85 research outputs found
Developing a Drift Rate Distribution for Technosignature Searches of Exoplanets
A stable-frequency transmitter with relative radial acceleration to a
receiver will show a change in received frequency over time, known as a "drift
rate''. For a transmission from an exoplanet, we must account for multiple
components of drift rate: the exoplanet's orbit and rotation, the Earth's orbit
and rotation, and other contributions. Understanding the drift rate
distribution produced by exoplanets relative to Earth, can a) help us constrain
the range of drift rates to check in a Search for Extraterrestrial Intelligence
(SETI) project to detect radio technosignatures and b) help us decide validity
of signals-of-interest, as we can compare drifting signals with expected drift
rates from the target star. In this paper, we modeled the drift rate
distribution for 5300 confirmed exoplanets, using parameters from the
NASA Exoplanet Archive (NEA). We find that confirmed exoplanets have drift
rates such that 99\% of them fall within the 53 nHz range. This implies a
distribution-informed maximum drift rate 4 times lower than previous
work. To mitigate the observational biases inherent in the NEA, we also
simulated an exoplanet population built to reduce these biases. The results
suggest that, for a Kepler-like target star without known exoplanets, 0.44
nHz would be sufficient to account for 99\% of signals. This reduction in
recommended maximum drift rate is partially due to inclination effects and bias
towards short orbital periods in the NEA. These narrowed drift rate maxima will
increase the efficiency of searches and save significant computational effort
in future radio technosignature searches.Comment: 15 pages, 8 figure
The Breakthrough Listen Search for Intelligent Life: A 3.95-8.00 GHz Search for Radio Technosignatures in the Restricted Earth Transit Zone
We report on a search for artificial narrowband signals of 20 stars within
the restricted Earth Transit Zone as a part of the ten-year Breakthrough Listen
(BL) search for extraterrestrial intelligence. The restricted Earth Transit
Zone is the region of the sky from which an observer would see the Earth
transit the Sun with an impact parameter of less than 0.5. This region of the
sky is geometrically unique, providing a potential way for an extraterrestrial
intelligence to discover the Solar System. The targets were nearby (7-143 pc)
and the search covered an electromagnetic frequency range of 3.95-8.00 GHz. We
used the Robert C. Byrd Green Bank Telescope to perform these observations with
the standard BL data recorder. We searched these data for artificial narrowband
(Hz) signals with Doppler drift rates of Hz s. We found
one set of potential candidate signals on the target HIP 109656 which was then
found to be consistent with known properties of anthropogenic radio frequency
interference. We find no evidence for radio technosignatures from
extraterrestrial intelligence in our observations. The observing campaign
achieved a minimum detectable flux which would have allowed detections of
emissions that were to times as powerful as the signaling
capability of the Arecibo radar transmitter, for the nearest and furthest stars
respectively. We conclude that at least of the systems in the restricted
Earth Transit Zone within 150 pc do not possess the type of transmitters
searched in this survey. To our knowledge, this is the first targeted search
for extraterrestrial intelligence of the restricted Earth Transit Zone. All
data used in this paper are publicly available via the Breakthrough Listen
Public Data Archive (http://seti.berkeley.edu/bldr2).Comment: 17 pages, 8 figures, submitted to Ap
A 4-8 GHz Galactic Center Search for Periodic Technosignatures
Radio searches for extraterrestrial intelligence have mainly targeted the
discovery of narrowband continuous-wave beacons and artificially dispersed
broadband bursts. Periodic pulse trains, in comparison to the above
technosignature morphologies, offer an energetically efficient means of
interstellar transmission. A rotating beacon at the Galactic Center (GC), in
particular, would be highly advantageous for galaxy-wide communications. Here,
we present blipss, a CPU-based open-source software that uses a fast folding
algorithm (FFA) to uncover channel-wide periodic signals in radio dynamic
spectra. Running blipss on 4.5 hours of 4-8 GHz data gathered with the Robert
C. Byrd Green Bank Telescope, we searched the central 6' of our Galaxy for
kHz-wide signals with periods between 11-100 s and duty cycles ()
between 10-50%. Our searches, to our knowledge, constitute the first FFA
exploration for periodic alien technosignatures. We report a non-detection of
channel-wide periodic signals in our data. Thus, we constrain the abundance of
4-8 GHz extraterrestrial transmitters of kHz-wide periodic pulsed signals to
fewer than one in about 600,000 stars at the GC above a 7 equivalent
isotropic radiated power of W at . From an astrophysics standpoint, blipss, with its utilization of a
per-channel FFA, can enable the discovery of signals with exotic radio
frequency sweeps departing from the standard cold plasma dispersion law.Comment: 20 pages, 11 figures, published in AJ, in press
(http://seti.berkeley.edu/blipss/
A Green Bank Telescope search for narrowband technosignatures between 1.1-1.9 GHz during 12 Kepler planetary transits
A growing avenue for determining the prevalence of life beyond Earth is to
search for "technosignatures" from extraterrestrial intelligences/agents.
