We present an unbinned likelihood analysis formalism employing photon weights-the probabilities that events are associated with a particular source. This approach is applicable to any ...photon-resolving instrument and thus well suited to high-energy observations; we focus here on GeV γ-ray data from the Fermi Large Area Telescope. Weights connect individual photons to the outputs of a detailed, expensive likelihood analysis of a much larger data set. The weighted events can be aggregated into arbitrary time spans ranging from microseconds to years. Such retrospective grouping permits time- and frequency-domain analysis over a wide range of scales and enables characterization of disparate phenomena like blazar flares, γ-ray bursts, pulsar pulses, novae, γ-ray binaries, and other variable sources. To demonstrate the formalism, we incorporate photon weights into the Bayesian blocks algorithm and perform a hierarchical timescale analysis of 3C 279 activity. We analyze pulsar pulse profiles and estimate the unpulsed emission level and the optimal division of the data into on- and off-pulse intervals. We extend the formalism to Fourier analysis and derive estimators for power spectra, used to search for and characterize periodic sources. We show how the fast Fourier transform can be used to probe orbital periods as short as a minute, and we discuss the mitigation of spurious signals. Our final example combines time- and frequency- domain analysis to jointly characterize the flares and orbital modulation of Cygnus X-3, yielding the strongest detection of the orbital signal (>13 ) to date. Finally, we discuss extensions of the work to other GeV sources and to X-ray and TeV observations.
All Delta *g-ray telescopes suffer from source confusion due to their inability to focus incident high-energy radiation, and the resulting background contamination can obscure the periodic emission ...from faint pulsars. In the context of the Fermi Large Area Telescope, we outline enhanced statistical tests for pulsation in which each photon is weighted by its probability to have originated from the candidate pulsar. The probabilities are calculated using the instrument response function and a full spectral model, enabling powerful background rejection. With Monte Carlo methods, we demonstrate that the new tests increase the sensitivity to pulsars by more than 50% under a wide range of conditions. This improvement may appreciably increase the completeness of the sample of radio-loud Delta *g-ray pulsars. Finally, we derive the asymptotic null distribution for the H-test, expanding its domain of validity to arbitrarily complex light curves.
Abstract
The Fermi Large Area Telescope receives ≪1 photon per rotation from any
γ
-ray pulsar. However, out of the billions of monitored rotations of the bright pulsars Vela (PSR J0835−4510) and ...Geminga (PSR J0633+1746), a few thousand have ≥2 pulsed photons. These rare pairs encode information about the variability of pulse amplitude and shape. We have cataloged such pairs and find the observed number to be in good agreement with simple Poisson statistics, limiting any amplitude variations to <19% (Vela) and <22% (Geminga) at 2
σ
confidence. Using an array of basis functions to model pulse-shape variability, the observed pulse phase distribution of the pairs limits the scale of pulse-shape variations of Vela to <13%, while for Geminga we find a hint of ∼20% single-pulse-shape variability most associated with the pulse peaks. If variations last longer than a single rotation, more pairs can be collected, and we have calculated upper limits on amplitude and shape variations for assumed coherence times up to 100 rotations, finding limits of ∼1% (amplitude) and ∼3% (shape) for both pulsars. Because a large volume of the pulsar magnetosphere contributes to
γ
-ray pulse production, we conclude that the magnetospheres of these two energetic pulsars are stable over one rotation and very stable on longer timescales. All other
γ
-ray pulsars are too faint for similar analyses. These results provide useful constraints on rapidly improving simulations of pulsar magnetospheres, which have revealed a variety of large-scale instabilities in the thin equatorial current sheets where the bulk of GeV
γ
-ray emission is thought to originate.
Abstract
PSR J0740+6620 has a gravitational mass of 2.08 ± 0.07
M
⊙
, which is the highest reliably determined mass of any neutron star. As a result, a measurement of its radius will provide unique ...insight into the properties of neutron star core matter at high densities. Here we report a radius measurement based on fits of rotating hot spot patterns to Neutron Star Interior Composition Explorer (NICER) and X-ray Multi-Mirror (XMM-Newton) X-ray observations. We find that the equatorial circumferential radius of PSR J0740+6620 is
13.7
−
1.5
+
2.6
km (68%). We apply our measurement, combined with the previous NICER mass and radius measurement of PSR J0030+0451, the masses of two other ∼2
M
⊙
pulsars, and the tidal deformability constraints from two gravitational wave events, to three different frameworks for equation-of-state modeling, and find consistent results at ∼1.5–5 times nuclear saturation density. For a given framework, when all measurements are included, the radius of a 1.4
M
⊙
neutron star is known to ±4% (68% credibility) and the radius of a 2.08
M
⊙
neutron star is known to ±5%. The full radius range that spans the ±1
σ
credible intervals of all the radius estimates in the three frameworks is 12.45 ± 0.65 km for a 1.4
M
⊙
neutron star and 12.35 ± 0.75 km for a 2.08
M
⊙
neutron star.
