143 research outputs found
Pulsar data analysis with PSRCHIVE
PSRCHIVE is an open-source, object-oriented, scientific data analysis
software library and application suite for pulsar astronomy. It implements an
extensive range of general-purpose algorithms for use in data calibration and
integration, statistical analysis and modeling, and visualisation. These are
utilised by a variety of applications specialised for tasks such as pulsar
timing, polarimetry, radio frequency interference mitigation, and pulse
variability studies. This paper presents a general overview of PSRCHIVE
functionality with some focus on the integrated interfaces developed for the
core applications.Comment: 21 pages, 5 figures; tutorial presented at IPTA 2010 meeting in
Leiden merged with talk presented at 2011 pulsar conference in Beijing;
includes further research and development on algorithms for RFI mitigation
and TOA bias correctio
Relativistic spin precession in the binary PSR J11416545
PSR J11416545 is a precessing binary pulsar that has the rare potential to
reveal the two-dimensional structure of a non-recycled pulsar emission cone. It
has undergone of relativistic spin precession in the
years since its discovery. In this paper, we present a detailed Bayesian
analysis of the precessional evolution of the width of the total intensity
profile, to understand the changes to the line-of-sight impact angle ()
of the pulsar using four different physically motivated prior distribution
models. Although we cannot statistically differentiate between the models with
confidence, the temporal evolution of the linear and circular polarisations
strongly argue that our line-of-sight crossed the magnetic pole around MJD
54000 and that only two models remain viable. For both these models, it appears
likely that the pulsar will precess out of our line-of-sight in the next
years, assuming a simple beam geometry. Marginalising over suggests
that the pulsar is a near-orthogonal rotator and provides the first
polarization-independent estimate of the scale factor () that
relates the pulsar beam opening angle () to its rotational period ()
as : we find it to be at 1.4
GHz with 99\% confidence. If all pulsars emit from opposite poles of a dipolar
magnetic field with comparable brightness, we might expect to see evidence of
an interpulse arising in PSR J11416545, unless the emission is patchy.Comment: Accepted for publication in Astrophysical Journal Letter
The importance of early diagnosis and treatment of obstructive sleep apnoea in patients with cardiovascular diseases
Obstructive sleep apnoea (OSA) is one of the most common sleep-related breathing disorders. New epidemiological studies show that the disease is much more prevalent in the general population than previously believed. Individuals with cardiovascular diseases are a special group of patients suffering from OSA as the prevalence of the disorder among them is much greater than in the general population, and it can constitute an isolated risk factor for the development of some cardiovascular diseases. This article will discuss methods for diagnosing OSA, its epidemiology among patients with particular cardiovascular diseases and the prospects for the development of screening examinations
Waga wczesnego rozpoznania i leczenia obturacyjnego bezdechu podczas snu w grupie pacjentów obciążonych kardiologicznie
Obturacyjny bezdech podczas snu (OSA) jest jednym z najczęściej występujących zaburzeń oddychania we śnie. Nowe badania epidemiologiczne wskazują na dużo większe rozpowszechnienie schorzenia w ogólnej populacji niż wcześniej sądzono. Szczególną grupą chorych są pod tym względem pacjenci obciążeni chorobą układu sercowo-naczyniowego, wśród których OSa występuje zdecydowanie częściej niż w ogólnej populacji oraz może stanowić izolowany czynnik ryzyka rozwoju niektórych schorzeń kardiologicznych. W artykule omówiono metody diagnostyki OSA, epidemiologię w poszczególnych schorzeniach kardiologicznych oraz perspektywy rozwoju badań przesiewowych.Obturacyjny bezdech podczas snu (OSA) jest jednym z najczęściej występujących zaburzeń oddychania we śnie. Nowe
badania epidemiologiczne wskazują na dużo większe rozpowszechnienie schorzenia w ogólnej populacji niż wcześniej
sądzono. Szczególną grupą chorych są pod tym względem pacjenci obciążeni chorobą układu sercowo-naczyniowego,
wśród których OSa występuje zdecydowanie częściej niż w ogólnej populacji oraz może stanowić izolowany czynnik
