In one and a half years, the Imaging X-ray Polarimetry Explorer has demonstrated the role and the potentiality of Polarimetry in X-ray Astronomy. The next steps include extension to higher energies. ...There is margin for an extension of the photoelectric approach up to 20–25 keV, but above that energy the only technique is Compton Scattering. Grazing incidence optics can focus photons up to 80 keV, not excluding a marginal extension to 150–200 keV. Given the physical constraints involved, the passage from photoelectric to scattering approach can make less effective the use of optics because of the high background. I discuss the choices in terms of detector design to mitigate the problem and the guidelines for future technological developments.
Since the very beginning of X-ray Astronomy, polarimetry has been suggested as a tool of diagnostics, of great potentiality. While almost all measurements of X-rays were based on detectors using the ...photoelectric effect, the first attempt to perform polarimetry were based on Compton scattering and Bragg diffraction. The use of photoelectric effect also for polarimetry has been hypothesized and attempted for many years but never accomplished. Only 40 years from the start of X-ray astronomy, the Gas Pixel Detector (GPD) was developed, compatible with an X-ray optics, and capable of measuring energy, time, position and polarization simultaneously. Only after 20 more years, the Imaging X-ray Polarimetry Explorer, based on the GPD detectors, will be launched. I present the story of the development of photoelectric polarimetry that arrived to the Gas Pixel Detector, and discuss the possible future evolutions.
Abstract
Imaging X-ray Polarimetry Explorer (IXPE) is a Small Explorer mission by NASA and Agenzia Spaziale Italiana, launched on 2021 December 9, dedicated to investigating X-ray polarimetry ...allowing angular-, time-, and energy-resolved observations in the 2–8 keV energy band. IXPE is in the science observation phase since 2022 January; it is comprised of three identical telescopes with grazing-incidence mirrors, each one having in the focal plane a gas pixel detector. In this paper, we present a possible guideline to obtain an optimal background selection in polarimetric analysis, and a rejection strategy to remove instrumental background. This work is based on the analysis of IXPE observations, aiming to improve as much as possible the polarimetric sensitivity. In particular, the developed strategies have been applied
as a case study
to the IXPE observation of the 4U 0142+61 magnetar.
...the diseases, not the drugs, are the orphans because all drugs are very expensive,3 having marrying this success story (table). ...in some cases, several OMPs are available for the same disease; ...for example, three drugs are licensed for treatment of Gaucher's disease (imiglucerase, velaglucerase alfa, and taliglucerase alfa).15 No evidence favours any one product over the other, and each drug costs about US$200 000 per patient per year. In a landmark departure from previous practice in 2014, the US Senate requested information on developmental costs and numerous other details for sofosbuvir, a drug for radical treatment of hepatitis C virus infection.19 Individual EU member state governments have since increasingly been requesting that industry disclose information about costs incurred during drug development that justify drug prices, but without legal obligations, these requests have largely been evaded. First synthesised in 1869, hydroxyurea has been used for decades in patients with myeloproliferative disorders and is now also indicated for sickle-cell disease.22,23 In the 2017 issue of the British National Formulary, one type of hydroxyurea for myeloproliferative disorders is listed at £0·24 per g, and another type of hydroxyurea for sickle-cell disease is listed at £16·7 per g. Common sense suggests that something must be wrong here.