The measurement error of pulse times of arrival (TOAs) in the high signal-to-noise ratio limit is dominated by the quasi-random variation of a pulsar's emission profile from rotation to rotation. ...Like measurement noise, this noise is only reduced as the square root of observing time, posing a major challenge to future pulsar timing campaigns with large aperture telescopes, e.g. the Five-hundred-metre Aperture Spherical Telescope and the Square Kilometre Array. We propose a new method of pulsar timing that attempts to approximate the pulse-to-pulse variability with a small family of ‘basis’ pulses. If pulsar data are integrated over many rotations, this basis can be used to measure subpulse structure. Or, if high-time resolution data are available, the basis can be used to ‘tag’ single pulses and produce an optimal timing template. With realistic simulations, we show that these applications can dramatically reduce the effect of pulse-to-pulse variability on TOAs. Using high-time resolution data taken from the bright PSR J0835−4510 (Vela), we demonstrate a 25–40 per cent improvement in TOA precision. Crucially for pulsar timing applications, we further establish that these techniques produce TOAs with Gaussian residuals. Improvements of this level halve the telescope time required to reach a desired TOA precision. Although some gains can be achieved with existing data, the greatest improvements result from the ‘tagging’ approach, which in turn requires online or post hoc analysis of single pulses, an important consideration for the design of future instrumentation.
Background Chronic thromboembolic pulmonary hypertension (CTEPH) is a known sequela of acute pulmonary embolic disease and yet remains underdiagnosed. Although nonsurgical options for patients with ...CTEPH have become increasingly available, including pulmonary artery hypertensive medical therapy, surgical endarterectomy provides the most appropriate intervention as a potential cure for this debilitating disorder. This article summarizes the most recent outcomes of pulmonary endarterectomy at a single institution over the past 12 years, with emphasis on the surgical approach to segmental-level chronic thromboembolic disease. Methods More than 2,700 pulmonary endarterectomy operations have been performed at the University of California, San Diego Medical Center. Because of recent changes in the patient population and in surgical results, 1,500 patients with symptomatic chronic thromboembolic disease who underwent pulmonary endarterectomy between March 1999 and December 2010 were analyzed. The outcomes for the more recent 500 patients, compared with the previous 1,000 were studied. Results In-hospital mortality for the cohort of 1,000 patients (group 1) was 5.2% compared with 2.2% for the last 500 operations (group 2) ( p < 0.01). There was no mortality in the last 260 consecutive patients undergoing isolated pulmonary endarterectomy. More patients presented with segmental type III disease in the more recent 500 patients (21.4% versus 13.1%; p < 0.001). Between the 2 patient groups, there was a comparable decline in pulmonary vascular resistance (PVR) (group 1: 861.2 ± 446.2 to 94.8 ± 204.2 dynes/sec/cm−5 ; group 2: 719.0 ± 383.2 to 253.4 ± 148.6 dynes/sec/cm−5 ) and mean pulmonary artery (PA) pressures (group 1: 46.1 ± 11.4 to 28.7 ± 10.1 mm Hg; group 2: 45.5 ± 11.6 to 26.0 ± 8.4 mm Hg) after endarterectomy. Conclusions Despite a patient population with more distal disease, results continue to improve. Pulmonary endarterectomy for patients with CTEPH results in significant pulmonary hemodynamic improvement, with favorable outcomes achievable even in patients with distal segmental-level chronic thromboembolic disease.
The impact of epilepsy is multifaceted and extensive on its effects. The occurrence of seizures is unpredictable and often dangerous, increasing the risk of injury, hospitalization and mortality, and ...adversely affecting a patient's mental health, often resulting in anxiety, depression or cognitive impairment. Seizures can also result in stigmatization and social exclusion, with detrimental effects on an individual's confidence and self‐esteem. However, the burden of epilepsy extends beyond the effects of seizures themselves. In particular, individuals with epilepsy are significantly more likely to have medical or psychiatric comorbidities than those without epilepsy, and comorbidity in patients with epilepsy has been shown to be strongly correlated with negative impacts on subjective health status and quality of life (QoL). In addition, antiepileptic drug (AED) treatment is commonly associated with side effects, which further impair patients' QoL. Patient surveys provide valuable insights into what matters to patients in their daily lives and highlight important discrepancies between the perceptions of patients and their physicians. For example, survey data show that physicians underestimate the number of patients experiencing AED side effects and the impact of these on patients. Screening questionnaires can help physicians to quickly identify problems with treatment side effects; also, to recognize comorbidities such as depression that are otherwise difficult to identify in a time‐limited consultation. Ultimately, successful management of epilepsy requires a holistic approach to care, with treatment tailored to the individual patient's needs; this can only be achieved through effective doctor–patient communication and the full involvement of a multidisciplinary care team.
Child maltreatment (CM) is associated with mental and physical health disorders in adulthood. Some studies have identified elevated markers of systemic inflammation in adult survivors of CM, and ...inflammation may mediate the association between CM and later health problems. However, there are methodological inconsistencies in studies of the association between CM and systemic inflammation and findings are conflicting. We performed a systematic review to examine the association of CM with systemic inflammation in adults.
