2,075 research outputs found
Post-outburst X-ray flux and timing evolution of Swift J1822.3-1606
Swift J1822.3-1606 was discovered on 2011 July 14 by the Swift Burst Alert
Telescope following the detection of several bursts. The source was found to
have a period of 8.4377 s and was identified as a magnetar. Here we present a
phase-connected timing analysis and the evolution of the flux and spectral
properties using RXTE, Swift, and Chandra observations. We measure a spin
frequency of 0.1185154343(8) s and a frequency derivative of
at MJD 55761.0, in a timing analysis that include
significant non-zero second and third frequency derivatives that we attribute
to timing noise. This corresponds to an estimated spin-down inferred dipole
magnetic field of G, consistent with previous estimates
though still possibly affected by unmodelled noise. We find that the
post-outburst 1--10 keV flux evolution can be characterized by a
double-exponential decay with decay timescales of and
days. We also fit the light curve with a crustal cooling model which suggests
that the cooling results from heat injection into the outer crust. We find that
the hardness-flux correlation observed in magnetar outbursts also characterizes
the outburst of Swift J1822.3-1606. We compare the properties of Swift
J1822.3-1606 with those of other magnetars and their outbursts.Comment: 12 pages, 8 figures, accepted for publication in Ap
Magnetar-like Emission from the Young Pulsar in Kes 75
We report detection of magnetar-like X-ray bursts from the young pulsar PSR
J1846-0258, at the center of the supernova remnant Kes 75. This pulsar, long
thought to be rotation-powered, has an inferred surface dipolar magnetic field
of 4.9x10^13 G, higher than those of the vast majority of rotation-powered
pulsars, but lower than those of the ~12 previously identified magnetars. The
bursts were accompanied by a sudden flux increase and an unprecedented change
in timing behavior. These phenomena lower the magnetic and rotational
thresholds associated with magnetar-like behavior, and suggest that in neutron
stars there exists a continuum of magnetic activity that increases with
inferred magnetic field strength.Comment: 17 pages, 2 figures, accepted for publication in Science. Note: The
content of this paper is embargoed until February 21, 200
Red Noise in Anomalous X-ray Pulsar Timing Residuals
Anomalous X-ray Pulsars (AXPs), thought to be magnetars, exhibit poorly
understood deviations from a simple spin-down called "timing noise". AXP timing
noise has strong low-frequency components which pose significant challenges for
quantification. We describe a procedure for extracting two quantities of
interest, the intensity and power spectral index of timing noise. We apply this
procedure to timing data from three sources: a monitoring campaign of five
AXPs, observations of five young pulsars, and the stable rotator PSR B1937+21.Comment: submitted to the proceedings of the "40 Years of Pulsars" conferenc
A Survey of 56 Mid-latitude EGRET Error Boxes for Radio Pulsars
We have conducted a radio pulsar survey of 56 unidentified gamma-ray sources
from the 3rd EGRET catalog which are at intermediate Galactic latitudes (5 deg.
< |b| < 73 deg.). For each source, four interleaved 35-minute pointings were
made with the 13-beam, 1400-MHz multibeam receiver on the Parkes 64-m radio
telescope. This covered the 95% error box of each source at a limiting
sensitivity of about 0.2 mJy to pulsed radio emission for periods P > 10 ms and
dispersion measures < 50 pc cm-3. Roughly half of the unidentified gamma-ray
sources at |b| > 5 deg. with no proposed active galactic nucleus counterpart
were covered in this survey. We detected nine isolated pulsars and four
recycled binary pulsars, with three from each class being new. Timing
observations suggest that only one of the pulsars has a spin-down luminosity
which is even marginally consistent with the inferred luminosity of its
coincident EGRET source. Our results suggest that population models, which
include the Gould belt as a component, overestimate the number of isolated
pulsars among the mid-latitude Galactic gamma-ray sources and that it is
unlikely that Gould belt pulsars make up the majority of these sources.
