The low-energy
γ
-ray (0.1-30 MeV) sky has been relatively unexplored since the decommissioning of the COMPTEL instrument on the Compton Gamma-Ray Observatory (CGRO) satellite in 2000. However, the ...study of this part of the energy spectrum (the “MeV gap”) is crucial for addressing numerous unresolved questions in high-energy and multi-messenger astrophysics. Although several large MeV
γ
-ray missions like AMEGO and e-ASTROGAM are being proposed, they are predominantly in the developmental phase, with launches not anticipated until the next decade at the earliest. In recent times, there has been a surge in proposed CubeSat missions as cost-effective and rapidly implementable “pathfinder” alternatives. A MeV CubeSat dedicated to
γ
-ray astronomy has the potential to serve as a demonstrator for future, larger-scale MeV payloads. This paper presents a
γ
-ray payload design featuring a CdZnTe crystal calorimeter module developed by IDEAS. We report the detailed results of simulations to assess the performance of this proposed payload and compare it with those of previous
γ
-ray instruments.
High sensitivity radio searches of unassociated γ-ray sources have proven to be an effective way of finding new pulsars. Using the Five-hundred-meter Aperture Spherical radio Telescope (FAST) during ...its commissioning phase, we have carried out a number of targeted deep searches of Fermi Large Area Telescope (LAT) γ-ray sources. On February 27, 2018 we discovered an isolated millisecond pulsar (MSP), PSR J0318+0253, coincident with the unassociated γ-ray source 3FGL J0318.1+0252. PSR J0318+0253 has a spin period of 5.19 ms, a dispersion measure (DM) of 26 pc cm−3 corresponding to a DM distance of about 1.3 kpc, and a period-averaged flux density of (∼11±2) µJy at L-band (1.05–1.45 GHz). Among all high energy MSPs, PSR J0318+0253 is the faintest ever detected in radio bands, by a factor of at least ∼4 in terms of L-band fluxes. With the aid of the radio ephemeris, an analysis of 9.6 years of Fermi-LAT data revealed that PSR J0318+0253 also displays strong γ-ray pulsations. Follow-up observations carried out by both Arecibo and FAST suggest a likely spectral turn-over around 350 MHz. This is the first result from the collaboration between FAST and the Fermi-LAT teams as well as the first confirmed new MSP discovery by FAST, raising hopes for the detection of many more MSPs. Such discoveries will make a significant contribution to our understanding of the neutron star zoo while potentially contributing to the future detection of gravitational waves, via pulsar timing array (PTA) experiments.
Clinicians, patients, policy makers, funders, programme managers, regulators, and science communities invest considerable amounts of time and energy in influencing or making decisions at various ...levels, using systematic reviews, health technology assessments, guideline recommendations, coverage decisions, selection of essential medicines and diagnostics, quality assurance and improvement schemes, and policy and evidence briefs. The criteria and methods that these actors use in their work differ (eg, the role economic analysis has in decision making), but these methods frequently overlap and exist together. Under the aegis of WHO, we have brought together representatives of different areas to reconcile how the evidence that influences decisions is used across multiple health system decision levels. We describe the overlap and differences in decision-making criteria between different actors in the health sector to provide bridging opportunities through a unifying broad framework that we call theory of everything. Although decision-making activities respond to system needs, processes are often poorly coordinated, both globally and on a country level. A decision made in isolation from other decisions on the same topic could cause misleading, unnecessary, or conflicted inputs to the health system and, therefore, confusion and resource waste.
The launch of the Fermi Gamma-ray Space Telescope has heralded a new era in the study of gamma-ray pulsars. The population of confirmed gamma-ray pulsars has gone from 6–7 to more than 60, and the ...superb sensitivity of the Large Area Telescope (LAT) on Fermi has allowed the detailed study of their spectra and light curves. Twenty-four of these pulsars were discovered in blind searches of the gamma-ray data, and twenty-one of these are, at present, radio quiet, despite deep radio follow-up observations. In addition, millisecond pulsars have been confirmed as a class of gamma-ray emitters, both individually and collectively in globular clusters. Recently, radio searches in the direction of LAT sources with no likely counterparts have been highly productive, leading to the discovery of a large number of new millisecond pulsars. Taken together, these discoveries promise a great improvement in the understanding of the gamma-ray emission properties and Galactic population of pulsars. We summarize some of the results stemming from these newly-detected pulsars and their timing and multi-wavelength follow-up observations.
The Fermi Large Area Telescope (LAT) has been scanning the gamma-ray sky since 2008. The number of pulsars detected by the LAT now exceeds 200, making them by far the largest class of Galactic ...gamma-ray emitters. I discuss some of the latest pulsar discoveries made by the LAT, in particular those made since the release of the Pass 8 data.
