Cluster Origin of Triple Star HD 188753 and its Planet

The recent discovery by M. Konacki of a ``hot Jupiter'' in the hierarchical triple star system HD 188753 challenges established theories of giant-planet formation. If the orbital geometry of the triple has not changed since the birth of the planet, then a disk around the planetary host star would probably have been too compact and too hot for a Jovian planet to form by the core-accretion model or gravitational collapse. This paradox is resolved if the star was initially either single or had a much more distant companion. It is suggested here that a close multi-star dynamical encounter transformed this initial state into the observed triple, an idea that follows naturally if HD 188753 formed in a moderately dense stellar system--perhaps an open cluster--that has since dissolved. Three distinct types of encounters are investigated. The most robust scenario involves an initially single planetary host star that changes places with the outlying member of a pre-existing hierarchical triple.Comment: Accepted by ApJL; minor changes from origina

Cost studies for commercial fuselage crown designs

Studies were conducted to evaluate the cost and weight potential of advanced composite design concepts in the crown region of a commercial transport. Two designs from each of three design families were developed using an integrated design-build team. A range of design concepts and manufacturing processes were included to allow isolation and comparison of cost centers. Detailed manufacturing/assembly plans were developed as the basis for cost estimates. Each of the six designs was found to have advantages over the 1995 aluminum benchmark in cost and weight trade studies. Large quadrant panels and cobonded frames were found to save significant assembly labor costs. Comparisons of high- and intermediate-performance fiber systems were made for skin and stringer applications. Advanced tow placement was found to be an efficient process for skin lay up. Further analysis revealed attractive processes for stringers and frames. Optimized designs were informally developed for each design family, combining the most attractive concepts and processes within that family. A single optimized design was selected as the most promising, and the potential for further optimization was estimated. Technical issues and barriers were identified

From climatological to small-scale applications: simulating water isotopologues with ICON-ART-Iso (version 2.3)

We present the new isotope-enabled model ICON-ART-Iso. The physics package of the global ICOsahedral Nonhydrostatic (ICON) modeling framework has been extended to simulate passive moisture tracers and the stable isotopologues HDO and H182O. The extension builds on the infrastructure provided by ICON-ART, which allows for high flexibility with respect to the number of related water tracers that are simulated. The physics of isotopologue fractionation follow the model COSMOiso. We first present a detailed description of the physics of fractionation that have been implemented in the model. The model is then evaluated on a range of temporal scales by comparing with measurements of precipitation and vapor. A multi-annual simulation is compared to observations of the isotopologues in precipitation taken from the station network GNIP (Global Network for Isotopes in Precipitation). ICON-ART-Iso is able to simulate the main features of the seasonal cycles in δD and δ18O as observed at the GNIP stations. In a comparison with IASI satellite retrievals, the seasonal and daily cycles in the isotopologue content of vapor are examined for different regions in the free troposphere. On a small spatial and temporal scale, ICON-ART-Iso is used to simulate the period of two flights of the IAGOS-CARIBIC aircraft in September 2010, which sampled air in the tropopause region influenced by Hurricane Igor. The general features of this sample as well as those of all tropical data available from IAGOS-CARIBIC are captured by the model. The study demonstrates that ICON-ART-Iso is a flexible tool to analyze the water cycle of ICON. It is capable of simulating tagged water as well as the isotopologues HDO and H182

Exploring the Nature of Weak Chandra Sources near the Galactic Centre

We present results from the first near-IR imaging of the weak X-ray sources discovered in the Chandra/ACIS-I survey (Wang et al. 2002) towards the Galactic Centre (GC). These ~800 discrete sources, which contribute significantly to the GC X-ray emission, represent an important and previously unknown population within the Galaxy. From our VLT observations we will identify likely IR counterparts to a sample of the hardest sources, which are most likely X-ray binaries. With these data we can place constraints on the nature of the discrete weak X-ray source population of the GC.Comment: In Proc. of ``Interacting Binaries: Accretion, Evolution, and Outcomes'', eds. L. A. Antonelli et al., AIP, Cefalu, Sicily, 200

