A new probe of the small-scale primordial power spectrum: astrometric microlensing by ultracompact minihalos

The dark matter enclosed in a density perturbation with a large initial amplitude (delta-rho/rho > 1e-3) collapses shortly after recombination and forms an ultracompact minihalo (UCMH). Their high central densities make UCMHs especially suitable for detection via astrometric microlensing: as the UCMH moves, it changes the apparent position of background stars. A UCMH with a mass larger than a few solar masses can produce a distinctive astrometric microlensing signal that is detectable by the space astrometry mission Gaia. If Gaia does not detect gravitational lensing by any UCMHs, then it establishes an upper limit on their abundance and constrains the amplitude of the primordial power spectrum for k~2700 Mpc^{-1}. These constraints complement the upper bound on the amplitude of the primordial power spectrum derived from limits on gamma-ray emission from UCMHs because the astrometric microlensing signal produced by an UCMH is maximized if the dark-matter annihilation rate is too low to affect the UCMH's density profile. If dark matter annihilation within UCMHs is not detectable, a search for UCMHs by Gaia could constrain the amplitude of the primordial power spectrum to be less than 1e-5; this bound is three orders of magnitude stronger than the bound derived from the absence of primordial black holes.Comment: 17 pages, 6 figures, references added and minor changes made to match version published in PR

A High Contrast Imaging Survey of SIM Lite Planet Search Targets

With the development of extreme high contrast ground-based adaptive optics instruments and space missions aimed at detecting and characterizing Jupiter- and terrestrial-mass planets, it is critical that each target star be thoroughly vetted to determine whether it is a viable target given both the instrumental design and scientific goals of the program. With this in mind, we have conducted a high contrast imaging survey of mature AFGKM stars with the PALAO/PHARO instrument on the Palomar 200 inch telescope. The survey reached sensitivities sufficient to detect brown dwarf companions at separations of > 50 AU. The results of this survey will be utilized both by future direct imaging projects such as GPI, SPHERE and P1640 and indirect detection missions such as SIM Lite. Out of 84 targets, all but one have no close-in (0.45-1") companions and 64 (76%) have no stars at all within the 25" field-of-view. The sensitivity contrasts in the Ks passband ranged from 4.5 to 10 for this set of observations. These stars were selected as the best nearby targets for habitable planet searches owing to their long-lived habitable zones (> 1 billion years). We report two stars, GJ 454 and GJ 1020, with previously unpublished proper motion companions. In both cases, the companions are stellar in nature and are most likely M dwarfs based on their absolute magnitudes and colors. Based on our mass sensitivities and level of completeness, we can place an upper limit of ~17% on the presence of brown dwarf companions with masses >40 MJ at separations of 1 arcsecond. We also discuss the importance of including statistics on those stars with no detected companions in their field of view for the sake of future companion searches and an overall understanding of the population of low-mass objects around nearby stars.Comment: Accepted to PASP, Figure 7 available upon reques

The Franchising Effect on the Al-Qaeda Enterprise and Related Transnational Terror Groups: Patterns of Evolution of Al-Qaeda Affiliates in the 21st Century

The attacks of September 11, 2001 by Al-Qaeda-sponsored militants represented a high- water mark for the terrorist organization in its self-styled journey to become the inspirational Islamic vanguard for disenchanted Muslims across the globe. In the years that followed these attacks, the Al-Qaeda enterprise underwent a constant rate of evolution and mutation, resulting in a phenomenon of parallel and like-minded Islamist groups pledging allegiance to Usama bin Laden and his ideological vision of a global jihad. Instead of strengthening the overall organization, this expansion diluted the command and control of Al-Qaeda senior leaders in their ability to shape the overall movement it once led, as well as displaced the locus of power for the larger movement among various powerbrokers with unpredictable agendas and worldviews. Instead, the affiliation and franchising of parallel groups proved to result in only temporary changes in organizational behavior of these affiliates, as the domestic social, political, and economic forces present in these regions and nation-states had much more effect on Al-Qaeda affiliates and their members than the traditional Al-Qaeda agenda. This dissertation is innovative in comparing Al-Qaeda Central in 2001 to its corollary manifestations as Al-Qaeda in Iraq (AQI), Al-Qaeda in the Arabian Peninsula (AQAP), and Al-Qaeda in the Islamic Maghreb (AQIM) across four variables of study and across time. The findings of this study help to explain the evolution of Al-Qaeda as the most capable and feared terrorist organization that it occupied at the beginning of the decade into a vague conglomerate of affiliates and sub-groups fifteen years later. The short term gains offered by affiliation for parallel movements under the AQ brand were exploited by these affiliates for their own particular interests, but ultimately discarded for domestic welfare of the affiliates themselves, even running counter to the transnational agenda of Bin Laden’s Al-Qaeda. Breaking new ground, this research attempts to understand the evolution of the organization through the affiliation of parallel movements, what effect this affiliation has, and to identify signposts and patterns that can be overlaid on future manifestations of the global Islamic jihadist movement, either under Al-Qaeda leadership or some other organization

