31,958 research outputs found
Solid state morphology and band gap studies of ETS-10 supported CdS nanoparticles
Engelhard titanosilicate (ETS-10) supported cadmium sulphide (CdS) nanoparticles were synthesized and characterized by various solid state techniques including: XRD, DR UV-Vis, TEM and FESEM. The effect of different synthesis routes of CdS nanoparticles on its physicochemical character was studied. It was observed that CdS nanoparticles prepared by both in situ sulphur reduction (CdS-IS) and reverse micelle (CdS-RM) methods showed similar properties. However, CdS-IS nanoparticles are more feasible and economically practical. The reflectance measurements of the as-synthesized CdS nanoparticles are apparently blue-shifted compared to bulk CdS. This phenomenon of blue-shifted absorption edge has been ascribed to an increase in bandgap energy with a decrease in particle sizes. The bandgap of the as-synthesized CdS samples was calculated from the linear correlation of [F(R) h?]2 and h?. The bandgap of CdS in ETS-10 was noticeably slightly reduced when compared with the as-synthesized CdS (8 nm) due to the formation of cluster arrays on the pores of ETS-10
High Magnetic Field Rotation-powered Pulsars
Anomalous X-ray pulsars and soft gamma repeaters have recently emerged as a
unified class of neutron stars, identified by dramatic X-ray and gamma-ray
outbursts and via luminous X-ray pulsations, both thought to be powered by the
decay of an enormous internal magnetic field. This "magnetar" hypothesis has
raised the question of these objects' physical relationship with conventional
rotation-powered pulsars (RPPs). The highest magnetic-field RPPs might
therefore be expected to be transition objects between the two populations. The
recently reported magnetar-like outburst of PSR J1846-0258, previously thought
to be purely rotation-powered, clearly supports this suggestion. Here we review
the observational properties of the highest magnetic-field RPPs known, and show
some common characteristics that are notable among RPPs, which are plausibly
related to their high fields. Using these objects, we consider the evidence for
proposed "magneto-thermal evolution" in neutron stars, and argue that while
some exists, it is not yet conclusive.Comment: 6 pages, 4 figures, Conference proceeding of "ASTROphysics of Neutron
Stars 2010 -- a conference in honor of M. Ali Alpar", 2-6 August 2010, Cesme,
Izmir, Turke
Data catalog series for space science and applications flight missions. Volume 4A: Descriptions of meteorological and terrestrial applications spacecraft and investigations
The National Space Science Data Center (NSSDC) provides data from and information about space science and applications flight investigations in support of additional studies beyond those performed as the principal part of any flight mission. The Earth-orbiting spacecraft for investigations of the earth and its atmosphere is discussed. Geodetic tracking data are included in this category. The principal subject areas presented are meteorology and earth resources survey, and the spacecraft selection is made according to those subjects. All experiments on board the spacecraft are described. No attempt is made to reference investigations that are related to the above disciplines, but that are described in other volumes of this series
Fermi Variability Study of the Candidate Pulsar Binary 2FGL~J0523.3-2530
The Fermi source 2FGL~J0523.32530 has recently been identified as a
candidate millisecond pulsar binary with an orbital period of 16.5 hrs. We have
carried out detailed studies of the source's emission properties by analyzing
data taken with the Fermi Large Area Telescope in the 0.2--300 GeV energy
range. Long-term, yearly variability from the source has been found, with a
factor of 4 flux variations in 1--300 GeV. From spectral analysis, we find an
extra spectral component at 2--3 GeV that causes the source brightening. While
no orbital modulations have been found from the Fermi data over the whole
period of 2008--2014, orbital modulation in the source's 2 GeV emission is
detected during the last 1.5 yrs of the Fermi observation. Our results support
the millisecond pulsar binary nature of 2FGL~J0523.32530. Multi-wavelength
observations of the source are warranted in order to find any correlated flux
variations and thus help determine the origin of the long-term variability,
which currently is not understood.Comment: 8 pages, 5 figures, comments from Referee were incorporated, accepted
for publication in Ap
Fitting Pulsar Wind Tori. II. Error Analysis and Applications
We have applied the torus fitting procedure described in Ng & Romani (2004)
to PWNe observations in the Chandra data archive. This study provides
quantitative measurement of the PWN geometry and we characterize the
uncertainties in the fits, with statistical errors coming from the fit
uncertainties and systematic errors estimated by varying the assumed fitting
model. The symmetry axis of the PWN are generally well determined, and
highly model-independent. We often derive a robust value for the spin
inclination . We briefly discuss the utility of these results in
comparison with new radio and high energy pulse measurementsComment: 15 pages, 3 figures, ApJ in pres
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