30 research outputs found
ExoClock Project: An open platform for monitoring the ephemerides of Ariel targets with contributions from the public
The Ariel mission will observe spectroscopically around 1000 exoplanets to further characterise their atmospheres. For the mission to be as efficient as possible, a good knowledge of the planets' ephemerides is needed before its launch in 2028. While ephemerides for some planets are being refined on a per-case basis, an organised effort to collectively verify or update them when necessary does not exist. In this study, we introduce the ExoClock project, an open, integrated and interactive platform with the purpose of producing a confirmed list of ephemerides for the planets that will be observed by Ariel. The project has been developed in a manner to make the best use of all available resources: observations reported in the literature, observations from space instruments and, mainly, observations from ground-based telescopes, including both professional and amateur observatories. To facilitate inexperienced observers and at the same time achieve homogeneity in the results, we created data collection and validation protocols, educational material and easy to use interfaces, open to everyone. ExoClock was launched in September 2019 and now counts over 140 participants from more than 15 countries around the world. In this release, we report the results of observations obtained until the 15h of April 2020 for 119 Ariel candidate targets. In total, 632 observations were used to either verify or update the ephemerides of 83 planets. Additionally, we developed the Exoplanet Characterisation Catalogue (ECC), a catalogue built in a consistent way to assist the ephemeris refinement process. So far, the collaborative open framework of the ExoClock project has proven to be highly efficient in coordinating scientific efforts involving diverse audiences. Therefore, we believe that it is a paradigm that can be applied in the future for other research purposes, too
Magnetic field spectral evolution in the inner heliosphere
Parker Solar Probe and Solar Orbiter data are used to investigate the radial evolution of magnetic turbulence between 0.06 ≲ R ≲ 1 au. The spectrum is studied as a function of scale, normalized to the ion inertial scale di. In the vicinity of the Sun, the inertial range is limited to a narrow range of scales and exhibits a power-law exponent of, αB = −3/2, independent of plasma parameters. The inertial range grows with distance, progressively extending to larger spatial scales, while steepening toward a αB = −5/3 scaling. It is observed that spectra for intervals with large magnetic energy excesses and low Alfvénic content steepen significantly with distance, in contrast to highly Alfvénic intervals that retain their near-Sun scaling. The occurrence of steeper spectra in slower wind streams may be attributed to the observed positive correlation between solar wind speed and Alfvénicity
ExoClock Project III: 450 new exoplanet ephemerides from ground and space observations
The ExoClock project has been created with the aim of increasing the
efficiency of the Ariel mission. It will achieve this by continuously
monitoring and updating the ephemerides of Ariel candidates over an extended
period, in order to produce a consistent catalogue of reliable and precise
ephemerides. This work presents a homogenous catalogue of updated ephemerides
for 450 planets, generated by the integration of 18000 data points from
multiple sources. These sources include observations from ground-based
telescopes (ExoClock network and ETD), mid-time values from the literature and
light-curves from space telescopes (Kepler/K2 and TESS). With all the above, we
manage to collect observations for half of the post-discovery years (median),
with data that have a median uncertainty less than one minute. In comparison
with literature, the ephemerides generated by the project are more precise and
less biased. More than 40\% of the initial literature ephemerides had to be
updated to reach the goals of the project, as they were either of low precision
or drifting. Moreover, the integrated approach of the project enables both the
monitoring of the majority of the Ariel candidates (95\%), and also the
identification of missing data. The dedicated ExoClock network effectively
supports this task by contributing additional observations when a gap in the
data is identified. These results highlight the need for continuous monitoring
to increase the observing coverage of the candidate planets. Finally, the
extended observing coverage of planets allows us to detect trends (TTVs -
Transit Timing Variations) for a sample of 19 planets. All products, data, and
codes used in this work are open and accessible to the wider scientific
community.Comment: Recommended for publication to ApJS (reviewer's comments
implemented). Main body: 13 pages, total: 77 pages, 7 figures, 7 tables. Data
