4,627 research outputs found
Development of an evaluation technique for strapdown guidance systems Interim scientific report
Evaluation technique to measure performance of strapdown guidance systems designed for unmanned interplanetary mission
SEASAT B orbit synthesis
Addition were made to Battelle's Interactive Graphics Orbit Selection (IGOS) program; IGOS was exercised via telephone lines from JPL, and candidate SEASAT orbits were analyzed by Battelle. The additions to the program enable clear understanding of the implications of a specific orbit to the diverse desires of the SEASAT user community
Spin frequency distributions of binary millisecond pulsars
Rotation-powered millisecond radio pulsars have been spun up to their present
spin period by a - yr long X-ray-bright phase of accretion of
matter and angular momentum in a low-to-intermediate mass binary system.
Recently, the discovery of transitional pulsars that alternate cyclically
between accretion and rotation-powered states on time scales of a few years or
shorter, has demonstrated this evolutionary scenario. Here, we present a
thorough statistical analysis of the spin distributions of the various classes
of millisecond pulsars to assess the evolution of their spin period between the
different stages. Accreting sources that showed oscillations exclusively during
thermonuclear type I X-ray bursts (nuclear-powered millisecond pulsars) are
found to be significantly faster than rotation-powered sources, while accreting
sources that possess a magnetosphere and show coherent pulsations (accreting
millisecond pulsars) are not. On the other hand, if accreting millisecond
pulsars and eclipsing rotation-powered millisecond pulsars form a common class
of transitional pulsars, these are shown to have a spin distribution
intermediate between the faster nuclear-powered millisecond pulsars and the
slower non-eclipsing rotation-powered millisecond pulsars. We interpret these
findings in terms of a spin-down due to the decreasing mass-accretion rate
during the latest stages of the accretion phase, and in terms of the different
orbital evolutionary channels mapped by the various classes of pulsars. We
summarize possible instrumental selection effects, showing that even if an
unbiased sample of pulsars is still lacking, their influence on the results of
the presented analysis is reduced by recent improvements in instrumentation and
searching techniques.Comment: Accepted for publication in A&A (6 pages, 4 figures
Comparing supernova remnants around strongly magnetized and canonical pulsars
The origin of the strong magnetic fields measured in magnetars is one of the
main uncertainties in the neutron star field. On the other hand, the recent
discovery of a large number of such strongly magnetized neutron stars, is
calling for more investigation on their formation. The first proposed model for
the formation of such strong magnetic fields in magnetars was through
alpha-dynamo effects on the rapidly rotating core of a massive star. Other
scenarios involve highly magnetic massive progenitors that conserve their
strong magnetic moment into the core after the explosion, or a common envelope
phase of a massive binary system. In this work, we do a complete re-analysis of
the archival X-ray emission of the Supernova Remnants (SNR) surrounding
magnetars, and compare our results with all other bright X-ray emitting SNRs,
which are associated with Compact Central Objects (CCOs; which are proposed to
have magnetar-like B-fields buried in the crust by strong accretion soon after
their formation), high-B pulsars and normal pulsars. We find that emission
lines in SNRs hosting highly magnetic neutron stars do not differ significantly
in elements or ionization state from those observed in other SNRs, neither
averaging on the whole remnants, nor studying different parts of their total
spatial extent. Furthermore, we find no significant evidence that the total
X-ray luminosities of SNRs hosting magnetars, are on average larger than that
of typical young X-ray SNRs. Although biased by a small number of objects, we
found that for a similar age, there is the same percentage of magnetars showing
a detectable SNR than for the normal pulsar population.Comment: 16 pages, 5 figures, Accepted for publication in MNRA
Gamma-ray upper limits on magnetars with 6 years of Fermi-LAT observations
We report on the search for gamma-ray emission from 20 magnetars using 6
years of Fermi, Large Area Telescope (LAT) observations. No significant
evidence for gamma-ray emission from any of the currently-known magnetars is
found. We derived the most stringent upper limits to date on the 0.1--10 GeV
emission of Galactic magnetars, which are estimated between
erg s cm. Gamma-ray pulsations were
searched for the four magnetars having reliable ephemerides over the observing
period, but none were detected. On the other hand, we also studied the
gamma-ray morphology and spectra of seven Supernova Remnants associated or
adjacent to the magnetars.Comment: 22 pages, 4 figures, 2 tables, submitted to Ap
The emotional contagion in children with autism spectrum disorder
Studies of the last decade have demonstrated that children with Autism
Spectrum Disorder (ASD) showed difficulties in language, social and relational
areas, but they had also impairment in the mechanisms of embodied simulation,
namely the imitative behaviors that allow the body to give an experiential
meaning to own and other’s emotions. The identification of this specific emotional
response in ASD children, also defined as emotional contagion, allows to move
the therapeutic focus from reducing the behavioral symptomatic expressions of
the child to promoting the expression of his ability of emotional regulation. The
aim of this study was to investigate the presence of emotional contagion in 53
ASD children aged between 22 and 66 months, through the Test of emotional
contagion and verify the presence of compromised emotional contagion areas.
