Modifications to the CLASY program

There are no author-identified significant results in this report

Spectra of cosmic X-ray sources

X-ray measurements provide the most direct probes of astrophysical environments with temperatures exceeding one million K. Progress in experimental research utilizing dispersive techniques (e.g., Bragg and grating spectroscopy) is considerably slower than that in areas utilizing photometric techniques, because of the relative inefficiency of the former for the weak X-ray signals from celestial sources. As a result, the term "spectroscopy" as applied to X-ray astronomy has traditionally satisfied a much less restrictive definition (in terms of resolving power) than it has in other wavebands. Until quite recently, resolving powers of order unity were perfectly respectable, and still provide (in most cases) the most useful spectroscopic data. In the broadest sense, X-ray photometric measurements are spectroscopic, insofar as they represent samples of the overall electromagnetic continua of celestial objects

High Resolution Spectroscopy of SN1987A's Rings: He I 10830 and H-alpha from the Hotspots

We present the first high-dispersion spectroscopy of He I 10830 from the hotspots in the ring around SN1987A, obtained at Gemini South, spatially resolving the near and far sides of the ring. We compare these line profiles to similar echelle spectra of H$\alpha$ and [N II] 6583 obtained at the Magellan Observatory. We find that the He I profiles are much broader than H-alpha or [N II], but the He I profiles also have different shapes -- they have enhanced emission at high speeds, with extra blueshifted emission on the north side of the ring, and extra redshifted emission on the south side. To explain this, we invoke a simple geometric picture where the extra He I emission traces hotter gas from faster shocks that strike the apex of the hotspots directly, while the H-alpha preferentially traces cooler lower-ionization gas from slower transverse shocks that penetrate into the sides of the ring.Comment: 3 pages. To appear in proceedings: "Supernova 1987A: 20 Years After: Supernovae and Gamma-Ray Bursters" AIP, New York, eds. S. Immler, K.W. Weiler, and R. McCra

UV spectroscopy of the blue supergiant SBW1: the remarkably weak wind of a SN 1987A analog

The Galactic blue supergiant SBW1 with its circumstellar ring nebula represents the best known analog of the progenitor of SN 1987A. High-resolution imaging has shown H-alpha and IR structures arising in an ionized flow that partly fills the ring's interior. To constrain the influence of the stellar wind on this structure, we obtained an ultraviolet (UV) spectrum of the central star of SBW1 with the HST Cosmic Origins Spectrograph (COS). The UV spectrum shows none of the typical wind signatures, indicating a very low mass-loss rate. Radiative transfer models suggest an extremely low rate below 10$^{-10}$ Msun/yr, although we find that cooling timescales probably become comparable to or longer than the flow time below 10$^{-8}$ Msun/yr. We therefore adopt this latter value as a conservative upper limit. For the central star, the model yields $T_{\rm eff}$=21,000$\pm$1000 K, $L\simeq$5$\times$10$^4$ $L_{\odot}$, and roughly Solar composition except for enhanced N abundance. SBW1's very low mass-loss rate may hinder the wind's ability to shape the surrounding nebula. The very low mass-loss rate also impairs the wind's ability to shed angular momentum; the spin-down timescale for magnetic breaking is more than 500 times longer than the age of the ring. This, combined with the star's slow rotation rate, constrain merger scenarios to form ring nebulae. The mass-loss rate is at least 10 times lower than expected from mass-loss recipes, without any account of clumping. The physical explanation for why SBW1's wind is so weak presents an interesting mystery.Comment: 12 pages, 6 figs. submitted to MNRAS. comments welom

WORKING MEMORY PERFORMANCE: IS SUBJECTIVE MEASUREMENT A BETTER PREDICTOR THAN COGNITIVE LOAD?

We rely on our capacity for rapid attention switching to conduct multiple tasks simultaneously. Leading working memory models assume that memory maintenance and attention-demanding secondary task processing cannot coincide. Any reduction in memory maintenance activities occurring due to secondary task processing leads to impaired recall. This temporal relationship is typically characterized through the proportion of time spent attending to the concurrent processing task, also called cognitive load. Although the primary determinant of forgetting in leading models, recent findings show limitations to cognitive load effects in multitasking. We investigated whether the effects of cognitive load are a byproduct of subjective task difficulty assessments by participants during a visuospatial working-memory dual-task by asking participants to complete subjective workload measurement (NASA-TLX). Results were compared to objective cognitive load to determine which measurement is a better model for predicting multitasking effects. The present findings inform our understanding of human working memory capabilities and the role of both subjective workload and objective cognitive load in driving memory performance during multitasking

Middle and High School Teachers\u27 Perception of Professional Development

Within the literature, a gap exists in understanding how teacher perceptions may be used to develop, implement, and evaluate professional development. The purpose of the qualitative case study was to describe the perceptions of middle and high school teachers regarding their professional development experiences in a rural school district in Florida. Guided by Chen and Chang\u27s whole teacher framework and Knowles\u27s theory of adult learning, the research questions addressed teachers\u27 needs, expectations, and perceptions of professional development. Triangulated data sources included face-to-face interviews with 10 teachers, participant journals, and professional development agendas. Data analysis included line-by-line coding, open coding, and theoretical coding. Emerging themes were (a) effective and meaningful professional development, (b) teacher contributions to professional development, (c) teacher perceptions of professional development, and (d) student achievement due to professional development. Results indicated that although teachers perceive professional development as a tool for learning, teacher leadership, analysis of student achievement data, and collaboration are needed to increase its effectiveness. This study may contribute to positive social change by improving professional development practices in school districts, leading to enhanced student academic achievement and preparation for careers

Core Students Win Fulbright Honors

Three University of Dayton seniors from the Core program won scholarships as part of Fulbright programs and are headed abroad as English teaching assistants