available at http://doi.org/10.17605/OSF.IO/P298
A large topographic feature on the surface of the trans-Neptunian object (307261) 2002 MS measured from stellar occultations
This work aims at constraining the size, shape, and geometric albedo of the
dwarf planet candidate 2002 MS4 through the analysis of nine stellar
occultation events. Using multichord detection, we also studied the object's
topography by analyzing the obtained limb and the residuals between observed
chords and the best-fitted ellipse. We predicted and organized the
observational campaigns of nine stellar occultations by 2002 MS4 between 2019
and 2022, resulting in two single-chord events, four double-chord detections,
and three events with three to up to sixty-one positive chords. Using 13
selected chords from the 8 August 2020 event, we determined the global
elliptical limb of 2002 MS4. The best-fitted ellipse, combined with the
object's rotational information from the literature, constrains the object's
size, shape, and albedo. Additionally, we developed a new method to
characterize topography features on the object's limb. The global limb has a
semi-major axis of 412 10 km, a semi-minor axis of 385 17 km, and
the position angle of the minor axis is 121 16. From
this instantaneous limb, we obtained 2002 MS4's geometric albedo and the
projected area-equivalent diameter. Significant deviations from the fitted
ellipse in the northernmost limb are detected from multiple sites highlighting
three distinct topographic features: one 11 km depth depression followed by a
25 km height elevation next to a crater-like depression with an
extension of 322 39 km and 45.1 1.5 km deep. Our results present an
object that is 138 km smaller in diameter than derived from thermal
data, possibly indicating the presence of a so-far unknown satellite. However,
within the error bars, the geometric albedo in the V-band agrees with the
results published in the literature, even with the radiometric-derived albedo
Recommended from our members
ExoClock Project. III. 450 New Exoplanet Ephemerides from Ground and Space Observations
The ExoClock project has been created to increase the efficiency of the Ariel mission. It will achieve this by continuously monitoring and updating the ephemerides of Ariel candidates, in order to produce a consistent catalog of reliable and precise ephemerides. This work presents a homogenous catalog of updated ephemerides for 450 planets, generated by the integration of ∼18,000 data points from multiple sources. These sources include observations from ground-based telescopes (the ExoClock network and the Exoplanet Transit Database), midtime values from the literature, and light curves from space telescopes (Kepler, K2, and TESS). With all the above, we manage to collect observations for half of the postdiscovery years (median), with data that have a median uncertainty less than 1 minute. In comparison with the literature, the ephemerides generated by the project are more precise and less biased. More than 40% of the initial literature ephemerides had to be updated to reach the goals of the project, as they were either of low precision or drifting. Moreover, the integrated approach of the project enables both the monitoring of the majority of the Ariel candidates (95%), and also the identification of missing data. These results highlight the need for continuous monitoring to increase the observing coverage of the candidate planets. Finally, the extended observing coverage of planets allows us to detect trends (transit-timing variations) for a sample of 19 planets. All the products, data, and codes used in this work are open and accessible to the wider scientific community
A short narrative review of the feasibility of adopting mild ovarian stimulation for IVF as the current standard of care.
Introduction
Mild ovarian stimulation has been conceived, proposed and implemented in clinical practice as a safer and cheaper alternative to conventional strategies of controlled ovarian hyperstimulation in preparation for in vitro fertilization (IVF). Our aim was to summarize the key evidence on this topic and explore its possible role as the standard treatment option for women undergoing IVF.
Materials and Methods
A short narrative review of the existing literature, with emphasis on mild ovarian stimulation clinical and cost effectiveness, as well as treatment limitations.
Results
Numerous studies highlight mild ovarian stimulation’s favorable characteristics with respect to oocyte/embryo quality, reduced patient risk, and ease of intervention. There is, however, a need for high-quality laboratory environment. Limitations regarding poor responders, older women, or those seeking ovarian stimulation for non-infertility indications should also be considered. Finally, outcomes on the cumulative success rates and the cost effectiveness of mild ovarian stimulation remain inconclusive.
