69 research outputs found
Latest results on gamma-ray pulsars with Fermi
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.Comment: 5 pages, to appear in Il Nuovo Cimento
Fermi-LAT searches for gamma-ray pulsars
The Large Area Telescope (LAT) on the Fermi satellite is the first gamma-ray
instrument to discover pulsars directly via their gamma-ray emission. Roughly
one third of the 117 gamma-ray pulsars detected by the LAT in its first three
years were discovered in blind searches of gamma-ray data and most of these are
undetectable with current radio telescopes. I review some of the key LAT
results and highlight the specific challenges faced in gamma-ray (compared to
radio) searches, most of which stem from the long, sparse data sets and the
broad, energy-dependent point-spread function (PSF) of the LAT. I discuss some
ongoing LAT searches for gamma-ray millisecond pulsars (MSPs) and gamma-ray
pulsars around the Galactic Center. Finally, I outline the prospects for future
gamma-ray pulsar discoveries as the LAT enters its extended mission phase,
including advantages of a possible modification of the LAT observing profile.Comment: Proceedings of the IAU Symposium 291, IAU XXVIII General Assembly,
Beijing, China, August 2012: "Neutron Stars and Pulsars: Challenges and
Opportunities after 80 years", Editor: Joeri van Leeuwen. To be published by
Cambridge University Press. 6 page
The two tails of PSR J2055+2539 as seen by Chandra: analysis of the nebular morphology and pulsar proper motion
We analyzed two Chandra observations of PSR J2055+2539 (for a total
integration time of 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 (3 level), that translates
into an upper limit on the transverse velocity of 700 km s, for an
assumed distance of 600 pc. A deep H 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, 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 " to " 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
J11016101). We speculate that a peculiar geometry of the powering pulsar may
play an important role in the formation of such features.Comment: 12 pages, 9 figures, 1 table; accepted by Astronomy & Astrophysic
6U MeV CubeSat Mission: A low-cost approach towards gamma-ray astronomy
The low-energy gamma-ray (0.1-30 MeV) sky has been poorly observed since the
decommissioning of the COMPTEL instrument on board the Compton Gamma-ray
Observer (CGRO) satellite in 2000. The study of photons from this energy band
(the MeV "gap") is, however, crucial to answer many unsolved questions in
high-energy and multi-messenger astrophysics. Although several MeV gamma-ray
missions have been proposed (e.g. AMEGO, e-ASTROGAM), these are mostly in the
planning phase, and their launch is not expected until the next decade, at the
earliest. Recently, there has been a proliferation of CubeSat missions proposed
as "pathfinder" alternatives due to their low cost and faster cycles of
implementation. Indeed, a MeV CubeSat for gamma-ray astronomy can be a suitable
demonstrator for future, larger-scale MeV payloads. In this paper, a gamma-ray
payload design with a silicon tracker and CsI calorimeter is proposed. We
report the results of simulations to assess the performance of this payload
possibility and compare these with other previous gamma-ray instruments.Comment: Submitted in Journal of Astronomical Telescopes, Instruments, and
Systems(SPIE). Manuscript# 23097G. 31 pages and 7 figure
Unraveling the Nature of Unidentified High Galactic Latitude Fermi/LAT Gamma-ray Sources with Suzaku
We report on the results of deep X-ray follow-up observations of four
unidentified Fermi/LAT gamma-ray sources at high Galactic latitudes using
Suzaku. The studied objects were detected with high significance during the
first 3 months of Fermi/LAT operation, and subsequently better localized in the
Fermi/LAT 1 year catalog (1FGL). Possible associations with pulsars and active
galaxies have subsequently been discussed, and our observations provide an
important contribution to this debate. In particular, an X-ray point source was
found within the 95% confidence error circle of 1FGL J1231.1-1410. X-ray
spectrum is well-fitted by a blackbody with an additional power-law. This
supports the recently claimed identification of this source with a millisecond
pulsar (MSP) PSR J1231-1411. Concerning 1FGL J1311.7-3429, two X-ray sources
were found within the LAT error circle. Even though the X-ray spectral and
variability properties were accessed, their nature and relationship with the
gamma-ray source remain uncertain. We found several weak X-ray sources in the
field of 1FGL J1333.2+5056, one coinciding with CLASS J1333+5057. We argue the
available data are consistent with the association between these two objects.
Finally, we have detected an X-ray source in the vicinity of 1FGL J2017.3+0603.
