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Enhanced Rates of Fast Radio Bursts from Galaxy Clusters
Fast Radio Bursts (FRBs) have so far been detected serendipitously across the
sky. We consider the possible enhancement in the FRB rate in the direction of
galaxy clusters, and compare the predicted rate from a large sample of galaxy
clusters to the expected cosmological mean rate. We show that clusters offer
better prospects for a blind survey if the faint end of the FRB luminosity
function is steep. We find that for a telescope with a beam of ~1 deg^2, the
best targets would be either nearby clusters such as Virgo or clusters at
intermediate cosmological distances of few hundred Mpc, which offer maximal
number of galaxies per beam. We identify several galaxy clusters which have a
significant excess FRB yield compared to the cosmic mean. The two most
promising candidates are the Virgo cluster containing 1598 galaxies and located
16.5 Mpc away and S34 cluster which contains 3175 galaxies and is located at a
distance of 486 Mpc
Radio pulsar populations
The goal of this article is to summarize the current state of play in the
field of radio pulsar statistics. Simply put, from the observed sample of
objects from a variety of surveys with different telescopes, we wish to infer
the properties of the underlying sample and to connect these with other
astrophysical populations (for example supernova remnants or X-ray binaries).
The main problem we need to tackle is the fact that, like many areas of
science, the observed populations are often heavily biased by a variety of
selection effects. After a review of the main effects relevant to radio
pulsars, I discuss techniques to correct for them and summarize some of the
most recent results. Perhaps the main point I would like to make in this
article is that current models to describe the population are far from complete
and often suffer from strong covariances between input parameters. That said,
there are a number of very interesting conclusions that can be made concerning
the evolution of neutron stars based on current data. While the focus of this
review will be on the population of isolated Galactic pulsars, I will also
briefly comment on millisecond and binary pulsars as well as the pulsar content
of globular clusters and the Magellanic Clouds.Comment: 16 pages, 6 figures, to appear in Proceedings of ICREA Workshop on
The High-Energy Emission from Pulsars and their Systems, Sant Cugat, Spain,
2010 April 12-16 (Springer
Transient radio bursts from rotating neutron stars
The `radio sky' is relatively unexplored for transient signals, although the
potential of radio-transient searches is high, as demonstrated recently by the
discovery of a previously unknown type of source which varies on timescales of
minutes to hours. Here we report a new large-scale search for radio sources
varying on much shorter timescales. This has revealed 11 objects characterized
by single, dispersed bursts having durations between 2 and 30 ms. The average
time intervals between bursts range from 4 minutes to 3 hours, with radio
emission typically detectable for < 1 s per day. From an analysis of the burst
arrival times, we have identified periodicities in the range 0.4 - 7 s for ten
of the 11 sources, suggesting a rotating neutron star origin. Despite the small
number of sources presently detected, their ephemeral nature implies a total
Galactic population which significantly exceeds that of the regularly pulsing
radio pulsars. Five of the ten sources have periods greater than 4 s, and
period derivatives have been measured for three of the sources, with one having
a very high inferred magnetic field of 5e13 G, suggesting that this new
population is related to other classes of isolated neutron stars observed at
X-ray and gamma-ray wavelengths.Comment: 10 pages, 4 figures. Accepted by Natur
Binary and Millisecond Pulsars at the New Millennium
We review the properties and applications of binary and millisecond pulsars.
Our knowledge of these exciting objects has greatly increased in recent years,
mainly due to successful surveys which have brought the known pulsar population
to over 1300. There are now 56 binary and millisecond pulsars in the Galactic
disk and a further 47 in globular clusters. This review is concerned primarily
with the results and spin-offs from these surveys which are of particular
interest to the relativity community.Comment: 59 pages, 26 figures, 5 tables. Accepted for publication in Living
Reviews in Relativity (http://www.livingreviews.org
Physics of Neutron Star Kicks
It is no longer necessary to `sell' the idea of pulsar kicks, the notion that
neutron stars receive a large velocity (a few hundred to a thousand km
s) at birth. However, the origin of the kicks remains mysterious. We
review the physics of different kick mechanisms, including hydrodynamically
driven, neutrino and magnetically driven kicks.Comment: 8 pages including 1 figure. To be published in "Stellar Astrophysics"
(Pacific Rim Conference Proceedings), (Kluwer Pub.
