Saint Mary's University

About: Saint Mary's University is a education organization based out in Halifax, Nova Scotia, Canada. It is known for research contribution in the topics: Population & Stars. The organization has 1931 authors who have published 4993 publications receiving 143226 citations.

MOST detects variability on τ Bootis A possibly induced by its planetary companion

Abstract: Context. There is considerable interest in the possible interaction between parent stars and giant planetary companions in 51 Peg-type systems. Aims. We shall demonstrate from MOST satellite photometry and Call K line emission that there has been a persistent, variable region on the surface of r Boo A, which tracked its giant planetary companion for some 440 planetary revolutions and lies ∼68° (Φ = 0.8) in advance of the sub-planetary point. Methods. The light curves are folded on a range of periods centered on the planetary orbital period, and phase-dependent variability is quantified by Fourier methods and by the mean absolute deviation (MAD) of the folded data for both the photometry and the Call K line reversals. Results. The region varies in brightness on the time scale of a rotation by ∼1 mmag. In 2004 it resembled a dark spot of variable depth, while in 2005 it varied between bright and dark. The 2004 light curve gives a spot rotation period of 3.5 ± 0.7 d compared to the known planetary orbital period of 3.3125 d. The amplitude spectrum of the 2005 light curve shows no marked peak at the orbital period but the mean absolute deviation (MAD) of the light curve has a well-defined maximum (half width ∼0.15 d) centered on the orbital frequency. Over the 123 planetary orbits spanned by the photometry, the variable region detected in 2004 and in 2005 are synchronized to the planetary orbital period within 0.0015 d. The Call K line in 2001, 2002, and 2003 also shows enhanced K-line variability centered on Φ = 0.8, extending coverage to some 440 planetary revolutions. Conclusions. The apparently constant rotation period of the variable region and its rapid variation make an explanation in terms of conventional star spots unlikely. The lack of complementary variability at Φ = 0.3 and the detection of the variable region so far in advance of the sub-planetary point excludes tidal excitation, but the combined photometric and Call K line reversal results make a good case for an active region induced magnetically on the surface of T Boo A by its planetary companion.

Substructure: Clues to the Formation of Clusters of Galaxies

Abstract: We have examined the spatial distribution of substructure in clusters of galaxies using Einstein X-ray observations. Subclusters are found to have a markedly anisotropic distribution that reflects the surrounding matter distribution on supercluster scales. Our results suggest a picture in which cluster formation proceeds by mergers of subclusters along large-scale filaments. The implications of such an anisotropic formation process for the shapes, orientations, and kinematics of clusters are discussed briefly.

Positive Leadership and Employee Well-Being

Abstract: We report two studies examining the relationship between positive leadership behaviors and employee well-being. In the first, data from 454 nursing home employees showed that (a) a newly developed measure of positive leadership was distinct from transformational leadership and (b) positive leadership behaviors predicted context-specific and context-free well-being after controlling for transformational and abusive leadership. In the second study, data from a daily diary study (N = 26) showed that (a) positive leadership predicted positive, but not negative, employee affect and (b) positive leadership interacted with transformational leadership to predict employees positive affect.

The Cool Interstellar Medium in S0 Galaxies. I. A Survey of Molecular Gas

Abstract: Lenticular galaxies remain remarkably mysterious as a class. Observations to date have not led to any broad consensus about their origins, properties, and evolution, although they are often thought to have formed in one big burst of star formation early in the history of the universe and to have evolved relatively passively since then. In that picture, current theory predicts that stellar evolution returns substantial quantities of gas to the interstellar medium; most is ejected from the galaxy, but significant amounts of cool gas might be retained. Past searches for that material, though, have provided unclear results. We present results from a survey of molecular gas in a volume-limited sample of field S0 galaxies selected from the Nearby Galaxies Catalog. CO emission is detected from 78% of the sample galaxies. We find that the molecular gas is almost always located inside the central few kiloparsecs of a lenticular galaxy, meaning that in general it is more centrally concentrated than in spirals. We combine our data with H I observations from the literature to determine the total masses of cool and cold gas. Curiously, we find that, across a wide range of luminosity, the most gas-rich galaxies have ~10% of the total amount of gas ever returned by their stars. That result is difficult to understand within the context of either monolithic or hierarchical models of evolution of the interstellar medium.