810 research outputs found
Orbital and physical properties of planets and their hosts: new insights on planet formation and evolution
We explore the relations between physical and orbital properties of planets
and properties of their host stars to identify the main observable signatures
of the formation and evolution processes of planetary systems. We use a large
sample of FGK dwarf planet hosts with stellar parameters derived in a
homogeneous way from the SWEET-Cat database to study the relation between
stellar metallicity and position of planets in the period-mass diagram. In the
second part we use all the RV-detected planets orbiting FGK stars to explore
the role of planet-disk and planet-planet interaction on the evolution of
orbital properties of planets with masses above 1MJup. We show that planets
orbiting metal-poor stars have longer periods than those in metal-rich systems.
This trend is valid for masses at least from 10MEarth to 4MJup. Earth-like
planets orbiting metal-rich stars always show shorter periods (fewer than 20
days) than those orbiting metal-poor stars. We also found statistically
significant evidence that very high mass giants have on average more eccentric
orbits than giant planets with lower mass.Finally, we show that the
eccentricity of planets with masses higher than 4MJup tends to be lower for
planets with shorter periods. Our results suggest that the planets in the P-MP
diagram are evolving differently because of a mechanism that operates over a
wide range of planetary masses. This mechanism is stronger or weaker depending
on the metallicity of the respective system. One possibility is that planets in
metal-poor disks form farther out from their central star and/or they form
later and do not have time to migrate as far as the planets in metal-rich
systems. The trends and dependencies obtained for very high mass planetary
systems suggest that planet-disk interaction is a very important and
orbit-shaping mechanism for planets in the high-mass domain. Shortened.Comment: 8 pages, 4 figures and 1 table. Accepted for publication in A&
FLICK: developing and running application-specific network services
Data centre networks are increasingly programmable, with application-specific network services proliferating, from custom load-balancers to middleboxes providing caching and aggregation. Developers must currently implement these services using traditional low-level APIs, which neither support natural operations on application data nor provide efficient performance isolation. We describe FLICK, a framework for the programming and execution of application-specific network services on multi-core CPUs. Developers write network services in the FLICK language, which offers high-level processing constructs and application-relevant data types. FLICK programs are translated automatically to efficient, parallel task graphs, implemented in C++ on top of a user-space TCP stack. Task graphs have bounded resource usage at runtime, which means that the graphs of multiple services can execute concurrently without interference using cooperative scheduling. We evaluate FLICK with several services (an HTTP load-balancer, a Memcached router and a Hadoop data aggregator), showing that it achieves good performance while reducing development effort
Constraining planet structure from stellar chemistry: the cases of CoRoT-7, Kepler-10, and Kepler-93
We explore the possibility that the stellar relative abundances of different
species can be used to constrain the bulk abundances of known transiting rocky
planets. We use high resolution spectra to derive stellar parameters and
chemical abundances for Fe, Si, Mg, O, and C in three stars hosting low mass,
rocky planets: CoRoT-7, Kepler-10, and Kepler-93. These planets follow the same
line along the mass-radius diagram, pointing toward a similar composition. The
derived abundance ratios are compared with the solar values. With a simple
stoichiometric model, we estimate the iron mass fraction in each planet,
assuming stellar composition. We show that in all cases, the iron mass fraction
inferred from the mass-radius relationship seems to be in good agreement with
the iron abundance derived from the host star's photospheric composition. The
results suggest that stellar abundances can be used to add constraints on the
composition of orbiting rocky planets.Comment: A&A Letters, in pres
Potential for an underwater glider component as part of the Global Ocean Observing System