Particle acceleration mechanisms in supermassive black hole jets, such as shock acceleration, magnetic reconnection, and turbulence, are expected to have observable signatures in the multiwavelength ...polarization properties of blazars. The recent launch of the Imaging X-Ray Polarimetry Explorer (IXPE) enables us, for the first time, to use polarization in the X-ray band (2–8 keV) to probe the properties of the jet synchrotron emission in high-synchrotron-peaked BL Lac objects (HSPs). We report the discovery of X-ray linear polarization (degree Πx = 15% ± 2% and electric vector position angle ψx = 35° ± 4°) from the jet of the HSP Mrk 421 in an average X-ray flux state. At the same time, the degree of polarization at optical, infrared, and millimeter wavelengths was found to be lower by at least a factor of 3. During the IXPE pointing, the X-ray flux of the source increased by a factor of 2.2, while the polarization behavior was consistent with no variability. The higher level of Πx compared to longer wavelengths, and the absence of significant polarization variability, suggest a shock is the most likely X-ray emission site in the jet of Mrk 421 during the observation. The multiwavelength polarization properties are consistent with an energy-stratified electron population, where the particles emitting at longer wavelengths are located farther from the acceleration site, where they experience a more disordered magnetic field.
The COVID-19 pandemic made explicit the issues of communicating science in an information ecosystem dominated by social media platforms. One of the fundamental communication challenges of our time is ...to provide the public with reliable content and contrast misinformation. This paper investigates how social media can become an effective channel to promote engagement and (re)build trust. To measure the social response to quality communication, we conducted an experimental study to test a set of science communication recommendations on Facebook and Twitter. The experiment involved communication practitioners and social media managers from select countries in Europe, applying and testing such recommendations for five months. Here we analyse their feedback in terms of adoption and show that some differences emerge across platforms, topics, and recommendation categories. To evaluate these recommendations' effect on users, we measure their response to quality content, finding that the median engagement is generally higher, especially on Twitter. The results indicate that quality communication strategies may elicit positive feedback on social media. A data-driven and co-designed approach in developing counter-strategies is thus promising in tackling misinformation.
Abstract
The first X-ray pulsar, Cen X-3, was discovered 50 yr ago. Radiation from such objects is expected to be highly polarized due to birefringence of plasma and vacuum associated with ...propagation of photons in the presence of the strong magnetic field. Here we present results of the observations of Cen X-3 performed with the Imaging X-ray Polarimetry Explorer. The source exhibited significant flux variability and was observed in two states different by a factor of ∼20 in flux. In the low-luminosity state, no significant polarization was found in either pulse phase-averaged (with a 3
σ
upper limit of 12%) or phase-resolved (the 3
σ
upper limits are 20%–30%) data. In the bright state, the polarization degree of 5.8% ± 0.3% and polarization angle of 49.°6 ± 1.°5 with a significance of about 20
σ
were measured from the spectropolarimetric analysis of the phase-averaged data. The phase-resolved analysis showed a significant anticorrelation between the flux and the polarization degree, as well as strong variations of the polarization angle. The fit with the rotating vector model indicates a position angle of the pulsar spin axis of about 49° and a magnetic obliquity of 17°. The detected relatively low polarization can be explained if the upper layers of the neutron star surface are overheated by the accreted matter and the conversion of the polarization modes occurs within the transition region between the upper hot layer and a cooler underlying atmosphere. A fraction of polarization signal can also be produced by reflection of radiation from the neutron star surface and the accretion curtain.
•β-THAL is one of the most prevalent blood disorders in some regions of the world.•However, given its prevalence, in the EU and the US it is classified as a rare disease.•A wide array of therapeutic ...approaches has been developed over the past decades.•β-THAL is a learning case on the potential global impact of Orphan Legislations.•Gene therapy for β-THAL is promising, but scenarios for global access are missing.
In many countries, β-thalassemia (β-THAL) is not uncommon; however, it qualifies as a rare disease in the US and in European Union (EU), where thalassemia drugs are eligible for Orphan Drug Designation (ODD). In this paper, we evaluate all 28 ODDs for β-THAL granted since 2001 in the US and the EU: of these, ten have since been discontinued, twelve are pending, and six have become licensed drugs available for clinical use. The prime mover for these advances has been the increasing depth of understanding of the pathophysiology of β-THAL; at the same time, and even though only one-fifth of β-THAL ODDs have become licensed drugs, the ODD legislation has clearly contributed substantially to the development of improved treatments for β-THAL.
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