Discovery of the 2010 Eruption and the Pre-Eruption Light Curve for Recurrent Nova U Scorpii

We report the discovery by B. G. Harris and S. Dvorak on JD 2455224.9385 (2010 Jan 28.4385 UT) of the predicted eruption of the recurrent nova U Scorpii (U Sco). We also report on 815 magnitudes (and 16 useful limits) on the pre-eruption light curve in the UBVRI and Sloan r' and i' bands from 2000.4 up to 9 hours before the peak of the January 2010 eruption. We found no significant long-term variations, though we did find frequent fast variations (flickering) with amplitudes up to 0.4 mag. We show that U Sco did not have any rises or dips with amplitude greater than 0.2 mag on timescales from one day to one year before the eruption. We find that the peak of this eruption occurred at JD 2455224.69+-0.07 and the start of the rise was at JD 2455224.32+-0.12. From our analysis of the average B-band flux between eruptions, we find that the total mass accreted between eruptions is consistent with being a constant, in agreement with a strong prediction of nova trigger theory. The date of the next eruption can be anticipated with an accuracy of +-5 months by following the average B-band magnitudes for the next ~10 years, although at this time we can only predict that the next eruption will be in the year 2020+-2.Comment: Astronomical Journal submitted, 36 pages, 3 figures, full table

Community Engagement and Service-Learning Reciprocity

This paper was presented at the 2020 Schools of Thought Conference hosted by the Christopher C. Gibbs College of Architecture at the University of Oklahoma.As part of the University of Oklahoma’s Christopher C. Gibbs College of Architecture, the Urban Design Studio prepares graduate students from diverse backgrounds in its Master of Urban Design program to practice as urban design professionals. The studio uses a reciprocal community engagement and service-learning approach that benefits cities and residents of Oklahoma and provides students with meaningful educational experiences. Four case studies of studio projects are considered here. Each case study focuses on a different type of project, including creative urban design practice, participatory action research, community-based planning, and real-life, real-time placemaking. The studio regularly collaborates with communities on urban design studies and interventions. One such project focused on the revitalization of a three-mile stretch of Route 66 running through the heart of Tulsa. Participatory action research is represented by Tulsa Photovoice, an example of how studio faculty and students collaborate with communities to discover knowledge. Working in a more traditional framework, studio students led a community-based planning process for the downtown plan of the city of Muskogee, Oklahoma, entitled a Landscape of Hope. Finally, placemaking activities like the one for the Chapman Green illustrate how students learn by making. Each case study explains how the project was initiated, what community engagement techniques were used, and how students participated. Project outcomes are also summarized.Ye

Accurate pre- and post-eruption orbital periods for the dwarf/classical nova V1017 Sgr

V1017 Sgr is a classical nova (from 1919) that displayed an earlier dwarf nova eruption (from 1901) and underwent two more dwarf nova events (in 1973 and 1991). Previous work on this bright system in quiescence (V = 13.5) has consisted only of a few isolated magnitudes, a few spectra and an ambiguous claim of an orbital period of 5.714 d based on nine radial velocities. To test this period, we have collected 2896 magnitudes (plus 53 in the literature) in the UBVRIJHKL bands from 1897-2016, making an essentially complete photometric history of this unique cataclysmic variable. We find that the light curve in all bands is dominated by the ellipsoidal modulations of a G giant companion star, with a post-eruption (after the 1919 nova event) orbital period of 5.786290 ± 0.000032 d. This is the longest period for any classical nova; the accretion must be powered by the nuclear evolution of the companion star and dwarf nova events occur only because the outer parts of the large disc are cool enough to be unstable. Further, we measure the pre-eruption orbital period (from 1907-1916). The orbital period has decreased by 273 ± 61 parts per million across the 1919 eruption, with the significance of the period change being at the 5.7σ confidence level. This is startling and mystifying for nova theory, because the three known period-change effects cannot account for a period decrease in V1017 Sgr, much less one of such a large size

Morphological change in Newfoundland caribou: Effects of abundance and climate

The demographic and environmental influences on large mammal morphology are central questions in ecology. We investigated the effects of population abundance and climate on body size and number of male antler points for the La Poile and Middle Ridge caribou (Rangifer tarandus, L. 1758) herds, Newfoundland, Canada. Across 40 years and 20-fold changes in abundance, adult males and females exhibited diminished stature as indicated by jawbone size (diastema and total mandible length) and the number of antler points at the time of harvest. Associations between jawbone size and population abundance at birth were consistently negative for both herds, both sexes, and all age classes. Large-scale climate patterns, as measured by the North Atlantic Oscillation in the winter prior to birth, were also negatively associated with jawbone size. Declines in male antler size, as measured by the number of antler points, were not well predicted by either abundance or climate, suggesting other factors (e.g., current, rather than latent, foraging conditions) may be involved. We conclude that these morphological changes indicate competition for food resources