Technosignatures require significant energy to be visible across interstellar
space and thus intentional signals might be concentrated in frequency, in time,
or in space, to be found in mutually obvious places. Therefore, it could be
advantageous to search for technosignatures in parts of parameter space that
are mutually-derivable to an observer on Earth and a distant transmitter. In
this work, we used the L-band (1.1-1.9 GHz) receiver on the Robert C. Byrd
Green Bank Telescope (GBT) to perform the first technosignature search
pre-synchronized with exoplanet transits, covering 12 Kepler systems. We used
the Breakthrough Listen turboSETI pipeline to flag narrowband hits (3 Hz)
using a maximum drift rate of 614.4 Hz/s and a signal-to-noise threshold
of 5 - the pipeline returned apparently-localized
features. Visual inspection by a team of citizen scientists ruled out 99.6% of
them. Further analysis found 2 signals-of-interest that warrant follow-up, but
no technosignatures. If the signals-of-interest are not re-detected in future
work, it will imply that the 12 targets in the search are not producing
transit-aligned signals from 1.1-1.9 GHz with transmitter powers 60 times
that of the former Arecibo radar. This search debuts a range of innovative
technosignature techniques: citizen science vetting of potential
signals-of-interest, a sensitivity-aware search out to extremely high drift
rates, a more flexible method of analyzing on-off cadences, and an extremely
low signal-to-noise threshold.Comment: 18 pages, 11 figure
Precise Measurements of Self-absorbed Rising Reverse Shock Emission from Gamma-ray Burst 221009A
The deaths of massive stars are sometimes accompanied by the launch of highly
relativistic and collimated jets. If the jet is pointed towards Earth, we
observe a "prompt" gamma-ray burst due to internal shocks or magnetic
reconnection events within the jet, followed by a long-lived broadband
synchrotron afterglow as the jet interacts with the circum-burst material.
While there is solid observational evidence that emission from multiple shocks
contributes to the afterglow signature, detailed studies of the reverse shock,
which travels back into the explosion ejecta, are hampered by a lack of
early-time observations, particularly in the radio band. We present rapid
follow-up radio observations of the exceptionally bright gamma-ray burst GRB
221009A which reveal an optically thick rising component from the reverse shock
in unprecedented detail both temporally and in frequency space. From this, we
are able to constrain the size, Lorentz factor, and internal energy of the
outflow while providing accurate predictions for the location of the peak
frequency of the reverse shock in the first few hours after the burst.Comment: 11 figures, 4 table
Mapping 123 million neonatal, infant and child deaths between 2000 and 2017
Since 2000, many countries have achieved considerable success in improving child survival, but localized progress remains unclear. To inform efforts towards United Nations Sustainable Development Goal 3.2—to end preventable child deaths by 2030—we need consistently estimated data at the subnational level regarding child mortality rates and trends. Here we quantified, for the period 2000–2017, the subnational variation in mortality rates and number of deaths of neonates, infants and children under 5 years of age within 99 low- and middle-income countries using a geostatistical survival model. We estimated that 32% of children under 5 in these countries lived in districts that had attained rates of 25 or fewer child deaths per 1,000 live births by 2017, and that 58% of child deaths between 2000 and 2017 in these countries could have been averted in the absence of geographical inequality. This study enables the identification of high-mortality clusters, patterns of progress and geographical inequalities to inform appropriate investments and implementations that will help to improve the health of all populations
Measuring universal health coverage based on an index of effective coverage of health services in 204 countries and territories, 1990–2019 : A systematic analysis for the Global Burden of Disease Study 2019
Background
Achieving universal health coverage (UHC) involves all people receiving the health services they need, of high quality, without experiencing financial hardship. Making progress towards UHC is a policy priority for both countries and global institutions, as highlighted by the agenda of the UN Sustainable Development Goals (SDGs) and WHO's Thirteenth General Programme of Work (GPW13). Measuring effective coverage at the health-system level is important for understanding whether health services are aligned with countries' health profiles and are of sufficient quality to produce health gains for populations of all ages.
