2,670 research outputs found
An investigation of pulsar searching techniques with the Fast Folding Algorithm
Here we present an in-depth study of the behaviour of the Fast Folding
Algorithm, an alternative pulsar searching technique to the Fast Fourier
Transform. Weaknesses in the Fast Fourier Transform, including a susceptibility
to red noise, leave it insensitive to pulsars with long rotational periods (P >
1 s). This sensitivity gap has the potential to bias our understanding of the
period distribution of the pulsar population. The Fast Folding Algorithm, a
time-domain based pulsar searching technique, has the potential to overcome
some of these biases. Modern distributed-computing frameworks now allow for the
application of this algorithm to all-sky blind pulsar surveys for the first
time. However, many aspects of the behaviour of this search technique remain
poorly understood, including its responsiveness to variations in pulse shape
and the presence of red noise. Using a custom CPU-based implementation of the
Fast Folding Algorithm, ffancy, we have conducted an in-depth study into the
behaviour of the Fast Folding Algorithm in both an ideal, white noise regime as
well as a trial on observational data from the HTRU-S Low Latitude pulsar
survey, including a comparison to the behaviour of the Fast Fourier Transform.
We are able to both confirm and expand upon earlier studies that demonstrate
the ability of the Fast Folding Algorithm to outperform the Fast Fourier
Transform under ideal white noise conditions, and demonstrate a significant
improvement in sensitivity to long-period pulsars in real observational data
through the use of the Fast Folding Algorithm.Comment: 19 pages, 15 figures, 3 table
Limits on the Mass, Velocity and Orbit of PSR J19336211
We present a high-precision timing analysis of PSR J19336211, a
millisecond pulsar (MSP) with a 3.5-ms spin period and a white dwarf (WD)
companion, using data from the Parkes radio telescope. Since we have accurately
measured the polarization properties of this pulsar we have applied the matrix
template matching approach in which the times of arrival are measured using
full polarimetric information. We achieved a weighted root-mean-square timing
residuals (rms) of the timing residuals of 1.23 , 15.5
improvement compared to the total intensity timing analysis. After studying the
scintillation properties of this pulsar we put constraints on the inclination
angle of the system. Based on these measurements and on mapping we put
a 2- upper limit on the companion mass (0.44 M). Since this
mass limit cannot reveal the nature of the companion we further investigate the
possibility of the companion to be a He WD. Applying the orbital period-mass
relation for such WDs, we conclude that the mass of a He WD companion would be
about 0.260.01 M which, combined with the measured mass function
and orbital inclination limits, would lead to a light pulsar mass
1.0 M. This result seems unlikely based on current neutron star
formation models and we therefore conclude that PSR J19336211 most likely
has a CO WD companion, which allows for a solution with a more massive pulsar
XY checkerboard antiferromagnet in external field
Ordering by thermal fluctuations is studied for the classical XY
antiferromagnet on a checkerboard lattice in zero and finite magnetic fields by
means of analytical and Monte Carlo methods. The model exhibits a variety of
novel broken symmetries including states with nematic ordering in zero field
and with triatic order parameter at high fields.Comment: 6 page
The Microscopic Approach to Nuclear Matter and Neutron Star Matter
We review a variety of theoretical and experimental investigations aimed at
improving our knowledge of the nuclear matter equation of state. Of particular
interest are nuclear matter extreme states in terms of density and/or isospin
asymmetry. The equation of state of matter with unequal concentrations of
protons and neutrons has numerous applications. These include heavy-ion
collisions, the physics of rare, short-lived nuclei and, on a dramatically
different scale, the physics of neutron stars. The "common denominator" among
these (seemingly) very different systems is the symmetry energy, which plays a
crucial role in both the formation of the neutron skin in neutron-rich nuclei
and the radius of a neutron star (a system 18 orders of magnitude larger and 55
orders of magnitude heavier). The details of the density dependence of the
symmetry energy are not yet sufficiently constrained. Throughout this article,
our emphasis will be on the importance of adopting a microscopic approach to
the many-body problem, which we believe to be the one with true predictive
power.Comment: 56 pages, review article to appear in the International Journal of
Modern Physics
Discovery of 59ms Pulsations from 1RXS J141256.0+792204 (Calvera)
We report on a multi-wavelength study of the compact object candidate 1RXS
J141256.0+792204 (Calvera). Calvera was observed in the X-rays with XMM/EPIC
twice for a total exposure time of ~50 ks. The source spectrum is thermal and
well reproduced by a two component model composed of either two hydrogen
atmosphere models, or two blackbodies (kT_1~ 55/150 eV, kT_2~ 80/250 eV,
respectively, as measured at infinity). Evidence was found for an absorption
feature at ~0.65 keV; no power-law high-energy tail is statistically required.
