AskMN FY10 Report Highlights

In December, Minitex released the AskMN: The Librarian is In! FY10 annual report. In FY10 AskMN received and surpassed its 10,000th question receiving a total of 18,701 requests in all. It was a very active and productive year for online reference users. The service grew exponentially from FY08/09 seeing a rise of 57% more requests in FY10. Please visit our poster session to see detailed highlights of that fiscal year in review and engage in discussion about AskMN activity and growth. ABOUT THE PRESENTER: Carla Pfahl is a Reference/Outreach & Instruction Librarian at Minitex

Impact of Stellar Dynamics on the Frequency of Giant Planets in Close Binaries

Hostile tidal forces may inhibit the formation of Jovian planets in binaries with semimajor axes of ≾50 AU, binaries that might be called "close" in this context. As an alternative to in situ planet formation, a binary can acquire a giant planet when one of its original members is replaced in a dynamical interaction with another star that hosts a planet. Simple scaling relations for the structure and evolution of star clusters, coupled with analytic arguments regarding binary-single and binary-binary scattering, indicate that dynamical processes can deposit Jovian planets in <1% of close binaries. If ongoing and future exoplanet surveys measure a much larger fraction, it may be that giant planets do somehow form frequently in such systems

Binary Disruption by Massive Black Holes in Globular Clusters

A massive (~10^2-10^4 Msun) black hole at the center of a globular cluster will tidally disrupt binaries that pass sufficiently close. Such an encounter results in the capture of one binary component by the black hole and ejection of the other star. A 10^3 Msun black hole disrupts one binary every 1-10 Myr; captured stars orbit with initial periods of days to decades. Although >~100 stars are captured in only 1 Gyr, the number with periods of <10 yr at any one time is probably less than 10, regulated by stellar interactions and tidal disruption by the black hole. Binary disruption and stellar capture should be critically examined with detailed numerical simulations, in order to corroborate the analytic results given here and to weigh possible observational consequences.Comment: 4 pages, 1 figure, Accepted by ApJ, minor correction

Relativistic Binary Pulsars with Black-Hole Companions

Binaries containing a stellar-mass black hole and a recycled radio pulsar have so far eluded detection. We present a focused investigation of the formation and evolution of these systems in the Galactic disk, highlighting the factors that limit their numbers and the reasons why they may be extremely rare. We surmise that the birthrate of black-hole/recycled-pulsar binaries in the Galactic disk is probably no higher than ~10^{-7}/yr, and may be much less. Simple arguments regarding common-envelope evolution suggest that these binaries should have orbital periods less than 10 hr and an average lifetime of <~10^8 yr before coalescence due to the emission of gravitational radiation. We expect that fewer than ~10 of these compact, relativistic binaries currently reside in the Galactic disk, less than 0.1--1% of the number of double neutron stars. The discovery of two or more black-hole/recycled-pulsar binaries using current radio telescopes would tightly constrain certain ideas regarding the evolution of massive stars, dynamical mass transfer, and black-hole formation.Comment: 10 pages, 6 figures, accepted by ApJ, minor change

Formation of Compact Binaries in Globular Clusters

We report here on two complementary population synthesis studies which relate directly to the formation and evolution of neutron star binaries in globular clusters. In the first, we compute the probability of retaining neutron stars in globular clusters, and quantitatively confirm the idea that the retention fraction for neutron stars born in binary systems is greatly enhanced over those born in isolated stars. However, the retention fraction may well be insufficient to explain the current population of neutron star binaries. In the second study, we follow a large population of primordial binaries and neutron stars throughout the lifetime of a globular cluster whose properties may be similar to 47 Tuc. We directly compute all 3-body interactions among binary systems, neutron stars, and isolated field stars throughout the history of the cluster. The evolution of certain types of neutron star binaries is followed up to the current epoch. The numbers of close, recycled, binary radio pulsars are evaluated and compared with the results of radio observations.Comment: 14 pages; to appear in Evolution of Binary and Multiple Star Systems, a Meeting in Celebration of Peter Eggleton's 60th Birthday, Bormio, Italy, ASP Conference Series, eds. P. Podsiadlowski et a

Wind loads on heliostats and photovoltaic trackers

New findings on wind loads help to reduce solar energy cos

Processes determining heat waves across different European climates

This study presents a comprehensive analysis of processes determining heat waves across different climates in Europe for the period 1979–2016. Heat waves are defined using a percentile‐based index and the main processes quantified along trajectories are adiabatic compression by subsidence and local and remote diabatic processes in the upper and lower troposphere. This Lagrangian analysis is complemented by an Eulerian calculation of horizontal temperature advection. During typical summers in Europe, one or two heat waves occur, with an average duration of five days. Whereas high near‐surface temperatures over Scandinavia are accompanied by omega‐like blocking structures at 500 hPa, heat waves over the Mediterranean are connected to comparably flat ridges. Tracing air masses backwards from the heat waves, we identify three trajectory clusters with coherent thermodynamic characteristics, vertical motions, and geographic origins. In all regions, horizontal temperature advection is almost negligible. In two of the three clusters, subsidence in the free atmosphere is very important in establishing high temperatures near the surface, while the air masses in the third cluster are warmed primarily due to diabatic heating near the surface. Large interregional differences occur between the British Isles and western Russia. Over the latter region, near‐surface transport and diabatic heating appear to be very important in determining the intensity of the heat waves, whereas subsidence and adiabatic warming are of first‐order importance for the British Isles. Although the large‐scale pattern is quasistationary during heat wave days, new air masses are entrained steadily into the lower troposphere during the life cycle of a heat wave. Overall, the results of the present study provide a guideline as to which processes and diagnostics weather and climate studies should focus on to understand the severity of heat waves