The contributions of autonomous underwater gliders as an observing platform in the in-situ global ocean observing system (GOOS) are investigated. The assessment is done in two ways: First, the existing in-situ observing platforms contributing to GOOS (floats, surface drifters, moorings, research/commercial ships) are characterized in terms of their current capabilities in sampling key physical and bio-geochemical oceanic processes. Next the glidersâ capabilities are evaluated in the context of key applications. This includes an evaluation of 140 references presented in the peer-reviewed literature. It is found that GOOS has adequate coverage of sampling in the open ocean for several physical processes. There is a lack of data in the present GOOS in the transition regions between the open ocean and shelf seas. However, most of the documented scientific glider applications operate in this region, suggesting that a sustained glider component in the GOOS could fill that gap. Glider data are included for routine product generation (e.g. alerts, maps). Other noteworthy process-oriented applications where gliders are important survey tools include local sampling of the (sub)mesoscale, sampling in shallow coastal areas, measurements in hazardous environments, and operational monitoring. In most cases, the glider studies address investigations and monitoring of processes across multiple disciplines, making use of the ease to implement a wide range of sensors to gliders. The maturity of glider operations, the wide range of applications that map onto growing GOOS regional needs, and the maturity of glider data flow all justify the formal implementation of gliders into the GOOS. Remaining challenges include the execution of coordinated multinational missions in a sustained mode as well as considering capacity-building aspects in glider operations as well as glider data use
Imaging features of retroperitoneal extra-adrenal paragangliomas in 10 dogs
Retroperitoneal paragangliomas are rare tumors of the neuroendocrine system. Only a few canine case reports are available with rare descriptions of their imaging features. The objectives of this multi-center, retrospective case series study were to describe the diagnostic imaging features of confirmed retroperitoneal paragangliomas and specify their location. Medical records and imaging studies of 10 affected dogs with cytological or histopathologic results concordant with retroperitoneal paragangliomas were evaluated. Dogs had a median age of 9 years. Four of them had clinical signs and laboratory reports compatible with excessive production of catecholamines. Six ultrasound, four CT, four radiographic, and one MRI studies were included. The paragangliomas did not have a specific location along the aorta. They were of various sizes (median 33 mm, range: 9â85 mm of length). Masses had heterogeneous parenchyma in six of 10 dogs, regardless of the imaging modality. Strong contrast enhancement was found in all CT studies. Encircling of at least one vessel was detected in six of 10 masses, clear invasion of a vessel was identified in one of 10 masses. In five of 10 cases, the masses were initially misconstrued as lymph nodes by the on-site radiologist. Retroperitoneal paragangliomas appear along the abdominal aorta, often presenting heterogeneous parenchyma, possibly affecting the local vasculature, and displaying strong contrast enhancement on CT. Clinical signs can be secondary to mass effects or excessive catecholamine production. Underdiagnosis and misdiagnosis of this tumor are suspected as they can be silent, of small size, or confused with other structures
Comparison of the spread of two different volumes of contrast medium when performing ultrasound-guided transversus abdominis plane injection in dog cadavers
ObjectivesTo compare, via CT imaging, the spread of different volumes of diluted iodinated contrast medium in the transversus abdominis muscle plane of dog cadavers.MethodsProspective, randomised study. An electro stimulation or a SonoTAP needle was inserted in plane with the ultrasound beam in the fascia between the internal oblique and transversus abdominis muscles. A test dose of 1âml of diluted contrast (30âmg/mL iohexol) was injected to confirm positioning, followed by 0 · 5âmL/kg (n=14) or 1âmL/kg (n=12) and the distribution of the fluid compared.ResultsContrast medium was identified exclusively in the transversus abdominis plane in 19 of 26 dogs. In one dog, the contrast lay between the external and internal oblique muscles and partially in three dogs. Intraperitoneal contrast was detected in 6 of 26 dogs (23%). No significant differences were found in the dorso-ventral or cranio-caudal spread or area of distribution but a significant difference was found in the transverse spread. There was an association between poor ultrasound visualisation of the tip of the needle and intraperitoneal injection.Clinical significanceInjection of 1âmL/kg of diluted contrast did not result in wider cranio-caudal spread in the transversus abdominis muscle plane of dog cadavers when compared with 0 · 5âmL/kg. Intraperitoneal injection is a risk and might be reduced with good needle visualisation
The HARPS search for southern extra-solar planets XXXV. The interesting case of HD41248: stellar activity, no planets?