However, the possibility of steep pulsar radio spectra and the confusion of
terrestrial radio interference with long-period pulsars (P > 200 ms) having
very low dispersion measures (< 10 pc cm-3, expected for sources at a distance
of less than about 1 kpc) prevent us from strongly ruling out this hypothesis.
Our results also do not support the hypothesis that millisecond pulsars make up
the majority of these sources. Non-pulsar source classes should therefore be
further investigated as possible counterparts to the unidentified EGRET sources
at intermediate Galactic latitudes.Comment: 24 pages, including 4 figures and 3 tables. Accepted for publication
in Ap
Overlooking the front line : impacts of front‐line worker inclusion on implementation and outcomes of collaborative innovation
Policymakers acknowledge the need to drive innovation in health and social care, given the complex, "wicked" problems that such services are tasked with solving and the concept of collaborative innovation is proposed as a tool in which to reach solutions to these problems. Prior case studies have overlooked the element of front-line worker inclusion on processes of collaborative innovation. This research explores this element through a case study of an intermediate care facility in Scotland. This collaboration produced innovation, but the strength of the innovative solution was diluted by the omission of front-line workers in key phases of the innovation process. This paper contributes to the broader public administration literature by operationalizing a novel conceptual framework of collaborative innovation and by exploring the problematic implications of neglecting to include front line worker perspectives throughout the process of collaborative innovation
No detectable radio emission from the magnetar-like pulsar in Kes 75
The rotation-powered pulsar PSR J1846-0258 in the supernova remnant Kes 75
was recently shown to have exhibited magnetar-like X-ray bursts in mid-2006.
Radio emission has not yet been observed from this source, but other
magnetar-like sources have exhibited transient radio emission following X-ray
bursts. We report on a deep 1.9 GHz radio observation of PSR J1846-0258 with
the 100-m Green Bank Telescope in late 2007 designed to search for radio
pulsations or bursts from this target. We have also analyzed three shorter
serendipitous 1.4 GHz radio observations of the source taken with the 64-m
Parkes telescope during the 2006 bursting period. We detected no radio emission
from PSR J1846-0258 in either the Green Bank or Parkes datasets. We place an
upper limit of 4.9 \mu Jy on coherent pulsed emission from PSR J1846-0258 based
on the 2007 November 2 observation, and an upper limit of 27 \mu Jy around the
time of the X-ray bursts. Serendipitously, we observed radio pulses from the
nearby RRAT J1846-02, and place a 3\sigma confidence level upper limit on its
period derivative of 1.7 * 10^{-13}, implying its surface dipole magnetic field
is less than 2.6 * 10^{13} G.Comment: 15 pages, 2 figures, submitted to Ap
XMM-Newton X-ray Observation of the High-Magnetic-Field Radio Pulsar PSR J1734--3333
Using observations made with the XMM-Newton Observatory, we report the
probable X-ray detection of the high-magnetic-field radio pulsar PSR
J1734-3333. This pulsar has an inferred surface dipole magnetic field of B =
5.2e13 G, just below that of one anomalous X-ray pulsar (AXP). We find that the
pulsar has an absorbed 0.5-2.0 keV flux of (5-15)e-15 erg/s/cm^2 and that its
X-ray luminosity L_X is well below its spin down luminosity E_dot, with L_X <
0.1E_dot. No pulsations were detected in these data although our derived upper
limit is unconstraining. Like most of the other high-B pulsars, PSR J1734-3333
is X-ray faint with no sign of magnetar activity. We collect and tabulate the
properties of this and all other known high-B radio pulsars with measured X-ray
luminosities or luminosity upper limits and plot L_X versus B for them all.Comment: 14 pages, 2 tables, 3 figures, published in the Astrophysical
Journal. Includes updated Figure
Internet use
Children’s use of the internet has been increasing tremendously in the past decade. Prevalence rates of children’s online time, devices and activities are outlined. Some insight is offered into digital divides by geographic region and socioeconomic circumstances. A typology of online opportunities and risks for children is presented, followed by a brief discussion of online risks, concluding with theoretical models proposing approaches to identify risk and resilience factors with regards to children’s internet use
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