Conclusion
Mild ovarian stimulation protocols for IVF should currently be implemented only in carefully selected populations. Further research is needed to clarify the remaining controversies in this IVF approach.</p
A short narrative review of the feasibility of adopting mild ovarian stimulation for IVF as the current standard of care
Introduction: Mild ovarian stimulation has been conceived, proposed and implemented in clinical practice as a safer and cheaper alternative to conventional strategies of controlled ovarian hyperstimulation in preparation for in vitro fertilization (IVF). Our aim was to summarize the key evidence on this topic and explore its possible role as the standard treatment option for women undergoing IVF. Materials and Methods: A short narrative review of the existing literature, with emphasis on mild ovarian stimulation clinical and cost effectiveness, as well as treatment limitations. Results: Numerous studies highlight mild ovarian stimulation's favorable characteristics with respect to oocyte/embryo quality, reduced patient risk, and ease of intervention. There is, however, a need for high-quality laboratory environment. Limitations regarding poor responders, older women, or those seeking ovarian stimulation for non-infertility indications should also be considered. Finally, outcomes on the cumulative success rates and the cost effectiveness of mild ovarian stimulation remain inconclusive. Conclusion: Mild ovarian stimulation protocols for IVF should currently be implemented only in carefully selected populations. Further research is needed to clarify the remaining controversies in this IVF approach. © Springer-Verlag 2012
Evolution of switchbacks in the inner heliosphere
We analyze magnetic field data from the first six encounters of Parker Solar Probe, three Helios fast streams and two Ulysses south polar passes covering heliocentric distances 0.1 ≲ R ≲ 3 au. We use this data set to statistically determine the evolution of switchbacks of different periods and amplitudes with distance from the Sun. We compare the radial evolution of magnetic field variances with that of the mean square amplitudes of switchbacks, and quantify the radial evolution of the cumulative counts of switchbacks per kilometer. We find that the amplitudes of switchbacks decrease faster than the overall turbulent fluctuations, in a way consistent with the radial decrease of the mean magnetic field. This could be the result of a saturation of amplitudes and may be a signature of decay processes of large amplitude Alfvénic fluctuations in the solar wind. We find that the evolution of switchback occurrence in the solar wind is scale dependent: the fraction of longer-duration switchbacks increases with radial distance, whereas it decreases for shorter switchbacks. This implies that switchback dynamics is a complex process involving both decay and in situ generation in the inner heliosphere. We confirm that switchbacks can be generated by the expansion, although other types of switchbacks generated closer to the Sun cannot be ruled out
A short narrative review of the feasibility of adopting mild ovarian stimulation for IVF as the current standard of care.
Introduction Mild ovarian stimulation has been conceived, proposed and implemented in clinical practice as a safer and cheaper alternative to conventional strategies of controlled ovarian hyperstimulation in preparation for in vitro fertilization (IVF). Our aim was to summarize the key evidence on this topic and explore its possible role as the standard treatment option for women undergoing IVF. Materials and Methods A short narrative review of the existing literature, with emphasis on mild ovarian stimulation clinical and cost effectiveness, as well as treatment limitations. Results Numerous studies highlight mild ovarian stimulation’s favorable characteristics with respect to oocyte/embryo quality, reduced patient risk, and ease of intervention. There is, however, a need for high-quality laboratory environment. Limitations regarding poor responders, older women, or those seeking ovarian stimulation for non-infertility indications should also be considered. Finally, outcomes on the cumulative success rates and the cost effectiveness of mild ovarian stimulation remain inconclusive. Conclusion Mild ovarian stimulation protocols for IVF should currently be implemented only in carefully selected populations. Further research is needed to clarify the remaining controversies in this IVF approach.</p
Genetic diversity of Thaumetopoea pityocampa in Greece: the role of Quaternary changes in Aegean Sea
Thaumetopoea pityocampa, the winter pine
processionary moth, is one of the most important pests
of pine trees in the Mediterranean region. To learn more
about the refugial areas within the greater refugium
of Greece, samples from 15 local populations were
collected. Analysis of the Cytochrome Oxidase I region
identified 15 haplotypes. One strongly supported clade
was found, separating the Aegean island of Lesvos from
the mainland populations. Mdiv analysis showed that
this clade diverged from the general clade 155,000 y.a.,
suggesting the sea level changes during the Quaternary
Period as a possible reason for its seclusion. Additionally,
comparisons with similar studies in this region revealed
a possible colonization of the eastern Aegean islands
from the Turkish mainland rather than from Greece.
However, no strong isolation-by-distance events were
detected among the mainland populations, which could
be attributed to the joint effect of regular gene flow and
the lack of insurmountable geographic barriers. Finally,
regarding population structure, Bayesian analysis as well
as neutrality tests pointed towards an ongoing population
expansion which verifies the potential invasiveness of
this pest species, something that will have to be dealt with
under the influence of climate change