Flammability limits, ignition energy, and flame speeds in H₂–CH₄–NH₃–N₂O–O₂–N₂ mixtures

Experiments on flammability limits, ignition energies, and flame speeds were carried out in a 11.25- and a 400-liter combustion vessel at initial pressures and temperatures of 100 kPa and 295 K, respectively. Flammability maps of hydrogen–nitrous oxide–nitrogen, methane–nitrous oxide–nitrogen, ammonia–nitrous oxide–nitrogen, and ammonia–nitrous oxide–air, as well as lean flammability limits of various hydrogen–methane–ammonia–nitrous oxide–oxygen–nitrogen mixtures were determined. Ignition energy bounds of methane–nitrous oxide, ammonia–nitrous oxide, and ammonia–nitrous oxide–nitrogen mixtures have been determined and the influence of small amounts of oxygen on the flammability of methane–nitrous oxide–nitrogen mixtures has been investigated. Flame speeds have been measured and laminar burning velocities have been determined for ammonia–air–nitrous oxide and various hydrogen–methane–ammonia–nitrous oxide–oxygen–nitrogen mixtures. Lower and upper flammability limits (mixing fan on, turbulent conditions) for ignition energies of 8 J are: H₂–N₂O: 4.5 ∼ 5.0% H₂(LFL), 76 ∼ 80% H₂(UFL); CH₄–N₂O: 2.5 ∼ 3.0% CH₄(LFL), 43 ∼ 50% CH₄(UFL); NH₃–N₂O: 5.0 ∼ 5.2% NH₃(LFL), 67.5 ∼ 68% NH₃(UFL). Inerting concentrations are: H₂–N₂O–N₂: 76% N₂; CH₄–N₂O–N₂: 70.5% N₂; NH₃–N₂O–N₂: 61% N₂; NH₃–N₂O–air: 85% air. Flammability limits of methane–nitrous oxide–nitrogen mixtures show no pronounced dependence on small amounts of oxygen (<5%). Generally speaking, flammable gases with large initial amounts of nitrous oxide or ammonia show a strong dependence of flammability limits on ignition energy

Flammability limits, ignition energy, and flame speeds in H₂–CH₄–NH₃–N₂O–O₂–N₂ mixtures

Experiments on flammability limits, ignition energies, and flame speeds were carried out in a 11.25- and a 400-liter combustion vessel at initial pressures and temperatures of 100 kPa and 295 K, respectively. Flammability maps of hydrogen–nitrous oxide–nitrogen, methane–nitrous oxide–nitrogen, ammonia–nitrous oxide–nitrogen, and ammonia–nitrous oxide–air, as well as lean flammability limits of various hydrogen–methane–ammonia–nitrous oxide–oxygen–nitrogen mixtures were determined. Ignition energy bounds of methane–nitrous oxide, ammonia–nitrous oxide, and ammonia–nitrous oxide–nitrogen mixtures have been determined and the influence of small amounts of oxygen on the flammability of methane–nitrous oxide–nitrogen mixtures has been investigated. Flame speeds have been measured and laminar burning velocities have been determined for ammonia–air–nitrous oxide and various hydrogen–methane–ammonia–nitrous oxide–oxygen–nitrogen mixtures. Lower and upper flammability limits (mixing fan on, turbulent conditions) for ignition energies of 8 J are: H₂–N₂O: 4.5 ∼ 5.0% H₂(LFL), 76 ∼ 80% H₂(UFL); CH₄–N₂O: 2.5 ∼ 3.0% CH₄(LFL), 43 ∼ 50% CH₄(UFL); NH₃–N₂O: 5.0 ∼ 5.2% NH₃(LFL), 67.5 ∼ 68% NH₃(UFL). Inerting concentrations are: H₂–N₂O–N₂: 76% N₂; CH₄–N₂O–N₂: 70.5% N₂; NH₃–N₂O–N₂: 61% N₂; NH₃–N₂O–air: 85% air. Flammability limits of methane–nitrous oxide–nitrogen mixtures show no pronounced dependence on small amounts of oxygen (<5%). Generally speaking, flammable gases with large initial amounts of nitrous oxide or ammonia show a strong dependence of flammability limits on ignition energy