ryzyka rozwoju niektórych schorzeń kardiologicznych. W artykule omówiono metody diagnostyki OSA, epidemiologię
w poszczególnych schorzeniach kardiologicznych oraz perspektywy rozwoju badań przesiewowych
Long Term Variability of a Black Widow's Eclipses -- A Decade of PSR J20510827
In this paper we report on years of observations of PSR
J20510827, at radio frequencies in the range 110--4032 MHz. We investigate
the eclipse phenomena of this black widow pulsar using model fits of increased
dispersion and scattering of the pulsed radio emission as it traverses the
eclipse medium. These model fits reveal variability in dispersion features on
timescales as short as the orbital period, and previously unknown trends on
timescales of months--years. No clear patterns are found between the
low-frequency eclipse widths, orbital period variations and trends in the
intra-binary material density. Using polarisation calibrated observations we
present the first available limits on the strength of magnetic fields within
the eclipse region of this system; the average line of sight field is
constrained to be G G, while for the
case of a field directed near-perpendicular to the line of sight we find
G. Depolarisation of the linearly polarised pulses
during the eclipse is detected and attributed to rapid rotation measure
fluctuations of rad m along, or across,
the line of sights averaged over during a sub-integration. The results are
considered in the context of eclipse mechanisms, and we find scattering and/or
cyclotron absorption provide the most promising explanation, while dispersion
smearing is conclusively ruled out. Finally, we estimate the mass loss rate
from the companion to be yr,
suggesting that the companion will not be fully evaporated on any reasonable
timescale
Five new real-time detections of Fast Radio Bursts with UTMOST
We detail a new fast radio burst (FRB) survey with the Molonglo Radio
Telescope, in which six FRBs were detected between June 2017 and December 2018.
By using a real-time FRB detection system, we captured raw voltages for five of
the six events, which allowed for coherent dedispersion and very high time
resolution (10.24 s) studies of the bursts. Five of the FRBs show temporal
broadening consistent with interstellar and/or intergalactic scattering, with
scattering timescales ranging from 0.16 to 29.1 ms. One burst, FRB181017, shows
remarkable temporal structure, with 3 peaks each separated by 1 ms. We searched
for phase-coherence between the leading and trailing peaks and found none,
ruling out lensing scenarios. Based on this survey, we calculate an all-sky
rate at 843 MHz of events sky day to a fluence
limit of 8 Jy-ms: a factor of 7 below the rates estimated from the Parkes and
ASKAP telescopes at 1.4 GHz assuming the ASKAP-derived spectral index
(). Our results suggest that FRB
spectra may turn over below 1 GHz. Optical, radio and X-ray followup has been
made for most of the reported bursts, with no associated transients found. No
repeat bursts were found in the survey.Comment: 13 pages, 11 figures, submitted to MNRA
Timing analysis for 20 millisecond pulsars in the Parkes Pulsar Timing Array
We present timing models for 20 millisecond pulsars in the Parkes Pulsar
Timing Array. The precision of the parameter measurements in these models has
been improved over earlier results by using longer data sets and modelling the
non-stationary noise. We describe a new noise modelling procedure and
demonstrate its effectiveness using simulated data. Our methodology includes
the addition of annual dispersion measure (DM) variations to the timing models
of some pulsars. We present the first significant parallax measurements for
PSRs J1024-0719, J1045-4509, J1600-3053, J1603-7202, and J1730-2304, as well as
the first significant measurements of some post-Keplerian orbital parameters in
six binary pulsars, caused by kinematic effects. Improved Shapiro delay
measurements have resulted in much improved pulsar mass measurements,
particularly for PSRs J0437-4715 and J1909-3744 with
and respectively. The improved orbital
period-derivative measurement for PSR J0437-4715 results in a derived distance
measurement at the 0.16% level of precision, pc, one of the
most fractionally precise distance measurements of any star to date.Comment: 21 pages, 5 figures, 7 tables. Accepted for publication in MNRA
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