A pre-registered systematic review was performed following PRISMA guidelines. Medline, Embase, Scopus and PsychInfo were searched for studies of the association of CM with blood markers of inflammation in adults. Quality was assessed using the Crowe Critical Appraisal Tool. We had intended to perform a meta-analysis, but this was not possible due to variation in study design and reporting.
Forty-four articles met criteria for inclusion in the review. The most widely reported biomarkers were C-Reactive Protein (CRP) (n = 27), interleukin-6 (IL-6) (n = 24) and Tumour Necrosis Factor-alpha (TNF-a) (n = 17). Three studies were prospective (all relating to CRP) and the remainder were retrospective. 86% of studies were based in high income countries. In the prospective studies, CM was associated with elevated CRP in adulthood. Results of retrospective studies were conflicting. Methodological issues relating to the construct of CM, methods of analysis, and accounting for confounding or mediating variables (particularly Body Mass Index) may contribute to the uncertainty in the field.
There is some robust evidence from prospective studies that CM is associated with elevated CRP in adulthood. We have identified significant methodological inconsistencies in the literature and have proposed measures that future researchers could employ to improve consistency across studies. Further prospective, longitudinal, research using robust and comparable measures of CM with careful consideration of confounding and mediating variables is required to bring clarity to this field.
As reconnection begins and the enstrophy
$Z$
grows for two configurations, helical trefoil knots and anti-parallel vortices, two regimes of self-similar collapse are observed. First, during trefoil ...reconnection a new
$\sqrt{\unicodeSTIX{x1D708}}Z$
scaling, where
$\unicodeSTIX{x1D708}$
is viscosity, is identified before any
$\unicodeSTIX{x1D716}=\unicodeSTIX{x1D708}Z$
dissipation scaling begins. Further rescaling shows linearly decreasing
$B_{\unicodeSTIX{x1D708}}(t)=(\sqrt{\unicodeSTIX{x1D708}}Z)^{-1/2}$
at configuration-dependent crossing times
$t_{x}$
. Gaps in the vortex structures identify the
$t_{x}$
as when reconnection ends and collapse onto
$\unicodeSTIX{x1D708}$
-independent curves can be obtained using
$A_{\unicodeSTIX{x1D708}}(t)=(T_{c}(\unicodeSTIX{x1D708})-t_{x})(B_{\unicodeSTIX{x1D708}}(t)-B_{\unicodeSTIX{x1D708}}(t_{x}))$
. The critical times
$T_{c}(\unicodeSTIX{x1D708})$
are identified empirically by extrapolating the linear
$B_{\unicodeSTIX{x1D708}}(t)$
regimes to
$B_{\unicodeSTIX{x1D708}}^{{\sim}}(T_{c})=0$
, yielding an
$A_{\unicodeSTIX{x1D708}}(t)$
collapse that forms early as
$\unicodeSTIX{x1D708}$
varies by 256. These solutions are regular or non-singular, as shown by decreasing cubic velocity norms
$\Vert u\Vert _{L_{\ell }^{3}}^{}$
. For the anti-parallel vortices, first there is an exchange of circulation, from
$\unicodeSTIX{x1D6E4}_{y}(y=0)$
to
$\unicodeSTIX{x1D6E4}_{z}(z=0)$
, mediated by the viscous circulation exchange integral
$\unicodeSTIX{x1D716}_{\unicodeSTIX{x1D6E4}}(t)$
, which is followed by a modified
$B_{\unicodeSTIX{x1D708}}(t)$
collapse until the reconnection ends at
$t_{x}$
. Singular Leray scaling and mathematical bounds for higher-order Sobolev norms are used to help explain the origins of the new scaling and why the domain size
$\ell$
has to increase to maintain the collapse of
$A_{\unicodeSTIX{x1D708}}(t)$
and
$\unicodeSTIX{x1D716}_{\unicodeSTIX{x1D6E4}}$
as
$\unicodeSTIX{x1D708}$
decreases.
ABSTRACT
The smooth spin-down of young pulsars is perturbed by two non-deterministic phenomenon, glitches, and timing noise. Although the timing noise provides insights into nuclear and plasma ...physics at extreme densities, it acts as a barrier to high-precision pulsar timing experiments. An improved methodology based on the Bayesian inference is developed to simultaneously model the stochastic and deterministic parameters for a sample of 85 high-$\dot{E}$ radio pulsars observed for ∼10 yr with the 64-m Parkes radio telescope. Timing noise is known to be a red process and we develop a parametrization based on the red-noise amplitude (Ared) and spectral index (β). We measure the median Ared to be $-10.4^{+1.8}_{-1.7}$ yr3/2 and β to be $-5.2^{+3.0}_{-3.8}$ and show that the strength of timing noise scales proportionally to $\nu ^{1}|\dot{\nu }|^{-0.6\pm 0.1}$, where ν is the spin frequency of the pulsar and $\dot{\nu }$ is its spin-down rate. Finally, we measure significant braking indices for 19 pulsars and proper motions for 2 pulsars, and discuss the presence of periodic modulation in the arrival times of 5 pulsars.
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