All Transients, All the Time: Real-Time Radio Transient Detection with Interferometric Closure Quantities

We demonstrate a new technique for detecting radio transients based on interferometric closure quantities. The technique uses the bispectrum, the product of visibilities around a closed-loop of baselines of an interferometer. The bispectrum is calibration independent, resistant to interference, and computationally efficient, so it can be built into correlators for real-time transient detection. Our technique could find celestial transients anywhere in the field of view and localize them to arcsecond precision. At the Karl G. Jansky Very Large Array (VLA), such a system would have a high survey speed and a 5-sigma sensitivity of 38 mJy on 10 ms timescales with 1 GHz of bandwidth. The ability to localize dispersed millisecond pulses to arcsecond precision in large volumes of interferometer data has several unique science applications. Localizing individual pulses from Galactic pulsars will help find X-ray counterparts that define their physical properties, while finding host galaxies of extragalactic transients will measure the electron density of the intergalactic medium with a single dispersed pulse. Exoplanets and active stars have distinct millisecond variability that can be used to identify them and probe their magnetospheres. We use millisecond time scale visibilities from the Allen Telescope Array (ATA) and VLA to show that the bispectrum can detect dispersed pulses and reject local interference. The computational and data efficiency of the bispectrum will help find transients on a range of time scales with next-generation radio interferometers.Comment: Accepted to ApJ. 8 pages, 5 figures, 2 tables. Revised to include discussion of non-Gaussian statistics of techniqu

The Timing of Nine Globular Cluster Pulsars

We have used the Robert C. Byrd Green Bank Telescope to time nine previously known pulsars without published timing solutions in the globular clusters M62, NGC 6544, and NGC 6624. We have full timing solutions that measure the spin, astrometric, and (where applicable) binary parameters for six of these pulsars. The remaining three pulsars (reported here for the first time) were not detected enough to establish solutions. We also report our timing solutions for five pulsars with previously published solutions, and find good agreement with past authors, except for PSR J1701-3006B in M62. Gas in this system is probably responsible for the discrepancy in orbital parameters, and we have been able to measure a change in the orbital period over the course of our observations. Among the pulsars with new solutions we find several binary pulsars with very low mass companions (members of the so-called "black widow" class) and we are able to place constraints on the mass-to-light ratio in two clusters. We confirm that one of the pulsars in NGC 6624 is indeed a member of the rare class of non-recycled pulsars found in globular clusters. We also have measured the orbital precession and Shapiro delay for a relativistic binary in NGC 6544. If we assume that the orbital precession can be described entirely by general relativity, which is likely, we are able to measure the total system mass (2.57190(73) M_sun) and companion mass (1.2064(20) M_sun), from which we derive the orbital inclination [sin(i) = 0.9956(14)] and the pulsar mass (1.3655(21) M_sun), the most precise such measurement ever obtained for a millisecond pulsar. The companion is the most massive known around a fully recycled pulsar.Comment: Published in ApJ; 33 pages, 5 figures, 7 table

Modulation of Atmospheric River Occurrence and Associated Precipitation Extremes in the North Atlantic Region by European Weather Regimes

ISSN:0094-8276ISSN:1944-800

The future of midlatitude cyclones

This is the final version. Available from the publisher via the DOI in this record.Purpose of Review This review brings together recent research on the structure, characteristics, dynamics, and impacts of extratropical cyclones in the future. It draws on research using idealized models and complex climate simulations, to evaluate what is known and unknown about these future changes. Recent Findings There are interacting processes that contribute to the uncertainties in future extratropical cyclone changes, e.g., changes in the horizontal and vertical structure of the atmosphere and increasing moisture content due to rising temperatures. Summary While precipitation intensity will most likely increase, along with associated increased latent heating, it is unclear to what extent and for which particular climate conditions this will feedback to increase the intensity of the cyclones. Future research could focus on bridging the gap between idealized models and complex climate models, as well as better understanding of the regional impacts of future changes in extratropical cyclones.Natural Environment Research Council (NERC