13,765 research outputs found
Gravitational Microlensing by Neutron Stars and Radio Pulsars: Event Rates, Timescale Distributions, and Mass Measurements
We investigate properties of Galactic microlensing events in which a stellar
object is lensed by a neutron star. For an all-sky photometric microlensing
survey, we determine the number of lensing events caused by
potentially-observable radio pulsars to be for
background stellar sources. We expect a few detectable events per
year for the same number of background sources from an astrometric microlensing
survey. We show that such a study could lead to precise measurements of radio
pulsar masses. For instance, if a pulsar distance could be constrained through
radio observations, then its mass would be determined with a precision of
. We also investigate the time-scale distributions for neutron star
events, finding that they are much shorter than had been previously thought.
For photometric events towards the Galactic centre that last days,
around will have a neutron star lens. This fraction drops rapidly for
longer time-scales. Away from the bulge region we find that neutron stars will
contribute of the events that last less than days. These
results are in contrast to earlier work which found that the maximum fraction
of neutron star events would occur on time-scales of hundreds of days.Comment: 10 pages, accepted for publication in ApJ. v2 updated to reflect
change of title in proof stag
An intermediate distribution between Gaussian and Cauchy distributions
In this paper, we construct an intermediate distribution linking the Gaussian
and the Cauchy distribution. We provide the probability density function and
the corresponding characteristic function of the intermediate distribution.
Because many kinds of distributions have no moment, we introduce weighted
moments. Specifically, we consider weighted moments under two types of weighted
functions: the cut-off function and the exponential function. Through these two
types of weighted functions, we can obtain weighted moments for almost all
distributions. We consider an application of the probability density function
of the intermediate distribution on the spectral line broadening in laser
theory. Moreover, we utilize the intermediate distribution to the problem of
the stock market return in quantitative finance.Comment: 16 pages, 7 figure
4-Cyanoanilinium perchlorate
The title compound, C7H7N2
+·ClO4
−, comprises discrete ions which are interconnected by N—H⋯O hydrogen bonds, leading to a neutral one-dimensional network along the [100] direction
Identification of the white dwarf companion to millisecond pulsar J2317+1439
We report identification of the optical counterpart to the companion of the
millisecond pulsar J2317+1439. At the timing position of the pulsar, we find an
object with , and . The
magnitudes and colors of the object are consistent with it being a white dwarf.
By comparing with white dwarf cooling models, we estimate that it has a mass of
M, an effective temperature of
K and a cooling age of Gyr. Combining our
results with published constraints on the orbital parameters obtained through
pulsar timing, we estimate the pulsar mass to be
M. Although the constraint on the pulsar mass is still weak, there is
a significant possibility that the pulsar could be more massive than two solar
mass.Comment: 7 pages, 6 figures, accepted for publication in Ap
A cyclical period variation detected in the updated orbital period analysis of TV Columbae
The two CCD photometries of the intermediate polar TV Columbae are made for
obtaining the two updated eclipse timings with high precision. There is an
interval time \sim 17yr since the last mid-eclipse time observed in 1991. Thus,
the new mid-eclipse times can offer an opportunity to check the previous
orbital ephemerides. A calculation indicates that the orbital ephemeris derived
by Augusteijn et al. (1994) should be corrected. Based on the proper linear
ephemeris (Hellier, 1993), the new orbital period analysis suggests a cyclical
period variation in the O-C diagram of TV Columbae. Using Applegate's mechanism
to explain the periodic oscillation in O-C diagram, the required energy is
larger than that a M0-type star can afford over a complete variation period
\sim 31.0(\pm 3.0)yr. Thus, the light travel-time effect indicates that the
tertiary component in TV Columbae may be a dwarf with a low mass, which is near
the mass lower limit \sim 0.08Msun as long as the inclination of the third body
high enough.Comment: 10 pages, 5 figure
Search for a Radio Pulsar in the Remnant of Supernova 1987A
We have observed the remnant of supernova SN~1987A (SNR~1987A), located in
the Large Magellanic Cloud (LMC), to search for periodic and/or transient radio
emission with the Parkes 64\,m-diameter radio telescope. We found no evidence
of a radio pulsar in our periodicity search and derived 8 upper bounds
on the flux density of any such source of Jy at 1.4~GHz and
Jy at 3~GHz. Four candidate transient events were detected with
greater than significance, with dispersion measures (DMs) in the
range 150 to 840\,cmpc. For two of them, we found a second pulse at
slightly lower significance. However, we cannot at present conclude that any of
these are associated with a pulsar in SNR~1987A. As a check on the system, we
also observed PSR~B054069, a young pulsar which also lies in the LMC. We
found eight giant pulses at the DM of this pulsar. We discuss the implications
of these results for models of the supernova remnant, neutron star formation
and pulsar evolution.Comment: 7 pages, 3 figures, 2 tables. Accepted for publication in MNRA
A Data-augmented 3D Morphable Model of the Ear
Morphable models are useful shape priors for biometric recognition tasks. Here we present an iterative process of refinement for a 3D Morphable Model (3DMM) of the human ear that employs data augmentation. The process employs the following stages 1) landmark-based 3DMM fitting; 2) 3D template deformation to overcome noisy over-fitting; 3) 3D mesh editing, to improve the fit to manual 2D landmarks. These processes are wrapped in an iterative procedure that is able to bootstrap a weak, approximate model into a significantly better model. Evaluations using several performance metrics verify the improvement of our model using the proposed algorithm. We use this new 3DMM model-booting algorithm to generate a refined 3D morphable model of the human ear, and we make this new model and our augmented training dataset public
Compact electric-LC resonators for metamaterials
Alternative designs to an electric-LC (ELC) resonator, which is a type of
metamaterial inclusion, are presented in this article. Fitting the resonator
with an interdigital capacitor (IDC) helps to increase the total capacitance of
the structure. In effect, its resonance frequency is shifted downwards. This
implies a decreased overall resonator size with respect to its operating
wavelength. As a result, the metamaterial, composed of an array of IDC-loaded
ELC resonators with their collective electromagnetic response, possesses
improved homogeneity and hence is less influenced by diffraction effects of
individual cells. The impact of incorporating an IDC into ELC resonators in
terms of the electrical size at resonance and other relevant properties are
investigated through both simulation and experiment.Comment: 5 pages, 5 figure
- …