The search for planets orbiting metal-poor stars is of uttermost importance
for our understanding of the planet formation models. However, no dedicated
searches have been conducted so far for very low mass planets orbiting such
objects. Only a few cases of low mass planets orbiting metal-poor stars are
thus known. Amongst these, HD41248 is a metal-poor, solar-type star on which a
resonant pair of super-Earth like planets has In the present paper we present a
new planet search program that is using the HARPS spectrograph to search for
Neptunes and Super-Earths orbiting a sample of metal-poor FGK dwarfs. We then
present a detailed analysis of an additional 162 radial velocity measurements
of HD41248, obtained within this program, with the goal of confirming the
existence of the proposed planetary system. We analyzed the precise radial
velocities, obtained with the HARPS spectrograph, together with several stellar
activity diagnostics and line profile indicators. A careful analysis shows no
evidence for the planetary system previously announced. One of the signals,
with a period of about 25 days, is shown to be related to the rotational period
of the star, and is clearly seen in some of the activity proxies. The remaining
signal (P~18 days) could not be convincingly retrieved in the new data set. We
discuss possible causes for the complex (evolving) signals observed in the data
of HD41248, proposing that they may be explained by the appearance and
disappearance of active regions on the surface of a star with strong
differential rotation, or by a combination of the sparse data sampling and
active region evolution.Comment: Accepted for publication in A&
Planets around evolved intermediate-mass stars III. Planet candidates and long-term activity signals in six open clusters
[abridged]The aim of this work is to search for planets around evolved stars,
with a special focus on stars more massive than 2\,M in light of
previous findings that show a drop in planet occurrence around stars above this
mass. We used \texttt{kima} to find the Keplerian orbits most capable of
explaining the periodic signals observed in RV data. We also studied the
variation of stellar activity indicators and photometry in order to discard
stellar signals mimicking the presence of planets. We present a planet
candidate in the open cluster NGC3680 that orbits the 1.64\,M star No.
41. The planet has a minimum mass of 5.13M\, and a period of 1155 days.
We also present periodic and large-amplitude RV signals of probable stellar
origin in two more massive stars (5.84 and 3.05\,M in the clusters
NGC2345 and NGC3532). Finally, using new data, we revise the RV signals of the
three stars analysed in our previous paper. We confirm the stellar origin of
the signals observed in NGC2423 No. 3 and NGC4349 No. 127. On the other hand,
the new data collected for IC4651 No. 9122 (1.79\,M) seem to support
the presence of a bona fide planet of 6.22M\, at a period of 744 days,
although more data will be needed to discard a possible correlation with the
CCF-FWHM. The targets presented in this work showcase the difficulties in
interpreting RV data for evolved massive stars. The use of several activity
indicators (CCF-FWHM, CCF-BIS, \ha), photometry, and long-term observations
(covering several orbital and stellar rotational periods) is required to
discern the true nature of the signals. However, in some cases, all this
information is insufficient, and the inclusion of additional data -- such as
the determination of magnetic field variability or RV points in the
near-infrared -- will be necessary to identify the nature of the discovered
signals.Comment: accepted in A&
Planets around evolved intermediate-mass stars III. Planet candidates and long-term activity signals in six open clusters
Planets around evolved intermediate-mass stars III. Planet candidates and long-term activity signals in six open clusters
[abridged]The aim of this work is to search for planets around evolved stars,
with a special focus on stars more massive than 2\,M in light of
previous findings that show a drop in planet occurrence around stars above this
mass. We used \texttt{kima} to find the Keplerian orbits most capable of
explaining the periodic signals observed in RV data. We also studied the
variation of stellar activity indicators and photometry in order to discard
stellar signals mimicking the presence of planets. We present a planet
candidate in the open cluster NGC3680 that orbits the 1.64\,M star No.
41. The planet has a minimum mass of 5.13M\, and a period of 1155 days.
We also present periodic and large-amplitude RV signals of probable stellar
origin in two more massive stars (5.84 and 3.05\,M in the clusters
NGC2345 and NGC3532). Finally, using new data, we revise the RV signals of the
three stars analysed in our previous paper. We confirm the stellar origin of
the signals observed in NGC2423 No. 3 and NGC4349 No. 127. On the other hand,
the new data collected for IC4651 No. 9122 (1.79\,M) seem to support
the presence of a bona fide planet of 6.22M\, at a period of 744 days,
although more data will be needed to discard a possible correlation with the
CCF-FWHM. The targets presented in this work showcase the difficulties in
interpreting RV data for evolved massive stars. The use of several activity
indicators (CCF-FWHM, CCF-BIS, \ha), photometry, and long-term observations
(covering several orbital and stellar rotational periods) is required to
discern the true nature of the signals. However, in some cases, all this
information is insufficient, and the inclusion of additional data -- such as
the determination of magnetic field variability or RV points in the
near-infrared -- will be necessary to identify the nature of the discovered
signals.Comment: accepted in A&
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