Methods
Based on the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019, we assessed UHC effective coverage for 204 countries and territories from 1990 to 2019. Drawing from a measurement framework developed through WHO's GPW13 consultation, we mapped 23 effective coverage indicators to a matrix representing health service types (eg, promotion, prevention, and treatment) and five population-age groups spanning from reproductive and newborn to older adults (≥65 years). Effective coverage indicators were based on intervention coverage or outcome-based measures such as mortality-to-incidence ratios to approximate access to quality care; outcome-based measures were transformed to values on a scale of 0–100 based on the 2·5th and 97·5th percentile of location-year values. We constructed the UHC effective coverage index by weighting each effective coverage indicator relative to its associated potential health gains, as measured by disability-adjusted life-years for each location-year and population-age group. For three tests of validity (content, known-groups, and convergent), UHC effective coverage index performance was generally better than that of other UHC service coverage indices from WHO (ie, the current metric for SDG indicator 3.8.1 on UHC service coverage), the World Bank, and GBD 2017. We quantified frontiers of UHC effective coverage performance on the basis of pooled health spending per capita, representing UHC effective coverage index levels achieved in 2019 relative to country-level government health spending, prepaid private expenditures, and development assistance for health. To assess current trajectories towards the GPW13 UHC billion target—1 billion more people benefiting from UHC by 2023—we estimated additional population equivalents with UHC effective coverage from 2018 to 2023.
Findings
Globally, performance on the UHC effective coverage index improved from 45·8 (95% uncertainty interval 44·2–47·5) in 1990 to 60·3 (58·7–61·9) in 2019, yet country-level UHC effective coverage in 2019 still spanned from 95 or higher in Japan and Iceland to lower than 25 in Somalia and the Central African Republic. Since 2010, sub-Saharan Africa showed accelerated gains on the UHC effective coverage index (at an average increase of 2·6% [1·9–3·3] per year up to 2019); by contrast, most other GBD super-regions had slowed rates of progress in 2010–2019 relative to 1990–2010. Many countries showed lagging performance on effective coverage indicators for non-communicable diseases relative to those for communicable diseases and maternal and child health, despite non-communicable diseases accounting for a greater proportion of potential health gains in 2019, suggesting that many health systems are not keeping pace with the rising non-communicable disease burden and associated population health needs. In 2019, the UHC effective coverage index was associated with pooled health spending per capita (r=0·79), although countries across the development spectrum had much lower UHC effective coverage than is potentially achievable relative to their health spending. Under maximum efficiency of translating health spending into UHC effective coverage performance, countries would need to reach adjusted for purchasing power parity) in order to achieve 80 on the UHC effective coverage index. From 2018 to 2023, an estimated 388·9 million (358·6–421·3) more population equivalents would have UHC effective coverage, falling well short of the GPW13 target of 1 billion more people benefiting from UHC during this time. Current projections point to an estimated 3·1 billion (3·0–3·2) population equivalents still lacking UHC effective coverage in 2023, with nearly a third (968·1 million [903·5–1040·3]) residing in south Asia.
Interpretation
The present study demonstrates the utility of measuring effective coverage and its role in supporting improved health outcomes for all people—the ultimate goal of UHC and its achievement. Global ambitions to accelerate progress on UHC service coverage are increasingly unlikely unless concerted action on non-communicable diseases occurs and countries can better translate health spending into improved performance. Focusing on effective coverage and accounting for the world's evolving health needs lays the groundwork for better understanding how close—or how far—all populations are in benefiting from UHC
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