This object was recently suggested to be associated with a newly discovered MSP
PSR J2017+0603, because of the spatial-coincidence and the gamma-ray pulse
detection. We have only detected the X-ray counterpart of the CLASS J2017+0603,
while we determined an X-ray flux upper limit at the pulsar position. All in
all, our studies indicate while a significant fraction of unidentified high
Galactic latitude gamma-ray sources is related to the pulsar and blazar
phenomena, associations with other classes of astrophysical objects are still
valid options.Comment: Accepted for publication in the Ap
Prospects for Pulsar Studies at MeV Energies
Enabled by the Fermi Large Area Telescope, we now know young and recycled
pulsars fill the gamma-ray sky, and we are beginning to understand their
emission mechanism and their distribution throughout the Galaxy. However, key
questions remain: Is there a large population of pulsars near the Galactic
center? Why do the most energetic pulsars shine so brightly in MeV gamma rays
but not always at GeV energies? What is the source and nature of the pair
plasma in pulsar magnetospheres, and what role does the polar cap accelerator
play? Addressing these questions calls for a sensitive, wide-field MeV
telescope, which can detect the population of MeV-peaked pulsars hinted at by
Fermi and hard X-ray telescopes and characterize their spectral shape and
polarization.Comment: 8 pages, 4 figures, Astro2020 Science White Paper submitted to the
National Academies of Science
Systematic review on women's values and preferences concerning breast cancer screening and diagnostic services
Background: There is still lack of consensus on the benefit‐harm balance of breast cancer screening. In this scenario, women's values and preferences are crucial for developing health‐related recommendations. In the context of the European Commission Initiative on Breast Cancer, we conducted a systematic review to inform the
European Breast Guidelines.
Methods: We searched Medline and included primary studies assessing women's values and preferences regarding breast cancer screening and diagnosis decision making. We used a thematic approach to synthesise relevant data. The quality of evidence was determined with GRADE, including GRADE CERQual for qualitative research.
Results: We included 22 individual studies. Women were willing to accept the psychological and physical burden of breast cancer screening and a significant risk of overdiagnosis and false‐positive mammography findings, in return for the benefit of earlier diagnosis. The anxiety engendered by the delay in getting results of diagnostic tests was highlighted as a significant burden, emphasising the need for rapid and efficient screening services, and clear and efficient communication. The confidence in the findings was low to moderate for screening and moderate for diagnosis, predominantly because of methodological limitations, lack of adequate understanding of the outcomes by participants, and indirectness.
Conclusions: Women value more the possibility of an earlier diagnosis over the risks of a false‐positive result or overdiagnosis. Concerns remain that women may not understand the concept of overdiagnosis. Women highly value time efficient screening processes and rapid result delivery and will accept some discomfort for the
peace of mind screening may provide
Characteristics and impact of interventions to support healthcare providers’ compliance with guideline recommendations for breast cancer: a systematic literature review
BackgroundBreast cancer clinical practice guidelines (CPGs) offer evidence-based recommendations to improve quality of healthcare for patients. Suboptimal compliance with breast cancer guideline recommendations remains frequent, and has been associated with a decreased survival. The aim of this systematic review was to characterize and determine the impact of available interventions to support healthcare providers' compliance with CPGs recommendations in breast cancer healthcare.MethodsWe searched for systematic reviews and primary studies in PubMed and Embase (from inception to May 2021). We included experimental and observational studies reporting on the use of interventions to support compliance with breast cancer CPGs. Eligibility assessment, data extraction and critical appraisal was conducted by one reviewer, and cross-checked by a second reviewer. Using the same approach, we synthesized the characteristics and the effects of the interventions by type of intervention (according to the EPOC taxonomy), and applied the GRADE framework to assess the certainty of evidence.ResultsWe identified 35 primary studies reporting on 24 different interventions. Most frequently described interventions consisted in computerized decision support systems (12 studies); educational interventions (seven), audit and feedback (two), and multifaceted interventions (nine). There is low quality evidence that educational interventions targeted to healthcare professionals may improve compliance with recommendations concerning breast cancer screening, diagnosis and treatment. There is moderate quality evidence that reminder systems for healthcare professionals improve compliance with recommendations concerning breast cancer screening. There is low quality evidence that multifaceted interventions may improve compliance with recommendations concerning breast cancer screening. The effectiveness of the remaining types of interventions identified have not been evaluated with appropriate study designs for such purpose. There is very limited data on the costs of implementing these interventions.ConclusionsDifferent types of interventions to support compliance with breast cancer CPGs recommendations are available, and most of them show positive effects. More robust trials are needed to strengthen the available evidence base concerning their efficacy. Gathering data on the costs of implementing the proposed interventions is needed to inform decisions about their widespread implementation
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