Young neutron stars with soft gamma ray emission and anomalous X-ray pulsar
The observational properties of Soft Gamma Repeaters and Ano\-malous X-ray
Pulsars (SGR/AXP) indicate to necessity of the energy source different from a
rotational energy of a neutron star. The model, where the source of the energy
is connected with a magnetic field dissipation in a highly magnetized neutron
star (magnetar) is analyzed. Some observational inconsistencies are indicated
for this interpretation. The alternative energy source, connected with the
nuclear energy of superheavy nuclei stored in the nonequilibrium layer of low
mass neutron star is discussed.Comment: 29 pages, 13 figures, Springer International Publishing Switzerland
2016 A.W. Alsabti, P. Murdin (eds.), Handbook of Supernova
Binary and Millisecond Pulsars
We review the main properties, demographics and applications of binary and
millisecond radio pulsars. Our knowledge of these exciting objects has greatly
increased in recent years, mainly due to successful surveys which have brought
the known pulsar population to over 1700. There are now 80 binary and
millisecond pulsars associated with the disk of our Galaxy, and a further 103
pulsars in 24 of the Galactic globular clusters. Recent highlights have been
the discovery of the first ever double pulsar system and a recent flurry of
discoveries in globular clusters, in particular Terzan 5.Comment: 77 pages, 30 figures, available on-line at
http://www.livingreviews.org/lrr-2005-
Unique White Dwarfs Accompanying Recycled Pulsars
I introduce the two classes of pulsar, white-dwarf binaries, and describe for
each what we have learned from a specific system, PSR J1012+5307 and PSR
B0655+64, respectively, summarising what has been done, presenting new results,
and discussing what the future may hold. Briefly, for the companion of PSR
J1012+5307 we find a DA spectrum, and infer a mass of about 0.16Msun, the
lowest among all spectroscopically identified white dwarfs. Combined with a
radial-velocity orbit, a neutron-star mass between 1.5 and 3.2Msun (95% conf.)
is derived. The companion of PSR B0655+64 shows strong Swan C2 bands, i.e., it
is a DQ star. Unlike anything reported for other DQs, however, it shows
variations in strength of the bands by a factor two. Most likely, the
variations are periodic, with a period of about 9.7h. This is substantially
shorter than the 1-day orbital period, which can likely be understood in terms
of its past evolution.Comment: 6 pages of text and 2 figures, LaTeX using crckapb.sty (included) and
psfig.sty. To appear in Proc. 10th European Workshop on white dwarfs (Eds.
Isern, Hernanz, & Garcia-Berro
Transient pulsed radio emission from a magnetar
Anomalous X-ray pulsars (AXPs) are slowly rotating neutron stars with very
bright and highly variable X-ray emission that are believed to be powered by
ultra-strong magnetic fields of >1e14 G, according to the 'magnetar' model. The
radio pulsations that have been observed from more than 1,700 neutron stars
with weaker magnetic fields have never been detected from any of the dozen
known magnetars. The X-ray pulsar XTE J1810-197 was revealed (in 2003) as the
first AXP with transient emission when its luminosity increased 100-fold from
the quiescent level; a coincident radio source of unknown origin was detected
one year later. Here we show that XTE J1810-197 emits bright, narrow, highly
linearly polarized radio pulses, observed at every rotation, thereby
establishing that magnetars can be radio pulsars. There is no evidence of radio
emission before the 2003 X-ray outburst (unlike ordinary pulsars, which emit
radio pulses all the time), and the flux varies from day to day. The flux at
all radio frequencies is approximately equal -- and at >20 GHz XTE J1810-197 is
currently the brightest neutron star known. These observations link magnetars
to ordinary radio pulsars, rule out alternative accretion models for AXPs, and
provide a new window into the coronae of magnetars.Comment: accepted by Nature; some new data and significantly revised
discussio
Should young people be paid for getting tested? A national comparative study to evaluate patient financial incentives for chlamydia screening
<p>Abstract</p> <p>Background</p> <p>Patient financial incentives ("incentives") have been widely used to promote chlamydia screening uptake amongst 15-24 year olds in England, but there is scarce evidence of their effectiveness. The objectives of the study were to describe incentives used to promote chlamydia screening in Primary Care Trusts (PCTs) in England and to evaluate their impact on coverage and positivity rate.</p> <p>Methods</p> <p>PCTs that had used incentives between 1/1/2007 and 30/6/2009 (exposed) were matched by socio-demographic profile and initial screening coverage with PCTs that had not (unexposed). For each PCT, percentage point change in chlamydia screening coverage and positivity for the period before and during the incentive was calculated. Differences in average change of coverage and positivity rate between exposed and unexposed PCTs were compared using linear regression to adjust for matching and potential confounders.</p> <p>Results</p> <p>Incentives had a significant effect in increasing average coverage in exposed PCTs (0.43%, CI 0.04%-0.82%). The effect for voucher schemes (2.35%) was larger than for prize draws (0.16%). The difference was greater in females (0.73%) than males (0.14%). The effect on positivity rates was not significant (0.07%, CI -1.53% to 1.67%).</p> <p>Conclusions</p> <p>Vouchers, but not prize draws, led to a small absolute but large relative increase in chlamydia screening coverage. Incentives increased coverage more in females than males but had no impact on reported positivity rates. These findings support recommendations not to use prize draws to promote chlamydia screening and contribute to the evidence base of the operational effectiveness of using patient incentives in encouraging public health action.</p
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