The Time Variability Of Spectral Line Asymmetries And Equivalent Widths For The G8 Dwarf Xi Boo A: Evidence For A starpatch

The chromospherically active G8 dwarf Xi Boo A has been monitored spectroscopically for four observing seasons. A total of 121 high resolution, high signal-to-noise Reticon exposures (representing {dollar}\sim{dollar}300 hours of observing) were obtained at the University of Western Ontario\u27s 1.2 m telescope.;The data were analyzed for variations in the mean line asymmetry, line strength, and line broadening, using a combination of line bisector and Fourier techniques. Systematic variations in all quantities were found, which repeat with a period of 6.43 {dollar}\pm{dollar} 0.01 days. The line broadening variations show no evidence of being magnetic in nature, and there is no evidence of a change in period or phase shift over the four seasons.;A self-consistent model is presented, which is found to be very successful at explaining the observations. The model consists of a single surface feature, carried across the stellar disk by rotation. The characteristics of the feature have been determined through extensive use of numerical experiment. The feature\u27s most distinguishing characteristics is a velocity dispersion which is enhanced by a factor of 1.5-2.0 relative to the surrounding photosphere. The feature is found to cover 10% {dollar}\pm{dollar} 5% of the visible disk (2.5% of the total surface), and is {dollar}\sim{dollar}3.7% cooler ({dollar}\sim{dollar}200 K), and 15% fainter than the rest of the star. The feature lies at a relatively high latitude (55{dollar}\sp\circ{dollar} {dollar}\pm{dollar} 10{dollar}\sp\circ{dollar}), and has remained essentially unchanged for at least the four years of this investigation.;The deduced characteristics of the feature cannot be reconciled with the classical sunspot or plage. Therefore, it is believed that this is an entirely new type of stellar feature, quite distinct from both the classical sunspot and plage. The name Starpatch is suggested in order to distinguish it from its solar cousins.;A note is added in warning for those who are attempting to use single exposures of solar-type stars to obtain information on their granulation properties. The existence of starpatches makes conclusions based on a small amount of data very uncertain, since one cannot determine from such data whether or not a starpatch is in view

Duty at All Costs

In his Dereliction of Duty, H. R. McMaster describes the Joint Chiefs of Staff dur- ing Lyndon Johnson’s presidency as the “five silent men” who cooperated with Johnson in deceit instead of speaking the truth about what was happening in Vietnam. McMaster proffers several explanations as to why these officers re- mained silent: the unwritten code of the military professional to stay out of politics; loyalty to their commander in chief; loyalty to their services; and the belief that they could achieve more good on active duty than by retiring and speaking out

A study of the market development of a system of paper electrophoresis instruments

Thesis (M.B.A.)--Boston Universit

Design for a steel mill building

Design for a steel mill buildin

Baseline Shifts do not Predict Attentional Modulation of Target Processing During Feature-Based Visual Attention

Cues that direct selective attention to a spatial location have been observed to increase baseline neural activity in visual areas that represent a to-be-attended stimulus location. Analogous attention-related baseline shifts have also been observed in response to attention-directing cues for non-spatial stimulus features. It has been proposed that baseline shifts with preparatory attention may serve as the mechanism by which attention modulates the responses to subsequent visual targets that match the attended location or feature. Using functional MRI, we localized color- and motion-sensitive visual areas in individual subjects and investigated the relationship between cue-induced baseline shifts and the subsequent attentional modulation of task-relevant target stimuli. Although attention-directing cues often led to increased background neural activity in feature specific visual areas, these increases were not correlated with either behavior in the task or subsequent attentional modulation of the visual targets. These findings cast doubt on the hypothesis that attention-related shifts in baseline neural activity result in selective sensory processing of visual targets during feature-based selective attention

Statement of mining costs in the Butte district three months ending June first 1910

The following cost data were compiled from the monthly cost sheets of the several mines, through a period of three months, April, May and June 1910. These figures were obtained from the cost sheets of the Anaconda Copper Mining Co. and are exact in every instance. The scale of wages and the cost of supplies which prevailed during the period that these figures were created were as follows --page 3