Peat Formation Concentrates Arsenic Within Sediment Deposits of the Mekong Delta

Mekong River Delta sediment bears arsenic that is released to groundwater under anaerobic conditions over the past several thousand years. The oxidation state, speciation, and distribution of arsenic and the associated iron bearing phases are crucial determinants of As reactivity in sediments. Peat from buried mangrove swamps in particular may be an important host, source, or sink of arsenic in the Mekong Delta. The total concentration, speciation, and reactivity of arsenic and iron were examined in sediments in a Mekong Delta wetland by X-ray fluorescence spectrometry (XRF), X-ray absorption spectroscopy (XAS), and selective chemical extractions. Total solid-phase arsenic concentrations in a peat layer at a depth of 6 m below ground increased 10-fold relative to the overlying sediment. Extended X-ray absorption fine structure (EXAFS) spectroscopy revealed that arsenic in the peat was predominantly in the form of arsenian pyrite. Arsenic speciation in the peat was examined further at the micron-scale using μXRF and μX-ray absorption near-edge structure (XANES) spectroscopy coupled with principal component analysis. The multiple energy μXRF mapping and μXANES routine was repeated for both iron and sulfur phase analyses. Our μXRF/μXANES analyses confirm arsenic association with pyrite – a less reactive host phase than iron (hydr)oxides under anaerobic conditions. The arsenian pyrite likely formed upon deposition/formation of the peat in a past estuarine environment (∼ 5.5 ka BP), a process that is not expected under current geochemical conditions. Presently, arsenian pyrite is neither a source nor a sink for aqueous arsenic in our sediment profile, and under present geochemical conditions represents a stable host of As under the reducing aquifer conditions of the Mekong Delta. Furthermore, organic carbon within the peat is unable to fuel Fe(III) reduction, as noted by the persistence of goethite which can be reduced microbially with the addition of glucose

Tulsa Photovoice: A Participatory Action Research Project

The Tulsa PV project involved collaboration among OU-Tulsa School of Community Medicine (SCM), the Tulsa Area Community Schools Initiative (TACSI), faculty members from the Anne & Henry Zarrow School of Social Work, the Urban Design Studio, and the OU-Tulsa Library. The objectives of the Tulsa (PV) project were broad and varied due to the multiple constituencies. Objectives included:(1) the collection and analysis of qualitative data, both visual and oral, from a geographically distributed sample of Tulsa residents that will reflect their attitudes, perceptions, and behaviors about their communities, particularly those that may be related to health outcomes, (2) provide community residents the opportunity to examine and speak directly about their experiences living within their communities, (3) Provide opportunities for faculty, students, and staff participating in the OU School of Community Medicine Summer Institute to meet with community residents and learn more about their communities through direct experience in a research project (4) Involve teachers and school site coordinators at community schools in a qualitative research study as assistant investigators, and (5) Document and share the information collected with all the institute participants, the scholarly community, and the public.N

High Crime Neighborhoods as a Driver for Toxic Stress Leading to Asthma

BACKGROUND: Social determinants of health and allostatic load theory suggest social environment can drive asthma diagnoses via the mechanism of toxic stress, the prolonged activation of stress response systems. While research has linked neighborhood crime to asthma, multivariate causal modeling has not been used to test toxic stress as the mechanism that links the two. The current study investigates neighborhood crime as a driver of pediatric asthma diagnoses via toxic stress. METHODS: A retrospective geospatial analysis of health and crime data was conducted. Health data was collected from the OU-Tulsa General Pediatric Clinic’s Electronic Medical Record while crime data was collected from the Tulsa Police Department. All variables were mapped geospatially using census tract as the unit of analysis. Structural equation modeling was used to test the causal model. Neighborhood crime indicators included homicide, rape, and narcotic-related offenses. Diagnoses of conduct, attention deficit, and other anxiety disorders were used in the analysis as toxic stress indicators. Asthma diagnoses were the outcome variable. To further test the model, data from 2016 was used as a calibration sample while data from 2017 was used as a validation sample. RESULTS: A full mediation model of high crime neighborhoods (n = 134) as a driver of toxic stress resulting in increased asthma diagnoses fit the 2016 data well (Χ2 = 15.6, p =.27; df = 13; RMSEA = .04 [90% CI: .00, .10]; CFI: .99; SRMR = .04). The results indicated the model accounted for 78% (R2 = .78) of the variance in asthma diagnoses. The model also provided a good fit to the 2017 data (X2= 23.6, p<.001; df= 13; RMSEA = .08 [90% CI: .02, .13]; CFI: .96; SRMR=.06). CONCLUSION: The results of the current study have important practice and research implications. While clinicians and researchers have become increasingly aware of the impact of social determinants of health, there has been little focus on improving clinical practices. Physicians interested in alleviated the burden of toxic stress and asthma should explore ways to reduce neighborhood crime at the policy level while also being aware of each of their patients’ unique circumstances in relation to where they live.N

The KIC 8462852 light curve from 2015.75 to 2018.18 shows a variable secular decline

The star KIC 8462852 (Boyajian's Star) displays both fast dips of up to 20% on time scales of days, plus long-term secular fading by up to 19% on time scales from a year to a century. We report on CCD photometry of KIC 8462852 from 2015.75 to 2018.18, with 19,176 images making for 1,866 nightly magnitudes in BVRI. Our light curves show a continuing secular decline (by 0.023±0.003 mags in the B-band) with three superposed dips with duration 120-180 days. This demonstrates that there is a continuum of dip durations from a day to a century, so that the secular fading is seen to be by the same physical mechanism as the short-duration Kepler dips. The BVRI light curves all have the same shape, with the slopes and amplitudes for VRI being systematically smaller than in the B-band by factors of 0.77±0.05, 0.50±0.05, and 0.31±0.05. We rule out any hypothesis involving occultation of the primary star by any star, planet, solid body, or optically thick cloud. But these ratios are the same as that expected for ordinary extinction by dust clouds. This chromatic extinction implies dust particle sizes going down to ˜0.1 micron, suggesting that this dust will be rapidly blown away by stellar radiation pressure, so the dust clouds must have formed within months. The modern infrared observations were taken at a time when there was at least 12.4%±1.3% dust coverage (as part of the secular dimming), and this is consistent with dimming originating in circumstellar dust