orbits and includes the periastron
passages in 1990, 1994, 1997 and 2000. Changes in dispersion measure occurring
around the 1994, 1997 and 2000 periastrons are measured and accounted for in
the timing analysis. There is good evidence for a small glitch in the pulsar
period in 1997 August, not long after the 1997 periastron, and a significant
frequency second derivative indicating timing noise. We find that spin-orbit
coupling with secular changes in periastron longitude and projected semi-major
axis () cannot account for the observed period variations over the whole
data set. While fitting the data fairly well, changes in pulsar period
parameters at each periastron seem ruled out both by X-ray observations and by
the large apparent changes in pulsar frequency derivative. Essentially all of
the systematic period variations are accounted for by a model consisting of the
1997 August glitch and step changes in at each periastron. These changes
must be due to changes in the orbit inclination, but we can find no plausible
mechanism to account for them. It is possible that timing noise may mask the
actual changes in orbital parameters at each periastron, but the good fit to
the data of the step-change model suggests that short-term timing noise is
not significant.Comment: 9 pages, 7 figures, accepted by MNRA
3D UK? 3D History and the Absent British Pioneers
The recent television ârediscoveryâ of a small cohort of 1950s British 3D films (and the producers who made them) has offered a new route into considering how the historical stories told about 3D film have focused almost exclusively on the American experience, eliding other national contexts. This article challenges both the partiality of existing academic histories of 3D, and the specific popular media narratives that have been constructed around the British 3D pioneers. Offering a rebuttal of those narratives and an expansion of them based around primary archival research, the article considers how the British 3D company Stereo Techniques created a different business and production model based around non-fiction short 3D films that stand in contrast to the accepted view of 3D as an American feature film novelty. Through an exploration of the depiction (and absence) of these 3D pioneers from existing media histories, the article argues for a revision to both 3D studies and British cinema history
A Search for Radio Emission from the Young 16-ms X-ray Pulsar PSR J0537-6910
PSR J0537-6910 is a young, energetic, rotation-powered X-ray pulsar with a
spin period of 16 ms located in the Large Magellanic Cloud. We have searched
for previously undetected radio pulsations (both giant and standard) from this
pulsar in a 12-hour observation taken at 1400 MHz with the Parkes 64-m radio
telescope. The very large value of the magnetic field at the light cylinder
radius suggests that this pulsar might be emitting giant radio pulses like
those seen in other pulsars with similar field strengths. No radio emission of
either kind was detected from the pulsar, and we have established an upper
limit of ~ 25 mJy kpc^2 for the average 1400-MHz radio luminosity of PSR
J0537-6910. The 5-sigma single-pulse detection threshold was ~ 750 mJy for a
single 80-us sample. These limits are likely to be the best obtainable until
searches with greatly improved sensitivity can be made with next-generation
radio instruments.Comment: 4 pages, including 1 figure and 2 tables. Accepted for publication in
Advances in Space Research; Proceedings of Session E1.4 of the 35th COSPAR
Scientific Assembly, Paris, July 18-25 2004, "Young Neutron Stars and
Supernova Remnants", edited by C. Rakowski and S. Chatterje
Interactive Software for Guitar Learning
In this paper we present software designed to help address problems encountered by beginning guItarists, using interactive software to find effective solutions to enhance the learning process. Software can be utilised to improve a player's ability tdhear mistakes in theIr performance, as well as to create a fun and entertaining learning environment 'to motivate the player to practice. A software prototype ~~s been developed, which served as a basIs for usabllzty testmg, to highlight the usefulness of vari~us methods of feedback and provide a way forward in developing valuable software for guitar tuition
Flight Crew Health Stabilization Program
This document establishes the policy and procedures for the HSP and is authorized through the Director, Johnson Space Center (JSC). This document delineates the medical operations requirements for the HSP. The HSP goals are accomplished through an awareness campaign and procedures such as limiting access to flight crewmembers, medical screening, and controlling flight crewmember activities. NASA's Human Space Flight Program uses strategic risk mitigation to achieve mission success while protecting crew health and safety. Infectious diseases can compromise crew health and mission success, especially in the immediate preflight period. The primary purpose of the Flight Crew Health Stabilization Program (HSP) is to mitigate the risk of occurrence of infectious disease among astronaut flight crews in the immediate preflight period. Infectious diseases are contracted through direct person-to-person contact, and through contact with infectious material in the environment. The HSP establishes several controls to minimize crew exposure to infectious agents. The HSP provides a quarantine environment for the crew that minimizes contact with potentially infectious material. The HSP also limits the number of individuals who come in close contact with the crew. The infection-carrying potential of these primary contacts (PCs) is minimized by educating them in ways to avoid infections and avoiding contact with the crew if they are or may be sick. The transmission of some infectious diseases can be greatly curtailed by vaccinations. PCs are strongly encouraged to maintain updated vaccinations
Simulation and optimisation of terahertz emission from InGaAs and InP photoconductive switches
We simulate the terahertz emission from laterally-biased InGaAs and InP using
a three-dimensional carrier dynamics model in order to optimise the
semiconductor material. Incident pump-pulse parameters of current Ti:Sapphire
and Er:fibre lasers are chosen, and the simulation models the semiconductor's
bandstructure using parabolic Gamma, L and X valleys, and heavy holes. The
emitted terahertz radiation is propagated within the semiconductor and into
free space using a model based on the Drude-Lorentz dielectric function. As the
InGaAs alloy approaches InAs an increase in the emitted power is observed, and
this is attributed to a greater electron mobility. Additionally,
low-temperature grown and ion-implanted InGaAs are modelled using a finite
carrier trapping time. At sub-picosecond trapping times the terahertz bandwidth
is found to increase significantly at the cost of a reduced emission power.Comment: 9 pages, 7 figure
The evolving relation between star-formation rate and stellar mass in the VIDEO Survey since
We investigate the star-formation rate (SFR) and stellar mass ()
relation of a star-forming (SF) galaxy sample in the XMM-LSS field to using the near-infrared data from the VISTA Deep Extragalactic
Observations (VIDEO) survey. Combining VIDEO with broad-band photometry, we use
the SED fitting algorithm CIGALE to derive SFRs and and have adapted it
to account for the full photometric redshift PDF uncertainty. Applying a SF
selection using the D4000 index, we find evidence for strong evolution in the
normalisation of the SFR- relation out to and a roughly constant
slope of (SFR ) to . We
find this increases close to unity toward . Alternatively, if we
apply a colour selection, we find a distinct turnover in the SFR- relation
between at the high mass end, and suggest that this
is due to an increased contamination from passive galaxies. We find evolution
of the specific SFR at 10.5, out to
with an observed flattening beyond 2 with increased
stellar mass. Comparing to a range of simulations we find the analytical
scaling relation approaches, that invoke an equilibrium model, a good fit to
our data, suggesting that a continual smooth accretion regulated by continual
outflows may be a key driver in the overall growth of SFGs.Comment: 19 pages, 18 figures, accepted for publication in MNRA
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