We analyzed two Chandra observations of PSR J2055+2539 (for a total integration time of \(\sim\)130 ks) in order to measure its proper motion and study its two elongated nebular features. We did not ...detect the proper motion, setting an upper limit of 240 mas yr\(^{-1}\) (3\(\sigma\) level), that translates into an upper limit on the transverse velocity of \(\sim\)700 km s\(^{-1}\), for an assumed distance of 600 pc. A deep H\(\alpha\) observation did not reveal the bow-shock associated with a classical pulsar wind nebula, thus precluding an indirect measurement of the proper motion direction. We determined the main axes of the two nebulae, which are separated by an angle of 160.8\(^{\circ} \pm 0.7^{\circ}\), using a new approach based on the Rolling Hough Transformation (RHT). We analyzed the shape of the first 8' (out of the 12' seen by XMM-Newton) of the brighter, extremely collimated one. Based on a combination of our results from a standard analysis and a nebular modeling obtained from the RHT, we find that the brightest nebula is curved on an arcmin-scale, with a thickness ranging from \(\sim9\)" to \(\sim31\)" and a possible (single or multiple) helicoidal pattern. We could not constrain the shape of the fainter nebula. We discuss our results in the context of other known similar features, with particular emphasis on the Lighthouse nebula (associated with PSR J1101\(-\)6101). We speculate that a peculiar geometry of the powering pulsar may play an important role in the formation of such features.
Fermi has detected over 200 pulsars above 100 MeV. In a previous work, using 3 years of LAT data (1FHL catalog) we reported that 28 of these pulsars show emission above 10 GeV; only three of these, ...however, were millisecond pulsars (MSPs). The recently-released Third Catalog of Hard Fermi-LAT Sources (3FHL) contains over 1500 sources showing emission above 10 GeV, 17 of which are associated with gamma-ray MSPs. Using three times as much data as in our previous study (1FHL), we report on a systematic analysis of these pulsars to determine the highest energy (pulsed) emission fromMSPs and discuss the best possible candidates for follow-up observations with ground-based TeV instruments (H.E.S.S., MAGIC, VERITAS, and the upcoming CTA).
Exp Astron 57, 16 (2024) The low-energy $\gamma$-ray (0.1-30 MeV) sky has been relatively unexplored
since the decommissioning of the COMPTEL instrument on the Compton Gamma-Ray
Observatory (CGRO) ...satellite in 2000. However, the study of this part of the
energy spectrum (the ``MeV gap") is crucial for addressing numerous unresolved
questions in high-energy and multi-messenger astrophysics. Although several
large MeV $\gamma$-ray missions like AMEGO and e-ASTROGAM are being proposed,
they are predominantly in the developmental phase, with launches not
anticipated until the next decade at the earliest. In recent times, there has
been a surge in proposed CubeSat missions as cost-effective and rapidly
implementable ``pathfinder" alternatives. A MeV CubeSat dedicated to
$\gamma$-ray astronomy has the potential to serve as a demonstrator for future,
larger-scale MeV payloads. This paper presents a $\gamma$-ray payload design
featuring a CdZnTe crystal calorimeter module developed by IDEAS. We report the
detailed results of simulations to assess the performance of this proposed
payload and compare it with those of previous $\gamma$-ray instruments.
IntroductionThe Grading of Recommendations Assessment, Development and Evaluation (GRADE) and similar Evidence to Decision (EtD) frameworks require its users to judge how substantial the effects of ...interventions are on desirable and undesirable people-important health outcomes. However, decision thresholds (DTs) that could help understand the magnitude of intervention effects and serve as reference for interpretation of findings are not yet available.The objective of this study is an approach to derive and use DTs for EtD judgments about the magnitude of health benefits and harms. We hypothesise that approximate DTs could have the ability to discriminate between the existing four categories of EtD judgments (Trivial, Small, Moderate, Large), support panels of decision-makers in their work, and promote consistency and transparency in judgments.Methods and analysisWe will conduct a methodological randomised controlled trial to collect the data that allow deriving the DTs. We will invite clinicians, epidemiologists, decision scientists, health research methodologists, experts in Health Technology Assessment (HTA), members of guideline development groups and the public to participate in the trial. Then, we will investigate the validity of our DTs by measuring the agreement between judgments that were made in the past by guideline panels and the judgments that our DTs approach would suggest if applied on the same guideline data.Ethics and disseminationThe Hamilton Integrated Research Ethics Board reviewed this study as a quality improvement study and determined that it requires no further consent. Survey participants will be required to read a consent statement in order to participate in this study at the beginning of the trial. This statement reads: You are being invited to participate in a research project which aims to identify indicative DTs that could assist users of the GRADE EtD frameworks in making judgments. Your input will be used in determining these indicative thresholds. By completing this survey, you provide consent that the anonymised data collected will be used for the research study and to be summarised in aggregate in publication and electronic tools.PROTOCOL registration numberNCT05237635.
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