Using pn and MOS data we discovered pulsations in the X-ray emission at a
period P=59.2 ms. The detection is highly significant (> 11 sigma), and
unambiguously confirms the neutron star nature of Calvera. The pulse profile is
nearly sinusoidal, with a pulsed fraction of ~18%. We looked for the timing
signature of Calvera in the Fermi Large Area Telescope (LAT) database and found
a significant (~5 sigma) pulsed signal at a period coincident with the X-ray
value. The gamma-ray timing analysis yielded a tight upper limit on the period
derivative, dP/dt < 5E-18 s/s (dE_rot/dt <1E33 erg/s, B<5E10 G for magneto-
dipolar spin-down). Radio searches at 1.36 GHz with the 100-m Effelsberg radio
telescope yielded negative results, with a deep upper limit on the pulsed flux
of 0.05 mJy. Diffuse, soft (< 1 keV) X-ray emission about 13' west of the
Calvera position is present both in our pointed observations and in archive
ROSAT all-sky survey images, but is unlikely associated with the X-ray pulsar.
Its spectrum is compatible with an old supernova remnant (SNR); no evidence for
diffuse emission in the radio and optical bands was found. The most likely
interpretations are that Calvera is either a central compact object escaped
from a SNR or a mildly recycled pulsar; in both cases the source would be the
first ever member of the class detected at gamma-ray energies.Comment: 20 pages, 15 figures and 4 tables. Accepted for publication in MNRA
Dust from Mars-Analog Plains (Iceland): Physico-Compositional Properties as a Function of Grain-Size Fraction
Dust is a key component of the geological and climatic systems of Earth and Mars. On Mars, dust is ubiquitous. It coats rocks and soils, and, in the atmosphere, it interacts strongly with solar and thermal radiation. Yet, key questions remain about the genesis and fate of martian dust, as well as its sources, composition, and properties. We collected wind-blown dust from basaltic plains in SW Iceland at Skjaldbreiauhraun that represent a geologic Mars-analog environment. Icelandic dust differs from the typical continental sources (e.g. Sahara, Asia) because of its basaltic volcanogenic origin, which is similar to Mars. Dust collection took place in July of 2019 as a complementary project to the SAND-E: Semi-Autonomous Navigation for Detrital Environments project. Here we report preliminary analyses of this Mars-analog dust material, with the goal of understanding the processes that control the physico-chemical proper-ties of the different grain-size fractions
The GBT350 Survey of the Northern Galactic Plane for Radio Pulsars and Transients
Using the Green Bank Telescope (GBT) and Pulsar Spigot at 350MHz, we have
surveyed the Northern Galactic Plane for pulsars and radio transients. This
survey covers roughly 1000 square degrees of sky within 75 deg < l < 165 deg
and |b| < 5.5 deg, a region of the Galactic Plane inaccessible to both the
Parkes and Arecibo multibeam surveys. The large gain of the GBT along with the
high time and frequency resolution provided by the Spigot make this survey more
sensitive by factors of about 4 to slow pulsars and more than 10 to millisecond
pulsars (MSPs), compared with previous surveys of this area. In a preliminary,
reduced-resolution search of all the survey data, we have discovered 33 new
pulsars, almost doubling the number of known pulsars in this part of the
Galaxy. While most of these sources were discovered by normal periodicity
searches, 5 of these sources were first identified through single, dispersed
bursts. We discuss the interesting properties of some of these new sources.
Data processing using the data's full-resolution is ongoing, with the goal of
uncovering MSPs missed by our first, coarse round of processing.Comment: To appear in the proceedings of "Forty Years of Pulsars: Millisecond
Pulsars, Magnetars and More" held in Montreal, Canada, August 12-17, 2007. 3
pages, 2 figure
Acceptance and commitment therapy for symptom interference in metastatic breast cancer patients: a pilot randomized trial
PURPOSE:
Breast cancer is the leading cause of cancer mortality in women worldwide. With medical advances, metastatic breast cancer (MBC) patients often live for years with many symptoms that interfere with activities. However, there is a paucity of efficacious interventions to address symptom-related suffering and functional interference. Thus, this study examined the feasibility and preliminary efficacy of telephone-based acceptance and commitment therapy (ACT) for symptom interference with functioning in MBC patients.
METHODS:
Symptomatic MBC patients (N = 47) were randomly assigned to six telephone sessions of ACT or six telephone sessions of education/support. Patients completed measures of symptom interference and measures assessing the severity of pain, fatigue, sleep disturbance, depressive symptoms, and anxiety.
RESULTS:
The eligibility screening rate (64%) and high retention (83% at 8 weeks post-baseline) demonstrated feasibility. When examining within-group change, ACT participants showed decreases in symptom interference (i.e., fatigue interference and sleep-related impairment; Cohen's d range = - 0.23 to - 0.31) at 8 and 12 weeks post-baseline, whereas education/support participants showed minimal change in these outcomes (d range = - 0.03 to 0.07). Additionally, at 12 weeks post-baseline, ACT participants showed moderate decreases in fatigue and sleep disturbance (both ds = - 0.43), whereas education/support participants showed small decreases in these outcomes (ds = - 0.24 and - 0.18 for fatigue and sleep disturbance, respectively). Both the ACT and education/support groups showed reductions in depressive symptoms (ds = - 0.27 and - 0.28) at 12 weeks post-baseline. Group differences in all outcomes were not statistically significant.
CONCLUSIONS:
ACT shows feasibility and promise in improving fatigue and sleep-related outcomes in MBC patients and warrants further investigation
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