Our findings have shown that the severity of the disorder is closely related to
the inability of the child to respond to the emotional stimuli, regardless from
cognitive abilities, and that emotion to which children responded most frequently
was happiness, while the one who responded less was anger
A magnetic thrust action on small bodies orbiting a pulsar
We investigate the electromagnetic interaction of a relativistic stellar wind
with small bodies in orbit around the star. Based on our work on the theory of
Alfv\'en wings to relativistic winds presented in a companion paper, we
estimate the force exerted by the associated current system on orbiting bodies
and evaluate the resulting orbital drift. This Alfv\'enic structure is found to
have no significant influence on planets or smaller bodies orbiting a
millisecond pulsar. %influence on the orbit of bodies around a millisecond
pulsar. On the timescale of millions of years, it can however affect the orbit
of bodies with a diameter of 100 kilometres around standard pulsars with a
period 1 s and a magnetic field T. Kilometer-sized
bodies experience drastic orbital changes on a timescale of years.Comment: accepted for publication in "Astronomy and Astrophysics
Gamma-ray emission from PSR J0007+7303 using 7 years of Fermi Large Area Telescope observations
Based on more than seven years of Fermi Large Area Telescope (LAT) Pass 8
data, we report on a detailed analysis of the bright gamma-ray pulsar (PSR)
J0007+7303. We confirm that PSR J0007+7303 is significantly detected as a point
source also during the off-peak phases with a TS value of 262 ( 16
). In the description of PSR J0007+7303 off-peak spectrum, a power law
with an exponential cutoff at 2.71.21.3 GeV (the first/second
uncertainties correspond to statistical/systematic errors) is preferred over a
single power law at a level of 3.5 . The possible existence of a cutoff
hints at a magnetospheric origin of the emission. In addition, no extended
gamma-ray emission is detected compatible with either the supernova remnant
(CTA 1) or the very high energy (> 100 GeV) pulsar wind nebula. A flux upper
limit of 6.510 erg cm s in the 10-300 GeV energy
range is reported, for an extended source assuming the morphology of the
VERITAS detection. During on-peak phases, a sub-exponential cutoff is
significantly preferred (11 ) for representing the spectral
energy distribution, both in the phase-averaged and in the phase-resolved
spectra. Three glitches are detected during the observation period and we found
no flux variability at the time of the glitches or in the long-term behavior.
We also report the discovery of a previously unknown gamma-ray source in the
vicinity of PSR J0007+7303, Fermi J0020+7328, which we associate with the z =
1.781 quasar S5 0016+73. A concurrent analysis of this source is needed to
correctly characterize the behavior of CTA 1 and it is also presented in the
paper.Comment: 26 pages, 10 figures, 4 tables; Accepted for publication in Ap
From the emotional integration to the cognitive construction: the developmental approach of Turtle Project in children with autism spectrum disorder
Background: Children with autism spectrum disorder show a deficit in neurobiological processes. This deficit
hinders the development of intentional behavior and appropriate problem-solving, leading the child to implement
repetitive and stereotyped behaviors and to have difficulties in reciprocal interactions, empathy and in the
development of a theory of mind. The objective of this research is to verify the effectiveness of a relationship-based
approach on the positive evolution of autistic symptoms.
Method: A sample of 80 children with autism spectrum disorder was monitored during the first four years of
therapy, through a clinical diagnostic assessment at the time of intake and then in two follow-up.
Results: The results showed that through the Autism Diagnostic Observation Schedule it is possible to
assess the socio-relational key elements on which the therapy is based. There was evidence, in fact, of significant
improvements after two and four years of therapy, both for children with severe autistic symptoms and for those in
autistic spectrum.
Conclusions: Socio-relational aspects represent the primary element on which work in therapy with autistic
children and can be considered as indicators of a positive evolution and prognosis that will produce improvements
even in the cognitive are
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