The Effects of Seasonality of Manufactured Milk Production on Dairy Manufacturing Firms\u27 Efficiency

Seasonal variations in milk production have been a major problem of the South Dakota dairy manufacturing industry for a number of years. Processors faced throughout the year with wide fluctuations in the volume of milk received are prevented from obtaining optimum utilization of equipment, labor, and other plant facilities. Manufacturers cannot decrease operating costs materially as volume declines from peak levels since a major portion of the plant’s costs are fixed. The above generally indicates the nature of this study. How then, is South Dakota affected by this problem? Seasonality of milk production in South Dakota is decreasing, but the rate of decrease has not been sufficient to eliminate the existing problem nor has it been consistent over the last several years. The objective of this study were: to determine the degree of increased efficiency of the firm which might be expected to result from reducing the seasonal variations of milk production and increasing receipts to a level now attained only three months of the year, to estimate the effect of increased efficiency of the firm on producer milk prices

Laser-only adaptive optics achieves significant image quality gains compared to seeing-limited observations over the entire sky

Adaptive optics laser guide star systems perform atmospheric correction of stellar wavefronts in two parts: stellar tip-tilt and high-spatial-order laser-correction. The requirement of a sufficiently bright guide star in the field-of-view to correct tip-tilt limits sky coverage. Here we show an improvement to effective seeing without the need for nearby bright stars, enabling full sky coverage by performing only laser-assisted wavefront correction. We used Robo-AO, the first robotic AO system, to comprehensively demonstrate this laser-only correction. We analyze observations from four years of efficient robotic operation covering 15,000 targets and 42,000 observations, each realizing different seeing conditions. Using an autoguider (or a post-processing software equivalent) and the laser to improve effective seeing independent of the brightness of a target, Robo-AO observations show a 39+/-19% improvement to effective FWHM, without any tip-tilt correction. We also demonstrate that 50% encircled-energy performance without tip-tilt correction remains comparable to diffraction-limited, standard Robo-AO performance. Faint-target science programs primarily limited by 50% encircled-energy (e.g. those employing integral field spectrographs placed behind the AO system) may see significant benefits to sky coverage from employing laser-only AO.Comment: Accepted for publication in The Astronomical Journal. 7 pages, 6 figure

Multiplicity of the Galactic Senior Citizens: A high-resolution search for cool subdwarf companions

Cool subdwarfs are the oldest members of the low mass stellar population. Mostly present in the galactic halo, subdwarfs are characterized by their low metallicity. Measuring their binary fraction and comparing it to solar metallicity stars could give key insights into the star formation process early in the history of the Milky Way. However, because of their low luminosity and relative rarity in the solar neighborhood, binarity surveys of cool subdwarfs have suffered from small sample sizes and incompleteness. Previous surveys have suggested that the binary fraction of red subdwarfs is much lower than for their main sequence cousins. Using the highly efficient RoboAO system, we present the largest yet high-resolution survey of subdwarfs, sensitive to angular separations, down to 0.15 arcsec, and contrast ratios, up to 6 magnitude difference, invisible in past surveys. Of 344 target cool subdwarfs, 40 are in multiple systems, 16 newly discovered, for a binary fraction of 11.6 percent and 1.8 percent error. We also discovered 6 triple star systems for a triplet fraction of 1.7 percent and 0.7 percent error. Comparisons to similar surveys of solar metallicity dwarf stars gives a 3 sigma disparity in luminosity between companion stars, with subdwarfs displaying a shortage of low contrast companions.Comment: 13 pages, 10 figures, submitted to Ap